Clarke Champ Frame Compressor Fault

[Andrew Hart]

Any more thoughts from anybody before I bite the bullet and fit a manual unloading / dump valve?

 

[Dcal]

What HP is the motor?
Could the capacitor be the wrong value from the start? (I know you changed it like for like, could it be faulty?)

Is there any situation where it will not start when you are sure there is no air in the unloader circuit?
Must say you have tried everything I would have thought of and I'm pretty stumped now.

Do tell us how you fair.
You learn a lot more from the tricky problems.

 

[carbon]

One of the windings may have deteriorated causing the start problem. Why I asked if the original cap was close to 60uf when measured.

 

[Al Strachan]

Any more thoughts from anybody before I bite the bullet and fit a manual unloading / dump valve?

dont think thats your problem though. leave the delivery pipe off the head and see if it still does it.

What grade oil did you use? I'm in the middle of refurbing another clarke and its developed similar after replacing the oil. manual states SAE40, but the WWW seems to advise SAE30 for clarke piston comps.

 

[WorkshopChris]

One of the windings may have deteriorated causing the start problem. Why I asked if the original cap was close to 60uf when measured.

As soon as I started reading this my thoughts were electrical, either the capacitor and or a winding issue.

 

[carbon]

I usually check motors with a pat tester, insulation test to see if there are problems but not something everyone has access to. Had problems with one a while ago motor would run for about 10 seconds before rcb would trip. Motor had well under 1Mohm resistance but unlikely to find with a multimeter

 

[Andrew Hart]

What HP is the motor?
Could the capacitor be the wrong value from the start? (I know you changed it like for like, could it be faulty?)

Is there any situation where it will not start when you are sure there is no air in the unloader circuit?
Must say you have tried everything I would have thought of and I'm pretty stumped now.

Do tell us how you fair.
You learn a lot more from the tricky problems.

I am not sure of the rated motor power, there are no markings on it at all and I don’t have the manual for the exact model. It takes around 20 Amps after the initial starting current of 45-55 Amps, which is around 2.2KW or 3HP @ 110V. The original capacitor was 60uf 330v (measured 58uf), but I replaced it with a 60uf 440v item (no reason for the 440v except that’s all I could get quickly) and it made no difference.

First start of the day when it is cold and definitely no air in the unloader circuit it struggles to run. I have been researching this a lot and this can be a big issue in colder parts of the world, and a lot of countries fit “cold start valves” to their single phase AC compressors to unload them for the first few cycles until the motor is up to speed.

 

[Andrew Hart]

One of the windings may have deteriorated causing the start problem. Why I asked if the original cap was close to 60uf when measured.

I am starting to lean towards a motor problem myself. As above, 58uf when measured.

 

[Andrew Hart]

I usually check motors with a pat tester, insulation test to see if there are problems but not something everyone has access to. Had problems with one a while ago motor would run for about 10 seconds before rcb would trip. Motor had well under 1Mohm resistance but unlikely to find with a multimeter

Unfortunately my Megger (IR tester) has died, so I’m going to take it into work and get the electrical guys to check it out for the next step.

 

[Andrew Hart]

What HP is the motor?
Could the capacitor be the wrong value from the start? (I know you changed it like for like, could it be faulty?)

Is there any situation where it will not start when you are sure there is no air in the unloader circuit?
Must say you have tried everything I would have thought of and I'm pretty stumped now.

Do tell us how you fair.
You learn a lot more from the tricky problems.

I am not sure of the rated motor power, there are no markings on it at all and I don’t have the manual for the exact model. It takes around 20 Amps after the initial starting current of 45-55 Amps, which is around 2.2KW

dont think thats your problem though. leave the delivery pipe off the head and see if it still does it.

What grade oil did you use? I'm in the middle of refurbing another clarke and its developed similar after replacing the oil. manual states SAE40, but the WWW seems to advise SAE30 for clarke piston comps.

If I leave the delivery (discharge) pipe off the head it starts every time, hot or cold.

I used ISO 150 (SAE 40) mineral compressor oil when I did the oil change. The oil I dropped out was the original oil so I assume this spec too, and the compressor used to run fine. My original thoughts when I had this problem was corrosion in the bore as it had stood unused for 8-10 years until this year. When I stripped it down it was like new inside so I dismissed that theory.

 

[Dcal]

I am not sure of the rated motor power, there are no markings on it at all and I don’t have the manual for the exact model. It takes around 20 Amps after the initial starting current of 45-55 Amps, which is around 2.2KW or 3HP @ 110V. The original capacitor was 60uf 330v (measured 58uf), but I replaced it with a 60uf 440v item (no reason for the 440v except that’s all I could get quickly) and it made no difference.

First start of the day when it is cold and definitely no air in the unloader circuit it struggles to run. I have been researching this a lot and this can be a big issue in colder parts of the world, and a lot of countries fit “cold start valves” to their single phase AC compressors to unload them for the first few cycles until the motor is up to speed.

