Best option for line side tap

I'm looking at a couple of options for a line side tap and each has complications. I'd like to get views on the best way.

I have two SB7000 inverters feeding a combiner 100A load center with 40A breakers from each SB7000US ( max 34A output) feeding the load center bus and a 80A output breaker to a Square D 223 RB fused ( RK5 - 80A) which will feed my line tap. The RK5 fuses provide service panel level protection as they are tied directly to the meter line side bypassing and before my 200A Square D Combo CSED mains.



I have two basic options.

My Square D Combo has spare lugs on the meter service side into which I can simply insert and set my 2 #4AWG hot wires. A spare neutral lug is also available also on the utility side of the panel where the neutral can easily be set screwed in. The ground can be set to the service side ground bar.

This sounds very clean and as though Square D left spare lugs for each of my line side taps right on the meter lugs and neutral bar. Sounds fabulous but I must enter and punch access into the utility - PG&E compartment in order to access the ideal spare lugs. I have been told its difficult to get permission to enter and wire inside the PG&E compartment. Is this true? If not for punching the access holes and getting permission to make the modifications, its ideal.

There are no larger bus bars for my model above 200A and modifying that would violate UL. Square D did not recommend it and said PG&E was difficult.

The other strategy is to tap into the four #4 AWG wires Square D uses to carry power from the utility side meter lugs to the four ( 2 pairs) main disconnect breakers. I can either remove the wires from the mains and pull into a small splice box where I splice the line tap #4 AWG wire pair and the four #4AWG wires returning to the mains set screw ports. Basically I'm breaking into and taping the wires on the line side before they hit my mains.

I can also replace the existing Square D #4AWG wires with slightly longer ( 10" to maybe 18") and replace the existing wires and run them into a splice box through a waterproof port and run through a block that has 3 holes and set screws. I run the two = hot wires through two holes and splice my #4AWG with the third port and set screw. That way the wires are unbroken between the meter and mains but I need to replace the shorter wires.

If I use the existing wires from the meter to mains, they won't reach into a small splice box and back. That keeps me out of the utility compartment but the wires from the meter to mains are also spliced to make up the longer run back through the punched port to the mains. Then my line tap connects to the same spli8ce block pairs and also run through a port out into the main service compartment and then out to my disconnect ( about 10 ft.).

So one option is very nice but has the PG&E policy and approval road block. The other means I hang a small splice box just outside the service compartment near the mains and use watertight ports to run 4 + 4 + 2 #4AWG wires. This version has the "use the existing wires and splice) or ( swap to 4 longer meter<-> main wires and just pass through the splice block).

If I am using THWN-2 #4 AWG wire for the tap and the inverters maximum is 68A but the panel breaker is 80A as i8s the RK5 fuse, is there any problem with #4AWG in this application when its in conduit ( 3 wires + ground). The #4 AWG THWN-2 has a 95A at 90 degree and 85A at 75 degrees both of which exceed the 80A breakers. Is #4 acceptable give the continuous will be 68A or less and the 80A breaker and 80A fuse will prohibit more than 80A under fault conditions.

Any thoughts?

thanks:blush:

Does that make sense

Comments

  • dwhdwh Posts: 1,341Solar Expert ✭✭✭
    Re: Best option for line side tap

    Unfortunately, I only have a few minutes and don't have time to research this according to code today...so a few quick thoughts.

    If you tap into the lugs on the incoming side of the meter, then there is no way to "run the meter backwards".

    I can't remember offhand if line side *supply* taps are even allowed *ahead* of the meter. I know taps like that are allowed for multiple unit buildings, but those are normally taps FROM incoming service wire TO multiple meters. Those are load taps, not supply taps.

    From the sound of it, the panel has two "side by side" compartments. If so, and there is room in the meter/service entrance side, I would probably just replace the existing meter-to-buss wires with longer ones, and do a split bolt tap on them. (Strip not cut, connect with split bolt, tape with rubber tape, electrical tape and then friction tape.)

    That keeps all the building wiring on the load side of the meter, and all the supply lines in the service entrance side of the panel - and would also be a neat and tidy way to do it.
  • PgovetomPgovetom Posts: 30Solar Expert
    Re: Best option for line side tap

    Thanks for your response. I think you misread my explanation. I am putting the tap on the service side of the meter. So it will work correctly. My concern is meeting both NEC and PG&E. The two pairs of #4 wire that go from the meter service side lugs to the main 200A breakers are on the service side and are used to go from the PG&E utility compartment to the service compartment through 4 grommets in the steel wall. Those are the wires I need to tap if I am not allowed to just go inside the PG&E compartment and use the spare lugs.

    If I can't just use the PG&E side lugs, then I need to tap into those #4 wires before they hit my breakers. There isn't room to put a safe tap on them inside the service compartment as its pretty jammed with wire. So I need to pull those #4 wires outside into a small splice box and tap them and run them back into the service compartment and into the 200A breakers. Its conceptually simple but there just isn't room to put splices on those wires inside the space.

    Its also a little weird as they divided it into 2 pairs because the mains are actually 2 x 2 pole 100A so they just use 2 #4 wires per breaker/pole. I can't tap just two wires since the ampacity of the #4 is not enough for its own 100A plus my solar feed of 80A. ( actually 68A but the fuse and breakers are 80A). So I need to tie both wires from each side together with the splice block and then run a pair back to the mains. That way I have the ampacity of 2 x #4AWG and its identical to how Square D did it. That has to be done inside a small splice box I place directly behind my service side compartment just behind the 200A breakers so the wires are very short.

    Its quite a mess just because PG&E has dumb policies when they are supposed to be the solar leader!
  • n3qikn3qik Posts: 741Solar Expert ✭✭
    Re: Best option for line side tap

    Maybe wrong here, but I think I read somewhere the NEC does not allow doubling of conductors till you get over 0 AWG.
  • PgovetomPgovetom Posts: 30Solar Expert
    Re: Best option for line side tap

    Its the Square D Combo CSED that doubles the wires. Since the main breakers are actually 4 separate breakers, 2 100A per hot leg, they use 4 #4 wires from the meter lugs that go through grommets in the service/utility compartment wall and once in the service side go directly to and are set screwed tightened into the 4 breakers. It takes all four to cut off the 200A and each has wire, 2 per 120V side.

    I'm simply proposing running each 120V leg pair through a splice block and tightening with a set screw and then using a separate hole in the block and set screw for another #4 tap wire. I'm simply bringing the pair which were separate but electrically connected to the same lug together as they were at the lug 4 inches away and then continuing them on to the 2 sections of the 4 breakers ( the other 2 are identical but on the other 120V leg meter lug and go to the other 2 breaker set screw holes. One issue is the torque on the meter lugs ( if I pull and replace them) and then the torque for the main breakers.

