On Tue, 7 Jul 2009 08:02:42 -0700 (PDT), windcrest
wrote:

On Jul 7, 7:24Â*am, cj wrote:
i had my transformer in my heil furnace replaced last winter and the new
one hums rather loudly...is that a sign of a problem?also, does that
mean that the transformer is using electricity even if the furnace is
not running?

thanks, cj

There are a couple of other reasons a transformer will hum besides DC/
interference on the line or loose laminations/windings.

If a transformer was designed for 50Hz and you are using it in the US
at 60Hz it will hum, maybe the guy put on the wrong transformer.

If the transformer is underrated for the load it will hum more (and
also heat up and fail early) in this case up the rating of the
transformer. Maybe he was cutting corners by using a transformer that
was rated under or just at the load level, the cost of a transformer
is proportional to its current rating with all other factors the same.

If your mains voltage is too high the transformer will hum more, you
cant do anything about this, but a high quality transformer will
handle it better.

A poorly designed transformer with high magnetic field levels will hum
more, again this is probably your problem, a cheap-ass transformer.

Likely Chinese - or possibly Mexican manufacture - most definitely
"cheap" even if not low cost. ALL transformers hum a little bit - and
all use SOME current even with no load, but the better ones hum less
and use less power.