Solar Intall

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Energy-Miser

Senior Member
Location
Maryland
Greetings,
92 solar panels on the roof top, each with its own micro-inverter. Planning on bringing down (7) 15 amp rated circuits to a panel on the ouside of the house, and then taking (3) 35 amp rated circuits out of this panel box, so that each can feed into a 200 amp panel at a residential installation (this is a 600 amp service house). Would like some suggetions on the choice of the outside panel, and some dos and don'ts. All comments are appreciated. E/M.
 

cruzJD

Member
All the micro inverters I have seen were not UL listed for grid tie solar installations.

What the make and model of the unit you?re planning on using?
 

drive1968

Senior Member
energymiser, I'm guessing that you are referring to the Enphase product. I have done one of those installations, but it wasn't on as large of a scale as the project you have. On my project, I only had 14 panels that fed into one 15 amp breaker on the main panel.

I think I understand what you are describing, but I would probably avoid bringing the 7 circuits into one panel and then splitting it up to three different panels. The problem I envision is if two of the three 35 amp breakers are turned off. All the power could be diverted to that one remaining circuit. The 35 amp breaker would protect it, but it doesn't seem like the best way to handle it in my opinion.

I would probably run two or three 15 amp circuits directly to each of the 200 amp panels that you have. If you balance the load in the way you have set up the three 200 amp panels, I think you would make full use of your solar system. I see why you would want to centralize all the solar power before diverting it to the load centers, but I think it is unnecessary to maximize the use of the solar system and might make it more complicated than it needs to be.
 
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drive1968

Senior Member
One thing I should add - my local jurisdiction required that I backfeed the 15 amp breaker directly on the main panel. I couldn't place it on the subpanel loadcenter.
 

Energy-Miser

Senior Member
Location
Maryland
All the micro inverters I have seen were not UL listed for grid tie solar installations.

What the make and model of the unit you?re planning on using?
It is Enphase, model number I don't have handy right now, but each generates 0.88 amps ac at 240 volts (one inverter per panel). They must be listed, because the compnay I just started with has been using them for a while now, passing inspections, etc. E/M
 

Energy-Miser

Senior Member
Location
Maryland
energymiser, I'm guessing that you are referring to the Enphase product. I have done one of those installations, but it wasn't on as large of a scale as the project you have. On my project, I only had 14 panels that fed into one 15 amp breaker on the main panel.

I think I understand what you are describing, but I would probably avoid bringing the 7 circuits into one panel and then splitting it up to three different panels. The problem I envision is if two of the three 35 amp breakers are turned off. All the power could be diverted to that one remaining circuit. The 35 amp breaker would protect it, but it doesn't seem like the best way to handle it in my opinion.

I would probably run two or three 15 amp circuits directly to each of the 200 amp panels that you have. If you balance the load in the way you have set up the three 200 amp panels, I think you would make full use of your solar system. I see why you would want to centralize all the solar power before diverting it to the load centers, but I think it is unnecessary to maximize the use of the solar system and might make it more complicated than it needs to be.
Well, goal is to balance the feeds, and then take each to a respective 200 amp panel. We could divide the panels into three roughly equal piles, and combine outputs of each on the roof, and then bring the three circuits down. Alternatively we can bring 7 circuits of 15 amp each down and combine them somewhere on the outside of the house, before going into the house with the three resulting circuits. I am thinking that in the combiner panel, if any of the 35 amp breaker is turned off, then the other two will overload, and trip. This will cause the micro inverters to essentially see a loss of utility power, and shut down. The three 35 amp breakers are able to be turned on one at a time, because the micro inverters have a sufficient built in delay upon sensing the restoration of the utility power, giving the operator enough time to turn all three on. On the suggestion of brining in all 7 15-amp circuits, that would have been my first choice, except that the AHJ here would like to see a disconnect for each on the outside, near the meter, which obviously will not work well. If someone has experience with a similar system, I would appreciate further discussion. E/M
 

Energy-Miser

Senior Member
Location
Maryland
One thing I should add - my local jurisdiction required that I backfeed the 15 amp breaker directly on the main panel. I couldn't place it on the subpanel loadcenter.
Does he/she also require that a disconnect be installed outside of the house for each 15 amp circuit? E/M
 

Energy-Miser

Senior Member
Location
Maryland
Another Thought on that...

