[RE-wrenches] Can I handle the voltage drop?

[Gary Handelin]

Mark,

Enphase actually has a pretty good explanation of voltage drop calculations
in their downloads- it's under application notes and details the drop
through their cable so you can determine what voltage each of the
micro-inverters will see.  From that you can calculate additional losses and
see how close you are getting to the high limit.  You also need to know your
starting point- the foothills in CA have a lot of areas where nominal line
voltage is right up at the max allowable to start with, leaving very little
headroom.

Gary Handelin, P.E.

Solar Independence

 

From: re-wrenches-bounces at lists.re-wrenches.org
[mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Nick Soleil
Sent: Tuesday, February 15, 2011 10:01 AM
To: RE-wrenches
Subject: Re: [RE-wrenches] Can I handle the voltage drop?

 

Hi Mark:
    I wouldn't feel comfortable with that scenario, either.  Many inverters
do shut off at 254V-255V, but most of them can be adjusted if you have the
software and laptop for the job.  Enphase generally shuts off when the AC
voltage reaches 258V-259V.  Keep in mind that just the Enphase cabling can
add an additional 1.75% to the rise.  I break my Enphase circuits into two
sub-circuits of half length.
    Enphase is defintitely more tolerant of voltage issues than other
inverters.  Xantrex is the worst, but can be adjusted.

 

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: Mark Frye <markf at berkeleysolar.com>
To: RE-wrenches <re-wrenches at lists.re-wrenches.org>
Sent: Mon, February 14, 2011 7:42:11 PM
Subject: [RE-wrenches] Can I handle the voltage drop?

Folks, 

I am working on a proposal. It's a ground mount 300+ feet from the meter.
There is an existing, near by run of #2 copper I can tap into. The desired
system is relatively large, 64 amps AC max. I have modeled the yield using
PV watts hourly data, applying a power loss based on the voltage drop at the
varying current. This model shows a 3% loss in annual yield with the #2
copper. Because of the economics of the system, we can absorb this loss.

My concern however is that I do not want the inverters to shut down when
operating at higher currents. I do not want a high AC line voltage fault due
to the voltage drop on the line. At the 64 amps max, the drop  would be
about 4%. Of course all the manufactures I talk with recommend keeping the
drop on the AC below 1.5%.

I am looking at using Enphase inverters which spec an AC voltage range up to
264V, or 10% above 240V nominal. 

What experience have folks had out there? How far can one realistically push
the 1.5% limit and still avoid AC voltage faults when there is high voltage
drop on the line?

My guess is that everything would work out fine, but I stand to loss a huge
amount of energy if the inverters are spending all their time faulting and
resetting during daily peaks.

  
Mark Frye 
Berkeley Solar Electric Systems 
303 Redbud Way 
Nevada City,  CA 95959 
(530) 401-8024 
 <http://www.berkeleysolar.com> www.berkeleysolar.com  

 

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