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OT - Wiring my AC condenser fan motor
OK, I'm struggling with this problem and y'all might be able to help.
I have posted to alt.hvac, but most of those guys are really not very helpful to homeowners and just tell me to call a tech. background: AC quit working, would cut-out after startup. Thermostat was changed no result. Called Tech, who tested everything, put 2lbs of r-22 in it, indicated the condenser fan motor was giving trouble starting and that likely it had some bad windings or something. He tried changing the capacitor, no improvement. Wrote an estimate for changing the motor out of over $500. Being thrifty and handy enough to be dangerous, I decided this was too much for something I could do myself. I looked around and after getting the details on what the motor type was, I found a OEM replacement at Grainger. 1/4 horse, 220 volt, Y frame, counter clockwise rotation, sealed air-over, bottom shaft, etc. I got the motor changed out, substituted the new 12mfd capacitor that this motor required (vs the 5 mfd for the other). I took pains to connect the wires back just as it was before. The new motor had the same colors leads as the old one, a purple, a brown and a black. As I tested it, I discovered that this motor does not want to start either, in fact it makes the same loud humming noise when energized. When I spun the motor with a stick through the grill and it caught on and ran normally. Hmm.... The compressor runs strong and has no issues. After looking at the way it had been wired when I opened the case, their are two hot 220 leads and the case is ground. Going from either lead to ground is 115 volts. Obviously between the two leads is 220-250 volts. Of these two hots, one BLACK HOT wire goes to the contactor (relay) switch and then would connect to the purple fan motor wire when energized. The WHITE HOT connects to a wire that goes to a 3 way capacitor (runs the compressor), with a jumper directly from the input terminal sending power also to the condenser fan motor capacitor. The other two condenser fan motor leads, the brown and black, are connected to the starting capacitor, one on one side and one on the other. The black is connected to the same terminal as the hot lead. ---- Ok, I thought about it, and using my limited knowledge I figured the motor has two seprate windings for each hot leg, and by only having the starting capacitor hooked to the brown wire it was only getting 1/2 the starting power it should have. So, I moved the black fan lead to the same terminal as the brown lead, and then the fan would not run. I put these back the way they were, and then moved the hot lead to the brown lead side of the capacitor. Now the motor started with authority, but it ran backwards (clockwise) as you look at the end of the shaft. Ok that is where I am now. I have a upstairs unit that is wired the same way sans capacitor as the motor does not require it. Any suggestions? I'm perplexed why it runs better in the direction it is not supposed to go, and why it doesn't want to start, why the old motor gave the same trouble. I have a photo of the unit's power box and can get one of the wiring diagram, but I'd like to get this fixed. I know it just something simple. Thanks in advance... Scott |
#2
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OT - Wiring my AC condenser fan motor
In article . com, scott wrote:
OK, I'm struggling with this problem and y'all might be able to help. I have posted to alt.hvac, but most of those guys are really not very helpful to homeowners and just tell me to call a tech. alt.hvac is "really not very helpful to homeowners" = understatement of the week. There are some polite and knowledgeable HVAC people in alt.home.repair. You might try posting there. -- Regards, Doug Miller (alphageek at milmac dot com) It's time to throw all their damned tea in the harbor again. |
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