    If I could find a splice method small enough to fit right on the existing wires as is without removing them, it would be ideal. I can envision a small bar with one hole and set screw that accepts #4 with something like a bug where I could remove the end and slip the 2 #4 wires in with 3/8" of insulation removed , put the end back on and tighten down on the bare section of the wire. That would allow me to do the splice removing either end of the existing 4 #4 wires and only remove a little insulation so I could set it. I would need for it to be insulated quite well given what little room is available is around other wires, breakers and the compartment wall -- ground.

    Its a messy problem without just putting a 250A or 300A meter and using my Combo not as a Combo but just a panel without a meter. Then I could easily tap the connection between the meter and my Square D meterless main panel.
  • dwhdwh Posts: 1,341Solar Expert ✭✭✭
    Re: Best option for line side tap

    Again, no time right now to check code...but I still don't see why you are dead set against doing the tap on the other side of the divider.

    What is the exact model number of the panel and does the service come in underground or overhead?

    I'll try to look up a pic of the panel tomorrow (Wed.) and dig through some code.
  • PgovetomPgovetom Posts: 30Solar Expert
    Re: Best option for line side tap

    I do want to just go with the clean utility/PG&E side tap.

    It is a Square D 200A Combo ( Meter on left and 40 breaker slots in right side service compartment) CSED SC2040M200C. The Square D supports both underground or overhead bu mine is underground from PG&E. That leaves the overhead neutral lug unused and ideal for my line tap. It also has 3 holes in each meter lug but only uses 2 for those #4 wires so the spare hole is perfect for the #4 line tap wires. My system has a Square D D223NRB Disconnect switch with is fused with RK-5 ( 80A service rated at 200,000A) so it can be tied directly to the line as per NEC).

    I much prefer simply entering the unused overhead port ( I have the proper overhead access hardware ) via EMT conduit directly from my Disconnect and with the 2 120V #4 legs set screwed into the 2 spare meter lugs ( on the service side) and the neutral to the spare overhead neutral bar. Then The ground ties into the Square D ground bar and I;m done and its clean.

    I've been told its difficult top get PG&E approval to enter and wire to the lugs inside their utility side. If they said Yes, its a no brainer -- I would do it. I am struggling with PG&E permission in parallel with looking for my other approach should I fail to get approval. I want to make sure I don't fail my final inspection should I have to use the splice approach. Or even worse, replace the meter and get a 250A or 300A intermediate main panel where I perform a standard service tap via 40A breakers. Then I put my house main sup-panel and pool sub-panel and just come up with a whole new service.meter setup. That's a lot of work and expense --- yuck
  • dwhdwh Posts: 1,341Solar Expert ✭✭✭
    Re: Best option for line side tap

    Ah.

    Well, I can certainly see where they would be picky about you tapping in *ahead* of the meter - which is exactly what you would be doing if you used the spare lugs provided for the overhead service entrance. The upper and lower service entrance lugs will be connected to the same buss bars (which means they are hot right now).

    Still, there should be plenty of room in the lower (below the meter) compartment for you to do a tap between the meter and the main disconnect breakers. They *could* reasonably complain about having your tap in the same compartment with their live transformer feed.

    However I'm sure that there is a divider between the service wires and the wires from the meter to the main breakers - and that area would be a perfect place for the tap if you can get into it. Obviously, you would have to come in from the bottom for that since those top lugs are hot directly from the transformer and there won't be a divider in the top compartment.

    Again, I'll try to take a closer look tomorrow.
  • PgovetomPgovetom Posts: 30Solar Expert
    Re: Best option for line side tap

    I'm not sure why you continue to say I'm tapping ahead of the meter. Let me be clear. I am tapping on the house side --- NOT the PG&E side of the meter. I would NOT tap the PG&E side of the meter because it wouldn't work. Net metering requires as does the NEC that the tap be on the home side of the meter. I have never considered, would not consider nor have ever said I was tapping on the PG&E side of the meter. I hope that is clear.

    In order to use the spare lugs on the HOME SIDE OF THE METER -- I must go inside the PG&E compartment because that compartment houses the meter and underground wires attached to the utility side of the meter. The home side lugs are a few inches from the utility lugs on the back of the meter socket and so MUST be inside the utility/PG&E compartment.

    Because this is a Combo CSED, the utility and service/breaker compartments are adjacent and attached with a steel plate between them. Only the 4 -#4 wires that Square D uses to bring the home side power from meter socket ( after passing through the meter) pass via grommets to the service side and go directly to the main breaker gang of four breakers = 4 wires. Two of those wires are one leg of the 120V while the other two are the other leg 180 degrees out of phase making up 220V.

    In order to do a "line/supply side tap" on this Combo type unit, the tap must be made somewhere from the home side lugs on the meter ( not PG&E side) or along the 4 #4 wires are in holes with set screws in those lugs to where those wires enter the main breakers.

    Physically there are the home side lugs on the meter, the approximately 10 inches of #4 wire x 4 ( split two per 120V leg) and the breaker holes with set screws where the wires terminate. Along that path is the only place a tap can be made properly ( NOT on the utility side of the meter). The complication is that tapping the meter home side lugs spare holes/set screws requires entering and wiring INSIDE the PG&E utility compartment which they don't like. If someone goes inside their compartment and accidently drops a wrench and it falls on the underground wires, about 200,000 AMPS will explode the wrench and possibly damage the PG&E transformer. Those un-insulated connections are about 10 inches directly below the meter in their compartment. The home side lugs are also just above and near the PG&E side lugs which also are connected to the PG&E facilities. I don't blame them for having a policy that any electrician can't just go in that box and wire whatever they like. It puts their facilities at risk while the service side compartment has a 200A breaker isolating virtually anything that a falling wrench or screwdriver can do. They would just pop the 200A breaker but protect the PG&E facilities.

    That is why PG&E puts those small seals/locks on the utility compartment and it's actually against the law to cut them and enter the compartment. If you get permission because you are replacing the whole panel, you still aren't allowed to place wiring anywhere in that compartment because they want to be safe. Its dumb but its their policy. PG&E will actually cut the power at the transformer if necessary or allow the meter to be removed if say you needed to replace the main breakers due to failure. Then they will come back and put those little locks on the compartment to prevent just anybody from going in. They are easy to cut off but PG&E could file legal action if they wanted to -- not likely but they just want their facilities and wherever the wires land to be held sacred and safe.
  • mountaintopmountaintop Posts: 16Registered Users
    Re: Best option for line side tap

    Pgovetom
    First off it’s not against the law to cut the tag on your meter can and pull the meter. Most POCO’s will fine you for doing it and will pull the meter and make you get an inspection before they will reconnect. Most POCO’s can’t keep up with the tag numbers if it’s been on there for a few years. You can jump on the net and buy new ones pretty cheap. The new meters have a tattle tale in them and they can tell when it’s been pulled when it’s read.

