Motor running at higher amperage

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jerjwillelec

jerjwillelec

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Location
Nevada, IA
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Master Electrician
I have two 25 HP motors at an aquatic center. They are the filter pumps...FP1 & FP2. Namplates say 59 amps at 230 volt (208 volt system). FP1 is running just fine at around 56 to 58 amp. FP2 tripped the overloads in the Altistart 48 soft start yesterday and is running around 65 to 69 amp. Why the higher amperage draw?

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I replaced the connections at the motor which weren't the best but yet nothing has changed

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jerjwillelec said:
I have two 25 HP motors at an aquatic center. They are the filter pumps...FP1 & FP2. Namplates say 59 amps at 230 volt (208 volt system). FP1 is running just fine at around 56 to 58 amp. FP2 tripped the overloads in the Altistart 48 soft start yesterday and is running around 65 to 69 amp. Why the higher amperage draw?

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Bit too general.........
But a couple of suggestions.
Have you checked the current balance?
Does the motor/pump turn freely by hand?
 
jerjwillelec said:
I replaced the connections at the motor which weren't the best but yet nothing has changed

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Not a real help but have you checked to see if a replacement motor is nearby?
If it messes the bed someone is gonna have to move fast.
 
jerjwillelec said:
I have two 25 HP motors at an aquatic center. They are the filter pumps...FP1 & FP2. Namplates say 59 amps at 230 volt (208 volt system). FP1 is running just fine at around 56 to 58 amp. FP2 tripped the overloads in the Altistart 48 soft start yesterday and is running around 65 to 69 amp. Why the higher amperage draw?

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Sounds like a centrifugal pump that is operating outside its design curve. In other words there is not enough head and it is overloading the motor. You should have a valve on the discharge side to adjust and limit the flow.
 
texie said:
Sounds like a centrifugal pump that is operating outside its design curve. In other words there is not enough head and it is overloading the motor. You should have a valve on the discharge side to adjust and limit the flow.
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Kind of what I was thinking based on the quick research I've done. I don't know much about the mechanical side of things. Is this something that would need to be adjusted a lot? How does the head pressure change?

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Besoeker said:
Suggests a load problem.
Does the motor/pump turn freely by hand?
Click to expand...

I do not know...it's full of pool water. I'll see if I can drain that section to try and turn it by hand. What are you suggesting if it does or doesn't turn freely? And how do I guage "freely"

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jerjwillelec said:
Kind of what I was thinking based on the quick research I've done. I don't know much about the mechanical side of things. Is this something that would need to be adjusted a lot? How does the head pressure change?

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The main thing affecting head pressure in a filter loop is the back pressure of the filter with water flowing through it.
A hole in the filter medium or a general loss of filter medium (as in a diatomaceous earth filter) could reduce the head pressure and thus increase the flow rate and the load on the motor.
Do the two pumps feed different filters or are they plumbed in parallel to one set of filters?
A manual valve (possibly gate type rather than on off ball valve) might be inserted in the filter loop somewhere. If somebody noticed that the valve was not all the way open and "fixed" it or somebody closed that valve for maintenance and then opened it all the way that could cause your problem.
 
jerjwillelec said:
I do not know...it's full of pool water. I'll see if I can drain that section to try and turn it by hand. What are you suggesting if it does or doesn't turn freely? And how do I guage "freely"

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Is the motor/pump set submersed or dry?
 
jerjwillelec said:
Kind of what I was thinking based on the quick research I've done. I don't know much about the mechanical side of things. Is this something that would need to be adjusted a lot? How does the head pressure change?

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You mention that this is a filter pump. The flow rate and current will be higher with a clean filter and decrease as the filter collects debris.
You could get fancy and use a vfd with a pressure sensor to maintain a constant flow rate that is within the design curve.
 
GoldDigger said:
The main thing affecting head pressure in a filter loop is the back pressure of the filter with water flowing through it.
A hole in the filter medium or a general loss of filter medium (as in a diatomaceous earth filter) could reduce the head pressure and thus increase the flow rate and the load on the motor.
Do the two pumps feed different filters or are they plumbed in parallel to one set of filters?
A manual valve (possibly gate type rather than on off ball valve) might be inserted in the filter loop somewhere. If somebody noticed that the valve was not all the way open and "fixed" it or somebody closed that valve for maintenance and then opened it all the way that could cause your problem.
Click to expand...

Both pumps have their own filters

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jerjwillelec said:
Kind of what I was thinking based on the quick research I've done. I don't know much about the mechanical side of things. Is this something that would need to be adjusted a lot? How does the head pressure change?

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Click to expand...
What texie was really getting at was that load, on a centrifugal pump, is equal to flow. Flow is a factor of Total Dynamic Head (TDH) and fluid velocity. So if you have not changed the speed of the pump, the velocity would be the same, therefore you (or someone else) have done something to change the TDH. TDH consists of the static head pressure, which is based on elevation change and is not likely to have changed either, friction, meaning the number of bends and pipe diameter changes, and any restrictive elements, such as valves. So in all likelihood, the thing that is most probable to have affected the motor loading is that there is a valve somewhere that is not set correctly for the design of the system. Was it working fine for a while and then started tripping?

Damn, I have to remember to read BOTH pages before responding, because as per usual, GoldDigger beat me to it...

And in fact one-upped me on the blown-out filter medium possibility, hadn't though of that.
 
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Jraef said:
What texie was really getting at was that load, on a centrifugal pump, is equal to flow. Flow is a factor of Total Dynamic Head (TDH) and fluid velocity. So if you have not changed the speed of the pump, the velocity would be the same, therefore you (or someone else) have done something to change the TDH. TDH consists of the static head pressure, which is based on elevation change and is not likely to have changed either, friction, meaning the number of bends and pipe diameter changes, and any restrictive elements, such as valves. So in all likelihood, the thing that is most probable to have affected the motor loading is that there is a valve somewhere that is not set correctly for the design of the system. Was it working fine for a while and then started tripping?

Damn, I have to remember to read BOTH pages before responding, because as per usual, GoldDigger beat me to it...

And in fact one-upped me on the blown-out filter medium possibility, hadn't though of that.
Click to expand...

Thank you everyone! I'm headed back now to see about adjusting valves. Yes, to my knowledge it was working fine until yesterday

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