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Default Relay contacts sticking

"Innes Cathcart" wrote in message
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On Mon, 29 Mar 2004 22:50:11 +0000, Kelly E Jones wrote:

I've got a relay that controls the submersible pump which supplies
water to my house. (For reasons I won't go into, the pressure switch
and the pump power circuit are separated by a great distance, so the
pressure switch supplies a 30V signal to the relay which actually
switches the 240V to the pump). Yesterday, I noticed water coming out
of my overpressure relief valve, and after some frantic
troubleshooting discovered that the relay had stuck 'on' (the contacts
were in the 'on' position despite no juice to the coil). The relay is
being used within the current/voltage for which it is rated. A gentle
push with a screwdriver separated the contacts, and after that they
seemed to work fine.

Any idea what caused this, and how to prevent it in the future?

Thanks,

Kelly


Not too sure what caused it, and unless you can find the cause and
eliminate it I'll bet it will happen again. What make/model of relay are
you using? Perhaps a sealed one would be better. good luck,

Innes


Relays used to switch inductive loads, such as your pump motor, are prone to
arcing when they switch on and off. This is quite normal, and unless some
sort of arc suppression (snubber circuit) has been used across the contacts,
they will eventually fail. Failure modes are either of two conditions: one
is that they stick together, as you have found; the other is that they will
fail to make contact at all. The arcing is the cause of both types of
failure.
The solution to your problem is to replace the relay, or if they are
separately replaceable, the contacts themselves. Then enjoy your water
until the contacts fail again. That's just a fact of life when you live in
the boonies, as I do.

Cheers!!!!!!
--
Dave M

Good judgement comes from experience, and a lot of that comes from bad
judgement.