    If you are going with net metering then don’t you have to get the AC side of the system installed by an electrician, inspected, and most POCO will do a quick inspection before they will approve the install.
  • dwhdwh Posts: 1,341Solar Expert ✭✭✭
    Re: Best option for line side tap
    Pgovetom wrote: »
    I'm not sure why you continue to say I'm tapping ahead of the meter. Let me be clear. I am tapping on the house side --- NOT the PG&E side of the meter. I would NOT tap the PG&E side of the meter because it wouldn't work. Net metering requires as does the NEC that the tap be on the home side of the meter. I have never considered, would not consider nor have ever said I was tapping on the PG&E side of the meter. I hope that is clear.

    Quite clear. My mistake.

    As every time I read this thread I was in a bit of a hurry, I read it as you preferred to come into the box via the overhead service access (unused since you have underground) so that you could tie into the lugs there (also unused).

    Those lugs would naturally be on the utility side of the meter and thus a "Bad Idea(TM)".

    In order to use the spare lugs on the HOME SIDE OF THE METER -- I must go inside the PG&E compartment because that compartment houses the meter and underground wires attached to the utility side of the meter. The home side lugs are a few inches from the utility lugs on the back of the meter socket and so MUST be inside the utility/PG&E compartment.

    Because this is a Combo CSED, the utility and service/breaker compartments are adjacent and attached with a steel plate between them. Only the 4 -#4 wires that Square D uses to bring the home side power from meter socket ( after passing through the meter) pass via grommets to the service side and go directly to the main breaker gang of four breakers = 4 wires. Two of those wires are one leg of the 120V while the other two are the other leg 180 degrees out of phase making up 220V.

    In order to do a "line/supply side tap" on this Combo type unit, the tap must be made somewhere from the home side lugs on the meter ( not PG&E side) or along the 4 #4 wires are in holes with set screws in those lugs to where those wires enter the main breakers.

    Physically there are the home side lugs on the meter, the approximately 10 inches of #4 wire x 4 ( split two per 120V leg) and the breaker holes with set screws where the wires terminate. Along that path is the only place a tap can be made properly ( NOT on the utility side of the meter). The complication is that tapping the meter home side lugs spare holes/set screws requires entering and wiring INSIDE the PG&E utility compartment which they don't like. If someone goes inside their compartment and accidently drops a wrench and it falls on the underground wires, about 200,000 AMPS will explode the wrench and possibly damage the PG&E transformer. Those un-insulated connections are about 10 inches directly below the meter in their compartment. The home side lugs are also just above and near the PG&E side lugs which also are connected to the PG&E facilities. I don't blame them for having a policy that any electrician can't just go in that box and wire whatever they like. It puts their facilities at risk while the service side compartment has a 200A breaker isolating virtually anything that a falling wrench or screwdriver can do. They would just pop the 200A breaker but protect the PG&E facilities.

    That is why PG&E puts those small seals/locks on the utility compartment and it's actually against the law to cut them and enter the compartment. If you get permission because you are replacing the whole panel, you still aren't allowed to place wiring anywhere in that compartment because they want to be safe. Its dumb but its their policy. PG&E will actually cut the power at the transformer if necessary or allow the meter to be removed if say you needed to replace the main breakers due to failure. Then they will come back and put those little locks on the compartment to prevent just anybody from going in. They are easy to cut off but PG&E could file legal action if they wanted to -- not likely but they just want their facilities and wherever the wires land to be held sacred and safe.


    Yes. As I said, today I would try to take a closer look.

    According to your part number, your panel is:

    http://static.schneider-electric.us/docs/Electrical%20Distribution/Combination%20Service%20Entrance%20Devices/CSED,%20All-in-ones/SU/1973.pdf

    A (blurry) picture of your panel's 150a little brother can be found here (last page, right column, center):

    http://static.schneider-electric.us/docs/Electrical%20Distribution/Combination%20Service%20Entrance%20Devices/CSED,%20All-in-ones/4100PL0401CSED.pdf

    As you can see, there are quite a few different configurations for combi panels - just from SquareD. There is in fact, a huge variety of different configurations from different manufacturers.

    Many configurations have dividers *in the service entrance compartment*. Some OH/UG combo panels have an internal trough from bottom to top and only one set of incoming lugs - thus even coming in underground, you have to route the incoming wire "up and around" and come into the meter socket assembly from the top.

    What I have just described looks a bit like this:

    http://automation.usa.siemens.com/resident/images/metercombophotos/MC0606M21200R.jpg

    Obviously, that's a "stacked" configuration OH/UG combi panel and you have a "side-by-side". Yes, I know your panel has both upper and lower utility landing lugs. Nevertheless, I have personally seen side-by-side OH/UG combination load centers with both upper and lower landing lugs AND internal dividers on the service entrance side. (Made by who? Dunno, can't remember - but I have seen them.)

    In fact, if you look at the last page of that one pdf and you look at the entire second row from left to right, you will see that the other three panels all have some sort of internal divider in the service entrance compartment.

    Of particular interest; If you look carefully at the picture of the panel immediately to the left of your panel (the one that says "QC816F150C/CH (Shown)") - you will see that it has a fully enclosed trough from the the bottom through the breaker compartment AND an open top trough/divider in the top right side of the meter compartment:

    http://static.schneider-electric.us/docs/Electrical%20Distribution/Combination%20Service%20Entrance%20Devices/CSED,%20All-in-ones/4100PL0401CSED.pdf


    It's really not at all unusual to find a service entrance compartment which has been sub-divided.

    Thus:

    IF your panel had some sort of divider isolating the incoming feed from the load side of the meter socket (and for all I knew, it just might),

    AND the incoming solar supply line could enter that compartment WITHOUT occupying the same space as the utility's incoming wires (shouldn't be too tough if there was already an internal divider),

    THEN the line side tap could (maybe) be done in that compartment,

    BECAUSE the supply (utility) wiring and the load (meter to disconnect) wiring would be in physically separate compartments - even though both compartments are actually in the "service entrance" side of the combi panel.


    Never having actually seen your particular panel's layout however, until today I did not know whether that was a possibility.


    So the next question is whether to use the spare lugs/holes which you describe on the load side of the meter socket. Similar to the meter socket lugs in the pic below but with three holes on each leg?

    http://automation.usa.siemens.com/resident/images/metercombophotos/MM0404L1400RLM_Straight.jpg

    If so, I wonder what that extra hole is for. I.e., why did they fit that panel with a triple lug on the meter load side?


    I believe you stated that you are waiting for a ruling from PG&E as to whether you can use those lugs?

    Anyway, I'm out of time right now and have to run, so I'll have to come back to it later. Fun. :b
  • PgovetomPgovetom Posts: 30Solar Expert
    Re: Best option for line side tap

    My Square D Combo is similar but side by side versus upper/lower as in the Siemens photo. I could email photos as describing in these Forum posts is pretty hard and its easy to misunderstand.

