House/Garage

[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,

[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.

[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.

[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.

[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.

[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.

[solarix]

99%+ of all 200Amp panels have a 200A buss. 225A "solar ready" panels are a new option that few homebuilders use (except in California where solar ready is now mandated for new construction). Yes, by all means if you are building homes - put in a solar ready electric panel.
btw, 225 x 20% = 45, 45 + (225 - 200) = 70A.

[foo1bar]

but a 200amp panel with a 200 amp main breaker has a bus rated at 225amps.

That wasn't true with my 200A panel. It's a 200A main breaker and a 200A bus bar.
And it's not that mine is an old panel nor an unusual one.

[nosbod]

There seems to be some disparity between the US and Canada. My 60 amp panel in the garage and the 100 amp panel in my house both have 125 amp bus, and the last 200 amp service I installed 10 years ago had a 225 amp bus. So it seems there is some differences. The last 100 amp panel I installed 2 years ago, and I picked it up in the US, had a 125 amp bus.

[SunEagle]

There seems to be some disparity between the US and Canada. My 60 amp panel in the garage and the 100 amp panel in my house both have 125 amp bus, and the last 200 amp service I installed 10 years ago had a 225 amp bus. So it seems there is some differences. The last 100 amp panel I installed 2 years ago, and I picked it up in the US, had a 125 amp bus.

It really depends on the panel manufacturer. Some of the home style type panels (like Bryant) do not have the higher bus rating but if you look at the commercial panels (like Square D) they are rated higher and unfortunately also cost more.

[Ampster]

And now there are material shortages to deal with. I recently had to pay list price for a Solar ready 200 Amp panel because only one local supplier had the model I needed.

[nosbod]

I'm waiting to hear from the utility to find out what size wire is run from the transformer to the meter. I am hoping I can upgrade to 150 amps, if so I will buy a 200 amp panel and replace the main breaker with 150 which will give me 100 amps back feed. The problem being, the 200 amp panel will be $260.00 bucks and to replace the breaker, another 200 to 400 depending whether I go with the 10K or the 25K rated breaker. Spending 1000 bucks to replace my panel is a cheap price to pay so I can put in another 4.5 K system on top of my 9.2. With the price of hydro in Alberta which has got from 8 cents to 13 cents a kilowatt, the 1000 bucks will be recouped in 6 months.

[Ampster]

......I am hoping I can upgrade to 150 amps, if so I will buy a 200 amp panel and replace the main breaker with 150 which will give me 100 amps back feed. The problem being, the 200 amp panel will be $260.00 bucks and to replace the breaker, another 200 to 400 depending whether I go with the 10K or the 25K rated breaker. Spending 1000 bucks to replace my panel is a cheap price to pay so I can put in another 4.5 K system on top of my 9.2. With the price of hydro in Alberta which has got from 8 cents to 13 cents a kilowatt, the 1000 bucks will be recouped in 6 months.

That was my fallback plan when I upgraded from a 100 Amp service panel. Fortunately no transformer upgrade was needed for 200 Amp service and the new service drop was only $75 from PGE.I did spend the extra bucks for a panel with a 225 Amp bus to give me flexibility in terms up future upgrades.

[nosbod]

I haven't heard back from Fortis yet, but I do have a contingency plan if I can't put in a 200 amp panel. I will come off the meter and put a splitter before the 100 amp panel and then come off the splitter to a 20 amp disconnect to feed the garage inverter. Same type of thing as a line tap.

[foo1bar]

I haven't heard back from Fortis yet, but I do have a contingency plan if I can't put in a 200 amp panel. I will come off the meter and put a splitter before the 100 amp panel and then come off the splitter to a 20 amp disconnect to feed the garage inverter. Same type of thing as a line tap.

Not just the same type of thing - what you're describing *is* a line side tap.