# Motor FLA?



## Big John (May 23, 2010)

As much as everyone likes to blame the electricians, eliminate mechanical problems first. In my experience it is very, very rare for motor overload to be an electrical problem. This would be especially true if the current is equally balanced on all phases.

I'd uncouple the motor and see where the current is unloaded.

Wiggle the shaft. If there's any sort of play, it suggests bad bearings which might be dragging and causing hard rotation.


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## GEORGE D (Apr 2, 2009)

Yeah I was hoping to not have to do that, this is a jockey pump motor and I'd rather not get into their stuff if I didn't have to.


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## Big John (May 23, 2010)

I assume it runs for a while before the breaker trips, so this isn't a starting issue? Otherwise, if you don't have something else like undervoltage at the leads, then I'm out of ideas without digging into it.


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## JRaef (Mar 23, 2009)

GEORGE D said:


> This motor is running at 20 amps at 115 volts
> 
> View attachment 23197
> 
> ...


16A FLC, 1.3 Service Factor would mean the motor can run at 20.8A for short durations (not well defined). So from that aspect, and given that this is a jockey pump, this is not at all unusual. But it does mean that if the intent of the fire pump installer was to use the Service Factor of the motor like that, then it should NOT have been connected to a 20A circuit. If the intended load was to be 20.8A, then the circuit should have been sized to 125% of that (26A) and rounded up to the nearest standard size. So #10 wire and a 30A CB.


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## GEORGE D (Apr 2, 2009)

JRaef said:


> 16A FLC, 1.3 Service Factor would mean the motor can run at 20.8A for short durations (not well defined). So from that aspect, and given that this is a jockey pump, this is not at all unusual. But it does mean that if the intent of the fire pump installer was to use the Service Factor of the motor like that, then it should NOT have been connected to a 20A circuit. If the intended load was to be 20.8A, then the circuit should have been sized to 125% of that (26A) and rounded up to the nearest standard size. So #10 wire and a 30A CB.


Good because I went ahead and upsized as mentioned.


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## Big John (May 23, 2010)

GEORGE D said:


> Good because I went ahead and upsized as mentioned.


 My problem with this is that it used to work, correct? So regardless of whether the OCPD can be legally increased, it doesn't answer the question of why it needs to be. 

What's the motor duty? Running continuously in the service factor will shorten the life, especially if there's a degrading mechanical problem involved.


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## GEORGE D (Apr 2, 2009)

Big John said:


> My problem with this is that it used to work, correct? So regardless of whether the OCPD can be legally increased, it doesn't answer the question of why it needs to be.
> 
> What's the motor duty? Running continuously in the service factor will shorten the life, especially if there's a degrading mechanical problem involved.


You are right, but in this case management made the call so I did as requested. I will also note that in the past I responded to a call for this motor which had a bad starter contactor due to chattering caused from pressure switch. I recommended then, after their fire control guys verified the switch was good to get it resolved which no one ever did. I warned I would be back to change another contactor soon. Today I disassembled the contactor and checked actual contacts which showed quite a bit of charring on line terminal so I went ahead and replaced with fresh one from spare old contactor just to buy more time.


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## JRaef (Mar 23, 2009)

Big John said:


> My problem with this is that it used to work, correct? So regardless of whether the OCPD can be legally increased, it doesn't answer the question of why it needs to be.
> 
> What's the motor duty? Running continuously in the service factor will shorten the life, especially if there's a degrading mechanical problem involved.


Jockey pumps don't run continuously, they only come on for very short periods of time to re-pressurize fire sprinkler stand pipes as they leak and maybe once or twice a year for pressure testing. With age, the pipes start to lose pressure faster, so the pump has to cycle on and off more often than it used to. That could easliy be the straw that breaks the camel's back for the under sized breaker. 

But George D, Big John is right in that it could also mean something else, like the motor starting to fail or the pressure switch causing the pump to cycle too often. It's worth checking.


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## xlink (Mar 12, 2012)

Breakers loaded to their max can trip more easily when they get old, too.


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