"Pszemol" wrote in message
...
"George" wrote in message
news:TRZee.61608$WI3.54789@attbi_s71...
Hm... I do not advocate agains the GFCI.
I just said I do not expect it doing any change to his measurements!

If you read the whole thread you would found out he measured 48VAC
between tank water column and the cooper pipes for tap water...
I just know voltage measurements of this kind are worthless.
Yes, very similar to pH measurements of RO/DI water... ;-)

It will, in fact change his measurements completely, because 48 VAC will
likely carry significant amperage (more than 4 or 5 milliamps), which is more
than enough to trip the GFCI, and completely shut down everything. So after
this happens, he shouldn't read any voltage, and definitely no amperage.

I am taking from above that you did not read the original poster...
His 48VAC reading was even after he has unplugged all his devices.

Please read his original words

Could you explain then how GFCI could influence his voltage readings ?

No, what he said was "I measured the AC voltage from the copper inlet pipe to
the tank water -- by sticking the probe into the water. Was I surprised. I
measured 48 VOLTS AC !!!! I then began unplugging equipment. "

So he unplugged equipment 'after' he measured 48 volts, which means that
equipment was leaking current into the tank. He then proceeded to describe the
voltage he got after he unplugged various appliances. He also said in a later
post "I am installing a GFCI this weekend. I will then see what measurments I
get. Should have done this anyway - being around water." So we will have to
wait and see what his results are. I suspect that if he plugs all of the same
equipment (the ones that showed voltage leakage according to his measurements)
into that GFCI, it will trip the circuit, shutting off the power. He will
likely have to replace some of this equipment in order to prevent the GFCI from
tripping.