HVAC DIY biting me on the butt


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Old 10-08-13, 06:34 PM
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HVAC DIY biting me on the butt

I started out with the best intentions planning to stay within my skill set but as always...

Our HVAC unit has been replaced from the condenser to the outside evaporator. The gas furnace/blower component was left alone since it worked fine. It started humming often on start up so I knew that either my capacitor or motor was on the way out (turned out to be the motor, I could hardly turn it by hand). I got the information for the blower motor and headed to Grainger. Problem is, they were out of stock on a motor that exactly replaced mine so they offered me an alternative with a different MFD rating (10 MFD to 7.5 MFD). I also got the appropriate capacitor. Replaced everything, wired it all up according to the diagram and bam...nothing. The transformer will hum slightly but the blower motor won't start.

Having fallen off the knowledge cliff long ago I've been hitting google for weeks but I'm coming up dumb founded. The only thing I can find as far as the brand of furnace is this.


It came with this motor.


And runs on this transformer.
.

I have since installed this motor.
DAYTON Motor, 1/2hp, D/D Blower - Direct Drive Blower Motors - 3LU83|3LU83 - Grainger Industrial Supply

And this run capacitor.
DAYTON Run Capacitor, 7.5 MFD, 370 VAC, Oval - Capacitors - 2MDV6|2MDV6 - Grainger Industrial Supply

Everything is wired back exactly as before. The only thing I've thought that could be an issue is maybe the transformer has to be replaced to match the motor/capacitor combo?
 
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Old 10-08-13, 10:06 PM
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Welcome to the forums.

The transformer only activates the contactor. It doesn't have anything to actually do with the motor.

The old motor had black and white and the new motor has black and purple.
So black to black and white to purple would be your connections.

Have you put the motor direction jumpers together ? Purples/yellows

The fan isn't working.....but the compressor is coming on ?
If the compressor isn't coming on.... is the contactor engaging ?
 
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Old 10-13-13, 11:47 AM
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Hi PJmax!

Thanks for the reply! Sorry it took me so long to respond.

It turned out the issue wasn't anything to do with the motor, capacitor or the related wiring. The color of the wires actually matched except for the Med/Lo wire which was orange on the motor instead of blue as before. I had naturally checked every wire that I removed/replaced or even touched or bumped. The issue was a wire coming from the thermostat downstairs had broke inside the insulation and the insulation had stretched enough when I moved the circuit board to completely break contact. So even though I had good connections from the thermostat to the board I was loosing contact. Ended up being a quick fix.

The nice thing is that this episode made me research the hell out of HVAC systems and the next time I attempt a DIY I'll be better prepared if the issue is more extensive.

Thanks again! Your response got me checking all the wiring again but more extensively.

John
 
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Old 10-13-13, 12:27 PM
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Glad you got it sorted out ...... thanks for the update.
 
 

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