[RE-wrenches] AC wiring loss on micro-inverters

[markf at berkeleysolar.com]

Nick,

Good to see other wrenches looking at this issue.  However, remember that
in the interconnect cable between the last and the second to last Enphase,
the current is small. If you really want to see how the loss is adding up
you need a more detailed analysis that averages the voltage drop for the
entire system of interconnect cables.

Mark Frye
Berkeley solar Electric Systems

> Hello wrenches and Marv:
>     How many Enphase inverters do you put on a single parallel string?
> The Enphase manual allows for up to 15, but I have found that a single
> string of 15 can have very high voltage rise on the AC wiring.  Up to
> 1.5% loss just on the Enphase cables, and that does not take into
> account resistance at the plug connectors or any home-run wiring.
>     15 inverters x 190 watts = 2850 watts
>     2850 watts / 240 Volts = 11.875 Amps (however at the beginning of the
> string it is 0 Amps)
>     Average Amps on the Enphase cables is 11.875 / 2 = 5.9375 Amps
>     length of contacts + internal wiring = ~6'
>     Total Enphase cabling length (6' x 15 inverters) = ~90'
>     5.9375 Amps @ 240 V running 90' on #14 AWG CU = 1.4% loss
> It is pretty hard to design for 1.5% voltage  drop if you have to size for
> 0% loss on your wiring!  I hope Enphase will increase the size of the wire
> in their cables soon.  Have you experienced issues with micro-inverters
> shutting off due to high AC voltages?
>
>  Nick Soleil
> Project Manager
> Advanced Alternative Energy Solutions, LLC
> PO Box 657
> Petaluma, CA 94953
> Cell:   707-321-2937
> Office: 707-789-9537
> Fax:    707-769-9037
>
>
>
>
> ________________________________
> From: i2p <i2p at aol.com>
> To: RE-wrenches <re-wrenches at lists.re-wrenches.org>
> Sent: Thu, June 10, 2010 4:50:47 PM
> Subject: Re: [RE-wrenches] Real world PV production
>
>
>
> On Jun 10, 2010, at 7:57:53 AM, "Kelly Keilwitz, Whidbey Sun & Wind"
> <kelly at whidbeysunwind.com> wrote:
>
> PV Watts VASTLY underestimate PV production
>>  in our area.
> PV Watts underestimates in Central Ca too.
>
> Don
>
>
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