Abac compressor problem

[sixtwoeight]

Got a 3hp 150L abac compressor, its a few years old and not had a lot of use. Recently when you start it up, it fills as normal but when it reaches pressure it stops (as it should) but at the same time the reset button pops out and wont restart once the pressure has dropped unless the button is reset.
What is it likely to be?

Thankyou

 

[rtbcomp]

I take it you mean the reset button on the motor itself?

Do you get a distinctive hiss coming from the pressure switch when it stops?

 

[sixtwoeight]

Yes the reset button on the motor/compressor.

Hiss...mmmm i think so, didnt really take a lot of notice??

 

[rtbcomp]

Best to check, it's important.

This fault is slightly odd in that if the hiss isn't present then the cutout would most likely trip when the compressor tries to restart. In this case I'm wondering if the pressure switch isn't working and the motor stalls, but then I'd expect the safety valve to blow off first.

 

[rikrobson]

The hiss is the unloading valve. this empties the air pressurised air in the cylinder. thus when the motor starts up it can get the flywheel storing energy instead of pressing against the full tank pressure. there exactly is the reset button? the motor is one part and the compressor the outher so saying motor/compressor unfortunatelt doesnt tell us anything.
there is a wee black box with the cut off/unloader in is the reset button on that? this controlls the motor depending on the pressure in the tank. it will turn on at one pressure and off at another depending on the screw setting.

 

[rtbcomp]

The hiss is the unloading valve. this empties the air pressurised air in the cylinder...

and the air in the pipe between the pump and the tank.

A photo of the reset button would clear up any confusion.

 

[sixtwoeight]

Sorry for not being clear, a link to the same compressor...http://www.ebay.co.uk/itm/ABAC-pro-a39b-150-fm3-2026-0012-/262484485425

On top of the motor there is a black box and within that is a round pop in/out button, which on it says circuit breaker reset.

I will start it up again tomorrow and listen for the hiss or not.

 

[sixtwoeight]

Ok this is a little odd.

I have 2 compressors exactly the same, only 1 was causing me a problem so this morning i filled it as normal a few times, it didnt once pop the button. I listened for this hiss, sometimes as it switched off it gave a short sharp hiss followed by pathetic little hiss 5-10secs long, and other times just a short sharp hiss.
I did the same with the other compressor which has always been fine, but, once it had filled there was no hiss, then as it went to switch back on to fill it blew a fuse ( not the button on the motor).

So obviously something isnt quite right, maybe with both of them?? They havnt been used that often recently if that makes a difference?

Any help much appreciated.

 

[rtbcomp]

The first one - that's probably OK, the length of the hiss depends on the pressure it switches off at, sometimes it splutters if there's moisture in the air. Sometimes the cutouts get a bit sensitive, you could try changing it, they're not expensive.

The 2nd one, that's a standard fault, the unloader valve isn't working so there is pressure in the pump and the delivery pipe (between the pump & tank) so the motor stalls and trips the fuse or whatever. There could be a blockage in the thin pipe that goes between the tank (non-return valve) and the pressure switch. Are the compressors sucking in clean air, i.e. not contaminated with paint spray &c?

On the 2nd one try switching it off at the pressure switch (red button) just before it switches off normally and see if it hisses then.

 

[sixtwoeight]

Excellent, thankyou for your advice.

Both are in a purpose built small shed so air is clean, door is always open so as not to overheat. Air filters are clean, and will also change the oil in both as its probably due anyway.

So when you are talking about the first one - what is the part called that i could try changing? (sorry im lacking a bit up top)

Many thanks.

 

[dobbslc]

It might be worth checking the capacitors on top of the motor to see if they are leaking or have any loose connection. A bad start capacitor will cause the little round reset button to pop out as the motor tries to draw max current for too long. Are your compressors fitted with a standard 13 amp plug?

 

[rtbcomp]

The cutout on the motor, it'll come under various names such as thermal cutout, motor overload button, reset button. Look to see if there's a make or part number on the side. They come in a range of operating currents, that should be marked on the component.

 

[sixtwoeight]

It might be worth checking the capacitors on top of the motor to see if they are leaking or have any loose connection. A bad start capacitor will cause the little round reset button to pop out as the motor tries to draw max current for too long. Are your compressors fitted with a standard 13 amp plug?

Yes they are on a 13a plug. Probably not correct but as they had worked ok i assumed that was fine ????

The cutout on the motor, it'll come under various names such as thermal cutout, motor overload button, reset button. Look to see if there's a make or part number on the side. They come in a range of operating currents, that should be marked on the component.

Thanks, once again.

 

[sixtwoeight]

Here we go again...

Ive found where i can buy the thermal cutout part.

Can you buy the unloader valve on its own, am i correct in saying it is within the pressure switch box of gubbins, as most list only the pressure switch as a unit.

On a side note, i told my wife my about not being able to get on and paint, she said whats wrong with your impressor....made me chuckle anyway.

 

[Bill Edwards]

I would think you will have to get the entire pressure switch assembly, they aren't usually expensive. It might not be impossible to get the unloader valve on its own but they can sometimes be a bit fiddly to access.

But just before condemning the valve remove the pipe into it and make sure there's air coming through it (rule out a blockage) and then squirt some WD40 or equivalent into the valve from everywhere you can. Make sure the compressor is unplugged while you do this, don't get a shock.
Sometimes they can free off with some lubrication.

 

[sixtwoeight]

Cheers chaps,

I replaced the thermal cutout switch on the one, and they both did a day of prep and spraying no trouble so hopefully all ok now.

Thanks for your help.