2HP AC Single Phase Motor very weak at start or hums
2HP AC Single Phase Motor very weak at start or hums
(OP)
I have an A.O. Smith 2HP, 220Single-Phase pool pump motor that started giving me trouble.
It has been working for the past year or so, but just started having starting problems.
When I turn it on sometimes it starts, most of the time it just hums.
If I give the shaft end a spin, it will always start but I can always hold on to the shaft with two fingers and it will never start.
I did a search here and saw the answers about the cap possibly being bad, but I did the VOM test at 10K and it seems to pass.
After discharging it, it starts out at zero ohms then takes about 10 seconds to swing across the dial.
I read about looking at the centrifugal switch, but I think this one doesn't have one...or is it I just don't know where to look?
I attached a link to the manual for this motor.
Should I try replacing the cap, even though it seems to pass the test?
Shouldn't this motor have way more starting torque than two fingers of a weak, computer programmers hand?
It has been working for the past year or so, but just started having starting problems.
When I turn it on sometimes it starts, most of the time it just hums.
If I give the shaft end a spin, it will always start but I can always hold on to the shaft with two fingers and it will never start.
I did a search here and saw the answers about the cap possibly being bad, but I did the VOM test at 10K and it seems to pass.
After discharging it, it starts out at zero ohms then takes about 10 seconds to swing across the dial.
I read about looking at the centrifugal switch, but I think this one doesn't have one...or is it I just don't know where to look?
I attached a link to the manual for this motor.
Should I try replacing the cap, even though it seems to pass the test?
Shouldn't this motor have way more starting torque than two fingers of a weak, computer programmers hand?





RE: 2HP AC Single Phase Motor very weak at start or hums
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If we learn from our mistakes I'm getting a great education!
RE: 2HP AC Single Phase Motor very weak at start or hums
Either way, it was re-painted all black and the only thing
I can see a a message saying
A.O. Smith Centurian Switchless - No Switch / No Governor - Total HP=2.00
It has only two spade terminals, marked L1 and L2 (plus a ground screw)
It has one 25UF 370V Cap mounted on the side.
I put new bearings in it to see if that would help, but is was already spining very easily...it take about 15 seconds to stop spinning when I shut it off.
RE: 2HP AC Single Phase Motor very weak at start or hums
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RE: 2HP AC Single Phase Motor very weak at start or hums
The two possibilities I would explore are a knackered starting cap or an open-circuit winding. Electrically there are two windings, one of which has the capacitor in series with it. The individual connections could be tricky to get to, but if you can find them you should find each winding has a resistance of a few ohms. If the windings are ok then I'd suspect the cap. Obviously you can't measure resistance through the cap, so you need to get at the connection to the winding itself.
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If we learn from our mistakes I'm getting a great education!
RE: 2HP AC Single Phase Motor very weak at start or hums
Do you know the tune it is humming...?
RE: 2HP AC Single Phase Motor very weak at start or hums
Are you sure you're applying 220 V and not 110 V ?
Muthu
www.edison.co.in
RE: 2HP AC Single Phase Motor very weak at start or hums
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: 2HP AC Single Phase Motor very weak at start or hums
Cheap capacitor very often lose a part of the nominal capacitance and the rest is not sufficient to start the motor.
The only thing you can do is try with a new capacitor.
If is same case again, it is necessary to rewind motor.
Zlatkodo
RE: 2HP AC Single Phase Motor very weak at start or hums
In answer to the replies, I verified that the motor is indeed seeing 220VAC by using the VOM accross L1 and L2.
I'm going to look around this weekend and see if I can find a cap to see if that helps.
I checked on MCMasters and didn't see the exact same rating (25UF - 370VAC about 1-5/8" diameter and 3" long), so I'm going to try a motor repair shop if I can locate one open this weekend.
Thanks again!
RE: 2HP AC Single Phase Motor very weak at start or hums
I see on Digikey a cap that has the same rating, but it's marked as a Motor Run, not a Motor Start.
I don't suppose there's any difference, but since I know more about computers than motors, I figured I'd ask just in case I can't find one tomorrow...
http://sea
RE: 2HP AC Single Phase Motor very weak at start or hums
Muthu
www.edison.co.in
RE: 2HP AC Single Phase Motor very weak at start or hums
The difference is that starting capacitors are adequate for starting duty but will generally fail if left in the circuit for an extended period of tie.
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: 2HP AC Single Phase Motor very weak at start or hums
by now, can I politely call attention to another possibility?
Was the motor actually being used for pumping water?
The comment(s), "...If I give the shaft end a spin, it will always start but I can always hold on to the shaft with two fingers and it will never start..." alludes or implies the impeller end is exposed.
And, "...I put new bearings in it to see if that would help, but is was already spining very easily...it take about 15 seconds to stop spinning when I shut it off..." would indicate the shaft seal is completely wore out or removed.
These two comments raise the question of "up-n-down" motor shaft play which is typically a trademark failure in pool pump motors.
If the motor is all electrically "O.K.", the impeller end shaft journal, or bearing housing fit is suspect due to the corrosive environment of pool pump motors, and either fit could be wore out.
The motor will hum and not come up to speed if this is the case because the rotor is being pulled off electrical center when energized. A very wore out fit would not likely allow the motor
to start at all. Hence returning to the suggestion of an open circuit... either in the capacitor, or the start winding.
"Winding Down" on a Tuesday evening,
John
RE: 2HP AC Single Phase Motor very weak at start or hums
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RE: 2HP AC Single Phase Motor very weak at start or hums
I put a brand new one in and it gave the same results.
I've been running the pump all day after starting it by hand because my pool started turning very green.
I hope running it won't make the problem worse, but at this point I think I'm going to have to buy a whole new motor anyways.
As for how I start it by hand, this model has a plastic cover on the opposite side from the main shaft.
It has two flats on it so you can hold the shaft while you unscrew the impeller.
I just remove the cover and give it a spin while it's humming and it starts right up and runs fine.
Before I give in and charge up an already maxxed out credit card for a new rebuild, is there anything else I can check?
Thanks again to everyone for all the help with this!
RE: 2HP AC Single Phase Motor very weak at start or hums
Sorry it didn't work out the new cap.
Muthu
www.edison.co.in
RE: 2HP AC Single Phase Motor very weak at start or hums
RE: 2HP AC Single Phase Motor very weak at start or hums
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: 2HP AC Single Phase Motor very weak at start or hums
RE: 2HP AC Single Phase Motor very weak at start or hums
It spinned but I could stop the shaft with my hand
The problem was the squirrel cage. It was damaged
I had to replace the whole motor
RE: 2HP AC Single Phase Motor very weak at start or hums
Can you measure the voltage on the motor when it tries to start (without your help)?
Also you can try to add second cap (you already have it). Connect it in parallel with the first cap, through the push button (or just manually for testing ), but only temporarily, during a start.
Note: discharge cap before working on it!
Zlatkodo