[RE-wrenches] GFP and multiple charge controllers

[boB at midnitesolar.com]

A lot of good replies have come by here but here goes another one...

The GFP cannot be used for dual purpose as a disconnect for battery
or PV input and you are not allowed to un-ground the system by turning
off the DC input or output breaker.

4 AWG should be fine for 80 amps. If you need/want to use smaller wire
than that required for an 80 amp GFP, MidNite makes a 63 amp GFP.

boB




On 4/17/2012 6:42 PM, William Miller wrote:
> 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  <http://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 <mailto:nathan at arcticsun-llc.com>
>>> Office: 907/457-1297
>> _________
>
> Voice :805-438-5600
> email: william at millersolar.com
> http://millersolar.com
> <http://millersolar.com/>License No. C-10-773985
>
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