Backfed breaker or Line side tap?

After a couple of iterations on my one line diagram with the fine folks at Huntsville Utilities I figured out that they were trying to tell me that they do not permit load side or backfed breaker interconnect to the grid with any grid tie equipment. It also appears that they are afraid I will use my grid tie setup as backup power (against rules) and that the grid tie inverter will continue to provide power to the grid when the grid is down. It is apparent that grid tied installations are not common in this district.

From trolling the www I have concluded that back fed breaker interconnection to the grid seems to be very much more common than line side tap for residential grid tie applications. Is this true?
«1

Comments

  • BB.BB. Super Moderators, Administrators Posts: 32,740 admin
    Re: Backfed breaker or Line side tap?

    Are they complaining about the safety of gt systems, how best to make the connection (through the main panel vs a line side tap--which is rare, can be difficult, and most inspectors appear to hate/not allow--at least for residential), or questioning are gt inverters safe...

    Or they do not have the billing capability for metering--Or more likely, they don't want to loose revenue and they are looking for any reason to put road blocks in your way?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • nielniel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Backfed breaker or Line side tap?

    or they're just plain dumb. i lean they fear competition, which is also dumb for them to feel as it still indicates they are ignorant of the facts.
  • dreesdrees Solar Expert Posts: 482 ✭✭✭
    Re: Backfed breaker or Line side tap?
    Macaw wrote: »
    From trolling the www I have concluded that back fed breaker interconnection to the grid seems to be very much more common than line side tap for residential grid tie applications. Is this true?
    Yes - for residential installs back fed breakers are the norm - line side taps are much less common.
  • solar_davesolar_dave Solar Expert Posts: 2,392 ✭✭✭✭
    Re: Backfed breaker or Line side tap?

    My code department said they would not allow a line side tap on residential, but it was acceptable practice on commercial, but a back feed breaker was acceptable on my residential install. We were trying to do a line side tap to prevent upgrading of the service entrance/breaker panel, and ended up relenting and doing the service entrance upgrade.
  • ggunnggunn Solar Expert Posts: 1,973 ✭✭✭
    Re: Backfed breaker or Line side tap?
    Macaw wrote: »
    After a couple of iterations on my one line diagram with the fine folks at Huntsville Utilities I figured out that they were trying to tell me that they do not permit load side or backfed breaker interconnect to the grid with any grid tie equipment. It also appears that they are afraid I will use my grid tie setup as backup power (against rules) and that the grid tie inverter will continue to provide power to the grid when the grid is down. It is apparent that grid tied installations are not common in this district.

    From trolling the www I have concluded that back fed breaker interconnection to the grid seems to be very much more common than line side tap for residential grid tie applications. Is this true?
    They are living in the past. Any grid-tied inverter MUST by law shut down its connection to the grid when the grid goes down and the manufacturers build them that way. Anyway, whether the interconnection is through a backfed breaker or a line side tap has nothing to do with that; if an inverter were to remain connected and producing during a grid outage through a backfed breaker, it would act that way through a line side connection as well.

    And yes, most residential PV is interconnected through a backfed breaker under what is commonly referred to as the "20% rule" in the NEC. For a 200A service panel (200A rated busbar and 200A main breaker), up to a 40A backfed breaker is allowed as long as it is installed at the opposite end of the busbar from the main.
  • arcturusk1arcturusk1 Solar Expert Posts: 26
    Re: Backfed breaker or Line side tap?
    ggunn wrote: »
    And yes, most residential PV is interconnected through a backfed breaker under what is commonly referred to as the "20% rule" in the NEC. For a 200A service panel (200A rated busbar and 200A main breaker), up to a 40A backfed breaker is allowed as long as it is installed at the opposite end of the busbar from the main.

    Gunn, I have two questions about your quoted part.

    1) As you said, with the 20% rule for a 200A panel, one can put in a 40A breaker. With that said, the inverter that would be feeding said breaker must be supplying less than or equal to 32A, correct?
    x*1.25=<40A
    x=<32A

    That is, the 40A breaker that's installed has the appropriate safety factor (125%) already applied. I know it's a dumb question but I just wanted to make sure.

