compressor blowing fuse within seconds of starting

[jasongtr]

bit of background

Its a 150 L 3 hp on a standard 13amp plug (not on an extension lead) i know some will say thats not a good enough supply but its been absolutely fine for over 2 years and never blown a fuse.

A couple of weeks ago it blew a fuse, then a week later another one.

Today i used it fine, then as the tank emptied it kicked in to refill, made a screeching sound like the belt was squealing and cut out, fuse gone - changed it and the same thing happened, got through 4 fuses (then ran out of fuses) and couldn't get any further.

both the motor and the pump rotate fine so not seized, the belt looks fine too.

I have posted about recommendations about a new compressor but if this can be fixed on the cheap thats a bonus, but i dont want to be chucking money at it for no reason then have to buy another one.

As far as i know it has a clark motor (i bought the compressor used just after the motor was fitted) i have since changed the head gasket on the pump as it blew across the cylinders, its been totally fine since then.

any ideas what it could be

 

[the snooper]

have you used is successfully in the cold weather it could be purely down to temperature and oil thickening up, try warming the pump and see how you go if it cures it change the oil

 

[jasongtr]

i use it all the time in the cold, never had an issue before, only ever blew fuses from 2 weeks ago. Also as i had already had it on to fill earlier in the day i would expect it to have crapped itself the 1st time - not on the 2nd fill.

 

[the snooper]

bit of a strange one then I think that if you find what causes the squeal you've found your problem, is the belt tension ok and is the unloader valve working also empty your tank totally and take the non return valve apart and clean it, make sure its not back pressure stopping the pump

 

[jasongtr]

squealing sounds like the belt, hence i thought either the motor or the pump were seized, but they both rotate, ill have a look tomorrow and check what i can, not knowing much about them though could prove interesting

 

[the snooper]

the motor has to be fine if it makes the belt squeal, I wold firstly clean the non return valve where the delivery pipe enters the tank, then run it and make sure you get the big hiss when it reaches pressure

 

[jasongtr]

not sure where the non return valve is but ill have a look

 

[the snooper]

just remove the cap and clean and inspect for wear, also does it start fine when completely empy

 

[the snooper]

not sure where the non return valve is but ill have a look

follow the pipe from the pump that gets hot, its at then end of it

 

[jasongtr]

OK thanks ill check it out. cheers

 

[Bill Edwards]

My first place to look would be the non return valve and the unloader valve.
If the unloader valve doesn't work (you should get a big hiss when it cuts out at full pressure) of if the non return valve then leaks back it will struggle/fail to start due to the pressure in the pipe.

If you crack off the pipe from the compressor to the non return valve then start it up, and it doesn't blow any fuses, then you're on the right track.

 

[normspanners]

i use it all the time in the cold, never had an issue before, only ever blew fuses from 2 weeks ago. Also as i had already had it on to fill earlier in the day i would expect it to have crapped itself the 1st time - not on the 2nd fill.

The reason it stopped after the second fill is probably the fact, that first time it started from empty so NO real load on the motor till it got warm, the second time it will have had air pressure in it, a massive difference to the motor.
You probably need to do as snoop dog says and look at the check valve, do yourself a favour and change the oil it thickens up when old and cold ---(like me) also the capacitor could be getting past its sell by and needs replacing.
DONT keep throwing fuses at it you will eventually screw it.

 

[jasongtr]

wasn't the compressor at all as it goes, where my unit is there was a problem with the main isolator so at some points during the day the voltage into the area was down to 190v, so i assume that the squealing was the belt suddenly stoping the motor pulley when it was half way through a pump cycle, either way once i heard the isolator issue was sorted this morning i changed the fuse again and it works fine.

thanks for all the help, i think ill still get my sparky mate to come and fit me a 16amp socket/plug for it though

 

[normspanners]

A couple of weeks ago it blew a fuse, then a week later another one.

I personally think you still have a problem, the squealing would not be caused by low voltage just the opposite in fact, up to you, but I would change the oil anyway cost couple of quid and save £££S

 

[rtbcomp]

I've had a situation on my Clarke 3HP where the belt was not tight enough to get the pump over the compression stroke and the belt just slipped. So I reckon it takes less torque to slip the belt than it does to get over the compression stroke.

The motor bolts are a sod to get at and I suspect the motor moved due to the bolts not being tight enough when I up-ended the compressor to get underneath it. Tightening the belt and making sure the motor bolts were tight fixed it.

I run mine from a 16A plug.

As Norm says change the oil if you haven't done recently and check the belt tension.

 

[Screwdriver]

Problem is most likely an under specified supply cable. How long is the cable running from a known good 240v supply?

If the cable is too thin, you will experience extreme losses and low voltage at the shed end. Your compressor might be ok under normal operating conditions but with a stone cold pressurised system to run, you might not be able to draw enough amps.

S.

 

[jasongtr]

the compressor hasn't changed in the 2 years i have had it, only had the problems blowing these fuses since the lights were flickering a little in the unit, that was diagnosed today to be a the main site supply voltage, thats been cured, the compressor now works, belt tension is as its always been that i can tell.
The double socket the compressor is plugged into is 4 inches below the board.

Spoke to my mate and he will still be fitting a 16 amp socket for me

 

[dannyp]

low voltage will cause fuse blowing, if the motor cant get upto speed and become syncronus it's like its still trying to spin up all the time and it'll pull more curent.

 

[jasongtr]

just remove the cap and clean and inspect for wear, also does it start fine when completely empy

View attachment 58796

might have another slight issue with this compressor, its hissing a little when full from the oil level dipstick, with reference to this non return valve, i checked the pipe from the pump to the main cylinder and there isn't a valve, just a hose from one to the other, a hose that looks suspiciously like a plumbing tap flex pipe, its been like this for the 2 years i have had it.

I assume the hissing from the oil level dipstick isnt normal and related to the fact i have no non return valve and the compressed air is finding its way back through the pump into the oil sump and out of the dipstick tube -

 

[the snooper]

Yeah if it's hissing fr the pump when stopped its the non return if it did work ok it must have a non return valve or it would never work at all as the pressure going back into the pump would stop it from starting up like its doing now