Original message
| Dog Biscuit
 |  "Contactor Chatter"
, posted Sat 24 Jun 19:04  
This is a 208/3/60 contactor with a 24vac coil on a Lennox 5 ton
furnace/Condensing unit. With an initial 22.6vac available, just as the call for CU to act the voltage drops to 15vac and the contactor chatters and fails to engage. With a manual boost to the contactor it engages and the compressor starts and continues to run. Old contactor did same as the new one just installed. The thermostat is a single stage mercury bulb on cooling. On 3 other identical systems, 22.6 volts works fine.
1.) Should 22.6vac be enough to pull in a 24vac coil?
2.) On a call for cooling, what could cause the voltage to drop
to 15vac.
3.) Are contactors with a 24vac coil used much today?
(Yes, we removed all items between call for cooling and the contactor coil: IE: anti-recycle-timer, high pressure cutout, etc, on the low-voltage circuit.)
To err is human to repair divine
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Replies:
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| jimhermansen
| "jimhermansen" , posted Wed 9 Aug 21:47
try jumpering R and Y at the furnace. If the trans. is dropping to 15volts, this will not close the contactor. try a new tx or looj for bad connections.
jimher
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