Why do you have to match blower motor amps if voltage and RPM are the same? Particularly interested in why Carrier and Bryant blower motors are so expensive. The one I am replacing is 3/4 HP 1075 RPM and 12 amps. Wholesale is nearly $.
DAVID PRATHER
No. RPM is based on the number of poles.
6 poles= 1075 on a PSC.
8 poles= 825 on a PSC.
'Problem comes from Load Applied.
You use an over hp'd motor,it will work but because you do not have it properly Loaded,it actually overworks itself causing failure at a later point exhausting itself from over exertion from Less than It was designed for.
The RPM will be the same regardless as this is How/What the motor was designed to run at unless you Over Load it with Weight or Static causing It to slow down which in turns causes It to draw more Current to 'try' to produce what it was designed for.
Then, you meet Mr. Internal Overload.
Elementary at best,but I'm no 'Brain either.
Just Saying.
6 poles= 1075 on a PSC.
8 poles= 825 on a PSC.
'Problem comes from Load Applied.
You use an over hp'd motor,it will work but because you do not have it properly Loaded,it actually overworks itself causing failure at a later point exhausting itself from over exertion from Less than It was designed for.
The RPM will be the same regardless as this is How/What the motor was designed to run at unless you Over Load it with Weight or Static causing It to slow down which in turns causes It to draw more Current to 'try' to produce what it was designed for.
Then, you meet Mr. Internal Overload.
Elementary at best,but I'm no 'Brain either.
Just Saying.
And you wonder 'why' an OEM Motor costs SO much?
Because IT is designed to Their spec's.
I changed a 'simple,Bryant Cond motor in 15 min having said motor in hand at the time.
How?
It Fit,Exactly and did Exactly what It was Designed for.
Cost more but I did not have to guess 'anything' or Modify,Nothing.
When you go aftermarket. As always,
"Some modification may be required" which = Time & Money.
YOU weigh the 'Option' of and the Circumstance 'involved.
If afforded the option,I will go OEM because it ends up being the Best option but some day's,you have no option even with OEM from some Manuf's and Experience takes precedent,with me anyway.
Best of Luck in your Choice.
You'll need it Today.
Because IT is designed to Their spec's.
I changed a 'simple,Bryant Cond motor in 15 min having said motor in hand at the time.
How?
It Fit,Exactly and did Exactly what It was Designed for.
Cost more but I did not have to guess 'anything' or Modify,Nothing.
When you go aftermarket. As always,
"Some modification may be required" which = Time & Money.
YOU weigh the 'Option' of and the Circumstance 'involved.
If afforded the option,I will go OEM because it ends up being the Best option but some day's,you have no option even with OEM from some Manuf's and Experience takes precedent,with me anyway.
Best of Luck in your Choice.
You'll need it Today.
I agree 100% with mr Kelley. I worked at a school district when I first got into the field. When I started we were changing motors in mcquay classroom ventilators like crazy. Noticed old motors were ge and new motors we were getting from a supplier.
The motors from the supplier were maybe lasting a year tops, and had to run them on medium to last that long or else they would Overamp.
This isn't right I thought. So I called the factory. The oem motor ran off a speed control transformer which I already knew. They said each speed has a specific voltage it sends to the motor which runs it faster or slower based on setting. I knew this but let the guy talk.
I give him model numbers of the oem motor and the model numbers on what was being put in its place.
The thermistors were rated different as was the class of insulation I believe. He said it may cross to this but isn't made to last at all.
I told the bosses this. They said the oem motors are sixty more each. I said yeah and the speed control transformer is twice that and we are burning those up as well as these motors what's being saved.
So the director of the department sided with me and said ok buy 10 of them. Write the install date on the motor and keep a log of where the motors are installed the classroom building etc.
we kept the motors at the shop and a guy had to sign out where the motors were going before given one. That was over 5 years ago and 9/10 motors are still running.
The one that bit the dust wasn't really premature failure. Some kid threw some pencils in the blower locking it up.
Ever since then I go OEM. Better fit, less hassle, better service life, and improved reputation.
The motors from the supplier were maybe lasting a year tops, and had to run them on medium to last that long or else they would Overamp.
This isn't right I thought. So I called the factory. The oem motor ran off a speed control transformer which I already knew. They said each speed has a specific voltage it sends to the motor which runs it faster or slower based on setting. I knew this but let the guy talk.
I give him model numbers of the oem motor and the model numbers on what was being put in its place.
The thermistors were rated different as was the class of insulation I believe. He said it may cross to this but isn't made to last at all.
I told the bosses this. They said the oem motors are sixty more each. I said yeah and the speed control transformer is twice that and we are burning those up as well as these motors what's being saved.
So the director of the department sided with me and said ok buy 10 of them. Write the install date on the motor and keep a log of where the motors are installed the classroom building etc.
we kept the motors at the shop and a guy had to sign out where the motors were going before given one. That was over 5 years ago and 9/10 motors are still running.
The one that bit the dust wasn't really premature failure. Some kid threw some pencils in the blower locking it up.
Ever since then I go OEM. Better fit, less hassle, better service life, and improved reputation.
I think there might be a distinction here between commercial and residential. I have heard several times that OEM can be more critical when it comes to commercial. Personally, my work is over 95% residential. I use whatever Rescue type motor that the supply house has on sale. As long as the HP, RPM's and Voltage matches I've almost never had a problem.
I have always wondered about this. See it all the time on here. In 40 years in the trade I have always went HP for HP? never had a problem with it.Never had to put another motor on same unit after years of use? I do a lot o wood working. run a table saw or hours. I"ll bet the amp draw under no load is less than amp draw ripping Oak. My dad had that saw for 40 years i had it another 30 of heavy use still on same motor? It may kick overload after hours of ripping cooldown and restart.I"ll try a amp draw with load/ no load just for kicks.
Pay attention to service factors. Carrier had rooftop units with oem motors with 1.5 sf. A replacement of the same hp and lower service factor would not move enough air and larger hp was not available in the same frame size.
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