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pwkelly · Sep 16, 2007, 09:09 PM

Hi,

I have an older (~40 years, the original with the house) Coleman furnace. The blower motor (General Electric, 1/6 hp, 110 V, 60 Hz, 3.6 amps, PH 1, 1725 rpm) burnt out the other morning. I went to the local shop (RONA) to find a replacement and they didn't have the exact motor. Instead, the fellow working in the furnace department recommended a replacement GE motor (1/3 hp, 6.6 amps, 115V, 60Hz, PH 1, 1725 rpm). My question is will the furnace be able to handle the higher voltage and amps of the new motor, or will it damage the existing circuitry and wiring?

Thanks - Patrick

hvac1000 · Sep 16, 2007, 09:21 PM

There are 1/4 hp motors available. You can probably use the 1/3 it only draws 6.6 amps but you probably do not have a Amprobe to check the current draw after it is installed. That is why I recommend the 1/4 HP unit.

labman · Sep 16, 2007, 10:21 PM

I am sure the furnace is wired up with at least #14 if not #12 wire which is good for about twice the rated amps. The voltage is determined by your incoming power. The new motor will draw the amps needed for the load, about the same as the old.

hvac1000 · Sep 16, 2007, 11:50 PM

He has what I believe to be a 1725 RPM single speed motor. When you go from a 1/6th to a 1/3 motor it does not mean that the motor will draw the same current because the new 1/3 hp motor has 3 or 4 speeds available. What speed is he going to pick that is equal to the 1/6 th HP motor because the slowest speed on the 1/3 HP replacement motor is usually rated 1/6 but that speed may not be powerful enough to do the job since it will be running at a lower speed than the original fixed speed 1725 RPM unit. Work load is work load but you still have to pick a speed.That is why I added the Amprobe statement and he probably does not have one to use to test. As far a the circuit from the breaker panel to the furnace you are absolutely correct in the fact that it is a 14 or 20 amp circuit but we are not concerned with that circuit. We have no idea what the wire size is going to the blower that is in the furnace. That is why I am more comfortable recommending a 1/4 hp since it is just one step above the original rate of the motor and not two steps. With a 1/4 HP motor it is close enough to the 1/6th that he could just wire it up at the highest speed with out a problem.

labman · Sep 17, 2007, 05:51 AM

The blower needs to turn at the same speed as before without a recheck of the temperature rise. A lower speed could mess up the efficiency of the furnace or lead to overheating. Likely it would be better to use a slower speed and a larger pulley, but the easiest and surest thing would be to just bolt in the new motor and connect it up to run at 1725.