Tripping breaker [RE-wrenches]

Jeff Irish jeff at hvce.com
Thu May 3 05:35:42 PDT 2007


Andrew,

Some ideas...
1. Try replacing the breaker; they do have manufacturing tolerances and you
can get a poorly tuned or bad one.  I've seen a few.
2. Check all connections on your AC side for tightness and check wire sizes.
3. What voltage is the inverter seeing when it trips out?  What resistance
do you measure from the inverter to the breaker?  Don't know where you are
located, but in the NE this time of year people are turning off their
heaters and the utilities are beginning to crank up their voltage for peak
summer load and we see an rash of high power tripouts at peak sun due to
voltage rise on the AC side.  Manifests itself in all sorts of weird ways.

Jeff Irish

-----Original Message-----
From: Andrew Truitt [mailto:atruitt at gmail.com] 
Sent: Wednesday, May 02, 2007 4:39 PM
To: RE-wrenches at topica.com
Subject: Tripping breaker [RE-wrenches]


Wrenches,

We are having issues with a backfeed breaker from a Fronious IG 3000
tripping.  Here is the situation from what I have been told:

- The 200A main panel is loaded with about 500A of breakers per pole
(many tandems).
- The initial 25A backfeed breaker was replaced with a 30A and moved
further from the main breaker on the busbar with no effect.  The
breaker is still only 1/2 way down the busbar, though.
- The breaker trips about twice a month, generally on sunny days.
- Fronious has examined the info from the data logger and can see
nothing wrong with the inverter.  Even more telling: the 16A AC
breaker in the Fronious hasn't tripped once.
- None of the other breakers in the panel are tripping.
- The run from the inverter to the main panel is 15' of #6 UF that
runs behind a 900 lb refrigerator that has not been moved but the rest
of the run has been visually inspected and appears fine.

First off, I know that this is a jacked up inter-tie - it was done by
an independent electrician a year ago who I would not ever let touch
one of my systems on penalty of toenail removal Wierd-Al-Yankovic
style.

My guess - there is a ground fault in the UF behind the fridge that is
so slight that it only occurs at max current.   But wouldn't that trip
the Fronious breaker?  If an overheated busbar were the culprit then
ours would not be the only breaker tripping, especially not after
changing it and moving it.  If replacing the wire doesn't do it then I
am inclined to try a supply-side tap but I'm just not convinced that
it will help unless there is something about the fact that the breaker
is backfeeding that makes it more prone to trip than the load
breakers.

Any other ideas?

I am going down to take a look for myself later this week with some
10-2 MC-lite and bible.


Andrew Truitt
Standard Solar Inc.


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