Re: UGH Transformers

From: Jim Hurley <hurleyj at arachnaut_org>
Date: Wed, 22 Jan 1997 23:01:50 -0800

>>After talking to a few transformer suppliers I have concluded that
>>finding a transformer that does not have the primary and secondary
>>windings on the same core is just not practical.
> I have never use undergravel heaters, but I don't understand this
> issue.

When Uwe Behle posted the original DIY heating coil article, he
mentioned that the safest transformer has the primary and secondary
windings on separate bobbins.  Some transformers have the primary and
secondaries wound on the same bobbin or wound on the same metal core.
There exists the potential for the insulation of the wires to be
breached, thus connecting the primary directly to the secondary and
feeding 110v into your tank.  

Personally, I don't think this is a problem.  Use a good quality
transformer and don't pound on it with a hammer.  Or, if you're
paranoid, buy a Duplamat for about $300; for that price, it's probably
pretty safe.