Motors not lasting long?

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electricblue

Senior Member
Location
Largo, Florida
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EC
I have a customer that has a 3ph 5 hp commercial pool pump. They say it does not last longer than 6 mos. I checked voltage. It's a 208 system. The voltage at source is 204 to 203 a little VD. It is a long run but voltage is with in 3% to 5%. Any ideas? It has has motors heater for protection.:-?
 

mcclary's electrical

Senior Member
Location
VA
I have a customer that has a 3ph 5 hp commercial pool pump. They say it does not last longer than 6 mos. I checked voltage. It's a 208 system. The voltage at source is 204 to 203 a little VD. It is a long run but voltage is with in 3% to 5%. Any ideas? It has has motors heater for protection.:-?

Are the heaters sized correctly for the motor? I suspect they are overloading the pump, and the overloads are not sized correctly.
 

Jraef

Moderator, OTD
Staff member
Location
San Francisco Bay Area, CA, USA
Occupation
Electrical Engineer
I have a customer that has a 3ph 5 hp commercial pool pump. They say it does not last longer than 6 mos. I checked voltage. It's a 208 system. The voltage at source is 204 to 203 a little VD. It is a long run but voltage is with in 3% to 5%. Any ideas? It has has motors heater for protection.:-?
Do you know what is going bad on the motors? Windings, bearings, etc?
If it's the windings, do they get them examined by a competent motor shop to see what kind of damage it is? There are ways for them to tell what type of event caused the failure by how the damage looks and tests out.

Do they have any current imbalance?

Did someone crank up the OL dial because they got tired of resetting it?
If so, is it because the motor too small, or did they change the flow so that even if it was sized right in the beginning, it isn't now?

Are the motors exposed to the pool chemicals? Acid and Chlorine are really nasty on motors and I have seen a number of places where they store the chemicals in the equipment room. Of course they are not supposed to spill the chemicals in the room, but Joe-Bob the pool guy won't rat himself out if he does, so when asked he always saws "No!"

Even though they have winding heaters, does Joe-Bob realize that when he flips all the breakers off at night, he's killing power to the heaters too? (See that one a lot).

Lots more possibilities on this.
 

sid123456

Member
Do you know what is going bad on the motors? Windings, bearings, etc?
If it's the windings, do they get them examined by a competent motor shop to see what kind of damage it is? There are ways for them to tell what type of event caused the failure by how the damage looks and tests out.

Do they have any current imbalance?

Did someone crank up the OL dial because they got tired of resetting it?
If so, is it because the motor too small, or did they change the flow so that even if it was sized right in the beginning, it isn't now?

Are the motors exposed to the pool chemicals? Acid and Chlorine are really nasty on motors and I have seen a number of places where they store the chemicals in the equipment room. Of course they are not supposed to spill the chemicals in the room, but Joe-Bob the pool guy won't rat himself out if he does, so when asked he always saws "No!"

Even though they have winding heaters, does Joe-Bob realize that when he flips all the breakers off at night, he's killing power to the heaters too? (See that one a lot).

Lots more possibilities on this.

I don't have any motor rebuilder info. The motors heaters are a little on the high side but not out of wack. Also, the motor is outside not in a room exposed to chems.
 

charlie b

Moderator
Staff member
Location
Lockport, IL
Occupation
Retired Electrical Engineer
This is a long shot, but is the pump powered and controlled by a VFD? If so, and if the motor is not designed for a VFD, that might be the problem.
 

Jraef

Moderator, OTD
Staff member
Location
San Francisco Bay Area, CA, USA
Occupation
Electrical Engineer
Seems like pumps are always sized to run well into the service factor amps. Combine that with 24/7 use and maybe 6 mos is a long life.
Part of the never ending debate on the real meaning of "Service Factor". OEMs tend to use the most liberal interpretation they can get away with, end users suffer the consequences.
 

mbeatty

Senior Member
Location
Illinois
Are the heaters sized correctly for the motor? I suspect they are overloading the pump, and the overloads are not sized correctly.

I agree. The heaters should already have a built in 1.15 overload factor and should protect the motor if properly sized based on namplate FLA and the Service Factor. I am also curious if the motor is VFD operated but not rated for it.
Regards,
Mark
 

Open Neutral

Senior Member
Location
Inside the Beltway
Occupation
Engineer
I recall a bizarre case that a decade+ ago I read about in an IEEE pub. Motors all over an office building would regularly fail shorted. Not just mere small ones, but HVAC and elevator ones.

After a major clue hunt, they found a large photocopy machine that was suspected. It was fed with 208-240 on a dedicated circuit. They applied significant lightning/transient suppression to the machine, and all the problems ceased. [Sometimes the lightning is within, and seeking to escape, it seems...]

So we go back to Jraef's query. Do we know the failure mode?
 
aren't even the 3 to 5 HP range of motors listed with a DUTY CYCLE (or something very similar)?? Meaning they are rated for either continuous or short duty cycles. Seems to me the first thing I'd look for is the DUTY rating, six months out of motor doesn't seem like much....

If they check out OK for continuous duty, then maybe someone decided long ago they could use a 3 HP frame that is common with a 5 HP frame and thought they could save money on motors that way (it is really only a short term savings).
 

hurk27

Senior Member
What is the voltage rating of the motor?
If it is a 230 volt rated motor it will not run at full HP on 208 or 204 for that matter, this is a common over look when replacing motors and equipment, owners don't know this and they order 230 volt equipment when they need to make sure it is rated for 208, also if the motor is rated for 208, the name plate should say 200 volts, other then maybe it's being wire in a Y instead of a delta, the only other thing is startup current causing a far greater voltage drop then when running, try to watch the voltage when starting the motor, this can cause a much longer starting period in where the motor is not in sync for a longer time.
 

broadgage

Senior Member
Location
London, England
As suggested by others, probable causes are undersized or overloaded motor, 230/240 volt motor on 208 volt supply, motor used on VFD and not rated for such use, or a short time rated motor subjected to continous duty, or attack by pool chemicals.
Another possibility, not yet suggested, is overheating. If the motor is outside and exposed to intense sunlight, or indoors in a small or poorly ventilated enclosure then it might well overheat even if worked just within its rating.
Or might be an inferior type of imported motor.
 
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