Condenser relay work close

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Old 05-04-18, 04:34 PM
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Condenser relay work close

I was replacing the contactor on my compressor as PM (AC is 16 years old).
Now my compressor won't turn on. It seems like I am not getting 24 volts at the control board in the furnace so the compressor doesn't turn on.
When the thromostat demands, the furnace blower turns on but the compressor does not.

Did my control board die? Problem with the thermostat?

Apprecaite any comments
 
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Old 05-04-18, 05:06 PM
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Did you turn off the power to the furnace before replacing the contactor? If not, you probably shorted out the 24VAC control voltage. Check to see if there is a fuse on the furnace and if it's blown. The only thing that seems odd is that if you lost the 24V, I wouldn't expect the furnace blower to come on.
 
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Old 05-04-18, 05:19 PM
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Thanks for chiming in. I had the power off at the panel by the compressor but obviously something happened. To much of a coincidence to think it wasn't me <grin>
THe 24v fuse is not blown. The board is generating 24V as the furnace blower is working as well as the sump for the drain. It is possible that the furance blower is running all of the time though. WIll check that next.
Ian
 
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Old 05-04-18, 05:29 PM
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You need to check for 24vac at R and C. If a fuse was blown...... the blower would be running non stop.

You need to turn the power off at the air handler when working on the 24vac wiring.
Also remember that there is a 5 minute compressor delay on most thermostats.
 
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Old 05-04-18, 06:22 PM
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Think I figured it out THe thermostat can no longer send 24V on cooling demand. IT still controls the fan correctly so temporarily I have hooked the compressor up to the fan control (on Auto) until I can determine if I can fix the thermostat ( a Honeywell Lyric Round). WIll see what I can do tomorrow.
 
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Old 05-04-18, 07:46 PM
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That sounds like you blasted the control base. Not likely to be able to repair it.
 
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Old 05-04-18, 07:48 PM
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Must have done something stupid. Live and learn. Thanks for the comments.
 
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Old 05-04-18, 08:08 PM
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Most of the other Honeywell stats use relays. I believe that uses electronic switching.
Just like the Nest..... it's not too forgiving when shorted.
 
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