House/Garage

[nosbod]

Every panel is protected by the main breaker. You cannot draw any more power than the breaker will supply or it will trip, and you cannot send any more power out to the grid than the main breaker size or it will trip. There is no way you can melt the bus or burn your house down. You are either using power from the utility or you are using solar and sometimes you are using both if your solar is not enough for your load draw, but under no circumstances can you draw more than your main breaker without it tripping.

[SunEagle]

Every panel is protected by the main breaker. You cannot draw any more power than the breaker will supply or it will trip, and you cannot send any more power out to the grid than the main breaker size or it will trip. There is no way you can melt the bus or burn your house down. You are either using power from the utility or you are using solar and sometimes you are using both if your solar is not enough for your load draw, but under no circumstances can you draw more than your main breaker without it tripping.

But if you add what you draw from the grid to what you produce from a large solar array you can exceed the panel rating. It has nothing to do with the main breaker. Why is that so hard for you to understand?

[nosbod]

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.

[SunEagle]

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.

Listen. Do whatever is legal in Canada. It is your issue to explain to your local inspector. If they approve your installation then this discussion is mute

I am just trying to make sure others on this Forum follow the legal electrical installation rules put in place to protect the homeowner.

Oh by the way. I have seen way too many circuit breakers pass more amps then they are rated for. It really comes down to their tripping mechanism which is not always foolproof.

[oregon_phil]

Section 64-112 refers to the breaker connect to the bus. My 7.7 inverter is rated at maximum output of 7660 watts, and according to SMA 32 amps should be the maximum output. However inverter s are mechanical devices and often are not subject to the laws of man. At 32 amps going by the 80% rule my over current device should be 40 amps, however my inverter was putting out 7860 this summer which means based on the 80% rule the 40 amp breaker is not large enough. So 64-112 64-112 tells me the overcurrent device (breaker) can be 120% or a 48 amp breaker which they don't make, so 64-112 (d) allows you to go to 125% which in term means a 50 amp breaker can be installed.

I hope I haven't made this to confusing.

That who article in the code deals strictly with installation, overcurrent protection, rapid shut down, grounding etc.

My house has a 100 AMP service. Based on the 80% rule I can draw more than 80 Amps without starting to overload the main breaker. Electricity is like water or air, it takes the path of least resistance, so when your electric supplier sends out power, it doesn't automatically come to your house, it waits outside on the street until you turn on a light and then it sends only enough power to run your light. So when you have solar and it's running in the day time anything you use in the house runs first from the solar and if it isn't producing enough then power from your supplier comes in to make up the short fall. Subsequently if you are producing more power than you are using the extra goes and joins your electric supplier and travels down the road to the next house.

The only way I can over load my system is if I had a solar array producing more than 80 AMPs.

Bi directional meters are mechanical devices which measure what's coming and what's going out and that's all they do, but if every house in the US put a 15K solar array on their roof I can guarantee you your suppliers lines would be toast.

Your 20% rule, is this in every state?

I believe 64-112 closely follows NEC 2020. 64-112 also covers more than just breakers.

Δ 64-112 Interactive point of connection (see Appendix B)

4c) notwithstanding Section 14, the sum of the ampere ratings of the overcurrent devices in source circuits supplying power to a busbar or conductor shall be permitted to exceed the busbar or conductor rating to a maximum of 120% of the rating of the busbar or conductor;

4d) notwithstanding Section 14, for a dwelling unit, the sum of the ampere ratings of the overcurrent devices in source circuits supplying power to a busbar or conductor shall be permitted to exceed the busbar or conductor rating to a maximum of 125% of the rating of the busbar or conductor

There is also an article on load side line side inverter connection pro's and con's at http://neighbourpower.com/blog/ce-co...us%20ampacity.

A screen shot of the panel overloading issue is attached. I know you are in Canada and most of us are in the US. In my particular jurisdiction, county inspectors are not liable for any faults, omissions or other acts. Proof of certified county electrical inspection does not make the county liable for code violations the inspector did not catch.

I have an SMA 7.7 -40 and also occasionally have AC power at 7860 watts. During these 7860 watt episodes, almost without exception, line voltage is running on the higher side 124/125VAC with inverter current at or slightly below 32 amps.

[foo1bar]

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.

What they are talking about is NOT about what you draw from the grid.

When I have a 100A main breaker, a 40A solar breaker, and a dozen 20A breakers for loads, there can be >100A flowing in that bus-bar. There will be 100A flowing from the main into the bus bar. And 32A flowing from the solar into the bus bar. (And 132 amps being consumed by the various load breakers)
This can continue without any breakers tripping because none of the breakers are exceeding their rating.
If the bus-bar is only rated for 100A, there's more than 100A running in it - and it could fail (probably not because the manufacturers put enough of a safety margin in)
But let's say you increase it even more - and you have 100A of solar breakers and a 100A main. And you're still using a 100A busbar. Now you could have 200A worth of current in that busbar which was only designed to handle 100A (plus some safety margin). Will that result in the busbar failing? (maybe not - but I wouldn't bet my house or my life on it)

This risk of having significantly larger currents in the busbar than they were rated for is why there is the "120% rule"

BTW - even my first example would run into problems with code unless it's a 125A bus bar with a 100A main. 125A bus bar * 120% = 150A; So maximum of 150A for both. 100A main + 40A solar would be less than 150A, so would be OK. Doing same calculations with 100A bus bar shows us: 100A busbar * 120% = 120A ; And 120A < 100A + 40A, so that is NOT OK.

If you have the solar backfeed being attached *before* the main breaker, ie. a "line side tap", then this doesn't apply. And that is what PVAndy was mentioning - having some of these connections for the backfeed and/or garage be in between the meter and the main breaker, via a supply (line) tap.

[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.

[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.

[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.

[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.

[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]

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.

[solarix]

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

[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.

[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)