Compressor trips out mains

[Julian]

Hi all, the problem ive had for a little while and im only just getting round to trying to fix it, is my clarke compressor which has had a new motor on it for 2 years and did work fine, but now when i flick the mains switch it trips out the main fuse, when I got the thing 1 of the bearings was missing so did both( v twin pump) and it worked great but now just trips out the mains, question is what can be causing it, anyone have any ideas, I did think about a new twin pump, around £137.
Any one have a clue as its getting to that time when my daughter wants her car another colour and i really should get it back running save using my mates 1. I need help guys

 

[chevy2]

I'm no electrician but you may need a motor rated breaker? C type instead of a domestic B type?
My mig kept knocking out the breaker on the new power supply in the garage until i uprated the breaker.

 

[wheresmejumper]

what exactly do you mean when you say mains,an MCB?

 

[eil]

Does it trip straight away with no pressure in it, can you turn it by hand, slacken the motor off remove the belts and see if the motor starts up on its own.

 

[Julian]

Sorry should have pointed out that the compressor is sited at my unit.
It trips out the Main MCB mains that supplies my unit with all its power so when I try to start it I lose all power to the unit, until I reset the switch, and yes it does trip out with no pressure , I have moved the pump wheel and it seems to move freely but I have not tried the motor without the belts on it, I will try that tomorrow.

 

[eil]

If it trips the whole unit looks like you have a dead short.

 

[brightspark]

it would help if u told us what size breaker its tripping out and is it the only one in the line between the comp and the mains supply . is it an mcb or an rccb that is tripping??

 

[Julian]

All i know is that there are 3 breakers all 32 amps or so it says on them and they go from on to off,i think its mcb Mains board that is near in the metering box that then supplies a mains Board in my unit without taking pictures and posting it here to find out.
I did however do as suggested and did take of both belts and start the compressor which fired up then I put 1 belt back on leaving 1 off and it fired up and ran like normal, but i want to avoid this from happening in the future.

 

[norsa]

Little unclear as to how you have it wires and whether its a single ph or 3. Ill tell you my story. Have a 3hp single ph in the workshop. Plugged it in and every twice or three times it fired up from cold (empty) it would trip the fuse. Hard wired it to a junction box and its never let me down in 5 years now. Any help?
Nick

 

[rich r]

What sensitivity rating are the breakers? As said above, compressors and welders generally need a C rated one rather than the usual domestic B rating, due to the high surge when they start up.

It'll say 'B32' or similar if they're 32A B rated ones.

 

[Terrapin]

sounds like earth leakage - a dead short and it would not run at all? Have an electrician check out your motor for you - could be bad capacitor if it is a CS/CR motor

 

[Flathead_Dave]

If it's been ok for 2 years,and your supply hasn't been changed,then I wouldn't think it's a supply/breaker problem.
When you say "flick the main switch",if you mean on the wall,then does that mean there's no switch on the compressor?If there is,you should use that to start/stop the motor.
On mine,I switch on the compressor switch,the capacitor prevents the intial jolt to the mains,and the soft start valve blows off till the motor is at full speed.The valve then closes and fills the tank.
It could be as said above,the start capacitor burnt out,or the compressor switch has been damaged by turning on and off at the mains.

 

[eil]

Its pretty clear there isn't a dead short on the motor now, but the goalposts have been moved since my previous post, It could even be a damp motor causing the trip who is to know as there isn't enough info to pin anything down until then everything is going to be conjecture.

 

[Tiggy_dorset]

Possibly something as simple as a dodgy breaker/mcb/rcb/cbeebies or whatever they are? Brother in law had one that would trip randomly each day. Took him ages to figure out the problem what a faulty rcb (they do break occasionally). He replaced it and has not had a problem since.

Last one i bought was less than a tenna, so not expensive to replace.

 

[wheresmejumper]

internet forum probably wont do much good.an electrician needs to see it.

 

[Julian]

It seems to be working now with just 1 belt on it, and the problem I had was that we have a Main board in a cupboard that houses all the meters witch take both mcb and rccb , and they dont have much on them then I have a mains board inside the unit witch has mcbs which control most of the 3 phase, some 240 sockets and lights.
So thats where the problem was which board to look at as the Main one in with the meters is where it was tripping, but all seems right at the moment, after taking 1 belt of the pulleys and letting it run with just 1 instead of the 2 belts.
But hopefully now its working it may keep working, but I am going to swap the pump for a new one as It did have 1 missing bearing when i brought it, although both were replaced it may be that the bottom end is out of balance as its never been that quiet.

 

[the snooper]

i dont see what difference the second belt makes unless you had too much tension on them in the frirst place.
the bottom end if it is out of balance wouldnt stop it starting and it would be vibrating a lot

 

[tigler]

The second belt would cause additional friction but very little, if the motor is that marginal to be affected by that then it has problem.