Box Fan

[James Cowan]

I have a six blade 42 inch fan that i am using for a shop fan. Just replaced the motor and now it shuts off on high heat. The motor is a 3/4 hp 1750 rpm. Looks like the pulleys are 2 inch on the motor and 14 inch on the fan blade. Should i up size the motor or change the pulley sizes. Thanks

 

[larry_g]

You should first monitor the motor current. Then either solution you put forth may work, but without the current you will not know what size motor to upgrade to or the ratio change needed. I do know that some of the industrial fan vendors have charts to say what HP is needed to spin the fan at a given speed. One other variable you have is to restrict the flow of air through the fan which will reduce the power consumed.

lg
no neat sig line

 

[Jim greengo]

Is it the same hp/rpm as original motor?

 

[James Cowan]

Not sure. Did not or do not remember the hp on the original and i think i just threw it out. Shame to get old. Seems that i changed it because it was overheating also but assumed it was because it was 30 years old.

 

[James Cowan]

Guess i need to check the amp draw on the new motor. If it is pulling too much i want to try to change the pulleys to bring it down. Cannot find a site to give me the correct size for this size fan and motor i have. Thanks

 

[Jim greengo]

Post a picture of the fan,maybe someone on here has one we can compare it to.

 

[rkevins]

Are the bearings on the blade shaft in good shape, spin freely? Have you tried running it with the belt off to make sure it's not the motor? It's been years sense we had 48" fans but I think they had 1hp motors, you could look at granger and compare what they sell.

 

[James Cowan]

I checked the amps on it yesterday and it’s only pulling about 8 amps. I have it on a 120 volt 20 amp circuit.

 

[Bert_]

Doesn't matter what size circuit it's on. How many amps is the motor rated for. It will be listed as FLA or just Amps.

 

[Jim greengo]

Doesn't matter what size circuit it's on. How many amps is the motor rated for. It will be listed as FLA or just Amps.

 

[James Cowan]

Good point. Motor says 10.6 at 115

 

[3rdgendslmech]

When I first bought my house the attic fan was locked up. So trying to be slick I bought a complete attic fan and tried to swap out only the motor. Both motors rated for same amps and fla. What was different was the old vent had more pitch on the blade and the new motor couldn't handle it. Second motor I changed the blade and the motor and everything has been fine since.