Furnace blower motor replacement
#1
02-09-16, 08:38 AM
Furnace blower motor replacement
My Conquest 90 furnace blower motor died on me.
Ordered an equivalent motor and a new replacement capacitor.
Old motor : GE Brand, 1/2hp, 7.5uF/370V cap, 6.3A, 115V, 3 speed
New motor: Protech Brand, 1/6hp-1/2hp, capacitor varies based on hp, 5.8A, 115V, 4 speed.
1) The new motor chart states that at 1/2hp, the capacitor should be 10uF. With a 7.5uF capacitor, the hp would actually be 1/3 hp according to the chart. Should I upgrade to a 10uF capacitor or stick with a 7.5uF capacitor, which is what the original motor had.
2) The new motor is 4 speed (low, med low, med high, high), the old one was 3 speed (low, med, high). Which wire should I cap off, the med-high or the medium-low?
Thanks in advance for the help!
Ordered an equivalent motor and a new replacement capacitor.
Old motor : GE Brand, 1/2hp, 7.5uF/370V cap, 6.3A, 115V, 3 speed
New motor: Protech Brand, 1/6hp-1/2hp, capacitor varies based on hp, 5.8A, 115V, 4 speed.
1) The new motor chart states that at 1/2hp, the capacitor should be 10uF. With a 7.5uF capacitor, the hp would actually be 1/3 hp according to the chart. Should I upgrade to a 10uF capacitor or stick with a 7.5uF capacitor, which is what the original motor had.
2) The new motor is 4 speed (low, med low, med high, high), the old one was 3 speed (low, med, high). Which wire should I cap off, the med-high or the medium-low?
Thanks in advance for the help!
#2
02-09-16, 09:11 AM
Member
I'd use the 10uf. If the cage was designed for 1/2 horse motor you will likely overheat at 1/3HP.
With the exact model number you can look up what the original blower speeds were and then choose the taps to get as close to those as possible.
With the exact model number you can look up what the original blower speeds were and then choose the taps to get as close to those as possible.
#4
02-09-16, 06:09 PM
Got the 10uF capacitor.
After running the furnace for over an hour, put my hand on the motor and it was hot. Not too hot to touch but hot. I could keep my hand on it indefinitely but barely. Is that normal or do I have another issue that cause my original motor to fail?
After running the furnace for over an hour, put my hand on the motor and it was hot. Not too hot to touch but hot. I could keep my hand on it indefinitely but barely. Is that normal or do I have another issue that cause my original motor to fail?
#5
02-09-16, 06:34 PM
Group Moderator
It's really hard to say how hot is too hot as motors today run hotter than they used to.
What speed is it running at ?
What speed is it running at ?
#7
02-09-16, 07:07 PM
Group Moderator
I never really understood the using of multiple capacitors to change rated horsepower. Basically the larger cap is causing that motor to work harder and run harder.
Personally.... I'd try the 7.5uf cap in there and see how it performs.
Personally.... I'd try the 7.5uf cap in there and see how it performs.
#8
02-09-16, 07:17 PM
Member
If you can leave your hand on it, but just, then it's around 55 degrees C. (DAMHIKT) It would not be unusual for a motor to run at that temperature. Doesn't mean there isn't a problem, but if the bearings spin freely and the blowers not all loaded up with gunk or the airflow restricted, there's not a lot else to cause it run hot, short of it being underpowered. It's easy to make a motor that runs cooler, but it adds cost and, well, you know how that goes....