    2) I had heard the "opposite end" rule before but still haven't heard a good explanation as to why. What is it about putting a solar-supplied breaker at the end of the busbar that makes it any different from putting it near the main? From an electrical standpoint, electrical energy shouldn't care where it's at on the busbar. The busbar is just another metal conductor through which the electrons will flow. Whether it's 1" or 1' away shouldn't matter (except for some very minor voltage drop, no?).
  • ggunnggunn Solar Expert Posts: 1,973 ✭✭✭
    Re: Backfed breaker or Line side tap?
    arcturusk1 wrote: »
    Gunn, I have two questions about your quoted part.

    1) As you said, with the 20% rule for a 200A panel, one can put in a 40A breaker. With that said, the inverter that would be feeding said breaker must be supplying less than or equal to 32A, correct?
    x*1.25=<40A
    x=<32A

    That is, the 40A breaker that's installed has the appropriate safety factor (125%) already applied. I know it's a dumb question but I just wanted to make sure.

    2) I had heard the "opposite end" rule before but still haven't heard a good explanation as to why. What is it about putting a solar-supplied breaker at the end of the busbar that makes it any different from putting it near the main? From an electrical standpoint, electrical energy shouldn't care where it's at on the busbar. The busbar is just another metal conductor through which the electrons will flow. Whether it's 1" or 1' away shouldn't matter (except for some very minor voltage drop, no?).

    1) Yes. That's a 40A breaker, and the biggest inverter you can connect with a 40A breaker is one with a 32A rated output.

    2) My understanding of the thinking behind the "opposite end rule" is that if the backfed breaker is at the top of the busbar (directly under the main), and the loads in the panel consume the max current of both the main breaker and the backfed breaker, the current density in the busbar at the point right below the backfed breaker will exceed the rating of the busbar.

    I believe there's actually a formula for figuring out if this is necessary, figuring in the total of the load breakers, but many jurisdictions just require backfed breakers to be at the lower end of the busbar, period.
  • rickrick Administrators Posts: 133 admin
    Re: Backfed breaker or Line side tap?

    In my years of designing and installing solar systems, I've never made a line side tap. I've always back fed circuit breakers and it works great. Arizona's utility companies are fairly well versed in solar, so they've never even inquired about this type of connection. If you're using new equipment, the inverter will not allow you to run your system for back-up power when the utility grid goes down. If the grid-tie inverter does not detect the presence of the grid, it will not supply you with power. If you make a line side tap, you have to be very careful. The line side will need to be turned off by the utility company so that it's safe to work on. You don't want to risk shorting the two legs coming from their transformer. It's much safer and easier to back feed a breaker.
    Website administrator for Northern Arizona Wind & Sun
  • ggunnggunn Solar Expert Posts: 1,973 ✭✭✭
    Re: Backfed breaker or Line side tap?
    rick wrote: »
    In my years of designing and installing solar systems, I've never made a line side tap. I've always back fed circuit breakers and it works great. Arizona's utility companies are fairly well versed in solar, so they've never even inquired about this type of connection. If you're using new equipment, the inverter will not allow you to run your system for back-up power when the utility grid goes down. If the grid-tie inverter does not detect the presence of the grid, it will not supply you with power. If you make a line side tap, you have to be very careful. The line side will need to be turned off by the utility company so that it's safe to work on. You don't want to risk shorting the two legs coming from their transformer. It's much safer and easier to back feed a breaker.
    If you can't get in under the 20% rule, a line side tap will probably be much less expensive than a service upgrade; we've run into that a few times.
  • MacawMacaw Solar Expert Posts: 36
    Re: Backfed breaker or Line side tap?

    I see one disadvantage of the line side tap and that is now I need to add overcurrent protection on the line between the inverter and the grid to protect the conductors between the PV meter and the inverter from potential overcurrent caused by a short on the AC side of the inverter. This will require yet another electrical box plus ground bar plus circuit breaker hardware....More holes in the side of the house, more signage warning of yet more potentially dangerous events should the new box ever be opened...:confused:
  • MacawMacaw Solar Expert Posts: 36
    Re: Backfed breaker or Line side tap?

