PLEASE Help with furnace motor - brrrrrrrrrrrrr.

[Frank]

Hi all. I just bought a new G.E. single phase 1/2hp, 115V, 1725rpm motor for my furnace blower. Installed and wired it up ok but I need to reverse rotation. The label says to swap two wires at the jumper terminals (red and black) and when I do this, the motor does turn in the opposite direction but only for a few seconds before it shuts down, after which it picks up again and continues this cycle.

Am I missing something here or do I just have a bad motor?

Thanks in advance for any help, the hardware stores are all closed and it's cold outside!

FG

[Me]

Call a qualified HVAC tech!

Am I missing something here or do I just have a bad motor?

Thanks in advance for any help, the hardware stores are all closed and it's cold outside!

FG

[Anthony Diodati]

[Frank]

Hey Anthony, thanks for taking the time and showing some compassion, something Mr. "me" didn't.

I got the problem fixed. After bench testing the motor and finding nothing wrong, I searched and found a mechanical problem (motor not coming up to speed fast enough) which was remedied by reducing belt tension and using a smaller motor-end pulley.

Peace, FG

[Terry]

I think this is the point that "Me" was making.

You replaced your worn out motor with a motor that fails to supply the same amount of air without going off on overload. So the cure was to lower the air flow.

I suppose that if your A/C compressor becomes hard to start you could just remove some of the refrigerant.

Call a tech

[Joseph Meehan]

I have to agree with Terry. If you have changed the air flow, you now could have created a problem with the furnace or the AC.

[CBhvac]

Actually...he did. You see...read below.

So, you replaced the motot that you had with the EXACT same rating as before? You put a new cap on there too?? If all you did was pull the belt sheave off, and put it back on the new motor, used a straightedge to properly line the belt pulleys, and you did not change the sheave.....you still have a problem. By lowering the CFM across your heat exchanger, you have changed the operation characteristics of the furnace, and perhaps, none for the better. By trying to save $100, you might have just cost yourself a grand. But....a pro would have known that....this one does.

[Frank]

Thanks for the constructive comments CBhvac.

Although the new motor is the same hp rating, it is a little beefier and has a slightly higher rated current according to the nameplate. Due to the slightly larger design, the center of the motor axis is further away from the blower making the belt too tight if the same pulley ("sheave": new word of the day) and belt are used, so I used a sheave that was just a little smaller in diameter - 3/4" smaller to get me through the night. Now my house is warm again.

Today I plan to go back to the original diameter sheave and put a longer belt on which should get me back to the original cfm design of the furnace.

BTW, the new motor never did drop out on overload, it just couldn't complete it's start cycle and come up to speed before kicking off due to the increased tension on the shaft.

Peace, FG

[Me]

"Remove some refrigerant"?!? Oh my God, what are you smoking?

You replaced your worn out motor with a motor that fails to supply the same amount of air without going off on overload. So the cure was to lower the air flow.

I suppose that if your A/C compressor becomes hard to start you could just remove some of the refrigerant.

Call a tech

[Me]

Thank you for applying some common sense CBhvac.

Actually...he did. You see...read below.

So, you replaced the motot that you had with the EXACT same rating as before? You put a new cap on there too?? If all you did was pull the belt sheave off, and put it back on the new motor, used a straightedge to properly line the belt pulleys, and you did not change the sheave.....you still have a problem. By lowering the CFM across your heat exchanger, you have changed the operation characteristics of the furnace, and perhaps, none for the better. By trying to save $100, you might have just cost yourself a grand. But....a pro would have known that....this one does.

[RB]

If it is higher current but the same horsepower is is less efficient. Sort of like confusing "fat" with "beefier." Bigger is not always better.

RB

Frank wrote: