Clarke compressor start capacitor

[AVI_8]

I picked up a couple of second hand Clarke compressors at the weekend, one had a known problem, it wouldn’t start, it came with another motor which works but has noisy bearings which I’ll replace.
I removed the start capacitor on the non starting motor and de soldered the diode (I think that’s what it is) the capacitor is showing over 180 microfarads, it’s supposed to be 150.
Presumably an excess of 30 microfarads could be the cause of the starting issue? I know that if it’s under it would cause a problem, the capacitor doesn’t give a range on it ie plus or minus

 

[Red'n'Black]

The component across the terminals is a bleed resistor to leak away the charge when the power is off, 150uF charged up to mains voltage would give you quite a belt.

I wouldn't worry about the capacitance measuring a bit high, electrolytic caps have a fairly large tolerance - +80/-20% is quite common.

What the meter won't tell you is if the cap has dried out and gone high resistance so the only easy way to check them is by substitution.

 

[brightspark]

the cap looks manky anyhow just replace it for what they cost . wouldnt bother with the resistor to be honest

 

[Guineafowl]

Discharge resistor looks added on. The cap would discharge through the windings anyway, so a bit pointless.

 

[AVI_8]

Yes will do thanks guys, can’t seem to locate a 350v would a 450v be fine as a substitUte, such as this one

150uf Motor Star Capacitor 150mfd AC 450V for HVAC Single-Phase 50/60Hz AC Motor | eBay

Specification:Capacitance: 150uf (150mfd)Tolerance: -10% - +20%Rated Voltage: AC 450VFrequency: 50/60 HzOperating Temperature: -40℃-55℃Terminal Type: Insulated Wire LeadsDimensions:Case Diameter: 50mm (1.97")Case Height: 104mm (4.09")Wire Length: 220mm (8.66")About CD60 Capacitors:-CD60 series...

www.ebay.co.uk

 

[Guineafowl]

^ looks fine.

 

[Seadog]

450v is fine.

 

[Turbo]

If you look on the motor plate it will often give you the correct uf for the capacitor, just in case it is not correct. Unless its a very big motor 150uf does sound a bit big for a start cap.
Normally an oversize cap causes the motor to run hot, using it too long like that will eventually cook the windings!
Look at the other compressor & spare motor to check what size of start cap they use.

 

[AVI_8]

If you look on the motor plate it will often give you the correct uf for the capacitor, just in case it is not correct. Unless its a very big motor 150uf does sound a bit big for a start cap.
Normally an oversize cap causes the motor to run hot, using it too long like that will eventually cook the windings!
Look at the other compressor & spare motor to check what size of start cap they use.

The replacement motor I got has a 60uf start and run cap, as you said it’s stamped on the plate, both of these machines I picked up have a 150uf start cap and a separate smaller run cap. Clarke must have changed their motor design at some point giving, I think their later motors 2 caps.

 

[Turbo]

The replacement motor I got has a 60uf start and run cap, as you said it’s stamped on the plate, both of these machines I picked up have a 150uf start cap and a separate smaller run cap. Clarke must have changed their motor design at some point giving, I think their later motors 2 caps.

A single cap motor is not really suitable for equipment needing a high starting torque such as a compressor. That spare motor would be more suitable for something like a bench drill.

 

[AVI_8]

A single cap motor is not really suitable for equipment needing a high starting torque such as a compressor. That spare motor would be more suitable for something like a bench drill.

Well it’s physically identical to the original motors, has, the same 3HP and the same rpm stamped on the plate.
I’ll see, I’m hoping that get the original motor working anyway.

 

[AVI_8]

I swapped over 2 known good capacitors onto this motor and still no joy, decided to take it apart as a practice run for the working motor that needs bearings.
Don‘t think it’s meant to be lubricated with water !!! No wonder it was humming.
I’ve cleaned up the stator and rotor with electrical spray, they were quite wet, got a lot of dirt out, they actually look ok now, cleaned the contacts and mechanism for the centrifugal clutch thingy, seems to work ok, brought the stator inside in front of the fire for the evening to dry out the windings, the large bearing came off ok but I can’t seem to be able to remove the plastic fan at the other end, think it’s just a press fit, I’ve tried it with 2 large screwdrivers but don’t want to break it.
It‘s just an experiment, if it works when I put it back together I’ll strip it down and fit new bearings, the old ones aren’t bad but they’re not perfect.

 

[AVI_8]

This has more or less dried out

 

[Seadog]

I put my wet motors in the oven. Gas mark 2 for an hour
The fan is a push fit, but you need to lever near to the boss or it will break. Possibly a bit of rust making it more difficult to remove.

 

[Turbo]

I put my wet motors in the oven. Gas mark 2 for an hour
The fan is a push fit, but you need to lever near to the boss or it will break. Possibly a bit of rust making it more difficult to remove.

The warming oven on our oil cooker doubles as a motor drying oven. Anything too big to fit goes into our hot press for a few days.

If you are very careful you can warm the fan with a hot air gun to soften the plastic making it easier to lever off. Only lever on the centre boss on the motor shaft, never the face of the fan.

 

[AVI_8]

The warming oven on our oil cooker doubles as a motor drying oven. Anything too big to fit goes into our hot press for a few days.

If you are very careful you can warm the fan with a hot air gun to soften the plastic making it easier to lever off. Only lever on the centre boss on the motor shaft, never the face of the fan.

Thanks, good tip for getting fan off, I’ll try that as it’s otherwise well stuck.