How to combine AC strings from the microinverters?

[Naptown]

Rich,

I was planning on feeding the solar array through the main service panel, you mention that I will be forced to do a line tap. I have no idea what that means

or why it would be necessary. would you mind elaborating a bit more?

My local power compnay requires that I install a manual disconnect "level" style within 8 feet of the meter. so I was planning on running from the subpanel at the solar array, to the disconnect, then on to the main service panel.

Jim

How many amp service do you have and the size of the main breaker?

[billvon]

So far everyone here is wrong.
enphase M190's you can put up to 15 on a circuit
enphase M215 you can put up to 17 on a circuit

Per the Enphase installation and operations manual you can connect 14 M200's or 16 M175's to a single branch circuit. What gives you the additional derating?

[inetdog]

No additional overcurrent protection is required at that point it will be handled at the main panel.
The 120% rule would apply if he is backfeeding a panel through a breaker.

Thanks!
In this case, it sounds to a layman that he will be backfeeding the proposed 60A subpanel through his 4 15A breakers, yes? Or is that not considered a backfeed but instead a fused combiner if there are no actual loads connected to the same subpanel? The 60A breaker protecting the subpanel would for sure be a backfeed unless a line tap connection is used instead?

[jkonzelman]

service amperage

How many amp service do you have and the size of the main breaker?

I have 400 amp service to the house. 2 x 200 amp main breakers. 2 subpanels in the basement, 200 amp each.

Where the meterbox is on teh side of the house, there are also 2 x 200 amp breakers and a subpanel attached.

[jkonzelman]

m215s

Per the Enphase installation and operations manual you can connect 14 M200's or 16 M175's to a single branch circuit. What gives you the additional derating?

enphase says M215s can have up to 17

[Naptown]

Where you will tie in if you want to run one sub panel at what I assume to be a ground mount and not two is in one of the disconnects on the outside of the house not in the sub panels in the basement. If there are lugs to tie into on the load side of the breaker you can tie into those,(One wire per terminal screw you can't put two wires under one lug or screw) otherwise google piercing line taps and use those to connect directly to the wire on the load side of the breaker between the breaker and the panels in the basement.
You will still need a fused disconnect before the tap between the line tap and the module sub panel.

CAUTION THIS IS SOMETHING THAT SHOULD BE DONE BY A LICENSED ELECTRICIAN WHO IS FAMILIAR WITH THESE TYPES OF INSTALLATIONS

[jkonzelman]

Definetly an Electrician!

Where you will tie in if you want to run one sub panel at what I assume to be a ground mount and not two is in one of the disconnects on the outside of the house not in the sub panels in the basement. If there are lugs to tie into on the load side of the breaker you can tie into those,(One wire per terminal screw you can't put two wires under one lug or screw) otherwise google piercing line taps and use those to connect directly to the wire on the load side of the breaker between the breaker and the panels in the basement.
You will still need a fused disconnect before the tap between the line tap and the module sub panel.

CAUTION THIS IS SOMETHING THAT SHOULD BE DONE BY A LICENSED ELECTRICIAN WHO IS FAMILIAR WITH THESE TYPES OF INSTALLATIONS

Owh I agree! I plan to just everything close, then call in the experts! but for now I need to get a line drawing to my power company. and find an experienced electrician, so far no luck around here!

Thanks for the info! very valuable!

[Mike90250]

.....
I was thinking of 4 curcuits each on a 15 amp breaker, so a 60 amp subpanel box sholuld work? and just send the output to the house and hook it up to a 60 amp breaker in the house panel.....

Nope, you have (in the USA) "Split Phase Power" with 2 hot lines, and a neutral wire. Loads/sources need to be matched/paired as much as feasible, so you should feed two, 30A breakers, on opposite phases, not the same phase (line).

[jkonzelman]

two 30 amp breakers, how?

Nope, you have (in the USA) "Split Phase Power" with 2 hot lines, and a neutral wire. Loads/sources need to be matched/paired as much as feasible, so you should feed two, 30A breakers, on opposite phases, not the same phase (line).

OK, I sort of understand what you are saying. but how would I take 4 strings of AC power from my solar array, and feed that into two 30 amp breakers?

[inetdog]

OK, I sort of understand what you are saying. but how would I take 4 strings of AC power from my solar array, and feed that into two 30 amp breakers?

He is saying that your subpanel needs to be a 240 volts subpanel, fed either by a single 30 amp 240 breaker in the main panel (actually two breakers but in one housing.) Or else fed from two separate 30 amp 120 volt breakers in the main panel on opposite phases. There is no 60 amp breaker in the main panel.

Then at the subpanel you connect two of the 15 amp breakers to one side of the 240 and the other two to the other side. (You do this by putting the breakers in the appropriate slots in the panel to connect to one bus of the other.

No problem at all for the qualified electrician who actually wires it up.

