Buss Bar rating?

[jeffvoltaic]

Can anybody tell what size this busbar is and can I then prove it to the AHJ?022.jpg023.jpg

[inetdog]

I do not think that anyone here can tell you from the pictures what the bus rating of that combined meter/main panel is. Except that it is pretty likely at least 200A because of the breakers installed.
The only authoritative answer will come from finding the exact model number of the panel and checking with technical support at the manufacturer. (Good luck!).
It is frequently not even listed in the basic published specs of the panel, although sometimes the spare parts listing will give a number which cross references to a bus assembly with a listed current rating.

P.S.: Welcome to Solar Panel Talk!

[Sunking]

Is this a Duplex home?

[foo1bar]

Can anybody tell what size this busbar is and can I then prove it to the AHJ?[ATTACH=CONFIG]6127[/ATTACH]

I don't think it matters. I don't see any room in there for another breaker. (or a spot that you can do a "supply side tap")

Presumably you are attaching the inverter to one of the two sub-panels those 100A breakers feed. And that will be where it will matter what busbar capacity is.

Good luck.

[jeffvoltaic]

my goal

The plan is to replace the existing 125A sub panel with a 200A sub panel with a 100A breaker but in order to feed to the main I need to know that it is indeed also rated for 200A? As I am tryin to put 60A of solar to it one SB5000TL(22A) and one SB6000TL (25A). 38 Sunpower 327s.

I am going to try to get more information about the panel when I redo the site visit.

Thanks for the replies and help!

[sensij]

The plan is to replace the existing 125A sub panel with a 200A sub panel with a 100A breaker but in order to feed to the main I need to know that it is indeed also rated for 200A? As I am tryin to put 60A of solar to it one SB5000TL(22A) and one SB6000TL (25A). 38 Sunpower 327s.

I am going to try to get more information about the panel when I redo the site visit.

Thanks for the replies and help!

If you have the 100 A breaker protecting backfeed from the sub to the main, you don't need to worry about any additional load on the main. As foo1bar suggested, if the PV breaker is on the sub, that is the one you need to worry about. It sounds like you have that covered, since 60 A into a 200 A bus with a 100 A breaker should be ok. Just make sure the 60 and 100 A breakers are bidirectional.

[foo1bar]

The plan is to replace the existing 125A sub panel with a 200A sub panel with a 100A breaker but in order to feed to the main I need to know that it is indeed also rated for 200A? As I am tryin to put 60A of solar to it one SB5000TL(22A) and one SB6000TL (25A). 38 Sunpower 327s.

I am going to try to get more information about the panel when I redo the site visit.

Thanks for the replies and help!

If the wire coming to that panel is sized for 200A, I would probably assume that it was sized properly when installed, and it's a 200A panel. (assuming couldn't find any model numbers or anything to indicate otherwise.)

[J.P.M.]

The plan is to replace the existing 125A sub panel with a 200A sub panel with a 100A breaker but in order to feed to the main I need to know that it is indeed also rated for 200A? As I am tryin to put 60A of solar to it one SB5000TL(22A) and one SB6000TL (25A). 38 Sunpower 327s.

I am going to try to get more information about the panel when I redo the site visit.

Thanks for the replies and help!

You're using Sunpower because you're cramped for space ? If not, have you sought quotes using other panels ? You may find you're leaving a bundle of cash on the table. Or are you the installer/vendor ?

[inetdog]

If you have the 100 A breaker protecting backfeed from the sub to the main, you don't need to worry about any additional load on the main. As foo1bar suggested, if the PV breaker is on the sub, that is the one you need to worry about. It sounds like you have that covered, since 60 A into a 200 A bus with a 100 A breaker should be ok. Just make sure the 60 and 100 A breakers are bidirectional.

Don't jump the gun too fast here.

If the backfeed into the 200A subpanel will be via a 60A breaker, then the size of the 100A feeder to the sub from the main is not important, but you still have to apply the 120% rule to the main and some AHJs will want you to apply the 120% rule to the wire size of the feeder itself (100A + 60A = 160A, 160/1.2 =133, so your feeder wire must be rated for 133A not just 100.)
At the main panel, if you have a 200A breaker and a 200A bus you can only allow 40A of backfeed even though it is coming in by way of the subpanel.

If the OP is covered by the 2014 NEC, then he could use the actual maximum inverter output circuit amps (rated times 1.25) to calculate the backfeed at each point along the way rather than having to use the 60A breaker size. It would also be less likely that the AHJ would try to apply the 120% rule to the feeder.

The OP did not state either the main breaker size or the nominal panel amperage at the main, so that question is still open.

Just looking at the picture of the open meter/main combined panel, I would say that he has a 200A service and his service disconnect consists of the two 100A breakers, each feeding a separate subpanel. The bus is being fed from the meter section via the built in bus bar assembly.
The main disconnect does not have to be a single breaker in a case like this. But the situation in the "main" panel is a little hard to interpret. If the PV were connected via a dedicated breaker to the bus, then it would actually be a supply side tap and not subject to the 120% rule. With the backfeed coming into the unprotected bus from the meter via one of the service disconnect breakers, the AHJ will have a lot of room to develop strange ideas. <sigh>

[sensij]

Yes, sorry, the way I replied could be taken as a general answer that would be incorrect.

My answer was based on a simple application of 2011 NEC 705.12(D)(2) to the panel pictured:

(2) Bus or Conductor Rating.
The sum of the ampere ratings of overcurrent devices in circuits supplying power to a busbar or conductor shall not exceed 120 percent of the rating of the busbar or conductor.

As pictured in its current state, the sum of the overcurrent devices supplying power to the busbar is zero (since there are none). If one of the 100 A breakers were to become bi-directional because an inverter is hooked up that becomes a source, the sum would then be no more than 100 A, still within 120% of the (presumable) 200 A rating of the bus. Although it seems funny to think about it like this, I think that functionally, it is OK. I can't think of a way to get more than 200 A on that bus if inverters are hooked up to either (or both) of the subpanels supplied.

My simple application of this rule might not be how the AHJ wants to look at it, so that conversation is important. Treating it like a line side tap does seem possible too, although if the subpanel through which the inverter is connected also has loads, that interpretation is messy, too.

[inetdog]

Yes indeed. The fact that we have two switches (with OCPD) making up the service disconnect makes the whole situation one which is more familiar to industrial than to residential electricians.
The typical meter/main combo box will have a single main breaker either on its own or between the meter and a bus with multiple load breakers.