Enphase microinvertors (M215) question

stevehull · 12-01-13, 08:23 AM

Not sure where to ask this, but here it goes.

How many Enphase microinvertors (M215) can be put on a string. I see 17 are listed, but this is for a 20 A circuit breaker.

I am needing about 40 panels for a 10 kW system with two rows of portrait panels (each row 20 panels).

Can I do a 30 amp breaker, use a larger wire gauge and put 20 invertors on a string?

Thanks,

Steve

pinballlooking · 12-01-13, 01:55 PM

Quote:

Originally Posted by stevehull

Not sure where to ask this, but here it goes.

How many Enphase microinvertors (M215) can be put on a string. I see 17 are listed, but this is for a 20 A circuit breaker.

I am needing about 40 panels for a 10 kW system with two rows of portrait panels (each row 20 panels).

Can I do a 30 amp breaker, use a larger wire gauge and put 20 invertors on a string?

Thanks,

Steve

It would be best to start your own post for this question.

Here is the data sheet for them M215
http://enphase.com/global/files/M215_DS_EN_60Hz.pdf

No you cannot put 20 M215 and use a larger breaker.

Each M215 is .9 amps you can have not more than 17 going to a 20 amp breaker.

These docs give you the voltage rise.
http://enphase.com/global/files/Enph...tions_M215.pdf
http://enphase.com/global/files/Enph...Vdrop_M215.pdf
You usually end up breaking up the 17 run in smaller groups (they call this center feeding) then going to a Jbox then take that wire to the 20 amp breaker.

Here are two diagrams one is for 40 modules using four 15 amp breakers.
The other is 50 modules using two 20 amp breakers and two 15 amp breakers.

Mikesolar · 12-01-13, 08:02 PM

Quote:

Originally Posted by pinballlooking

It would be best to start your own post for this question.

Here is the data sheet for them M215
http://enphase.com/global/files/M215_DS_EN_60Hz.pdf

No you cannot put 20 M215 and use a larger breaker.

Each M215 is .9 amps you can have not more than 17 going to a 20 amp breaker.

These docs give you the voltage rise.
http://enphase.com/global/files/Enph...tions_M215.pdf
http://enphase.com/global/files/Enph...Vdrop_M215.pdf
You usually end up breaking up the 17 run in smaller groups (they call this center feeding) then going to a Jbox then take that wire to the 20 amp breaker.

The Canadian and, I think the NEC, calls for the total amperage X 1.25 to give you wire and therefore fuse size so .9 X 17=15.3 x 1.25 (safety factor) = 19.125A. All our wiring must have the 25% safety.

pinballlooking · 12-02-13, 12:23 AM

Yes the NEC requires the same here.The Enphase trunk cable is not rated for more than that.That is the limiting factor that keeps you only having 17 microinverters with M215 and you showed the math why you need a 20 amp breaker.

stevehull · 12-02-13, 06:28 AM

Got it. The Enphase TRUNK cable is limited, not physical issues other than that.

Given that, what would your recommendations be for the maximum number of inverters per string?

TIA,

Steve

gasstingy · 12-02-13, 08:04 AM

You may also want to check and see how many inverters Enphase says the EMU will accommodate. When I bought mine, my EMU manual said it could only handle a string of 14. That was from early 2009.

pinballlooking · 12-02-13, 08:12 AM

I would max out each run I did not do that and when and if you upgrade it will help if you max each run.
But I would center feed so there is no more than 5 micreinverters before being tied into a Jbox this keeps the voltage rise lower. How far away it your array going to be from your house?
I put in 40 modules thinking I would never put more in but it soon wanted to zero out and added more solar quickly.
The EMU can handle 17 per run with the M215

where2 · 12-08-13, 05:31 PM

I designed my system with two trunks. Each trunk has 10 inverters. My goal was to fit 20 inverters and panels on my second floor roof, and this was the most efficient method to get to that goal. I considered center feeding since I had a gap between a group of 6 panels and a group of 4 panels in a row (had to avoid a plumbing vent stack). I weighed the pro's and con's and finally decided against center feeding since the best logical location for my weather head and roof penetration was at the upper left corner of the array.

