Compressor motor

[ukracer]

I have a motor on my compressor that will not start under load.

It hums loudly and trips the MCB.

Is it likely to be the motor windings.

Or brushes

Or capacitor at fault?

 

[bigegg]

I have a motor on my compressor that will not start under load.

It hums loudly and trips the MCB.

Is it likely to be the motor windings.

Or brushes

Or capacitor at fault?

will it turn by hand?

 

[rtbcomp]

When you say "under load" they're not supposed to start under load on a compressor. Will it start when the tank is empty and the outlet opened?

Will it start if you take the belt off (assuming it's belt driven)?

 

[brightspark]

no brushes on an induction motor does it run with belt off

 

[carbon]

If it doesn't run with the belt off, i'd check the capacitor for the correct capacitance.

 

[ukracer]

will it turn by hand?

Yes VERY easily without Belt. Reasonably easy with Belt on.

 

[ukracer]

no brushes on an induction motor does it run with belt off

Lol yeah we found that out. looked high and low for them.
But yes it runs fine without belt connected.
This is why favoured capacitor issues ....possibly.

 

[eLuSiVeMiTe]

Had similar issues with the motor on one of mine. Had to pull the release valve above the piston to let the pressure out then the motor would start.

 

[ukracer]

Had similar issues with the motor on one of mine. Had to pull the release valve above the piston to let the pressure out then the motor would start.

Its been fine and just suddenly started playing up.

It has got two capacitors fitted.

 

[eLuSiVeMiTe]

Mine wasn't a motor issue. The motor couldn't turn because too much pressure above the piston stopping it turning the crank.

Does it start without the belt attached.

 

[carbon]

It may have a switch in the motor to switch one of the capacitors out when its up to speed, and the switch may be stuck. Or the capacitance may be lower than the tolerance rating on the capacitor.

 

[ukracer]

Mine wasn't a motor issue. The motor couldn't turn because too much pressure above the piston stopping it turning the crank.

Does it start without the belt attached.

Yes it does start fine without the belt on...

 

[ukracer]

It may have a switch in the motor to switch one of the capacitors out when its up to speed, and the switch may be stuck. Or the capacitance may be lower than the tolerance rating on the capacitor.

Switch seems clean and free. I am guessing its got a start and run capacitor.. just a guess though.

 

[eLuSiVeMiTe]

Yes it does start fine without the belt on...

So perhaps not a motor issue at all. Worth exploring. Have you got something else you can use to load the motor to test. Or another motor to test on the comp.

 

[carbon]

If it has a start cap these usually have a higher capacitance value than the run cap. Depending on speed and motor size the run cap could be 40 - 80 uF and the start above 200 uF. Values can somestimes be marked on the motor data plate if lucky

 

[ukracer]

If it has a start cap these usually have a higher capacitance value than the run cap. Depending on speed and motor size the run cap could be 40 - 80 uF and the start above 200 uF.

Problem is i cànt see any markìngs on the caps.....i need to search for the model in the morning i know its a SIP thats all till morning.

 

[ukracer]

So perhaps not a motor issue at all. Worth exploring. Have you got something else you can use to load the motor to test. Or another motor to test on the comp.

Well the pump is new But......it has worked fine for 2 days...just started playing up today.

 

[rtbcomp]

Will it start when the tank is empty and the outlet opened?

Did you try this?

 

[ukracer]

Did you try this?

Still wont start....just hums and trips.

There seems to be no difference to starting the pump with the tank full or empty.

 

[ukracer]