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Honeywell "wait" after many rapid power outages - possibly the float switch?

Honeywell "wait" after many rapid power outages - possibly the float switch?

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Old 08-04-20, 01:58 PM
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Honeywell "wait" after many rapid power outages - possibly the float switch?

My Honeywell RTH8500 thermostat has a "wait" message and the compressor is not turning on. During the tropical storm that just went through this afternoon I had probably thirty power outages that lasted for a split second over the course of an hour. But they were enough for my UPS battery backup to kick in every time so they were more than just brownouts. Now my thermostat won't get out of "wait" mode. I've tried throwing the circuit breakers for both the evaporator (which also powers the thermostat) and the compressor, with no change.

I also have an overflow float switch on the system that breaks the yellow wire. Would that be the cause of it? (I really don't want to go up in the attic and check lol.) I'm thinking that if the yellow wire were open the blower would still run when the thermostat was calling for cooling, I just wouldn't actually get any cooling? Right now nothing runs. (But if I switch from Auto to On the blower/fan does in fact run, the compressor doesn't).

Thanks

Update: The thermostat keeps restarting every 5-10 minutes. Just powering off and restarting. (As I said in my post, it's powered from the evaporator in the attic.) Thoughts?
 
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Old 08-04-20, 03:15 PM
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On a call for cooling..... the wait light should come on for 5 minutes and then go out.
Some wait lights flash for the 5 minutes and then go solid when the condenser starts.

If the float is in the yellow wire.... it won't interrupt the t'stat.
You really need to check from R to C to see if power is failing.

You may possibly have a short on the yellow/Y wire and when it powers up every 5 minutes and shorts.... it cause the stat to reset. You could try disconnecting the Y from the stat and see if it still has a power problem.
 
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Old 08-04-20, 03:16 PM
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The contactor does not look great with the soot marks, but it does get 8.8 ohms of resistance though across the low voltage contacts. This is sounding more and more like the overflow float switch opened the yellow wire? Can anyone confirm that blower would not run if it was calling for cooling (in addition to the compressor)?

edit: I was replying with this before I saw your reply @pjmax


 
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Old 08-04-20, 03:36 PM
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Sorry when you say check from R to C you mean take the faceplate off and use a multimeter in between them? I also have an Rc if that matters.

It does sound like a short on the yellow wire, because the thermostat sounds like it's clicking to turn on cooling a split second before it shuts off entirely.
 
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Old 08-04-20, 06:13 PM
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R and Rc means two power sources.... like A/C and separate furnace.
Is that what you have ?

If the yellow line opens the condenser won't start and the stat shouldn't cycle.
Put you meter on Rc and C. You should see 24vAC.
While keeping your meter connected.... jump from Rc to Y. If you lose the 24v...... there is something shorted on the Y line. Your contactor should be in the area of 10-20 ohms. Depending on your meter... 8.8 ohms could be ok. The contacts have no affect on the coil being shorted.
 
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Old 08-05-20, 04:15 PM
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I do have a separate hot water boiler in addition to my A/C system.

I got it fixed this morning. Turned out to be a pinched wire on the float switch where it came out of the cabinet...must have just vibrated while turning off/on and shorted it. I repaired the wire and it's working fine now.

I hate going up in the attic (through a crawl space in the closet)!
 
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Old 08-05-20, 05:44 PM
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Yes sir..... a pinched line to metal would definitely do it.
 
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