[jkonzelman]

ok Thanks!

He is saying that your subpanel needs to be a 240 volts subpanel, fed either by a single 30 amp 240 breaker in the main panel (actually two breakers but in one housing.) Or else fed from two separate 30 amp 120 volt breakers in the main panel on opposite phases. There is no 60 amp breaker in the main panel.

Then at the subpanel you connect two of the 15 amp breakers to one side of the 240 and the other two to the other side. (You do this by putting the breakers in the appropriate slots in the panel to connect to one bus of the other.

No problem at all for the qualified electrician who actually wires it up.

OK, so I understand almost all of that

so why not use a 60 amp breaker in the main panel? I'm pretty sure my oven is on a 60 amp breaker. What is different here?

and if I have for strings of solar panels, each producing 12 amps, I'll need more than 30 amps in the main panel wont I?

BTW- I found an electrician willing to work on this project with me! I just need to get a single line drawing to my power company now! I'm so psyched!

[Naptown]

OK
If you want to feed into the panels and not do a line tap you will have to split the two arrays into 2 combiner panels with 2 strings each and then feed each of them into a different panel.
You are trying to feed over 40 amps into a single panel the way you were heading with one combiner box.
The problem is with a 200 A panel you can only feed a maximum of 40A from solar into any one 200A panel (This is the 120% rule) meaning that the total of all feeds cannot be more than 120% of the rating of the buss bars in the panel. 20% of 200A = 40A
Now you are faced with three choices
1- line tap as I indicated earlier
2- split array to 24 inverters each on 2- 4 circuit combiner panels and feed both panels.
3- Take the main breaker out of the panel you want to feed and replace with a 150A main breaker. (This should be done on the panel that is loaded the least)

[jkonzelman]

my ignorance

OK
If you want to feed into the panels and not do a line tap you will have to split the two arrays into 2 combiner panels with 2 strings each and then feed each of them into a different panel.
You are trying to feed over 40 amps into a single panel the way you were heading with one combiner box.
The problem is with a 200 A panel you can only feed a maximum of 40A from solar into any one 200A panel (This is the 120% rule) meaning that the total of all feeds cannot be more than 120% of the rating of the buss bars in the panel. 20% of 200A = 40A
Now you are faced with three choices
1- line tap as I indicated earlier
2- split array to 24 inverters each on 2- 4 circuit combiner panels and feed both panels.
3- Take the main breaker out of the panel you want to feed and replace with a 150A main breaker. (This should be done on the panel that is loaded the least)

OK my ignorance is starting to evaporate!
1- do a line tap avoids the 120% rule- got it!
2-split the array sounds possible , especially since I already have two 200 amp panels in the house
3- this one I dont get remove the 200 amp breaker and replace with 150? sorry!
If I understand the gist, so long as all of the breakers in the house panel box do not add up to more than 240 amps, all should be ok. keep the load balanced if possible, and feed two seperate feeds from the solar array, one into each panel box and all should be ok. if this is not possible, then I need to do a line tap.

This helps alot! so now I know how to go about drawing up the line drawing, I'll then run that by my electrician, then on to the power company.

Thanks for all the discussion! I have learned a lot ( still dont quite get it all, but I feel like I can proceed with some degree of confidence)

Thanks!

[inetdog]

OK my ignorance is starting to evaporate!
1- do a line tap avoids the 120% rule- got it!
2-split the array sounds possible , especially since I already have two 200 amp panels in the house
3- this one I dont get remove the 200 amp breaker and replace with 150? sorry!
If I understand the gist, so long as all of the breakers in the house panel box do not add up to more than 240 amps, all should be ok. keep the load balanced if possible, and feed two seperate feeds from the solar array, one into each panel box and all should be ok. if this is not possible, then I need to do a line tap.

This helps alot! so now I know how to go about drawing up the line drawing, I'll then run that by my electrician, then on to the power company.

Thanks for all the discussion! I have learned a lot ( still dont quite get it all, but I feel like I can proceed with some degree of confidence)

Thanks!

The one missing link you have is that the 120% rule applies to the busbar inside the panel. When you change out the main breaker from 200 to 150 in the same panel, you still have the same busbar so you still have 240 total to work with. 60 + 200 is greater than 240. 60 + 150 is not.
You do not add up all of the breakers. You add up all of the breakers that are feeding power INTO the panel. That would be the main breaker and the PV breakers.

[jkonzelman]

aha!

The one missing link you have is that the 120% rule applies to the busbar inside the panel. When you change out the main breaker from 200 to 150 in the same panel, you still have the same busbar so you still have 240 total to work with. 60 + 200 is greater than 240. 60 + 150 is not.
You do not add up all of the breakers. You add up all of the breakers that are feeding power INTO the panel. That would be the main breaker and the PV breakers.

well now that you say it out loud, it makes perfect sense! Thanks!