Monitor a circuit.

[electricblue]

I need to monitor a 240v circuit to find out why a motor keep burning up. Can anyone recommend a piece of equipment to do so. It may take a few month.

 

[iwire]

I need to monitor a 240v circuit to find out why a motor keep burning up. Can anyone recommend a piece of equipment to do so. It may take a few month.

Rent a power quality recording meter.

http://www.test-equipment-rental.com/

 

[kwired]

Could be more than electrical problem.

Is motor sufficient size for the driven load?

Is there a problem with the driven load?

Is motor properly protected from overload?

Does motor have sufficient ventilation for cooling?

If it is conected to a variable speed drive it may need additional ventilation as it will not cool itself as well at reduced speeds. Improper drive settings can cause problems too.

Motors are not generally susceptable to minor voltage problems that may need long time recording to see. If these type of problems are severe enough then proper motor overload protection usually kicks in.

 

[iwire]

Recording the current for a period of time can be very helpful in identifying non-electrical problems.

 

[kwired]

Recording the current for a period of time can be very helpful in identifying non-electrical problems.

yes it can be.

 

[iceworm]

I need to monitor a 240v circuit to find out why a motor keep burning up. Can anyone recommend a piece of equipment to do so. It may take a few month.

Bob already gave you a good rental link so I won't add to that.

However, just for my own curiosity:
Single phase? Cap start? Cap run? No cap?
Integral protector or separate overload? Is someone resetting the protection regularly?
High ambient temp?
When you say "burned up" does that mean the windings are blackened/cooked looking? Are the bearings failed?
What is the application? HVAC fan? Pump? Conveyor? Continuous duty?
Is the load coupled to the shaft? Belt driven?

iceworm

 

[electricblue]

This is a 1 1/6 hp 2 speed spa motor. Controlled by a Len Gorden pneumatic timer. I've replaced timer 3 times. The motor is the 3rd one replaced by pool tech. I've taken apart the last timer to find the low speed micro switch that is rated for 2hp and 20 amp is fused together and the pump won't shut off because the micro switch can't open. Why is there not a scratching head imotacon?:?

 

[kwired]

This is a 1 1/6 hp 2 speed spa motor. Controlled by a Len Gorden pneumatic timer. I've replaced timer 3 times. The motor is the 3rd one replaced by pool tech. I've taken apart the last timer to find the low speed micro switch that is rated for 2hp and 20 amp is fused together and the pump won't shut off because the micro switch can't open. Why is there not a scratching head imotacon?:?

Now we are getting somewhere. You probably don't have much of a problem that recording meter will uncover other than excessive run time. If you have serious voltage problems you will likely have trouble with more than just this motor.

I don't like seeing microswitch or equivelant switching such heavy loads. Even if they are rated for it they don't seem to handle it very well. If motor is "stuck" in running position is it designed to run continuously?

Is there anything preventing the high speed winding from being energized at same time when this switch is stuck? That would not do the motor any good if both speeds are energized at same time.

 

[electricblue]

Now we are getting somewhere. You probably don't have much of a problem that recording meter will uncover other than excessive run time. If you have serious voltage problems you will likely have trouble with more than just this motor.

I don't like seeing microswitch or equivelant switching such heavy loads. Even if they are rated for it they don't seem to handle it very well. If motor is "stuck" in running position is it designed to run continuously?

Is there anything preventing the high speed winding from being energized at same time when this switch is stuck? That would not do the motor any good if both speeds are energized at same time.

Yes the high speed would work when the low speed was stuck running. Never thought of that. I should ask the HO if he used the spa once the timer was stuck.

 

[Pullnwire]

I would install a couple of definite purpose contactors with 240 volt coils, rated over the current of the motor. Let the contactor handle the load, and the existing timer can stay in place to drive the new set of contactors.