203 V supply to pool pump motor

[Peter Furrow]

My technician responded to a service call today at a condominium. The new pool pump motor installed by the on-site maintenance man was extremely hot to the touch. The last motor burned up.
Power is being delivered from the main distribution panel Reading 208 V. Approximately 200 feet downstream is the pool equipment room that was receiving 203 V to the pool pump motor. (Obvious voltage drop).
The pool pump motor nameplate rating says 208 -230v FLA 24Amps.
However, our actual reading was 203 V & ammeter read 30.4 Amps running load.

The 200 foot feeder conductors is #2 CU.
(Sufficient to handle the load.)
Obviously this voltage drop is causing the increase in the amperage draw.
What do you think is the best way to resolve this? How can I raise the voltage to the
208 and the 230 V requirement mentioned on the nameplate?
I think they’re gonna burn this new motor up if this voltage doesn’t get resolved .I just don’t know what to do at this point. To top it all off we are extremely busy right now but I want to take care of them. Ugghh..


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[texie]

It is likely there is nothing wrong except that the pump does not have enough head on it and it is operating outside of its design curve. See it all the time on commercial pools. It just needs to have a throttling valve on the discharge of the pump to get the flow in line with the pump curve. You just throttle the flow back until the amperage is in line with the motor data plate. If then you do not have enough system flow the you have a design issue and the pump is to small.

 

[winnie]

I think texie is correct about checking the mechanical loading on the motor.

A motor labeled for 208 V should have tolerances to operate below that value.

However if voltage is the issue a simple boost transformer would be viable here. Normally you don't want to use a boost transformer for voltage drop because when the load is off the voltage becomes excessive. But since you can go up to 240V safely this isn't a problem.

A 1kva 240:24V transformer would do the trick to solve the voltage problem, but again I believe that the mechanical problem angle should be investigated first.


Jon

 

[kwired]

203/208 is only 1% VD, which is better than a lot of installations often have.

I agree with others, pump is overloaded and probably needs restriction in the line to limit loading.

 

[texie]

In addition to what has been discussed, you should be asking yourself why the pump continues to run at such an overload. Is there a proper motor starter with the correct size overloads? And if this is an existing system that ran correctly for years it is likely something has changed. Could be something as simple as someone changing the discharge nozzles in the pool to a larger size.

 

[Peter Furrow]

It is likely there is nothing wrong except that the pump does not have enough head on it and it is operating outside of its design curve. See it all the time on commercial pools. It just needs to have a throttling valve on the discharge of the pump to get the flow in line with the pump curve. You just throttle the flow back until the amperage is in line with the motor data plate. If then you do not have enough system flow the you have a design issue and the pump is to small.

Very helpful thank you.


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[Jraef]

I agree with everything said here; 203V on a motor rated for 208V is not the issue, that's fine. 30.4A on a motor rated for 24.8A IS a huge issue, but you are likely jumping to the wrong conclusion about that being due to the voltage drop. NEMA motor designs are expected to handle +-10% of NAMEPLATE votlage. So the motor should be within spec for down to 187.2V, 203V is way good. So the cause of the overloading, especially on a pump, is a flow problem. In a centrifugal pump, load = flow. Too much flow leads to too much load. So either someone put in too large of a pump for the application, or there was / is a flow control device that has been altered (or it was a bad sesign from the outset). The fact that your previous motor "burned up" is also why Texie mentioned the starter for this pump; it SHOULD have protected the motor. So what happens is that someone kept getting trips on the OL relay and "solved" the problem by putting in larger heaters or turning up the dial. That is what lead to motor death. Once you fix the flow issue, fix the protection issue too.

 

[electricman2]

Anybody thought to find out why voltage is low? Check upstream voltage. Any other circuits experiencing low voltage, etc.

 

[Peter Furrow]

Anybody thought to find out why voltage is low? Check upstream voltage. Any other circuits experiencing low voltage, etc.

The upstream voltage is reading 208 at the main distribution panel. The feeders go two hundred feet into a pool equipment room and from there we are reading 203 V..


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[roger]

The feeders go two hundred feet into a pool equipment room and from there we are reading 203 V..


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That would do it. But as the others have said, the 5 volt drop is not a problem.

Roger

 

[texie]

That would do it. But as the others have said, the 5 volt drop is not a problem.

Roger

I agree and in addition the voltage drop will improve when he get the overload taken care of.

 

[electricman2]

I missed the 200 ft. number. That would account for the loss. As has been said, get the motor current down to nameplate FLC and that should clear things up.

 

[retirede]

Did you check voltage between all 3 phases? Imbalance can be a bigger issue than slightly low voltage.

 

[electricman2]

Did you check voltage between all 3 phases? Imbalance can be a bigger issue than slightly low voltage.

Where did OP say it was 3 phase/

 

[Eddie702]

Where did OP say it was 3 phase/

Good question we see 208 volt and automatically assume it's 3 phase. Could be single phase with overloads inside the motor. Could be a 7 1/2 hp if 3 phase

 

[retirede]

Where did OP say it was 3 phase/

Where did he say it wasn’t?

 

[electricman2]

Where did he say it wasn’t?

He didn't, just going by location, condominium, I'm guessing they have a 120/208 service but the pump is probably singe phase but I may be wrong

 

[Peter Furrow]

The main distribution panel is 3phase.
However, the feeders to The pool equipment room are single phase 208 V


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[Peter Furrow]

The main distribution panel is 3phase.
However, the feeders to The pool equipment room are single phase 208 V


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The motor is not three-phase


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[tom baker]

Reminds me of what a wise maintenance electrician once said
"Its always an electrical problem", meaning its never an electrical problem ...ie OL trip because the sewer pump is ragged up.