    My panel has a left compartment that is intended for the Utility connection and is configured to allow either overhead or underground. My uses underground. The only lug available in the overhead ( above the meter and below the hub at the top) is the large gauge neutral that is at the top of a beefy bar that also has an identical lug below the meter for the underground option. In my case the lower Neutral lug is used while the upper lug is free for my "Line Side Tap".

    As far as the two hot leads for underground, they are on the meter socket below and are also used for the two large gauge underground hot feeds. They are physically attached to the utility side of the meter socket.

    On the home side of the meter socket are two lugs that feed "after meter" power through the compartment steel wall ( side by side compartment divider). They use actually #2 wire ( I was mistaken before after just eyeing them) to connect the home side meter lugs through grommets in the divider steel wall directly to the center ( top -> bottom ) mounted quad main breaker. Since they use four breakers for the mains, they also use 4 #2 wires -- two from one meter home side lug through compartment wall and directly to two of the main breakers. Then there are two more #2 wires from the other hot leg to the remaining two main breakers. The main breakers feed 200A to the main bus bar.

    The home side meter lugs have two wires but Square D was kind to put a third set screw hole to support a third wire. Then the other home side leg lug also has a third hole/set screw. Those two set screws on the lug that are spare plus the spare overhead neutral are exactly what the doctor ordered. Those are the exact places the line side tap must attach and the lugs are unused. Its ideal except PG&E permission plus getting into the compartment.

    The only available port is the unused overhead which has a seal now. It can be removed and a hub installed and the compartment entered. The other option, less obvious is to punch a 1 - 1 1/4 hole through the steel wall between the two compartments and run the 3 wires through it rather than the ugly overhead hub and conduit. My tap wires already enter the home compartment via a spare conduit from my disconnect switch but I've yet to hook them up. It would be easier to punch the hole and be done. I don't feel good punching a hole into PG&E sacred space and how both they and the building inspector will react.

    My only totally clean option is throw away the Combo and separate the meter and panel and tap between them. I hate to go through all that cost and trouble when I know there is only policy and BS between me and my other solutions. Our country deserves the 30 feet of sea level rise when Greenland melts due to Global warming and C02 that causes it when this sort of Barrier blocks on PV installation. Its ridiculous.
  • dwhdwh Posts: 1,341Solar Expert ✭✭✭
    Re: Best option for line side tap
    Pgovetom wrote: »
    On the home side of the meter socket are two lugs that feed "after meter" power through the compartment steel wall ( side by side compartment divider). They use actually #2 wire ( I was mistaken before after just eyeing them) to connect the home side meter lugs through grommets in the divider steel wall directly to the center ( top -> bottom ) mounted quad main breaker. Since they use four breakers for the mains, they also use 4 #2 wires -- two from one meter home side lug through compartment wall and directly to two of the main breakers. Then there are two more #2 wires from the other hot leg to the remaining two main breakers. The main breakers feed 200A to the main bus bar.

    Just to mention - sometimes (often) those wires are aluminum.

    The home side meter lugs have two wires but Square D was kind to put a third set screw hole to support a third wire. Then the other home side leg lug also has a third hole/set screw. Those two set screws on the lug that are spare plus the spare overhead neutral are exactly what the doctor ordered. Those are the exact places the line side tap must attach and the lugs are unused. Its ideal except PG&E permission plus getting into the compartment.

    The only available port is the unused overhead which has a seal now. It can be removed and a hub installed and the compartment entered. The other option, less obvious is to punch a 1 - 1 1/4 hole through the steel wall between the two compartments and run the 3 wires through it rather than the ugly overhead hub and conduit. My tap wires already enter the home compartment via a spare conduit from my disconnect switch but I've yet to hook them up. It would be easier to punch the hole and be done. I don't feel good punching a hole into PG&E sacred space and how both they and the building inspector will react.

    The first issue here is "load wiring occupying the same compartment with utility wiring".

    Since load wiring (meter to disconnect) is *already* in the same compartment, it should be acceptable to use the *existing* (that's an important word when dealing with inspectors and utility company spotters - big mojo) spare lugs. (After all, Mr. Inspector, what else could those lugs possibly be for?)


    The second issue is "penetrating the divider".

    I'm not wild about the idea of punching a big hole through that divider. What I would probably suggest to the inspector is that if I drilled three small holes (just like the existing) with grommets (just like the existing) and ran the wires through them (just like the existing), and connected to the lugs (just like the existing) - then that should be *exactly* as safe - and thus acceptable - as what is already (existing) there.

    Essentially, you might be able to sell the inspector on the idea that you are only duplicating what SquareD has already done - and which has *already been approved* by his department. AND the spare lugs are already provided for it! (Looky here Mr. Inspector, see for yourself.)

    Rinse and repeat for the utility company field agent.


    If that doesn't work, then the next question is "what can be done if they won't let us do the reasonable thing"?

    I'm too tired tonight to study that, so I'll leave it for tomorrow.
  • BB.BB. Posts: 25,254Super Moderators admin
    Re: Best option for line side tap
    dwh wrote: »
    I'm not wild about the idea of punching a big hole through that divider. What I would probably suggest to the inspector is that if I drilled three small holes (just like the existing) with grommets (just like the existing) and ran the wires through them (just like the existing), and connected to the lugs (just like the existing) - then that should be *exactly* as safe - and thus acceptable - as what is already (existing) there.

    Essentially, you might be able to sell the inspector on the idea that you are only duplicating what SquareD has already done - and which has *already been approved* by his department. AND the spare lugs are already provided for it! (Looky here Mr. Inspector, see for yourself.

    I have not been following the conversation closely (my eyes glazed over when I used to get paid to design larger computer systems to code)...

    But the "...drilled three small holes..." caught my eye.

    Are you typing about three holes in a metal partition for the three wires in one set (A, B, neutral) or something else.

    I am 99.9998% sure that it is against code to bring electrically common sets of AC wires (1 phase, split-phase, 3-phase, etc.) carrying related currents through separate holes punched in a metal partition (or any metal/conductive barrier). DC would be OK, because there is no "transformer like" current induction from DC fields in the metal barrier.

    The problem is that while the "sum of the current" is zero for the set of wires (i.e., all current going down one wire is returned up its "mate") and having all wires (three in the split phase case) going through the same hole will have a net zero current/magnetic field (which is "cool").

    However, if you have (three split phase conductors) going through three separate holes in the metal barrier--the sum of the current is non-zero for each wire--so there will be an induced current in the sheet metal barrier--and can lead to overheating of the barrier. Which is not "cool".

    If this is not what you are talking about--please ignore me. :roll:

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • dwhdwh Posts: 1,341Solar Expert ✭✭✭
    Re: Best option for line side tap

    Yes, that's what I was talking about. The reason is because (from what I understand) that is what is already there.

    From the OP:

    "Since the main breakers are actually 4 separate breakers, 2 100A per hot leg, they use 4 #4 wires from the meter lugs that go through grommets in the service/utility compartment wall".