Another Thought on that...

I am also thinking, is there any reason why the 7 circuits could not be fed into a NEMA3 panel outside on the wall, the single outpout of that panel (something around 100 amps at 240 volts) go to a disconnect on the wall, near the meter, then into the house, and into a subpanel inside, and then divided into three roughly equal outputs, to feed each of the three 200 amp panels? Please comment on this, would like to see if I am missing something if I chose this approach. Thanks, E/M.
 

drive1968

Senior Member
<<<Does he/she also require that a disconnect be installed outside of the house for each 15 amp circuit?>>>

A separate disconnect switch was not required other than the 15 amp circuit breaker, which is on the main panel outside of the house. It is right next to the 200 amp breaker which feeds the loadcenter inside the house.

I'm not sure of your set up, but is it possible for you to feed all that solar power to your main outside the house? Perhaps you could bring all seven 15 amp circuits into one subpanel and then have a single 100 amp breaker feed into your main.
 

dereckbc

Moderator
Staff member
Location
Plano, TX
Energymiser I though the whol epurpose of the Enphase micro inverters is to parallel them all up, and then run one set of conductors to a single or two 240 volt breakers.
 

Energy-Miser

Senior Member
Location
Maryland
Energymiser I though the whol epurpose of the Enphase micro inverters is to parallel them all up, and then run one set of conductors to a single or two 240 volt breakers.
Well, I wish. But apparently their connecting cables are only rated at 15 amps, so you can only parallel so many of them in tandom. Of course, once you have your individual 15 amp circuits, you can paralell the individual circuits in a junction box, and connect a larger wire to carry the extra ampreage downstream, etc.
 

Energy-Miser

Senior Member
Location
Maryland
<<<Does he/she also require that a disconnect be installed outside of the house for each 15 amp circuit?>>>

A separate disconnect switch was not required other than the 15 amp circuit breaker, which is on the main panel outside of the house. It is right next to the 200 amp breaker which feeds the loadcenter inside the house.

I'm not sure of your set up, but is it possible for you to feed all that solar power to your main outside the house? Perhaps you could bring all seven 15 amp circuits into one subpanel and then have a single 100 amp breaker feed into your main.
Actually I am leaning toward this solution, it is cleaner than the alternatives, and the main can serve as the required disconnect. Size of the outdoor panel might become an issue for the HO. Does anyone know what brand makes the smallest panels (say 125 amps, 8 or 12 circuits?)? E/M
 

220/221

Senior Member
Location
AZ
I just did a smaller installation with 30 micro inverters. I took two 240v 15a circuits into a 4 space panel on the roof then one 30 amp circuit off the main lugs to the 200 amp main panel.

You are basically doing this three times. My first thought is how everything will back feed if you use a single combiner panel but I suppose it would still be backfeeding if you used three different combiner panels.

It has taken me 35 years to figure out circuitry going in one direction so I'll get back to you in 2044.
 

drive1968

Senior Member
energymiser, remember that each of the 15 amp breakers are two pole, so you'd need at least a 16 space subpanel if you go for that set up.
 

Energy-Miser

Senior Member
Location
Maryland
I just did a smaller installation with 30 micro inverters. I took two 240v 15a circuits into a 4 space panel on the roof then one 30 amp circuit off the main lugs to the 200 amp main panel.

You are basically doing this three times. My first thought is how everything will back feed if you use a single combiner panel but I suppose it would still be backfeeding if you used three different combiner panels.

It has taken me 35 years to figure out circuitry going in one direction so I'll get back to you in 2044.
Well, I am basically planning on doing the same thing, except near the ground, instead of on the roof. Also, agree, this bi-directional stuff takes a whole new frame of mind. I am not used to it either!
 

Energy-Miser

Senior Member
Location
Maryland
I just did a smaller installation with 30 micro inverters. I took two 240v 15a circuits into a 4 space panel on the roof then one 30 amp circuit off the main lugs to the 200 amp main panel.

You are basically doing this three times. My first thought is how everything will back feed if you use a single combiner panel but I suppose it would still be backfeeding if you used three different combiner panels.

It has taken me 35 years to figure out circuitry going in one direction so I'll get back to you in 2044.
If I did end up putting this panel on the roof, what is your recommended method of installing such panel up there, where of course you will be dealing with a pitched surface??
 
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