RE: Buzzing relays? Anyone help?

["Paul Gale" <groups@xxxxxxxxxxxxxxxx>]

I had a similar problem with my Comfort installation - the two power supply
transformers are bolted to the metal case, this in turn is bolted to a
plasterboard wall, the other side of the master bedroom. Result = loud
buzzing, especially noticeable at night :(

Solution: I mounted the transformers in the metal cases using rubber tap
washers. I also mounted the cases to the wall using slightly bigger
washers. This means that the cases are acoustically isolated from the wall
and no more buzzing :)

You may be able to do the same, depending on what type of fixing you use to
fix the din rails to the wall. The key is to not let any metal or solid
(screw) firmly touch both the wall and rail and allow the vibrations to be
transmitted. You may want to have a washer between the screw head and rail
and also between rail and wall. As long as the screw body does not then
touch the rail, you should notice a reduction in transmitted noise.

Hope that helps - let us know if it works - it's cheap too :)

Paul.



-----Original Message-----
From: mailinglists [mailto:mailinglists@xxxxxxx]
Sent: 22 January 2005 13:31
To: ukha_d@xxxxxxx
Subject: [ukha_d] Buzzing relays? Anyone help?


After a successful install of my automated hot water/central heating
controls (with many thanks to Neil Fuller for his donation of a foot of
DIN rail to securely mount the relays!), I've just noticed a small but
annoying problem.

The relays buzz slightly when they are off. The installation is
basically two big 240V relays connected into the CH/HW wiring, the
relays have 240V coils that are switched by a pair of X10 appliance
modules due to the distance between the server and the airing cupboard.

At a guess I'd say that the leakage current from the modules is enough
to make coils buzz. The problem is exacerbated by the relays being on
one side of a plasterboard partition wall, which seems to amplify the
buzz into the next room. Aside from the buzz everything else seems to
have worked just fine for the last few weeks.

The $64K question is how to stop the buzz? Any ideas?

Lee