    Another interesting point regarding the line side tap is that the meter can be pulled to the customer loads yet the alternate power source continues to supply the grid. Coincidence:roll:?
  • ggunnggunn Solar Expert Posts: 1,973 ✭✭✭
    Re: Backfed breaker or Line side tap?
    Macaw wrote: »
    Another interesting point regarding the line side tap is that the meter can be pulled to the customer loads yet the alternate power source continues to supply the grid. Coincidence:roll:?
    No, the tap is between the meter and the service panel. Once the meter is pulled, all current on the line (both directions) is shut off.
  • ggunnggunn Solar Expert Posts: 1,973 ✭✭✭
    Re: Backfed breaker or Line side tap?
    Macaw wrote: »
    I see one disadvantage of the line side tap and that is now I need to add overcurrent protection on the line between the inverter and the grid to protect the conductors between the PV meter and the inverter from potential overcurrent caused by a short on the AC side of the inverter. This will require yet another electrical box plus ground bar plus circuit breaker hardware....More holes in the side of the house, more signage warning of yet more potentially dangerous events should the new box ever be opened...:confused:
    Not necessarily. You are going to need a fused, lockable disconnect in most jurisdictions in either case, so there is your OCP. But the disconnect needs to be service rated irrespective of the current rating of the inverter for a line side tap, so it will be more expensive. Line side taps are only used when they are necessary because a backfed breaker will not work, most often (IME) because using one would violate the 20% rule in the main service panel.
  • MacawMacaw Solar Expert Posts: 36
    Re: Backfed breaker or Line side tap?
    ggunn wrote: »
    No, the tap is between the meter and the service panel. Once the meter is pulled, all current on the line (both directions) is shut off.
    I guess it could go either way but I was told by the experts at the local utility that the load side of my generation meter MUST go to the line side of the residential meter. That tells me that the generation and residential meters are in parallel, not series.
    In any case I think I need a 60 Amp fusible safety switch and to outfit it with 20 Amp fuses to protect my Fronius IG3000 from overcurrent on the AC side. If the fuses blow, then will I need to call the utility to replace them, or will I be able to open the safety switch enclosure and replace them myself? That is, will they want to lock the safety switch enclosure in the closed position?
  • BB.BB. Super Moderators, Administrators Posts: 32,740 admin
    Re: Backfed breaker or Line side tap?

    If I understand your question (and the code--not my area of expertise)--The meter will have a "seal" so they know if it has been tampered or not.

    The Fused and Lockable disconnect is a box that has a place for an electrician or lineman to place a small pad lock so they can "lock the power off" and ensure that the person working on the downstream (or upstream utility wiring in this case) cannot be electrocuted by somebody throwing the switch on without permission.

    I don't believe the utility will put a lock on the box/switch unless they are actively working in the area/on your home.

    And, in Northern California, our utility (PG&E) has accepted the fact that a UL Listed GT inverter cannot ever power an out-of-specification utility line and GT inverters are "safe" for their personnel--So the utility has dropped the lockable disconnect requirement a few years ago.

    The original threat (in our area at least) was that if a lockable disconnect was not installed, the utility had the right to pull your main meter and cut power to your whole home while working on the mains/service. Which could delay having power restored to your home after a power outage.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • dreesdrees Solar Expert Posts: 482 ✭✭✭
    Re: Backfed breaker or Line side tap?
    BB. wrote: »
    And, in Northern California, our utility (PG&E) has accepted the fact that a UL Listed GT inverter cannot ever power an out-of-specification utility line and GT inverters are "safe" for their personnel--So the utility has dropped the lockable disconnect requirement a few years ago.
    One of the smarter utilities. There is no need for a separate, redundant AC disconnect on UL rated PV systems.

