transformers produce AC not DC

> First, let me agree wholeheartedly, that, indeed, 120v AC can be quite
> lethal.  However, let me disagree that 10V DC will give you anything more
> than a funny buzz.

This is not amusing. 10V DC CAN kill you if it is applied to wet skin
ESPECIALLY if you have a cut in the skin. Low DC voltages are less
likely to kill people than large AC voltages but so what.

> Why this tirade?  I just wanted everyone to be clear on the fact that the
> real benefit of using a transformer for undergravel heating cables is NOT
> that you reduce the voltage from 120 volts to 10 volts (or whatever).  THE
> REAL reason is that you convert a potentially fatal AC line voltage to a
> much less harmful DC voltage.

Transformers do not convert AC to DC. Yes AC is more likely to cause
cardiac fibrilation than AC; it just means the miniscule amount of
current required to do the job is less. I don't want to counsel anyone
on this list who is not technically qualified and trained to try to
build any electrical devices to be used in or near water. Categorically.

The use of a transformer to reduce AC voltage BY ITSELF does not
render electricity safe near water. Low voltage DC devices that are
safety approved are the only kind that I would consider for an
undergravel heating device. Safety approved 120/220V AC devices
are fine for tank heaters or powerheads.

I'm speaking as a responsible engineer when I say this because we take
an oath similar to one for doctors which requires that we safeguard
human lives. I also think people should heed the advise of George
Booth because he is an electrical engineer. Remember all you engineers
or do-it-yourself electrical wizards, not everyone reading this
list understands the safety issues concerning electricity. I used
to work everyday with low voltage DC powersupplies on computer
equipment and they DRILLED safety into our heads.

OK, sorry for this. I just want it to be perfectly clear.
Safety first.