I thought the current draw was the problem until I remembered it is 110v.
Still I'd expect it to be drawing slightly less than that, if it's 3HP it's working hard and on the limit.

 

[Andrew Hart]

I thought the current draw was the problem until I remembered it is 110v.
Still I'd expect it to be drawing slightly less than that, if it's 3HP it's working hard and on the limit.

I’d agree. The integral overload is 20A so it is right on the limit of tripping in normal running. Unfortunately due to the design of the unit it is not possible to split the motor from the compressor to do an uncoupled run and see what the motor alone is consuming.

I am going to contact Clarke and see if they can provide the spec of the unit from pictures alone as there are no model numbers or serial numbers on the unit at all except the receiver plate.

 

[Al Strachan]

if I leave the delivery (discharge) pipe off the head it starts every time, hot or cold.

I used ISO 150 (SAE 40) mineral compressor oil when I did the oil change. The oil I dropped out was the original oil so I assume this spec too, and the compressor used to run fine. My original thoughts when I had this problem was corrosion in the bore as it had stood unused for 8-10 years until this year. When I stripped it down it was like new inside so I dismissed that theory.

Mine does the same, but from my poking around yesterday it looks like the my capacitor might be duff. I'll get that changed, but if there's still no success i'm strongly suspecting the oil in mine is too thick. SAE40 is in the manuals, but everywhere online is SAE30 for Clarke piston comps, and i dont think SAE20 would do any harm either, especially for the colder climate. my other Sealey compressor struggles in the depths of winter also with the manufacturers recommended grade.

On my one, even if the capacitor isn't the greatest, i've done nothing electrically to change the way it starts. OK, i have tightened up the piston/bore slightly, but the main issue could be that I've gone from whatever oil was in previously to SAE40.


Good luck!

 

[Andrew Hart]

Slight update, I found this under a sticker on the air end. So it is 1.5KW or 2HP and should take up to 16.5 Amps running and up to 99 Amps on startup according to Machine Mart.

so it looks like it is taking around 20% more current than it should when running. Ideas?

 

[Al Strachan]

Whats the voltage at the motor or switch when running? less than 110v will see a higher current draw
have you disassembled the check valve in the tank. its not sticking shut or partially shut is it?

duty is 7bar. you dont run it any higher do you? I'm assuming that the 16.5a is based on a service duty rather than max pressure?

Oil is too thick (not letting go of that one haha!!)

thats my tuppence.

 

[carbon]

Has it been happy running on the transformer you have? Definitely check voltage off load and on load. Other than a winding fault as you seem to have covered everything else.

 

[WorkshopChris]

As above it will require as a minimum 2.5mm extension cables ideally 4mm, from a transformer rated at least 5kva.
Volt drop on 110v is a big issue.
Had a customer with a hoist that kept coming back with an intermittent fault in the solenoid coil would not always hold. The thing was 100% when tested, in the workshop, I eventually went to test on-site top floor of a 5 story townhouse conversion. 10kva transformer at the site entrance, I counted 7 spider or splitter boxes before the box on the 5th floor. Measured roughly 45v offload, when the coil pulled in the best drop I measured was 36v phase to earth.

 

[Andrew Hart]

Whats the voltage at the motor or switch when running? less than 110v will see a higher current draw
have you disassembled the check valve in the tank. its not sticking shut or partially shut is it?

duty is 7bar. you dont run it any higher do you? I'm assuming that the 16.5a is based on a service duty rather than max pressure?

Oil is too thick (not letting go of that one haha!!)

thats my tuppence.

I have stripped the non return valve and it is definitely not sticking and Looks like new inside.

I have measured the transformer output voltage with the transformer disconnected and it’s giving 112V. With the compressor running and measuring at the overload switch it is down to 95V. That would explain the higher current draw than expected. I run it at 8 Bar normally, but I can’t see how that would only give me a problem when cold and usually the tank is flat at this point. My father in law has a 5KVA transformer so I am going to try that before I strip the motor.

 

[Andrew Hart]

As above it will require as a minimum 2.5mm extension cables ideally 4mm, from a transformer rated at least 5kva.
Volt drop on 110v is a big issue.
Had a customer with a hoist that kept coming back with an intermittent fault in the solenoid coil would not always hold. The thing was 100% when tested, in the workshop, I eventually went to test on-site top floor of a 5 story townhouse conversion. 10kva transformer at the site entrance, I counted 7 spider or splitter boxes before the box on the 5th floor. Measured roughly 45v offload, when the coil pulled in the best drop I measured was 36v phase to earth.

I like your thinking. As above, I’m down at 95V on load. I don’t use an extension, it’s cabled with 2.5mm2 on a 1/2 metre lead straight into the transformer.

 

[Andrew Hart]

Has it been happy running on the transformer you have? Definitely check voltage off load and on load. Other than a winding fault as you seem to have covered everything else.

It’s always been a problem on this transformer, but I’ve never tried a different one. That’s my next port of call, trying a 5KVA unit.