    In fact, the DOE (through the Solar ABCs project) has found that utilities basically NEVER use those disconnects, anyway, about half the systems currently installed do not have one (with no decrease in safety), so these disconnects only serve to raise the cost of PV installations.

    http://www.solarabcs.org/utilitydisconnect/
    Solar America Board for Codes and Standards Report - Utility External Disconnect Switch: Practical, Legal, and Technical Reasons to Eliminate the Requirement
  • ggunnggunn Solar Expert Posts: 1,973 ✭✭✭
    Re: Backfed breaker or Line side tap?
    Macaw wrote: »
    I guess it could go either way but I was told by the experts at the local utility that the load side of my generation meter MUST go to the line side of the residential meter. That tells me that the generation and residential meters are in parallel, not series.
    In any case I think I need a 60 Amp fusible safety switch and to outfit it with 20 Amp fuses to protect my Fronius IG3000 from overcurrent on the AC side. If the fuses blow, then will I need to call the utility to replace them, or will I be able to open the safety switch enclosure and replace them myself? That is, will they want to lock the safety switch enclosure in the closed position?

    In either case, it is a parallel connection, but I believe you are mistaken about the placement of the tap. If it were as you say, no one would be able to measure the output of your system and your system's output would not offset the charges from the utility. I can't see why anyone would ever want it to be that way. Every line side tap I have seen has been between the meter and the service. "Line" and "load" refer to the two sides of the main breaker, not the meter.

    As to the changing of fuses, irrespective of whether the tap is before or after the meter, when you open the disconnect switch (i.e., turn it off, not open the box - when it is in the on position you cannot open the box), the fuses are disconnected from the line. You can change them without interrupting the service. The only reason they would lock your disconnect is if they had a problem with your system, and it would be locked in the "off" position. There is no way to lock it "on".

    Incidentally, even if they have locked your disconnect, I am pretty sure that you can open the box to get at the fuses should you need to. The lock is there to hold the switch in the "off" position, not to keep you out of the box.
  • MacawMacaw Solar Expert Posts: 36
    Re: Backfed breaker or Line side tap?

    Ahhh now I see your confusion-- I will have two meters. One of them is hooked directly between the inverter and the grid with a safety switch between it and the grid. The utility technical expert used those exact words "the load side of my generation meter MUST go to the line side of the residential meter". My understanding is that they perform all of that line side hook up work themselves so I don't have to worry about how to design it. I wonder what they would do if I proposed a grid tied with battery backup system?:D
  • ggunnggunn Solar Expert Posts: 1,973 ✭✭✭
    Re: Backfed breaker or Line side tap?
    Macaw wrote: »
    Ahhh now I see your confusion-- I will have two meters. One of them is hooked directly between the inverter and the grid with a safety switch between it and the grid. The utility technical expert used those exact words "the load side of my generation meter MUST go to the line side of the residential meter". My understanding is that they perform all of that line side hook up work themselves so I don't have to worry about how to design it. I wonder what they would do if I proposed a grid tied with battery backup system?:D
    If that's what he said, your utility technical expert is at odds with the rest of the world, I'm pretty sure. Wouldn't be the first time that happened. :^)

    http://www.nmsu.edu/~tdi/pdf-resources/IAEI-1to2-06.pdf
    The diagram here clearly shows the tap between the service disconnect and the meter.

    In an arrangement such as you describe, the power from your array doesn't pass through the utility's meter on the way out, but on the way in to your loads, so that their meter reading shows the power you use as being bought from the utility whether it comes from the grid or from your PV system. They would have to subtract the reading on your PV meter from the reading on theirs to calculate how much power you pulled from the grid. Why in the world would they want to do that?

    Something is very screwy here. IMO, you either misunderstood him or he is not the expert he claims to be. Get another opinion.

    At the tap there is no difference between a straight grid tied system and one with a battery backup. Whether or not your utility understands that is another thing entirely, of course.
  • BB.BB. Super Moderators, Administrators Posts: 32,740 admin
    Re: Backfed breaker or Line side tap?

    I may be misunderstanding your concern... It is perfectly OK to add a second meter and do a supply side tap... From your link:
    Can a Service-Entrance Conductor be Tapped?

    Section 690.64(A) allows a supply (utility) side connection as permitted in 230.82(6).

