Can bad motor controller disable entire system?

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  #1  
Old 06-30-13, 01:47 PM
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Can bad motor controller disable entire system?

Hi folks:

I have a Trane Air handler with a Aprilaire 6303 controller. The trane unit has a GE ECM 2.3 half horse motor in it. The moto has what appears to be a soft-start speed controller in the end bell housing.

My symptoms: No operation at all. No movement at air handler or outside unit.
I put the thermostats in "Fan Mode" to see if the blower comes on but no go.
I checked the output of both transformers. Both @ 27VAC.
I checked for 230 VAC pre-contactor in the outdoor unit. OK

So my questions are:
a) if there was a problem with the outside unit wouldn't my blower come on regardless?
b) I thought the outside unit came on prior to the blower motor coming on to pre-cool or pre-heat the A frame coils. If my blower is bad would that influence the outside unit? I thought the outside unit would come on and just let the A frame freeze over if the blower wasn't running.
b) There are so many wires running into the GE motor. I have no way of knowing which does what. is there feedback to the system if a blower controller is not responsive? Is there a quick way to test this type of motor/speed controller?

My gut feeling is that it is something simpler but I just need a nudge in the right direction.

Thanks a million!
 
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  #2  
Old 06-30-13, 02:53 PM
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With the thermostat set for cooling & well below room temp you need to check some voltages at the air handler. Check R to C should be +/- 24VAC. Check R to G & R to Y both should be zero VAC. If voltage R to C is not as spec'd check for blown fuse. If R to G &/or R to Y show +/- 24VAC, you either have a thermostat problem or a broken wire.
 
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Old 06-30-13, 05:50 PM
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Thanks for the rapid response

Thanks Grady!

Wow that was quick.
Even better than the response time of the local $emergency$ repair outfit.

I will follow your troubleshooting guidelines and post my results.
 
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Old 06-30-13, 07:07 PM
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Test results

OK so like I thought R to C provided 28 VAC.
R to G and R to Y also provided 28VAC, which means something is bad per your directions.

This Aprilaire controller is a two zone controller.
So now I guess I have to troubleshoot either of the two thermostats or ultimately the controller.

So what wires should I cross at the air handler to get the system to fire up.
I would like to verify the air handler and outside unit are operational.
At least that way I could bring the temp of the house down tonight, unplug it after I get to a comfortable level and dig thru the thermostats tomorrow.

Thanks!!!!
 
  #5  
Old 06-30-13, 08:54 PM
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I got it to run

So I jumped R to G hoping to get the blower to come on.
Silly me forgot this was a smart motor so there is a long built in delay (about 30 secs) before the motor began to gradually spin up.
I was expecting it to buzz up to speed the minute the Green wire made contact.
After that I jumped the R to Y and I could here the refrigerant flowing.

So thank you very much.
At least now I can bring the house down to a modest temp and then take the system off-line until tomorrow. Then I can dig into those thermostat wires.
 
  #6  
Old 07-01-13, 03:27 PM
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The problem is likely in that stinking zone control. Your best bet is to tape a dollar to it & set it out by the road. At least somebody will have something when they find it. I've never seen a zoned system which worked as well or efficiently as two separate systems.
 
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