Blower moter overheats - http://www.hvacmechanic.com/ Forums
Original message
| db55047
 |  "Blower moter overheats"
, posted Tue 28 Oct 21:50  
I have a Goodman GMPN 120-5 Furnace that has been in service for 8 yrs. I have been running the blower 24/7 since installation. Yesterday the blower moter started shutting down on its internal overtemp protection. The motor is too hot to touch for more than a second. I have replaced the motor and cap, put in new filter, checked A coils for plugging and they are not. Have let the furnace blower run with air venting below the A coil to be sure it was not loadin the motor. The new motor is heating just like the original was. Don't know what else to check. Any ideas? The motor is 3/4 HP 3sp 1075 rpm by GE.
Thanks Don
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Replies:
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| yuri
| "Re(1):Blower moter overheats" , posted Tue 28 Oct 22:36:
Did you check the voltage to it? Should be 110-120 volts. Is it a factory OEM motor or a Universal type. If Universal is it turning in the correct direction, some can be reversed by changing 2 wires. You may have a bad circuit board, fan relay which is energizing 2 windings at once. Try it with only the heating speed wire on. Tape off the other 2. If it runs okay the board may be the problem, usually burns it out in a hurry. Will be back tomorrow.
Yuri
[this message was edited by yuri on Tue 28 Oct 22:44] |
| | db55047
| "Re(2):Blower moter overheats" , posted Wed 29 Oct 00:17:
Thanks for the reply. The voltage is 120V. The control board was new yesterday, the motor and cap are new today. Board should be good but I will try running with only one wire to motor. The motor is OEM the exact same as original motor built by GE but Goodman's part number. The motor gets so hot you cannot touch it and it only takes about 5 to 10 min, will eventually stop on thermal protection. This is a double shaft motor with two blower cages. everything turns free there is no draging. Discharge is free and clear as is intake side. It's all new stuff it should work, it worked for 8 years and nothing apparent has changed about the system. I'm out of ideas any help is appreaciated.
Thanks Don
[this message was edited by db55047 on Wed 29 Oct 00:19] |
| | db55047
| "Re(3):Blower moter overheats" , posted Wed 29 Oct 00:34
Addition to above post. The motor would not start without all three wires connected to the control board.
Don
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| | yuri
| "Re(4):Blower moter overheats" , posted Wed 29 Oct 20:08
Strange. The 3 wires usually are for 3 different speeds. Heating , cooling and a spare. Only 1 needs to be used at a time for one function at a time. When you are calling for heat there should be no voltage to ground from the cooling terminal. Goodmans are cr*ppy units in my opinion. My last company sold them and we had lots of problems with their circuit boards. The board and mount needs to be grounded properly and they had no ground wires on some of them back to the electrical box where the power comes into the furnace. Had to add a ground wire. The mounting bracket on the fan would come loose and the board would lose it ground connection. If you have a ampmeter try measure the amps draw of the furnace. See what the motor draws. The rest of the furnace draws very little power. That way you know if it is drawing too much current.
Yuri
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| | db55047
| "Re(5):Blower moter overheats" , posted Wed 29 Oct 23:50
I had thought about checking amps drawn by the motor but haven,t done so yet. I will try to get a reading tomorrow and also try to figure out whats going on with the motor not running with only one set of windings attached to the control board. I agree with you the motor should run that way. I'll post back with my findings. Currently I'm running with the blower in the auto mode so it gets time to cool a little between heating cycles but this is only a bandaid I need to figure out what's wrong.
Don
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| | db55047
| "Re(6):Blower moter overheats" , posted Fri 31 Oct 14:40
Got a chance to some more checking. I was wrong before, the blower will run on any one wire plus neutral and cap. I had the fan in the "on" position rather than "auto" and apparently in that mode only the high speed relay is energized. The motor pulls about 7.3-7.5 amps on high speed and about 5.0 amps on the two slower speeds. The draw is up to 13 amps on start up. The motor still seems to be heating excessivly if left to run but by running on auto it will work and not drop out on thermal overload. When to motor is running on a given speed there is no apparent current draw by the other windings. Any suggestions will be appreciated.
Thanks Don
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