Workshop compressor help

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PCUK

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Our 3hp compressor keeps tripping the RCCB, presumably due to an earth fault. We've been through it and can't find the leak so were wondering if there is any way to isolate it from the RCCB while still going through it (the RCCB). We can't by-pass it as the RCCB is in another building. Thanks.
 
If you can't find an earth leak you may want to check the piston isn't caught on a compression stroke with the tank already /largely preassurised. My compressor has an onboard trip at 8 amp and will regularly trip out if I start her with the tanks already at 6 Bar and above if the motor is trying to start up on a compression stroke.
 
A 2.4 kW motor will pull ~10amps running on full load, but could pull up to 70 on start up.

I assume this is a developed fault, that previously the compressor ran OK.

Is there a pattern to the trip, e.g. at first start, any time at random, at higher pressure cut out, or at re-start cut in ? With the tank at say 100 psi the start current will be higher.

Possibly a start or run capacitor breaking down - if these are metal cased then try replacing them one at a time.

Is the RCCB current rated or purely a Residual Current Device ?

Reducing the re-start cut in pressure might help.

When you say you couldn't find a leak what instrument did you use - a normal ohmmeter may not detect a winding fault ?

A 500v megger is needed to test for earth leakage on a 240v appliance.

Any possibility the motor has become damp ?

A socket tester will only tell you the polarity of the three connections is correct.
 
The compressor has always been a problem but in our previous shop we by-passed the RCCB. It seems to be an intermittent fault that occurs on restart. Also when draining the reservoir I get a tingle from the water and also touching any part with wet hands. Even when the mains socket is switched off. Unplugging it is the only way to avoid this. We just kept well away from it when plugged in and carried on as normal.
PS. looking for the leak was simply a visual test trying to find a loose wire or similar.
 
PCUK said:
Also when draining the reservoir I get a tingle from the water and also touching any part with wet hands. Even when the mains socket is switched off. Unplugging it is the only way to avoid this.
Click to expand...

AGH! I think you need to look in depth at your mains wiring. An urgent job I suggest for a qualified electrician!
 
Some sockets only switch the live side ,what earthing arrangements do u have I e tt tncs as said before you need the motor tested with a insulation resistance tester
 
Have you checked the neutral and earth are not reversed on the connection at the plug or where the supply cable wires connect to the terminals ?

As others have said this needs urgent attention. If your RCD packs up so might you !!!
 
sarabande said:
In suggesting a socket tester, I was trying to tick off possible 'upstream' causes.
Click to expand...
Fair enough. The OP perhaps needs to provide us with a bit more information to help provide guidance. Fault finding on AC motors and associated control systems is part of my day job, as is electrrical safety.

Bypassing an RCD (RCCB) whilst being aware there is a tingle from the equipment suggests the OP has never had a serous belt ... yet !
 
The tingle occurs even when going through an RCD and I've had my share of belts of various degrees. The problem is identical in the old shop and the new one so it's not the shop wiring. Perhaps I should take it to an electrician to sort it out!:nonchalance:
 
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