Sealey trips out

[alfapat]

I have been a few threads on compressors tripping out .
Mine is doing the same especially when cold. The tank needs to be empty before it wants to start. Its not too bad when warm by the way.
I get the feeling that it wants to dump more air so that it puts less strain on the motor as it is it trips out.
I was looking at the trip machanism and it has a plus and minus adjustment , perhaps this should be backed off to help it , is this the cause of the tripping out?

 

[rtbcomp]

Welcome to the Forum.

That adjustment sets the cut-off pressure and isn't the cause of the problem.

When it does run and trips out do you get a short distinctive hiss when the motor stops? If not then the valve that empties the delivery tube may be sticking.

If you get a long protracted hiss when the motor stops then the non-return valve on the top of the tank may be leaking.

If both of those are OK you could try a thinner oil now the weather's getting cold, or you may be looking at a motor or capacitor fault.

 

[alfapat]

Yeah its a fairly long hiss when it reaches top pressure.
Much , much less when it fails to restart and pops the overload switch.
I altered the setting up the way on the pressure switch but was wary I over did as the overpressure valve kicked off and the motor was still running. So I switched off immediately and backed off the adjustment.
How do I identify the dump valve that could be sticking, should the compressor just cut off without a hiss or just a short one, is this valve stuck on a line to the pump?
Thanks in anticipation of your reply and replies.

 

[rtbcomp]

You should get a very definite hiss.

There should be a thin pipe from the non return valve to the pressure switch. The unloader (dump) valve will be on the end of that, fastened to the baseplate of the switch. The valve is opened when the switch toggles over to "off".

Its purpose is to empty the delivery tube so the motor starts up under no-load conditions.

If you get a brief hiss when the fault occurs it sounds like the unloader valve is partially blocked. I had this on a brand new compressor, a bit of sealant found its way into the valve.

You may find some useful pics here

http://www.mig-welding.co.uk/forum/album.php?albumid=900

 

[alfapat]

many thanks , I will have to lay more time aside and check this out. Many thanks will be back!

 

[Jack155Q4]

Hi alfapat. Your not the fella with an Alfa 164 and LPG?
Cheers,
Jack

 

[alfapat]

Yep the same one Jack, still got the 164 minus the lpg , I removed after having engine problems and rebuit the complete unit , it may not have been a contributory factor , but was better to eliminate.
Will be putting up for sale shortly and currently running a 145 2.0l cloverleaf.

Still no joy with compressor ,thinking its capacitators now.

 

[Jack155Q4]

Cool. It was my dad who sold on the LPG to you
145s are nice cars especially in Cloverleaf form. I have a 155 (as you may have guessed).
Good luck.

 

[the snooper]

does your compressor only trip when starting from cold ?
the direct drive units seem quite bad for it, i had a small one at work just for inflating tyres and it always tripped when cold, warm it up a little with a hot air gun and it was ok until it got really cold again, my 3hp belt drive only does it when its extremely cold and again a little heat and its ok

 

[bigtip]

is it running at the right speed when it trips or a bit slow? have you got a decent enough electrical supply to it? when they start they draw a extra large current which if it isn't delivered will cause it to fail to get up to speed and therefore keep drawing too much current. a heavier or shorter cable form your fusebox to the compressor would solve it if this is the prob.

 

[alfapat]

moving on and a lot later I disconnected the capacitors and got them tested they are working fine but there is a resister that has either melted or blown across the two terminals on one capacitor, I am struggling to identify what ohms it is as the colours are obscure. Obviously I want to replace this as soon as now to eliminate fault , can anyone help please?

 

[tigler]

They are just bleed down resistors to discharge the standing charge in the cap when the motor is off, not strictly necessary for the motor to function but if you want to replace it use a 100 K Ohm, 1 watt carbon or metal film type resistor. You can just cut the failed resistor out to eliminate it as the cause of the fault. How were the capacitors tested ?

 

[alfapat]

The capacitors were checked with a Fluke across the terminals and measured thbe capacitance at 54uf for the 55uf capacitor and 63uf at the 65uf capacitor.That seemed OK to me and I had hoped that this had some influence on the problem I am getting . Are there any more tests I can do please?

 

[tigler]

That stands a good chance of being ok, the other test is high voltage breakdown but it needs a specialised tester.

 

[alfapat]

Would a high voltage insulation tester do the trick ie:500volts, a megger?

 

[tigler]

No because it can't give a read out for equivalent series resistance at working voltage.

 

[the snooper]

i think your gonna find its just a temeperture thing how was it in the summer ?

 

[alfapat]

Well thats what alerted me to that something was wrong as it has got worse from its winter mode and that was under a refill situation ,well it would kick in to top up when cold,and trip , alright in the summer.
It will kick in to top while using it, but wait an hour later it struggles and throws the protection overload.
Maybe the pressure regulator doesn,t dump enough from the cylinder.
Can you tell me what sort of instrument measures this resistance.

 

[tigler]

A laboratory capacitor tester. The temperature shouldn't really make a difference in my experience. I've been usine a 3.5 HP belt drive compressor intermittently over the last 2 weeks or so and it functions normally, even running off a normal 13 amp plug on a domestic ring main. You could measure the surge current drawn at full load start if you have a peak hold meter.

 

[the snooper]

you wont find anything wrong with it
i have one in the workshop for the last 5 years just to inflate the van tyres and its exactly the same symptoms as yours as are other peoples ive heard of.

if you think its anything to do with pressure buildup in the delivery pipe then remove the delivery pipe from the pump head (when empty) and try it that way but you will find it the same.
you could try putting a thinner oil in it that may help