Hi all,

got a weird issue. In an upstairs bedroom, I have a computer that is
running off a UPS. After investigating the wiring in the house, I have
found a significant number of grounds "bootlegged." Little by little I
am picking away at them, but until spring, the upstairs will remain as
is because it's darn cold in the attic at the moment.

So here's the deal. I have determined that there is one properly
grounded outlet in the room where the computer is, because that outlet
is fed directly from the breaker panel, and that homerun is in BX not
the cloth covered Romex that the rest of the concealed wiring is. So as
a stopgap until I get around to fixing everything correctly I wanted to
make sure that the computer's UPS was plugged into that particular
outlet for proper surge protection. I bought a heavy extension cord,
unplugged the UPS from the outlet that it was plugged into, plugged the
extension cord into the correct outlet. Then I plugged the UPS into the
extension cord, and the lights went out. Reset the breaker, figuring
that I just made an arc, if I plugged it in faster it would be OK. Same
effect. Reset the breaker, plugged the UPS back into the outlet that it
was using before, and everything is fine. This is a less than year old
APC unit.

Is there some fundamental incompatibility between this UPS and the AFCI?
I'm wondering if the UPS tests for the presence of an earth ground
(there is a "building wiring fault" light on it) and if so does that
cause enough current to trip the AFCI? (I wouldn't have found this
before, because the outlet into which it's currently plugged is not
grounded but has the ground bootlegged to the neutral.) I've heard that
some AFCIs are also GFCIs is why I'm asking. The AFCI is a Siemens
Q115AF breaker in the breaker panel.

I'll replace the receptacle in the morning (once it's light out) and see
if that solves the problem, but I'm not sure what kind of fault could be
in a receptacle that would cause a breaker, AFCI or not, to trip only
when a load is connected to it but not when a plug is inserted.

Does this mean also that I run the risk of having the AFCI trip if the
surge protection of the UPS kicks in?

Should I just give up the idea of having everything "to code" and ditch
the AFCI and/or investigate the possibility of running a dedicated
circuit to that bedroom to feed an outlet solely for the computer, not
protected by the AFCI?

any thoughts greatly appreciated...

nate

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