My run from the second floor attic to the combiner panel on the back of the house is all #10AWG UF. Inside a junction box in the attic, I transition from #10 AWG UF to a #12 AWG 4-conductor TCER cable to go up the weather head to a custom Hubbell-Weigman trunk cable termination panel on the roof. At that point, I transition to the #12 AWG Enphase trunk cable.

Looking at my graphs from today, a couple of my inverters saw 252v AC today. No error messages about the voltage, and it didn't correspond with peak panel output.

12-02-13, 06:28 AM	#5
stevehull Steve Hull Join Date: Dec 2012 Location: hilly, tree covered Arcadia, OK USA Posts: 826 Thanks: 241 Thanked 165 Times in 123 Posts	Got it. The Enphase TRUNK cable is limited, not physical issues other than that. Given that, what would your recommendations be for the maximum number of inverters per string? TIA, Steve __________________ consulting on geothermal heating/cooling & rational energy use since 1990

12-02-13, 08:12 AM	#7
pinballlooking Super Moderator Join Date: Jun 2013 Location: SC Posts: 2,923 Thanks: 172 Thanked 564 Times in 463 Posts	I would max out each run I did not do that and when and if you upgrade it will help if you max each run. But I would center feed so there is no more than 5 micreinverters before being tied into a Jbox this keeps the voltage rise lower. How far away it your array going to be from your house? I put in 40 modules thinking I would never put more in but it soon wanted to zero out and added more solar quickly. The EMU can handle 17 per run with the M215 Last edited by pinballlooking; 12-02-13 at 08:22 AM..

12-01-13, 08:23 AM	#1
stevehull Steve Hull Join Date: Dec 2012 Location: hilly, tree covered Arcadia, OK USA Posts: 826 Thanks: 241 Thanked 165 Times in 123 Posts	Enphase microinvertors (M215) question Not sure where to ask this, but here it goes. How many Enphase microinvertors (M215) can be put on a string. I see 17 are listed, but this is for a 20 A circuit breaker. I am needing about 40 panels for a 10 kW system with two rows of portrait panels (each row 20 panels). Can I do a 30 amp breaker, use a larger wire gauge and put 20 invertors on a string? Thanks, Steve __________________ consulting on geothermal heating/cooling & rational energy use since 1990

12-02-13, 12:23 AM	#4
pinballlooking Super Moderator Join Date: Jun 2013 Location: SC Posts: 2,923 Thanks: 172 Thanked 564 Times in 463 Posts	Yes the NEC requires the same here.The Enphase trunk cable is not rated for more than that.That is the limiting factor that keeps you only having 17 microinverters with M215 and you showed the math why you need a 20 amp breaker.

12-02-13, 08:04 AM	#6
gasstingy Journeyman EcoRenovator Join Date: Feb 2010 Location: Arab, AL Posts: 491 Thanks: 109 Thanked 49 Times in 43 Posts	You may also want to check and see how many inverters Enphase says the EMU will accommodate. When I bought mine, my EMU manual said it could only handle a string of 14. That was from early 2009.

12-08-13, 05:31 PM	#8
where2 DIY Geek Join Date: Apr 2013 Location: Sunny Florida Posts: 401 Thanks: 74 Thanked 83 Times in 73 Posts	I designed my system with two trunks. Each trunk has 10 inverters. My goal was to fit 20 inverters and panels on my second floor roof, and this was the most efficient method to get to that goal. I considered center feeding since I had a gap between a group of 6 panels and a group of 4 panels in a row (had to avoid a plumbing vent stack). I weighed the pro's and con's and finally decided against center feeding since the best logical location for my weather head and roof penetration was at the upper left corner of the array. My run from the second floor attic to the combiner panel on the back of the house is all #10AWG UF. Inside a junction box in the attic, I transition from #10 AWG UF to a #12 AWG 4-conductor TCER cable to go up the weather head to a custom Hubbell-Weigman trunk cable termination panel on the roof. At that point, I transition to the #12 AWG Enphase trunk cable. Looking at my graphs from today, a couple of my inverters saw 252v AC today. No error messages about the voltage, and it didn't correspond with peak panel output.