Annoying Compressor fault....?

[Noods]

Hi..

I've an annoying compresser fault where apon start up it blows the plug fuse.. It's a standard 13 amp fuse. I've found the only way I can overcome it is to initially drain the water from the tank and get the pressure low, then she starts up fine and will cut out when it reaches pressure.. If I initially start it up without draining the tank the motor struggles to turn a couple of rotations and then the fuse blows.. I've checked obv things and can't find anything yet.. When it reaches its pressure and the auto cut out kicks in you can hear the loud pssst of air etc.. Oil is fine, filters clean and have run a metre over it looking for shorts but nothing.. Normally she runs fine.. It's a Clarke 2 hp model only 16 months old and light use only..where the power comes into my workshop there's a trip box setup but it's not tripping everything out, just the plug fuse.
Appreciate any clues..

Many thanks

 

[james butler]

sounds like the motor is meeting too much resistance to start up again whilst theres pressure in the tank.
not entirely sure but isnt the auto cut out box supposed to relieve the pressure between the pump and the tank when it cuts out to aid restarting?

 

[Noods]

sounds like the motor is meeting too much resistance to start up again whilst theres pressure in the tank.
not entirely sure but isnt the auto cut out box supposed to relieve the pressure between the pump and the tank when it cuts out to aid restarting?

That sounds about right mTe not sure how the determin it for sure though ...

 

[Mee]

sounds like the motor is meeting too much resistance to start up again whilst theres pressure in the tank.
not entirely sure but isnt the auto cut out box supposed to relieve the pressure between the pump and the tank when it cuts out to aid restarting?

In theory yes, the problem with a lot of these cheaper compressors is with things such as the non return valve which is a cheap yellow (ish) metal and the actual valve is what I would describe as a cross between dense foam and rubber; they are pliable and you can squash them between your fingers and do not make a good seal as they rattle in the housing as they are such a slack fit and pressure gets through them.

 

[daleyd]

Sounds like the unloader valve is not working correctly.

Do you hear a short hiss when the compressor reaches pressure? This should be the unloader valve releasing pressure between pump and tank.

If it doesn't then the pump has to try and start against tank pressure, which is probably why it's struggling. The idea is the unloader valve vents when the pump stops, and closes after the motor starts - giving it time to spin up without pressure.

If the one way valve was leaking you would generally see the pressure dropping when standing.

 

[daleyd]

Sorry just re read your post and it says you can hear the hiss when it stops!

I'd be inclined to check further in that area though, perhaps slowly and very slightly loosen a joint further back towards the pump to see if it's holding some pressure in there? Could it possibly be a duff cap in the motor? (If it starts ok when drained then it does kind of suggest there's still pressure between tank and pump though)

 

[Badger1bear]

We had the same problem on the farm, we replaced the complete air on/off switch and the problem went away. The compressor would try and start under pressure which in turn blew the fuse. We also told users of the compressor not to turn it off until it had reached full pressure and turned itself off.

 

[Noods]

Yes there's deff a short hiss of air when the pressure level is reached.. If I can kinda keep the air sander etc busy, eg using it constantly, when the req pressure drops the motor does cut in OK and builds pressure ok, but, if I only use it for a short while and the tank sits there with pressure,when I go to use it again it will blow a fuse.. ?

 

[Noods]

https://www.clarkeservice.co.uk/manuals/compressors/boxer55.pdf

 

[julianf]

My unit does the same if I use it on an extension lead. If I plug it in direct, it is fine.

 

[dobbslc]

Page 20 on that PDF file, check the little valve if it's leaking slightly over time it'll re pressurise the pipe and cause this trouble.
If not then it could be the cut off pressure switch ( it was on my small Clarke)
Or a dicky capacitor.

 

[rtbcomp]

My SIP does the same.

On mine it's basically a design fault, the delivery pipe between the pump and the tank is too short, it fills up and closes the unloading valve before the motor has got up to speed. With an empty tank air can get past the non-return valve (NRV) so the problem doesn't occur.

It only happens in cold weather, once the pump has warmed up it's fine. You could try using thinner oil in winter, but this may have implications when the pump is up to operating temperature.

If the NRV is leaking enough to close the unloading valve you'll hear the air escaping (with the switch set to "off") and the thing won't start even when warmed up.

 

[brianblock]

I have similar on my Clarke compressor
When weather is hot or if it's up to temperature it works fine, but if it's cold even with an empty tank the motor struggles to turn it fast enough to get it running.
I've found in winter if I open all the line taps and remove the drain cock it will start, the once it's up to temp its fine. Just got to remember to use a little air every now and then to keep it warm otherwise I have to drain the whole system to get it going again

 

[Jonwhite]

Suppose you could check the obvious connection in the plug and where it connects to the compressor good luck.

 

[the snooper]

Page 20 on that PDF file, check the little valve if it's leaking slightly over time it'll re pressurise the pipe and cause this trouble.

It can't re-presurise the delivery pipe, while the switch is in the off position as the unloader valve remains open until the switch is in the on position

 

[rtbcomp]

... Could it possibly be a duff cap in the motor? ...

Mine had the wrong start cap. fitted, this may have been deliberate to try to overcome the problem, or a genuine error. I rang SIP and they sent me the correct one, but it didn't make any difference.

 

[the snooper]

If you know the power supply is fine my guess is temperature, try warming the pump cylinder before switching on, if it's temp related they usually re-start fine once they have reached pressure and warmed up

 

[dobbslc]

It can't re-presurise the delivery pipe, while the switch is in the off position as the unloader valve remains open until the switch is in the on position

If it's leaking won't it let tank pressure back into the compressor delivery pipe?

I could be wrong, wouldn't be the first time!

 

[james butler]

yes it would but the valve in the compressor wouldnt let it bleed out to atmosphere.
it just makes it neigh on impossible for the moter and pump to get up to speed because of the resistance of the backpressure in said pipe if the valve failed

 

[the snooper]

If it's leaking won't it let tank pressure back into the compressor delivery pipe?

I could be wrong, wouldn't be the first time!

Yes if non return leaks it will go into delivery pipe but then straight out of the unloader valve whilst the pressure switch is in the off position