[RE-wrenches] GFP and multiple charge controllers

[Darryl Thayer]

Nathan, the problem should not be in the size of the GFDI breaker, put the GFDI between the array and the charge controller.  certainly your array voltage is 100 or greater, meaning you have 45 amps of less through the breaker.   Also if you have a large array parallel the arrays, and run each of the "hots" through each of the two breakers in the Outback dual GFDI,.  Also increase the series string count and use a HV controller, such as Apollo T80HV or Classic.  If depending upon climate, you might be able to work near 150 V string.  or 9000+ watts, you will not find a charge controller this size.  If you are working at 48 volts the largest charge controller is about 3600 watts.  If you are working at 24 volts, you will need three strings, and I do not know if there is a 4x80 GFDI available.  The Trace Xantres used to offer a 4x80 GFDI but I have not seen for several years.  
 
BTW I am not sure if code allows the Xantrex 60 with fused GFDI to be paralleled at all.  
 
BTW never connect charge controllers in parallel on the Array side. and if you are connecting on the battery side besure the charge controllers can talk to each other,  If the charge controller is charging the second charge controller may interpet the batteries to be full and not be charging.  Apollo T-80 can be paralleled,  the old MX60 would trick itself and did not charge well in parallel.  .    
 

________________________________
 From: William Miller <william at millersolar.com>
To: RE-wrenches <re-wrenches at lists.re-wrenches.org> 
Sent: Tuesday, April 17, 2012 8:42 PM
Subject: Re: [RE-wrenches] GFP and multiple charge controllers
  

Friends:

Here is a related problem:  If we use an 80 amp GFD (ground fault
detection) breaker, even for a very small array, we have to use 3AWG CU
wire from the battery buss to the breaker and from the breaker to the FM
or MX60.  This seems like a big hassle for 5 or 10 amps of
charging.  A variety of sizes of GFD breakers would be
helpful.

Here is a bigger problem:  GFD breakers don't really work.  All
they do is turn off the charge function in hopes that someone will find
the problem.  In the meantime, the negative-to-ground bond is
removed and module mounting framework could be energized.  PV GFD
breakers are completely different from standard AC GFDI (ground fault
detection and interruption) receptacles and circuit breakers.  The
AC versions interrupt power upstream, the PV versions interrupt power downstream from the fault.

See: 
http://millersolar.com/MillerSolar/case_studies/ground_fauilt/_ground_fault.html
for some musings on the subject.

As they say on TV: "There had to be a better way!"

William Miller





At 05:54 PM 4/17/2012, Kent Osterberg wrote:

Nathan,
>
>I don't think anyone makes a 100-amp PV GFP. The panel mount breaker model that's being used for the PV GFP doesn't include a 100-amp breaker.
>
>The Classic has a built-in GFP so you shouldn't need an external GFP for it. You will need to add a GFP for the FM60 - a single 80-amp GFP would work.
>
>You can use the dual 80-amp GFP and shut down both PV arrays at the same time if the GFP is wired to disconnect the PV array from the charge controller input. That's where Outback's instructions used to show the GFP, and it is a better place for it than on the charge controller output anyway. Midnite's instructions show the GFP on the charge controller input, but their 80-amp GFP is a single.
>
>
>Kent Osterberg
Blue Mountain Solar, Inc. www.bluemountainsolar.com 
>On 4/17/2012 11:08 AM, Nathan Stumpff wrote: 
>
>Wrenches,
>> 
>>In a job coming up I have a customer with an existing FM60 controller,  520 watt (!!) array. We are doing a ton of work, including adding a 4 kW solar array with Classic 150 charge controller. I am trying to figure out how to handle the GFP.
>> 
>>For the Classic, I need a 90 or 100 A output breaker minimum. 80 A is not an option. The OutBack dual GFP is 80 A, and so it not an option.
>> 
>>Is there a 100 A GFP breaker assembly I have just never seen? Is there a way to use the Classic’s GFP to run an external relay via AUX (to trip the FM60 output breaker at the same time)? Any ideas?
>> 
>>Thanks,
>>-Nathan
>> 
>>--
>>Nathan J. Stumpff - Arctic Sun, LLC
>>NABCEP Ceritified PV Installer #091209-175
>>nathan at arcticsun-llc.com
>>Office: 907/457-1297
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