    Section 230.82(6) lists solar photovoltaic equipment as permitted to be connected to the supply side of the service disconnect.

    It is evident that the connection of a utility-interactive inverter to the supply side of a service disconnect is essentially connecting a second service-entrance disconnect to the existing service and many, if not all, of the rules for service-entrance equipment must be followed.

    Section 240.21(D) allows the service conductors to be tapped and refers to 230.91.

    Section 230.91 requires that the service overcurrent device be co-located with the service disconnect. A circuit breaker or a fused disconnect would meet these requirements.

    I have seen several different meter configurations (parallel meters or master/sub-meter). It all depends on the billing rules for each utility...

    Some utilities give a FIT for the solar power (say $0.15 per kWH) but charge the user for the power they generate at $0.08 per kWH.

    It is weird--but they do give you money for your own power and charge you for using it. But is because of the subsidies involved.

    The one meter (and net metering billing/credits) is the easiest--but easy has never slowed down state government public utility commissions before.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • MacawMacaw Solar Expert Posts: 36
    Re: Backfed breaker or Line side tap?

    Yes ggun I will be paid for all of the power passing through the generation meter at $0.15 above what I pay for coming in on the existing residential meter. Then the power they buy from me they sell to other consumers that want to pay extra to consume the green solar power. I am not allowed "to use" the power generated on my house unless I pay the extra $0.15 per kWh to the utility. This way my neighbor does not have to subsidize my solar array if they don't have any interest in it. And yes you did interpret my description correctly, the meters are in parallel and both of them tap directly into the grid.
  • ggunnggunn Solar Expert Posts: 1,973 ✭✭✭
    Re: Backfed breaker or Line side tap?
    Macaw wrote: »
    Yes ggun I will be paid for all of the power passing through the generation meter at $0.15 above what I pay for coming in on the existing residential meter. Then the power they buy from me they sell to other consumers that want to pay extra to consume the green solar power. I am not allowed "to use" the power generated on my house unless I pay the extra $0.15 per kWh to the utility. This way my neighbor does not have to subsidize my solar array if they don't have any interest in it. And yes you did interpret my description correctly, the meters are in parallel and both of them tap directly into the grid.
    Oh, I see now. You in essence have a PPA with the utility, and your PV system could be anywhere. This isn't really a line side tap into your service; your service is irrelevant and you are selling power to the utility through a feed in tariff. Thanks for the clarification.
  • arcturusk1arcturusk1 Solar Expert Posts: 26
    Re: Backfed breaker or Line side tap?
    ggunn wrote: »
    Not necessarily. You are going to need a fused, lockable disconnect in most jurisdictions in either case, so there is your OCP. But the disconnect needs to be service rated irrespective of the current rating of the inverter for a line side tap, so it will be more expensive. Line side taps are only used when they are necessary because a backfed breaker will not work, most often (IME) because using one would violate the 20% rule in the main service panel.
    If my input would be helpful; what ggunn describes is the very thing I have run into. An install for a local municipality is large enough such that we will be violating the 20% rule. I don't even want to think about how much it would cost to replace their large panel/breaker combo (probably 6' wide and more than 7' tall). A line-side connection is basically only going to require a bladed AC Disconnect with fuses and a sub-panel. Not exactly super-cheap, either, but way less than overhauling their existing equipment.
    drees wrote: »
    One of the smarter utilities. There is no need for a separate, redundant AC disconnect on UL rated PV systems.

    In fact, the DOE (through the Solar ABCs project) has found that utilities basically NEVER use those disconnects, anyway, about half the systems currently installed do not have one (with no decrease in safety), so these disconnects only serve to raise the cost of PV installations.

