Busbar Rating and PV Installation

If the panel is a 200 amp then the bus bar is 200 amp. You should be able to look inside at the label and it should tell you the max size breaker. A 60 amp should be ok. Where did you get the 20% rule? Did you do a total load calculation to verify that the panel will not be overloaded when you to add the inverter? What is your location?

I was told that the feed breaker cannot exceed 20% of either the panel rating or the bus bar rating and that the busbar rating is something higher than the panel rating.

We are in Los Angeles. There is a main panel (200) and a subpanel (100/busrating 125). Main panel has no visible label, specs, nor manufacturer information.

I did not do load calculations.

NEC code states that its also allowable to parallel up to three double pole breakers for a single higher amp circuit if a suitable breaker of needed value is not available.

I have installed 150 amp breakers in 200 amp services boxes and thats still within NEC codes. I personally have six 100 amp circuits in my 200 amp shop service panel and thats all within code.

I suggest you pick up a copy of the latest NEC book. Its well worth the $40 -50 and you can get it through most bookstores and countless online stores too.

I have the NEC code book, the problem is understanding how I can do a supply-side tap (which I assume is what you are referring to?) with the current configuration, since that seems to be my only option other than upgrading the service to a 400 amp.

However, if the current demand load allows it, couldn't I also reduce the current main breaker (200) to something smaller so that my total supply load doesn't exceed 240 amps?

I've never heard of this 20% rule and I believe it is not correct. You should be able to install the 60 amp breaker. I would be more concerned with this added load to the panel. This may not be a problem.

Its returning not taking. It goes against the other circuits peak load numbers.

Unless this is a very baddly designed AE system that uses power to run the solar panels!

That's correct. It's feed load I am talking about.

NEC 690.64 allows for the sum of the supply breakers feeding the busbar of a panel to be up to 120% of the busbar rating. As such, I am limited to a 40 amp supply breaker (from the inverter) because my main breaker is 200. 200+40= 240 which is 120% of the main panel rating. My hope is that the busbar rating is higher than the panel rating (which often is), however without a label or manufacturer specs, I have no idea how to find the busbar ratings. If my busbar is rated for 225 then I can add a 60 amp supply breaker, which is what my inverter load calls for.

True, however present combined possible loads do not likely have capability to ever exceed the original 200 amp input capacity if the panel was properly sized in the first place.

By adding your 40 amp return power you in effect reduce the line draw and also reduce the peak buss bar current at any point along it.

If all combined working loads equal say 150 amps peak, there wont be a problem. I do believe that the buss bar ratings are also considered for continuous duty which is something like 3 or more hours non stop. Other than electric heat systems there are very few home power usage conditions that will ever get any where near what a 200 amp service can supply.

If all of the combined loads equal 150 amps and your putting in 40 amps from the panels that means the main breaker is only supplying 110 amps. Also if the panel supply breaker is placed at the bottom of the panel its supply current will only back-feed up the buss bars to the circuit or circuits that are drawing that much power.

As far as I know its one of the safer grey areas that you can work in in regards to load distribution on a service panel.

Can you identify the panel by reading the make and model off of one of the breakers? I've never seen a panel that could take third-party breakers, or even breakers from the same manufacturer made for a different series (e. g., Square D QO and Homeline products are not interchangeable). From there, it is just a matter of finding the rating(s) of panels made to accommodate the number of breaker spaces provided. (Note: some panels have bars shorter than the number of breakout spaces in the front cover, so you have to look inside to get the correct number.)

The existing main service panel has a 200 amp busbar and 200 amp main breaker. The Maximum size solar breaker that can be installed is therefore 40 amps. You want to install a 60 amp breaker for your PV system. Replace the 200 amp main breaker with a 150 amp main breaker. Which will allow enough room, per NEC 690.64, for the 60 amp solar breaker.

150 amp main + 60 amp solar= 210 amps < 120% x 200 amp busbar rating = 240 amps