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Thread: Best option for line side tap

  1. #1

    Default 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?


    Does that make sense

  2. #2
    Join Date
    Mar 2009
    Los Angeles, Ca.

    Default 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 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.

  3. #3

    Default 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!

  4. #4
    Join Date
    Sep 2007

    Default 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.
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  5. #5

    Default 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.

  6. #6
    Join Date
    Mar 2009
    Los Angeles, Ca.

    Default 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.

  7. #7

    Default 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

  8. #8
    Join Date
    Mar 2009
    Los Angeles, Ca.

    Default Re: Best option for line side tap


    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.

  9. #9

    Default 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.

  10. #10
    Join Date
    Jul 2009
    Mountains of VA

    Default Re: Best option for line side tap

    First off itís not against the law to cut the tag on your meter can and pull the meter. Most POCOís will fine you for doing it and will pull the meter and make you get an inspection before they will reconnect. Most POCOís canít keep up with the tag numbers if itís 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 itís been pulled when itís read.

    If you are going with net metering then donít 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.

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