12-01-13, 08:23 AM | #1 |
Steve Hull
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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
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12-01-13, 01:55 PM | #2 | |
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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. Last edited by pinballlooking; 12-02-13 at 12:33 AM.. |
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12-01-13, 08:02 PM | #3 | |
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12-02-13, 12:23 AM | #4 |
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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.
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12-02-13, 06:28 AM | #5 |
Steve Hull
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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
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12-02-13, 08:04 AM | #6 |
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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.
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12-02-13, 08:12 AM | #7 |
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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.. |
12-08-13, 05:31 PM | #8 |
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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. |
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