Ground fault [RE-wrenches]

[Christopher Freitas - OutBack Power]

> Your comments suggest that nothing will prevent some problems from
> occurring, if GFIs and fusing aren't able to provide protection.

Yes - nothing can prevent some problems from occurring - if you make 
something idiot proof they will make a better idiot... The ultimate 
solution would ground fault protection, fuses in the positive and 
negative and all of the circuit breakers locked in the OFF position at 
all times! 

>In over 20 years of installing battery-based power systems, I've 
>never installed a GF protection device at the PV or battery primary 
>>wiring, seen one installed by anyone else, or seen any damage as a 
>>result of not installing one. 

You probably install systems well and live a charmed life... 

>for this occurrence to trigger mass installations of ground fault 
>protectors, which are problematic in themselves

I hardly would say that the PV ground fault protection system is 
problematic (which was first offered by Trace and then copied by Pulse, 
AEI GC1000/MultiMode and SMA Sunnyboy inverters).  Its an extremely 
simple design, uses very solid, well protected components (usually) and 
is non-electronic (so is reliable).  For someone who has never installed 
one or seen one you have a pretty strong opinion ... 

When we first started shipping them at Trace, I said I would answer all 
of the tech calls on them myself - I was amazed at the number of people 
who were having problems with them - but it turned out to be not the 
PV-GFP design but was that the systems had real legitimate installation 
problems... of course we only heard from the people who had problems...  

 
> If this issue is so all-fired important, why not include ground 
>fault protection in and for ALL DC control and conversion devices as 
>standard, from the factory? Hmmmmm?--- 

Gee - that is what SMA and AEI decided to do in their inverters.  We 
aren't doing this at OutBack because you do not need to have one for 
each inverter - just one for the system with a disconnect pole for each 
charge controller.  Its an easy option to add into our PSDC enclosure.  
We let you decide if you want it that way.  With our design you can also 
utilize multiple OBDC-GFP/2 units for larger systems with more than two 
charge controllers.

The design of the GFP system handles both DC and AC ground faults.  I 
have more than once found AC voltage/currents mixed with the the DC 
voltage/current - improper installation and internal inverter faults 
were the cause usually.  A GFP system would have stop it and alerted the 
customer.  But I usually am out in the field with a O-scope and check 
for such problems,  so I find them.  These systems were often normal 
operating systems with no signs of problems.

The GFP system we use will in fact respond to a ground fault anywhere in 
the DC system - not just from the PV array wiring.  This is really nice 
when part of the system is batteries which can deliver large amount of 
power into a fault. I had a friend who's GFP was tripping due to a 
leaking cell in a high voltage battery bank - try to find that one 
without killing yourself doing it.   

I suspect that a good portion of PV systems are installed even today 
with DC, AC or DC/AC ground faults and no one notices - and I 
acknowledge that only a few will result in fires.  Including a GFP will 
find these problems 99% of the time, I bet.  I think stopping a few 
houses from burning down is pretty important to me. 

The bottom line it is cheap and fairly easy to install.  A PV system is 
a LOT safer with it included.  It can save your butt if something does 
go wrong or a problem with a product occurs.  It assures you that the 
install is ok when you open your beer at the end of the day. I just feel 
better with them on the systems I am involved with.  

Seems like a no-brainer to me... 
  
Christopher Freitas
OutBack Power Systems, Inc.
cfreitas at outbackpower.com  www.outbackpower.com
Tel 360 435 6030  Arlington WA USA

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