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Thread: how many amps.....
06-06-2005, 09:25 PM #1
one of our techs went on a call today. 80% lennox gas furnace, less than 1 yr old, 5 ton drive. i assume this is a 3/4 hp motor. he says it is pulling 12 amps while running, 22 peak at startup. also says tag on unit does not indicate motor size or amp draw, but 12 amp max circuit, sounds high to me. return comes in on both sides of unit, clean filters and blower wheel.
should i order a motor? 12 amps (hi speed) sounds high to meIn the land of the blind the one eyed man is King! semper fi
06-06-2005, 09:29 PM #2
Did he check the run cap?"In this house we obey the laws of thermodynamics!"
- Homer Simpson
06-06-2005, 09:35 PM #3
CHeck your CFM
If the resistance of the duct is real low (very easy to move the air), then the blower will react much like you
riding downhill on a ten speed bicycle in 1st gear.
The blower amps tracks pretty close to total CFM.
If your CFM is correct, run capacitor is good, and voltage is OK, then I'd suspect a bad motor.
If you checked your static pressures and they line up ok on the cfm chart, then check the CFM with an alternate method to make sure. I use a velometer and return grille Ak factor. If all else fails, check the CFM using a heat rise.
I'd also check bearing condition and temp of motor after its run a while (forget temp if CFM is not right though)
What was the complaint the tech was sent to check for? (out of curiosity)
06-06-2005, 10:07 PM #4Professional Member*
- Join Date
- Nov 2004
- SW FL
SpecsOriginally posted by hvac4u
i assume this is a 3/4 hp motor. he says it is pulling 12 amps while running, 22 peak at startup.
should i order a motor?
a 2 HP .. BIGGER IS better.
TWICE the HP will get you HALF THE AMPS.
Just where you need to be ! !! !!! ?Designer Dan
It's Not Rocket Science, But It is SCIENCE with "Some Art".
Define the Building Envelope and Perform a Detailed Load Calc: It's ALL About Windows and Make-up Air Requirements. Know Your Equipment Capabilities
06-06-2005, 10:56 PM #5Professional Member*
- Join Date
- Nov 2001
- east kansas
Did he have the blower door on?