House/Garage

[nosbod]

One other note. I keeps seeing people saying on a 200 AMP panel the maximum breaker size is 40 amps, so that's the limit on back feed, but a 200amp panel with a 200 amp main breaker has a bus rated at 225amps. If you multiply 225 X 1.20 = 70 amps. 70 X 240= 16800 - 20% = 13400 .According to the NEC regulations you should be able to install a 13 Kilowatt system unless there is some other regulation limiting you to 40 amps.

[nosbod]

A 100 amp panel usually has a 125 amp bus. If the main breaker in the panel is 100 amp then you statement is correct , you can back feed 50 amps for solar keeping in mind the 80 % rule on breaker capacity. So 40 amps is right. However if the panel main breaker is 125 amps then you can only back feed 25 amps. In the US the NEC is 1.20. In Canada it is 1.25. If you take the cover off the panel it will tell you the bus rating.

[foo1bar]

(I'm not sure where his 125% came from or why a "100A panel" would have a 125A bus bar)

I don't know where 125% came from - I only know the 120% from NEC.

As for why a panel would have a 100A main breaker and a 125A bus bar - because they do.
125A panels are fairly common. Maybe not as much as 100A or 200A, but pretty common.
I think some of the manufacturers sell the same box and main bus bar as a 100A and 125A main breaker panel, just having different ampacity main breakers. If they've done the engineering for a design to handle 125A, they can easily put in a 100A main breaker (or even a 60A main breaker) and they can sell it to those markets - without having to spend on engineering and testing or having much for extra components.

[solarix]

[QUOTE=sdold;n428855]I thought I understood this too, but now I'm not so sure. They way I read the NEC, if he has a 125A rated busbar, 120% of that would be 150A and that would be the maximum sum of the overcurrent devices feeding the bus. So if the main breaker was 100A, that would leave up to 50A for the solar breaker with a system producing up to 40A. Is that right?

That's correct if the 50A solar breaker is at the opposite end of the bus from the main breaker. But, if the main 200A panel's buss is 200A, that limits the solar backfeed ampacity to 40A or 32A max.

[oregon_phil]

I understand what you are saying. My 100 amp panel bus is rated at 125 amps, multiply by 1.25 and I can back feed 56 amps. My current solar produces 33 amps at peak and protected by a 50 amp breaker. I have no room left to put panels on my garage without updating my panel to 200 amp which I am in the process of seeing if that's possible. If the hydro authority tells me the lines from the transformer to the meter can handle the extra load I will upgrade.

When I started this feed all I was asking if I could run 2 different size inverters from 2 separate location on the same line. A simple YES or NO would have sufficed. At this point I am still not sure if my question was answered. One person said YES and one person said NO, but it has been an interesting discussion.

I thought you answered your own question since you spoke to Alberta Hydro inspector. As you have stated in your earlier post, you already have a 50 amp breaker installed for the SMA 7.7 -41. 64-112 says for dwellings, you can have (125% * 125 amp bus bar rating) of OVER CURRENT devices for source circuits. By all practical matters, you are at that limit (100 amp main breaker + 50 amp solar inverter breaker).

The problem with talking with an inspector about one specific topic is that they will only answer your one specific question. I would suggest that you draw up a schematic of what you want to do and sit down with the Hydro Inspector. They will bleed all over that schematic with what needs to be done. You might even want to have them visit your site because there are many site specific issues they can point out before you pull a permit. I/we are not experts in Fortis or Alberta Hydro implementation of Canadian Electrical standards.

[SunEagle]

I thought I understood this too, but now I'm not so sure. They way I read the NEC, if he has a 125A rated busbar, 120% of that would be 150A and that would be the maximum sum of the overcurrent devices feeding the bus. So if the main breaker was 100A, that would leave up to 50A for the solar breaker with a system producing up to 40A. Is that right?