    So my suggestion was simply to duplicate whatever sort of penetration the factory did to that partition. I was stupidly assuming that "grommets" meant more than one hole, which was a dumb assumption and I suppose I should have asked for clarification.


    I do believe you are right though. So perhaps what he's actually got is a single hole through the wall with a grommet with multiple holes in the grommet.


    Either way, the point is to duplicate what is already there.

    Good catch. :)
  • PgovetomPgovetom Posts: 30Solar Expert
    Re: Best option for line side tap

    It is true that Square D already drilled 4 holes in the wall and put grommets in them to pass the 2 #2 AWG pairs (out of phase) of hot 120V wires but the neutral is carried by a large aluminum bar passing across the back. I would need to pass the two hots out of phase and neutral so its different.

    I do believe an inspector that was not overly sophisticated would see my wires looking exactly like the 4 Square D wires and it would look cleaner. There is a bend in the divider steel plate as it approaches the top ( last 5 or so inches) so it doesn't block the aerial port which is in the center of the entire box so they needed to turn it at about 45 degrees toward the service side. Putting either the large holes or 3 small holes with grommets there would be up top and possibly look clean but not overly obvious. If the holes were spaced 1 inch apart similar to what Square D did with grommets like Square D, the magnetic fields would be distant. My service and the utility wires of both phases and neutral and ground wires go everywhere. There fields cross every which way and the currents all vary, some are 220V while others are 120V with neutral currents. My 3 holes can't possibly be any issue electrically, only subjective and policy.

    Its so hard to believe the world is pumping out C02 and someone trying to do the right thing runs into crazy stuff like this.

    My options:

    Go into the utility compartment and use the spare lugs - very clean but policy issues

    1) through 3 holes drilled near the bottom or in the 45 degree steel plate that are exactly like Squared D did the 4 #4 meter to mains wires.

    2) cut a large 1 1/2" hole and do all 3 wires in a bunch also either in the bottom of the plate divider or near the top 45 degree section by aerial plate.

    3) use the Square D hub and enter through the existing aerial hole but have weird obvious right angle and again conduit looping back down to the ground or flying aerial to the inverter/disconnct panel 4 feet away. - Ugly but as legal as possible since PG&E would put the 2 hot legs and their neutral in that same port is its was an aerial configuration.

    Don't use utility compartment options

    1) pull the 4 #2 wires from the mains ( with meter removed) and splice with heat shrink longer wires that go 10 inches to insulated 2 x 3 way splice block inside top of home side compartment ( near 45 degree plate at to where there is plenty of room ) and bring the 4 #2 wires back down from the splice block and the "line side tap" wires from the splice other port. The pairs of #2 that are the same phase 120V are connected so tap current is tied equally to both as if they were on the meter lug. If the #2 wires were long enough to just have some isulation removed and passed through the splice hole and set then the 2 wires would be not broken. Not long enough.

    2) Do the same as number one above except do so in a splice box attached by a large port directly behind the mains so the wires just pull through. The only advantage is that the splice is done in a different box and not visible unless one looks in the rear splice box. Has the same "tie the same pairs together" oddity possibly violating a two wire rule but electrically clean and maybe the safest. It does require the shortest lengthening of the #2 wires.

    Throw in the towel

    Put in a new separate meter and panel and throw out the Combo Square D. Then the splice would be electrically done identically in a splice box in the wires from the meter box to the panel. Very legal but lots of work and expense for nothing except policy and subjective nonsense.

    Love to have any opinions as so far they are helpful

    T
  • dwhdwh Posts: 1,341Solar Expert ✭✭✭
    Re: Best option for line side tap

    Unfortunately, either of the second set of options feels a bit dodgy to me - which is why I focused on trying to get the tap into the utility side of the box.

    Right now, the feed from the meter to the disconnect breakers passes through the partition and directly into the breakers; a very short distance. Thus the only exposed "utility-hot" (not subject to disconnect by the breakers) points are the ends of the screws in the lugs in the breakers (and whatever micro-inch of wire might be exposed if the factory stripped a touch too much - but that's negligible).

    That's a pretty safe arrangement.


    With option B-1, there would be two small "utility-hot" buss bars in the top of the load side of the panel. As well, there would be the length of utility-hot wires running up and back down - plus the length of the solar wire, which itself would be utility-hot.

    All in all, it seems like just a bit too much of utility-hotness in the load compartment.

    [Though...if there was enough space, it might be an option to add a partition in the top of that compartment and do it there. (Electricians have to have both plumbing and sheet metal skills just to do their jobs - which is why I suppose some states refer to us as "electrical mechanics".)]


    With option B-2 (a separate splice box out the back), you are taking the utility hot and placing it in an outside box (access to which is on the other side of a wall? ! ) - so you now have to insure that down the road some clueless "electrician" doesn't open that splice box and screw up in some spectacular fashion.

    (Ignoring the length of hot wires for a moment; If the splice in the splice box were done with split bolts and taped, rather than running through a little buss bar, that would be more "foolproof" from a safety standpoint. I much prefer split bolts which are completely encased in tape over the idea of adding extra utility-hot buss bars. This is by the nature of "on general priciples" - I do understand that you are dealing with doubled wires so that a terminal block/buss bar is pretty much going to be required.)


    It would seem to me that if there would have to be a splice box, then I would try to attach it to the service entrance side of the panel. Perhaps by putting it on the top of the panel where the unused service entrance port is.

    Then, replace the "meter socket to disconnect" wires with longer ones, run them from the meter socket up into the splice box (unbroken) then back down and through the original holes/grommets into the disconnect breakers.

    Then, run the solar feed into the splice box and connect them to the meter-disconnect wires.

    This gives you the splice box, but keeps any new utility-hotness still in the service entrance side of the panel - more or less. As well, PG&E can attach their safety wire and lead crimp to that splice box, thus hopefully keeping some future homeowner from doing something really dumb.

    (If you really wanted to be trick/nifty/custom you could even stamp the cover of that box with something like "CAUTION - SOLAR DISCONNECT -> THATAWAY".)
  • PgovetomPgovetom Posts: 30Solar Expert
    Re: Best option for line side tap

    Thanks DWH ... You are really thinking about my problem creatively and you get it -- I can tell by the nuance and thought and accuracy of your comments. I appreciate it.

    I think your idea of keeping splice box as a part of the utility side and not the load side is important. It gets around the "wiring in the utility compartment" problem in spirit and shows an inspector I'm respecting the utility and safety in the future. Making a sign so its clear is not a bad idea either.

    I bought a splice block that is identical to the one John Wiles shows in his

    "Photovoltaic Power System And the 2005 National Electrical Code: Suggested Practices"

    document in Figure 8 on the left side. It is a block of hard plastic with one large gauge splice lug and 6 smaller ( but down to #2) so it can mount to a metal box with thick plastic protecting the 1 large and 6 smaller splice block of aluminum on 3 sides. I was thinking of using 2 of them in the "Utility Compartment extension splice Box".

