Bad Condenser Fan Motor & DOB Timer - Am I on the right track?


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Old 08-03-12, 09:48 PM
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Bad Condenser Fan Motor & DOB Timer - Am I on the right track?

Hi all,

We have a retro fit AC system that is a little over 15 years old. They put in separate systems for upstairs and downstairs.

Yesterday, the downstairs system stopped working. The blower fan was on but the condenser and condenser fan would not come on. Pressing the plunger on the contactor turned on the compressor but not the fan. The fan for the upstairs unit was replaced a couple years ago, but not the downstairs.

So, I switched the fan motors out so the downstairs would work as it is more important. I did that and everything worked fine.

Today, after the system was back on for about 24 hours, the same thing happened. I could press the contactor button and it would come on. I checked the 24V transformer and all is good there.

After some digging here and there I determined that the Delay On Break Timer has some corroded or burned traces on the circuit board. I bypassed the DOB timer and everything worked, but then stole the DOB from the upstairs unit. The damage on the bad DOB doesn't look recent.

So I'll have to order some of these. Are these something that are likely to go bad after this many years or could something else be causing all of these issues all at once? We have had a good amount of power outages this summer. During one power outage, power was coming on and off ever 5 minutes for about a couple hours... and I eventually shut the main to the house off.

Any other info or tips would be great. The system is all Rheem equipment.

ALSO- Is the DOB timer even necessary since I now have digital, battery powered stats? The digital stat makes you wait between cycles so I imagine this is doing the same thing for me. If I don't need the DOB I may just bypass it. I can't even find this part number (Watsco EAC-426/4-030-B).
 
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Old 08-04-12, 06:04 AM
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you do need the DOB timers if you have power outages like that. The thermostat has no way to tell that the power went out if they are not wired with a C connection.
 
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Old 08-04-12, 07:10 AM
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Well, the on/off every 5 min was a very rare occasion. I'll try to find replacements.
 
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Old 08-04-12, 07:12 AM
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Typically then, no, they are not needed do an internal DOB in the digital thermostat. If you have a lot of power outages then I would recommend a DOB in the a/c as well.
 
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Old 08-04-12, 07:14 AM
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I am having trouble finding this part number. Will any 24V/1A do? What is the time setting of this unit. My guess would be like 30 seconds? I see that many are adjustable.

Watsco EAC-426/4-030-B
 
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Old 08-04-12, 07:15 AM
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they should be 5 min. I typically use [h=1]ICM206B.[/h]
 
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Old 08-04-12, 07:23 AM
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Great, sounds good. Looks like that model replaced this same series of Watsco, but is adjustable.
 
 

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