excessive voltage drop across contactor

[resolutetech]

What voltage drop across a contactor is considered excessive and the contactor is declared no good.

[bananaboy]

The contactor should not have a big V drop, so you should be able to measure 25-26V when the unit is working.

[deanlin]

I usually recommend replacement if it reads .04v or higher

[danj]

Are you talking hi or low voltage? No drop on hi -- you usually need at least 24 v to energize the coil so what drop are you talking about?

[Edited by danj on 04-05-2005 at 09:59 PM]

[manfromsocal]

anything over half of a volt drop across the contact is too high

[resolutetech]

im talking about the high voltage drop across the contactor.

put your meter on voltage setting. place leads across open contactor and you usually see about 240 volts. energize the coil the contacts pull in, let system run awhile and now you read voltage across closed contactor. through the contacts that are now closed. i wish you could draw on here.

this is the voltage drop im talking about. my meter usually reads about .02 volts on a tipically good contactor. ok over years contacts burn because arcs form upon closing and resistance builds after repeated closing and burning. this resistance causes a small but growing voltage drop as the contacts age.

the company i work for has two electricians they feel the voltage drop is bad at .2 volts. i have heard another tech say .4 volts. i just would like to hear what most of you old pros think.