David Nebenzahl wrote:

On 5/29/2009 4:21 PM William R. Walsh spake thus:

Then don't worry about it, if it's only getting warm, rather
than hot.

That's the thing. The outer surface of the coil does get hot after
it's been on for a while. It's too hot to stand touching it for more
than a few seconds. (It isn't so hot that you immediately pull
back--there is more than enough time to think "gee, this is somewhat
hot".)

On the other hand, it has been running trouble free for some time
now, and I can't find any evidence from the original unit it was in,
that the power was in any way limited to the relay, such as by a
resistor.

Not sure how helpful this is, but this reminds me a lot of a repair I
did to a house I lived in about 10 years ago. House had an old old gas
furnace whose gas control finally gave up the ghost. The control was a
standard one, it turned out, operated through the thermostat with a
24-volt transformer.

Seemed simple enough: I installed the new control, wired it up. It
worked, but as soon as the thermostat called for heat, it made a
really horrible buzzing noise (60-cycle) that could be heard through
the entire house.

I carefully checked the installation instructions and the existing
transformer, which was emitting as close to 24 volts a.c. as no never
mind. The control was clearly rated for 24 v.a.c. Called the place I
bought the control, who were as puzzled as I was. They finally gave me
another unit as a replacement. But after installing it, got the same
result: BZZZZZZZZZZZZZZZZZZZZZZ!

I even contacted the manufacturer of the control, who tried but
couldn't offer me any fixes.

I finally did what any reasonable tinkerer would do: inserted a
resistor in series with the control, which reduced the buzzing to a
soft, tolerable level. I had to determine the value by trial and
error, high enough to reduce the sound but low enough so that the
control's solenoid would engage reliably. After that, the furnace
worked fine, for several years.


I've seen AC relays where the shading ring has not been fastened
properly buzz like that ! Often a tap with a hammer and punch in the
right place solves the noise problem.

--
Best Regards:
Baron.