    I made another discovery when I looked very close at the 4 #2 wires going from the meter lugs to the mains. The sheet metal that separates the utility and load sides actually has a cutout that is about 5" x 1.25" and the grommets are half in it and half in the main sheet metal wall. It has two small sheet metal screws holding it in place as it has a 1/4" right angle bend that is used to hold it in place. When I removed the two screws ( in a mock up Square D Combo CSED unit I bought at Home Depot that is identical to mine), the plate fell off and opened a large opening between the utility and load side between the 4 #2 wires and the back of the box. It does cause the grommets to lose the back half of the hole they are set into but the #2 wires are so stiff, they just stay in place. This openning is not very obvious since its under the mains looking from the load side and down behind the meter socket under the 4 wires on the utility side.

    Maybe they did that to break the magnetic fields so current doesn't heat around the holes with grommets since the holes are split between two pieces of metal only connected via the various screws holding the walls. There is a little tiny gap when the sheet metal piece is in place so current induced into the metal wall would have to go around and through the back of the box through screws. That split may very well be Square D's way of getting away with running 4 very high current wires without any balancing opposite current wires to minimize the magnetic field. Just a guess but it creates a very nice passage way for my splice wires should I want to try that route.

    It also gives me a way to run my wires from my utility box splice box back to the load side to exit via my underground conduit to the disconnect. Unless somebody knew about this little metal piece, if it was removed, it would not be noticeable and rather safe since nothing from the load side could "fall" or "get" under the mains 5 inches and through this passage without lots of effort.

    This passage is useful whether I go the splice box route or the direct connect to the meter lug spares route. I think I'll just go the direct to the lugs route and if called on it by the inspector, ask about the splice box and try and get his ok before plan B..

    I ca just remove the little doorway, epoxy the grommets so they are firmly held in place and run my 3 wires through some form of strain relief attached to the passage. Since the wires will just disappear behind all the breakers, it can't be seen from the load side. Form the utility side, its not easy to see and the 2 lugs on the meter are about 3 and 6 inches from the passage and just behind the 4 #2 wires. It would be very clean and safe and unless somebody knew this model, wouldn't know the metal piece was there at all.

    Electrically correct and safe comes first and inspectors and PG&Es attitude comes second. I doubt they will see it and unless they know the Square D model, it looks like the mains wire passage which is exactly how a line side tap should look. It follows the mains wires through the very well protected passage and quickly hits the lugs.

    If that becomes and issue, then I'll ask about the splice box approach as DWH described also using the passage or possibly the aerial hub port. If they won't but that then I'll beg and see what happens.l

    thanks for everyone's thoughts. It was very helpful. Its tricky describing something as obscure as this and it was understood. amazing!

    thanks
  • dwhdwh Posts: 1,341Solar Expert ✭✭✭
    Re: Best option for line side tap
    Pgovetom wrote: »
    Thanks DWH ... You are really thinking about my problem creatively and you get it -- I can tell by the nuance and thought and accuracy of your comments. I appreciate it.

    I think your idea of keeping splice box as a part of the utility side and not the load side is important. It gets around the "wiring in the utility compartment" problem in spirit and shows an inspector I'm respecting the utility and safety in the future. Making a sign so its clear is not a bad idea either.

    I bought a splice block that is identical to the one John Wiles shows in his

    "Photovoltaic Power System And the 2005 National Electrical Code: Suggested Practices"

    document in Figure 8 on the left side. It is a block of hard plastic with one large gauge splice lug and 6 smaller ( but down to #2) so it can mount to a metal box with thick plastic protecting the 1 large and 6 smaller splice block of aluminum on 3 sides. I was thinking of using 2 of them in the "Utility Compartment extension splice Box".

    Yea, Wiles calls it a splice block, but I've always known them as "power distribution blocks".

    http://www.grainger.com/Grainger/categories/electrical/terminal-blocks/power-distribution-blocks

    I'm not sure how you are going to "pass through" one of those with your #2 that runs from meter socket to disconnect breakers...but I presume you have the thing in your hand and can see that it can be done.

    I made another discovery when I looked very close at the 4 #2 wires going from the meter lugs to the mains. The sheet metal that separates the utility and load sides actually has a cutout that is about 5" x 1.25" and the grommets are half in it and half in the main sheet metal wall. It has two small sheet metal screws holding it in place as it has a 1/4" right angle bend that is used to hold it in place. When I removed the two screws ( in a mock up Square D Combo CSED unit I bought at Home Depot that is identical to mine), the plate fell off and opened a large opening between the utility and load side between the 4 #2 wires and the back of the box. It does cause the grommets to lose the back half of the hole they are set into but the #2 wires are so stiff, they just stay in place. This openning is not very obvious since its under the mains looking from the load side and down behind the meter socket under the 4 wires on the utility side.

    Maybe they did that to break the magnetic fields so current doesn't heat around the holes with grommets since the holes are split between two pieces of metal only connected via the various screws holding the walls. There is a little tiny gap when the sheet metal piece is in place so current induced into the metal wall would have to go around and through the back of the box through screws. That split may very well be Square D's way of getting away with running 4 very high current wires without any balancing opposite current wires to minimize the magnetic field. Just a guess but it creates a very nice passage way for my splice wires should I want to try that route.

    Could be.

    Or it might just be a handy time-saver for the assembly line - a way to lay-in pre-formed wire without having to fight it through the holes. Or maybe two birds with one stone.

    It also gives me a way to run my wires from my utility box splice box back to the load side to exit via my underground conduit to the disconnect.

    That's something else - running the feed from the solar "through" the load side of the panel...I think that's not such a great idea because those wires are going to be utility-hot.

    I think if you do a splice box, it would be best to run the solar feed conduit directly into the splice box.

    Unless somebody knew about this little metal piece, if it was removed, it would not be noticeable and rather safe since nothing from the load side could "fall" or "get" under the mains 5 inches and through this passage without lots of effort.

    This passage is useful whether I go the splice box route or the direct connect to the meter lug spares route. I think I'll just go the direct to the lugs route and if called on it by the inspector, ask about the splice box and try and get his ok before plan B...

    Yea, it's often a lot easier to get approval afterward than to get permission beforehand.

    I ca just remove the little doorway, epoxy the grommets so they are firmly held in place and run my 3 wires through some form of strain relief attached to the passage. Since the wires will just disappear behind all the breakers, it can't be seen from the load side. Form the utility side, its not easy to see and the 2 lugs on the meter are about 3 and 6 inches from the passage and just behind the 4 #2 wires. It would be very clean and safe and unless somebody knew this model, wouldn't know the metal piece was there at all.

    Electrically correct and safe comes first and inspectors and PG&Es attitude comes second. I doubt they will see it and unless they know the Square D model, it looks like the mains wire passage which is exactly how a line side tap should look. It follows the mains wires through the very well protected passage and quickly hits the lugs.