    http://www.solarabcs.org/utilitydisconnect/
    Solar America Board for Codes and Standards Report - Utility External Disconnect Switch: Practical, Legal, and Technical Reasons to Eliminate the Requirement
    Unless I've misread your quote, I also have wondered about the necessity of AC Disconnects for a while now. Of course, I learned throughout my training that it's prudent to put in an AC Disconnect, but I was told that the utility guys are trained extensively to properly ground and isolate the wiring they will be working on. That makes me ask the same question as drees: If inverters today are required designed to shut down upon loss of grid voltage, if utility workers are hit with a deluge of training and emphasis to ground and check the lines, and if inverters today also are shipping with built-in AC Disconnects, then where's the need for (sometimes) pricey standalone AC Disconnects? Any problem that crops up can be solved by hitting the DC Disconnect or built-in AC disconnect.
    Macaw wrote: »
    Yes ggun I will be paid for all of the power passing through the generation meter at $0.15 above what I pay for coming in on the existing residential meter. Then the power they buy from me they sell to other consumers that want to pay extra to consume the green solar power. I am not allowed "to use" the power generated on my house unless I pay the extra $0.15 per kWh to the utility. This way my neighbor does not have to subsidize my solar array if they don't have any interest in it. And yes you did interpret my description correctly, the meters are in parallel and both of them tap directly into the grid.
    :confused: I haven't encountered or heard of this, although I'm still a newb to the solar industry. I don't quite understand how that arrangement implies that other customers are not subsidizing your solar array. Ultimately, the utility is paying you for your power. Whether or not they collect 15c more from your neighbor, everyone's money is still going to the utility bank account, part of which is used to pay you for your power. I suppose your neighbor isn't paying for you in the spirit of things, but may still be when the money is pooled. And this admittedly nitpicky argument from me isn't even including possible hidden costs or rate increases that the utility did/will include that they're not telling you about. If they raise prices they're probably not going to tell you that a part of the reason for that is to pay for solar.
  • dreesdrees Solar Expert Posts: 482 ✭✭✭
    Re: Backfed breaker or Line side tap?
    arcturusk1 wrote: »
    Any problem that crops up can be solved by hitting the DC Disconnect or built-in AC disconnect.
    Or pulling the meter. Or tripping the circuit breaker and locking the main service panel.

    The lockable AC disconnect is redundant and never used - at least about half the utilities get it - the other half need to get with the program.
  • ggunnggunn Solar Expert Posts: 1,973 ✭✭✭
    Re: Backfed breaker or Line side tap?
    arcturusk1 wrote: »
    If my input would be helpful; what ggunn describes is the very thing I have run into. An install for a local municipality is large enough such that we will be violating the 20% rule. I don't even want to think about how much it would cost to replace their large panel/breaker combo (probably 6' wide and more than 7' tall). A line-side connection is basically only going to require a bladed AC Disconnect with fuses and a sub-panel. Not exactly super-cheap, either, but way less than overhauling their existing equipment.

    What he's got is not really a line side tap, at least not how I've seen them. He's selling the output of his PV directly to the grid under a feed in tariff and it's not a tap into his service at all. In that situation the size of his PV and the size of his service don't have any relationship, and it's why the tap is outside his meter. It took me a while to figure that out; sometimes I'm dense that way. ;^)
  • arcturusk1arcturusk1 Solar Expert Posts: 26
    Re: Backfed breaker or Line side tap?
    ggunn wrote: »
    What he's got is not really a line side tap, at least not how I've seen them. He's selling the output of his PV directly to the grid under a feed in tariff and it's not a tap into his service at all. In that situation the size of his PV and the size of his service don't have any relationship, and it's why the tap is outside his meter. It took me a while to figure that out; sometimes I'm dense that way. ;^)

    Haha, duly noted, although the nitpicky engineer part of me wants to say that technically, some of the electricity that the array produces may slip back into his house as there is still a connection there. Wherever the connection is, the PV wiring is making contact with the house wiring at some node. After all, electrons don't care about a contract. :p But my argument is really just being anal about things; after all, it's about what his house meter says compared to his PV meter. He pays for the amount used on his house meter and gets money back for the amount generated on his PV meter.