(I'm not sure where his 125% came from or why a "100A panel" would have a 125A bus bar)

Some panels come with a standard bus size but are de-rated on the name plate for the homeowners protection. I found similar rating confusion on Allen Bradley MCC's. Most are built with an 800Amp main bus but you can get a nameplate that indicates 600Amp even though the bus can handle 800amp. According to the people at the MFG plant it was just easier and actually cheaper to make one Main Bus size and use it in either the 600 or 800 amp rated MCC,

[sdold]

I thought I understood this too, but now I'm not so sure. They way I read the NEC, if he has a 125A rated busbar, 120% of that would be 150A and that would be the maximum sum of the overcurrent devices feeding the bus. So if the main breaker was 100A, that would leave up to 50A for the solar breaker with a system producing up to 40A. Is that right?

(I'm not sure where his 125% came from or why a "100A panel" would have a 125A bus bar)

[J.P.M.]

I think this is why electricians are required to be licensed...

These types of discussions make me consider the probability of how many homes that, at one time or another in their history were owned by DIYers who thought they knew all that was necessary, and either ignored or denigrated or were completely ignorant or all of codes and standards that come into play.

A bit scary.

[solarix]

I think this is why electricians are required to be licensed...

[nosbod]

I understand what you are saying. My 100 amp panel bus is rated at 125 amps, multiply by 1.25 and I can back feed 56 amps. My current solar produces 33 amps at peak and protected by a 50 amp breaker. I have no room left to put panels on my garage without updating my panel to 200 amp which I am in the process of seeing if that's possible. If the hydro authority tells me the lines from the transformer to the meter can handle the extra load I will upgrade.

When I started this feed all I was asking if I could run 2 different size inverters from 2 separate location on the same line. A simple YES or NO would have sufficed. At this point I am still not sure if my question was answered. One person said YES and one person said NO, but it has been an interesting discussion.

[PVAndy]

Why is it so hard for you to understand you can't draw any more than your main breaker. That's way you have overcurrent devices called breakers. The only power you will draw from the grid when you have solar is to make up for any load the solar isn't producing. It's either or and sometimes both but you cannot exceed the breaker size.

Just to chime in. Unfortunately you are the one who is not understanding. If you are feeding solar via a backfeed breaker, the max power you can supply to loads is the sum of the main breaker and the solar inverter breaker. If you go back to your original ask re adding solar to the garage subpanel please read my original response. It's a little complicated to calculate bus loading on subpanels. The 50% rule you mentioned has only to do with allowable backfeed to the grid, not panel bus protection

Andy

[nosbod]

The inspector is only concerned after the meter going to the house. Fortis owns the lines coming into the meter and they are the people I have contacted in regards to upgrading to 200 amp providing the underground cables to the meter can handle the load.

[foo1bar]

Thanks for the information. I contacted the hydro inspector and he said on a 100 amp service you can go 50amp for solar. My current solar array this summer put out 33 amps so I already have a 50 amp breaker in the panel. I have contacted the hydro authority for Alberta to see if the lines from the transformer to the meter can handle an upgrade to 200 amp. I will see what they say. If the lines can handle 200 amp then I will upgrade the service.

What I think the hydro inspector was saying is that you can backfeed up to 50A for a 100A service.
That is a totally separate consideration from the rules for keeping your breaker panel's bus-bar from being overloaded.

Is the "hydro inspector" representing the power company or an inspector for the building department / Authority Having Jurisdiction ? If they're from the power company, they don't really care what's going on past the meter - they only care about what goes in/out on the lines to your house.

[Ampster]

Thanks for the information. I contacted the hydro inspector and he said on a 100 amp service you can go 50amp for solar. .......

In the USA most power companies don't look at what circuitry is behind the meter. That is the job of the local Authority Having Jurisdiction. I am assuming that the "hydro" you are referring to is the power company. @foolbar gave a good explanation above about how the 120% rule is applied in the USA.

[nosbod]

Thanks for the information. I contacted the hydro inspector and he said on a 100 amp service you can go 50amp for solar. My current solar array this summer put out 33 amps so I already have a 50 amp breaker in the panel. I have contacted the hydro authority for Alberta to see if the lines from the transformer to the meter can handle an upgrade to 200 amp. I will see what they say. If the lines can handle 200 amp then I will upgrade the service.