    If that becomes and issue, then I'll ask about the splice box approach as DWH described also using the passage or possibly the aerial hub port. If they won't but that then I'll beg and see what happens.l

    thanks for everyone's thoughts. It was very helpful. Its tricky describing something as obscure as this and it was understood. amazing!

    thanks
  • PgovetomPgovetom Posts: 30Solar Expert
    Re: Best option for line side tap

    Yes my block is one version of Granger's distribution blocks. That is probably a better term since it has one large feeder lug and 6 smaller lugs -- so its a 6 way distribution from the large port. Since they are nicely insulated and the lugs tucked inside the plastic block, relatively safe and easy to mount in a box. I could use one to both tie the two #2 wires back into one circuit and pass 2 #2 wires on to the mains and tap /splice/distribute or whatever it should be called the solar disconnect hot leg. Then by using two, one per leg ( and #2 pair) I accomplish the splice but not to just one of the #2's ( as that wouldn't be appropriate) but to the equivalent of the meter lug before the 2 x #2 split and then re-split with 2 - #2s so I can wire to both main breakers ( then do that twice). That assumes I use my splice into the #2s option in the splice box that is an extension of the utility compartment as DWH has suggested to keep it as proper as possible.

    I believe the assembly basis for the sheet metal cut-out is probably the main reason. It would be almost impossible to push those #2 wires that are quite stiff through actual holes and then try and get the grommet set. By splitting the metal, it breaks any magnetic current flow up but makes assembly practical by just placing the little bracket first, then the wires with grommets already installed on the wires and push the large inter-compartment divider down onto it fitting the upper grommet side. That is a very perceptive observation given you don't have the unit laid out in front of you. You have good 3D visualization and must have been around manufacturing to spot that.

    My real dilemma is this

    Do I ask up front about any of these options to the powers such as my actual PG&E service manager or county inspector and then be stuck with their policy, liability, opinion etc.. and be forced to replace the whole mess with a new meter and separate box. I've been told by multiple reliable sources that for all the reasons we have discussed here plus UL issues plus liability, pass the buck, policy or whatever that asking squarely up front will result in being blocked and forced into a bureaucratic nightmare. My other option is find the best electrical and safest solution that isn't so obvious they see it and I'm down the bureaucratic rathole and just do it.

    If I use the overhead port on an underground installation, its so obvious, I worry I'm into the nightmare even though its the most appropriate and UL approved access port.

    The splice box outside is also so obvious it will draw a very close look and the bureaucratic trap may happen again.

    So what is the safest and electrically correct approach that also is not a BIG RED FLAG saying "bureaucratic me"!

    Since I installed a 1 1/2" spare conduit when the unit was installed that goes to my Cristie box, that is the least obvious and safe way to get inside the box. It does however go the the load side creating the "utility hot wires" in the load side problem. But its not a big red flag either.

    The wires could be partitioned with some form of flexible non-metalic conduit to route them from the 1 1/2" entry port up under the breakers and through a hole or cutout in the passage sheet metal. If I remove it, put a hole in it and terminate the flexible conduit arriving from the 1 1/2" port at the load compartment bottom and then the 3 wires all come out just behind the 4 #2 wires from the conduit path. Then they can go immediately to the 2 spare hot meter lugs and spare aerial lug.

    This approach uses the flexible conduit to avoid the utility hot wires in the load compartment space -- sorta like the splice box being an extension of the utility and NOT load is the best splice box compromise.

    Then the 3 wires are delivered together into the utility compartment only inches from proper lugs. I have been told by others that some utilities are ok with line side taps that actually use wires inside their compartment. Since the NEC language suggests it, its only utility policy that makes it riskier than the 4 #2 wires that enter the load compartment. If the grommets failed or somebody loosened the mains set screws on those #2 wires, the utility hot could short to the sheet metal if it cut through the insulation by the failed grommet. If somebody loosened the set screws on the mains, a half inch of exposed #2 wire would be right near the right side wall. So their are unlikely failure modes that create utility hot problems. I believe that if the tap wires are protected with flexible conduit and very short inside the utility compartment and have their own 1 1/2" conduit directly to the disconnect switch which has RK-5 200,000A rated fuses, the probability that setup will fail is in the same low order as the failed grommet or unscrewed main set possible modes.

    Its impossible to make the probability zero of a utility wire problem. Square D gets it low by keeping the wires short, grommets and direct termination in the main breakers. That is low but not zero. A line side tap will always have potential because by definition, its tapping the utility wires somewhere. No matter how you cut it, it adds some risk. If the risk is kept as 10 FITS then its irrelevant.

    The real issue is keeping the risk of failure VERY low AND avoiding the liability and policy based BS. If the utility had their way, there would not be line side taps as it adds liability. The county building department would also like to minimize or avoid liability so they pass the buck to the utility. The loop of buck passing goes round and round even if the NEC clearly shows and allows line side taps which must attach to the utility wires somewhere.

    I am looking for the safest solution that doesn't trigger that loop of liability. If the probability of failure is in the noise than it will never fail in my home's lifetime. that is what the Square D reliability engineers did. They used an approach that has very low probability of failure and with 1 million boxes over 100 years, there would be negligible failures and all would involve human error. I can do the same by very redundant insulation and isolation, short wires and using lugs designed exactly for this problem. If its done safely and not obvious, then that is the best route. If its looked at, then a smart person will see the safety and one just needs to hope they aren't inclined to be risk adverse.

    That is why this dilemma is so tricky for me. Its an electrical problem and reliability and human nature problem all tied into one. I want the best solution that isn't obvious but if examined will look very safe and if that fails I have multiple backup plans before replacing the whole mess which won't help the reliability but will solve the liability/human nature fear problem.
  • dwhdwh Posts: 1,341Solar Expert ✭✭✭
    Re: Best option for line side tap
    Pgovetom wrote: »
    That is a very perceptive observation given you don't have the unit laid out in front of you. You have good 3D visualization and must have been around manufacturing to spot that.

    Yes and yes. Also having personally done something like 60 or 70 service installs and upgrades, from 100a to 800a residential and commercial, and from 4 to 16 multiple meter setups as well - I've seen similar things here and there.

    My real dilemma is this

    Do I ask up front about any of these options to the powers such as my actual PG&E service manager or county inspector and then be stuck with their policy, liability, opinion etc.. and be forced to replace the whole mess with a new meter and separate box. I've been told by multiple reliable sources that for all the reasons we have discussed here plus UL issues plus liability, pass the buck, policy or whatever that asking squarely up front will result in being blocked and forced into a bureaucratic nightmare. My other option is find the best electrical and safest solution that isn't so obvious they see it and I'm down the bureaucratic rathole and just do it.

    If I use the overhead port on an underground installation, its so obvious, I worry I'm into the nightmare even though its the most appropriate and UL approved access port.