    Very interesting. Not sure if I'm wild about that idea (is that really how FITs work?) given that it's just so strange. Seems to me the same metering and payment plans could still be done if the array was connected on the load-side of the house. How is it any different if I read a PV meter that's electrically connected on the load-side vs line-side? Either way, the wattages should still sum to the same amount:

    House uses 300kWh that month
    PV generates 200kWh that month
    In the normal scenario with PV connected load-side, the house meter should read 100kWh. We could then look at our PV meter and say oh, I generated 200kWh. I must have used 300kWh total. Here come the warm fuzzies because we offset so much.
    In the weird line-side scenario that we're discussing, the house meter reads 300kWh and the PV still reads 200kWh. We still feel a warm fuzzy feeling; we just needed to do the math in our head to get 100kWh.

    Maybe it's because they want to do it in the spirit of things, so when they tell other customers that they don't have to subsidize solar, it makes them feel a little better or something. :D
  • ggunnggunn Solar Expert Posts: 1,973 ✭✭✭
    Re: Backfed breaker or Line side tap?
    arcturusk1 wrote: »
    Haha, duly noted, although the nitpicky engineer part of me wants to say that technically, some of the electricity that the array produces may slip back into his house as there is still a connection there.
    Probably all of it does when his house load exceeds the output of his PV. It makes no difference; once the kWh's are on the grid (outside his meter), they belong to the utility and are indistinguishable from those generated by the coal fired generator (or whatever) many miles away. It's really a simple system; there is one meter reading for his feed in that the utility pays him for and one for his usage that he pays them for. Perhaps ironically, the best economic position (at least in the short run) for him to take is NOT to pay the surcharge for green energy production.
  • MacawMacaw Solar Expert Posts: 36
    Re: Backfed breaker or Line side tap?
    arcturusk1 wrote: »
    I don't quite understand how that arrangement implies that other customers are not subsidizing your solar array. Ultimately, the utility is paying you for your power. Whether or not they collect 15c more from your neighbor, everyone's money is still going to the utility bank account, part of which is used to pay you for your power.

    Arcturusk1- The reason my neighbors are not subsidizing my installation is because somewhere in the vast number of power consumers there are a number of them that voluntarily pay 15c more per kWh so that they can use green, solar power. That 15c pays my subsidy. (12c actually)
  • rollandelliottrollandelliott Solar Expert Posts: 834 ✭✭
    Re: Backfed breaker or Line side tap?
    arcturusk1 wrote: »
    A line-side connection is basically only going to require a bladed AC Disconnect with fuses and a sub-panel. Not exactly super-cheap, either, but way less than overhauling their existing equipment.

    Is there a photo and perhaps some buying links for this gear. Perhaps it is a less expensive option than what I was going to do below:

    My home has a full circuit breaker box. I was thinking that I would install a new outdoor 200amp load center for $160 plus conduit and labor, and add a 40amp double pole breaker to that to receive the PV energy from a 5kw system, but if I ever wanted to expand the system in the future I couldn't because a 40amp breaker is the largest you can put in a 200amp load center.

    So how much more difficult/expensive is it to connect the solar before the meter via line side connection?



    what kind of gear would I need to do this?
    http://www.atensolar.com/m5/700-139--square-d-combination-service-entrance-device-csed-200-amp-for-photovoltaics.html
    Is this device what I need to accomplish the task, or is their a less expensive way?

    Maybe just hooking up two 200amp load centers would be a lot cheaper? $160x2 vs $1400.
  • solar_davesolar_dave Solar Expert Posts: 2,392 ✭✭✭✭
    Re: Backfed breaker or Line side tap?

    Rolland next steps for a panel back feed is to de-rate the main breaker to something less than 200 amps. For instance, you take the main breaker down to 175 amps, you can now back feed the 200 amp panel up to your 240 amp max bus bar. 240 - 175 = 65 amps. (60 amps is a common breaker size).

    I know I tried line side tap with my system and the code guys would not allow it and said it was only common in large commercial installs. My issue was the existing 200 amp panel was pretty loaded already and they would not allow the de-rating either, so it was a service entrance upgrade in my case to dual 200 amp panels, one de-rated to 175 amps with a 60 amp back feed breaker, with a service feed from the transformer upgrade to 400 amps on the meter side. Read $4300 later a 5% cost overrun.
Sign In or Register to comment.