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Posted by Mo Hoaner on October 21, 2007, 7:33 pm
>
>>
>>
>>> Thanks for the reply. Yes, we can "wire it before", as you say.
>>> However, since the furnace is all metal and sitting on a concrete
>>> floor, we thought that running the furnace _through_ the GFIC would
>>> provide some safety factor in case an internal short happens in the
>>> furnace. In other words, if there would be no problem having the
>>> furnace run on the GFIC, we would prefer to do it that way. Thanks. -
>>> Jesse
>>
>>And, that is the "perfect" situation. You've got no way to access anything
>>live, and the metallic outer case is bonded to a grounding conductor. It's
>>the same situation as with a refrigerator plugged into it's outlet next to
>>a
>>sink: Just have your electrician talk with your HVAC guy, and they'll
>>work
>>it out.
>>
>>The fact that you don't have a good understanding of the application and
>>function of a GFCI means that you probably shouldn't be playing
>>electrician
>>/ furnace installer. "In case an internal short happens in the furnace"
>>means that either you'll have a line to grounded conductor (neutral)
>>current
>>flow which will trip a properly sized protection device (breaker / fuse),
>>or
>>you'll have a line to grounding conductor ("since the furnace is all
>>metal"
>>("sitting on a concrete floor" really has no bearing on anything) current
>>flow which will trip a properly sized protection device (breaker / fuse).
>>
> Thank you for the info. And, you _may_ be right. Or, not. A few
> things. A licensed installer for the furnace (a swap for an
> oil/radiator system) installed the electrical box with a furnace
> cutoff switch and an outlet. At the time, that was the only outlet in
> the basement. The outlet was 2 pronged w/o a ground. Since that
> outlet is sometimes used when servicing the furnace - A/C system, we
> thought that it at least should be grounded.
There is no "may be right" about ANYTHING I wrote. "Or, not" does not enter
into my post. Go fuck yourself.
> (BTW, when another licensed HVAC person installed a humidifier on our
> central system a few years ago, he plugged the humidifier into this
> outlet - after cutting off the grounding prong from the humidifier's
> power cord. I don't know if the grounding prong is essential, but I
> think that someone thought it was.)
He probably shouldn't have done that. That was something to ask back then.
> As for "in case a short happens in the furnace", this concern came up
> because about a week ago there was s sludge backup in the A/C
> condensate drain tube and that caused water to back up and then flow
> down over the furnace's circuit board (including its connection to the
> 120v line) and create a puddle in which the furnace was sitting. And,
> I discovered this by chance when I went down to the basement barefoot
> to get something and noticed that I was standing in that same puddle.
> This situation brought to mind a story in the news within the last few
> years (from somewhere in the US) about someone who was electrocuted by
> a window A/C unit. As I recall the story, the unit created a puddle
> on a concrete slab and the person was standing on the slab and in the
> puddle when somehow a short from the A/C unit zapped the guy and
> killed him. A breaker does not protect people in that kind of
> situation - and, as I understand it, that is what a GFI device is for:
> As long as you only draw 15amps from a 15amp circuit, if the current
> is going from your panel through your body and then to ground the
> breaker won't trip but a GFI breaker/outlet will trip. Now, the A/C
> story may be completely different from what might ever occur with a
> furnace in a basement, but to this mere civilian there are some
> troubling similarities.
It is. If the furnace is properly grounded, it does not matter if the thing
is full of water. There will be no potential between the water and the
concrete floor.
That's not what a GFCI is supposed to be used for. In the case of the window
AC plugged into what was probably a non-grounded outlet, a GFCI would have
saved his ass. And, application of a GFCI in a non-grounding application IS
spelled out in the NEC.
>
> Overall, those posting here about the GFI tripping for no reason on a
> freezing weekend when we are away - and they do trip mysteriously
> sometimes - make a good point.
>
> Again, thanks to you and to all of the others who took the time to
> make suggestions. - Jesse
Go fuck yourself.
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