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!


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

 

[Anthony Diodati]

big help

 

[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

 

[CBhvac]

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

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

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.

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?


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

 

[Me]

Thank you for applying some common sense CBhvac.

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

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

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.

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.