    The splice box outside is also so obvious it will draw a very close look and the bureaucratic trap may happen again.

    So what is the safest and electrically correct approach that also is not a BIG RED FLAG saying "bureaucratic me"!

    The best approach is to draw it up in the form of plans (even better, have a licensed engineer or contractor draw them for you) and then try to get the plans through "plan check" and approved.

    Once that step is done, you do whatever the plans call for. Then if you get in a dispute with an inspector or the utility company field agent, you can usually win.

    Since I installed a 1 1/2" spare conduit when the unit was installed that goes to my Cristie box, that is the least obvious and safe way to get inside the box. It does however go the the load side creating the "utility hot wires" in the load side problem. But its not a big red flag either.

    The wires could be partitioned with some form of flexible non-metalic conduit to route them from the 1 1/2" entry port up under the breakers and through a hole or cutout in the passage sheet metal. If I remove it, put a hole in it and terminate the flexible conduit arriving from the 1 1/2" port at the load compartment bottom and then the 3 wires all come out just behind the 4 #2 wires from the conduit path. Then they can go immediately to the 2 spare hot meter lugs and spare aerial lug.

    This approach uses the flexible conduit to avoid the utility hot wires in the load compartment space -- sorta like the splice box being an extension of the utility and NOT load is the best splice box compromise.

    Um, it's a novel idea. Don't think I've ever seen that one before.

    Then the 3 wires are delivered together into the utility compartment only inches from proper lugs. I have been told by others that some utilities are ok with line side taps that actually use wires inside their compartment. Since the NEC language suggests it, its only utility policy that makes it riskier than the 4 #2 wires that enter the load compartment. If the grommets failed or somebody loosened the mains set screws on those #2 wires, the utility hot could short to the sheet metal if it cut through the insulation by the failed grommet. If somebody loosened the set screws on the mains, a half inch of exposed #2 wire would be right near the right side wall. So their are unlikely failure modes that create utility hot problems. I believe that if the tap wires are protected with flexible conduit and very short inside the utility compartment and have their own 1 1/2" conduit directly to the disconnect switch which has RK-5 200,000A rated fuses, the probability that setup will fail is in the same low order as the failed grommet or unscrewed main set possible modes.

    Well...the likelyhood of that fat, hard, pre-formed wire rubbing around and getting its insulation cut by the can "if the grommets failed" is pretty low. It would probably take a major earthquake or maybe a drunk driving through your living room to make it happen.

    As for the loosening of the lugs in the main disconnect breakers - that wire isn't going to just "pop out" of the breaker when you loosen the screws. If you had to replace the main breaker, you would first pull the meter, then loosen the lugs in the breaker, then unscrew the breaker from the buss bars and take it out. You wouldn't (couldn't) grab the wire and pull it out of the lugs, and either way the wire is dead because the meter is pulled.


    The problem really isn't whether the NMC in the load side is "as safe as" the factory setup - the problem is you are getting creative and doing something that the people you are dealing with haven't seen before.

    I think you have a hell of a lot better chance of getting away with sticking a pullbox on the top of the utility side than you do of getting away with running some plastic conduit inside of a panel box.

    The proper and clean way to do it would be to run the solar conduit directly into utility side of the panel (into the bottom if the solar conduit is underground) - because once the line side tap has been connected and the meter re-socketed, those wires *will be* utility-hot.

    The problem is getting the powers that be to approve it, and approved plans are probably the key to that.

    If you were dealing directly with the linemen there wouldn't be a problem. :)


    Here's the thing...you are going with a line-side tap. It's a good way to go, and it's *allowed by code*. Now, here's one good argument you can use:

    "Even if you upgrade the panel, you still need to get that solar feed into the utility side of the compartment BECAUSE once they are connected, those wires will be utility-hot."

    Thus, if they allow you to use a line-side tap at all - then they certainly should allow you to do it "properly".

    Its impossible to make the probability zero of a utility wire problem. Square D gets it low by keeping the wires short, grommets and direct termination in the main breakers. That is low but not zero. A line side tap will always have potential because by definition, its tapping the utility wires somewhere. No matter how you cut it, it adds some risk. If the risk is kept as 10 FITS then its irrelevant.

    The real issue is keeping the risk of failure VERY low AND avoiding the liability and policy based BS. If the utility had their way, there would not be line side taps as it adds liability. The county building department would also like to minimize or avoid liability so they pass the buck to the utility. The loop of buck passing goes round and round even if the NEC clearly shows and allows line side taps which must attach to the utility wires somewhere.

    I am looking for the safest solution that doesn't trigger that loop of liability. If the probability of failure is in the noise than it will never fail in my home's lifetime. that is what the Square D reliability engineers did. They used an approach that has very low probability of failure and with 1 million boxes over 100 years, there would be negligible failures and all would involve human error. I can do the same by very redundant insulation and isolation, short wires and using lugs designed exactly for this problem. If its done safely and not obvious, then that is the best route. If its looked at, then a smart person will see the safety and one just needs to hope they aren't inclined to be risk adverse.

    That is why this dilemma is so tricky for me. Its an electrical problem and reliability and human nature problem all tied into one. I want the best solution that isn't obvious but if examined will look very safe and if that fails I have multiple backup plans before replacing the whole mess which won't help the reliability but will solve the liability/human nature fear problem.

    Then, again, the best solution is plans. If the plans show in schematic that the solar feed comes into the "proper" lugs (load side spare lugs on the meter socket), and those plans get approved - then *how* you get into the compartment once you are in the field doing the install is pretty much a moot point as long as it's done to code.
  • PgovetomPgovetom Posts: 30Solar Expert
    Re: Best option for line side tap

    I would love to find a competent licensed electrical engineer who has experience at this sort of thing. I would pay for the plans and experience if I knew someone that wouldn't have the same liability fears. We live in such a litigious society even many licensed engineers just overkill things to CYA. I built a deck as part of a remodel and it had posts designed with 8 foot deep 15 inch piers with full steel cages. Then I had to pay to have him watch the drilling. He decided to take two holes to 12 feet and larger and the whole project stopped while we had custom steel cages built. He wouldn't allow us to use two eight foot cages wired together. Those posts were so far overkilled that they will hold my house in place.

    Then I had another structural guy who was really cool. He made really wild changes on the fly and signed them off. Those two engineers were the opposite. One was confident and didn't worry about litigation. The other over designed and sat and made $400/hr watching us drill. How can I find someone that just is so confident he will do it right and not cost a fortune when just attaching the wires through the aerial port to the lugs is about as safe and compliant as possible.

    Maybe I'll look for someone and see what happens. I designed and built the whole system myself and this one issue is baffling because its got people and attitudes involved and isn't just electrical or mechanical.
  • newenergynewenergy Posts: 291Solar Expert ✭✭✭✭✭✭
    Re: Best option for line side tap

    Anything decided/happen? Pics?
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