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Air compressor tripping in the cold - oil?


Cartman
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I have a V-twin 3hp comp out in the garage and in the extruded period of cold the mains fuse blows almost every time if it hasn't been used for a while. Once it starts it runs fine but it is the initial 'kick' over that causes the 13A fuse to go south. It all worked fine when the weather stayed above 5 Deg.C for a while ;)

The oil in there is probably what was supplied with the pump so would it be benificial to dump and change for a suitable syth with a wider temp band? :huh:

I don't have a manual for the pump so I cannot see what the suggested FLC is for the motor but I would guess it is close to 13A and the cold 'load' is kicking it over the edge?

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How about wiring it in to a dedicated circuit with say a 15A or 20A breaker on it?

I had a similar issue with my little Draper 2hp after it had been thrashed silly and overheated a couple of times doing stuff for work, it was very hard to start, didn't blow a fuse but was not willing to turn over initially. I found that after a bit of normal use it seemed to be better and it's still going 2 years later so I think the bore lubrication was probably the problem, so you may be barking up the right tree. Mine is also fine after it has had one duty cycle it fires up immediately for the rest of the day so I wonder if the piston is sticking in the bore slightly - I guess gloopy oil would have a similar effect. Never changed mine, perhaps I ought to :unsure:

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You might be better off trying a thinner grade of compressor oil, I'm guessing you have SAE 30 in at the moment, if so you could try SAE 20.

IMHO synthetic may be OTT if the unit is getting on a bit and there are issues with polycarbonate filter bowls and synthetic oils.

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Comp is only 2-3 years old and has hardly any use so basically as new I would say.

Rog,

Where would be the best place to get SAE20 easily? I have synth 5/40 engine oil, ATF etc. here but doubt any of them are suitable? I guess I could try Camberley's.

Boggy,

That is my fall back but we are moving in the new year (hopefully) so I didn't want to wire up the dedicated 16A socket....will happen in the new workshop without a doubt. :)

I need to use the comp this weekend so I will light the garage log burner up for a few hours to get some heat into the comp. Should work then. Hope so as I am running out of 13A fuses ;)

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Try dumping all the air pressure and have the water drain valve open to start it

Once its running do up the drain valve.

cheers

Steveb

Good call Steve. Reduce the load. Makes sense and I will give that a go :D

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Machine Mart sell SAE 20 & 30 compressor oil. Don't use modern multigrade detergent oil as the dirt in it will remain in suspension and not settle out.

There's a MM near the office so I will drop in next week and buy a litre ;)

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I have a V-twin 3hp comp out in the garage and in the extruded period of cold the mains fuse blows almost every time if it hasn't been used for a while. Once it starts it runs fine but it is the initial 'kick' over that causes the 13A fuse to go south. It all worked fine when the weather stayed above 5 Deg.C for a while ;)

The oil in there is probably what was supplied with the pump so would it be benificial to dump and change for a suitable syth with a wider temp band? :huh:

I don't have a manual for the pump so I cannot see what the suggested FLC is for the motor but I would guess it is close to 13A and the cold 'load' is kicking it over the edge?

There should be a rating plate on the motor giving FLC. If the voltage is too high that can push the current up ridiculously. If Cap start & run, you could fit an electronic soft start, or maybe your non-return valve is sticking or dead; there should be a non return valve in the feed to the tank so that the pump doesn't start against tank pressure. If the problem occurs on start, and then doesn't recur, ie when it has built pressure, it's probably not the valve though. OTOH if it keeps happening when using air, that has to be a prime suspect, as the oil will be thinned. You can get synth compressor oil significantly thinner when cold than SAE40 - Ingersoll Rand do it for one. If you put in 20 remember to change it back.

Nigel

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or maybe your non-return valve is sticking or dead;

No, it's the little (unloader) valve in the pressure switch connected to the thin pipe that relieves the pressure. If this jams closed you will get the symptoms Cackshifter describes. If it jams open you will get a constant hiss when the pump is running.

If the Non-return valve jams open you will get a constant hiss as long as there is pressure in the tank AND the unloader valve is open (either jammed or the switch is in the off position).

If you get a brief hiss as soon as the pressure switch turns off then the non-return and unloader valves are working OK.

If this is just a cold weather symptom then oil is the favourite or one of the capacitors could be playing up.

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I think your problem probably is oil related, but it's worth pointing out that the there is usually a fair amount of water in the outlet pipework of workshop compressors and this will freeze and prevent valves such as the unloader, the non return valve and possibly the pressure switch from working properly. Most modern workshop compressors have a combined unloader and pressure switch which uses a bellows arrangement to trigger both the switch and the unloader (i.e. there is no solenoid for the unloader) - I don't know how these behave when they freeze up.

My system has a solenoid unloader and I've had to put put linear heating tape and Rockwool insulation around the solenoid and auto water drain so I can use it during the cold weather.

Nick.

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That or chop a piece out of a 6 inch nail, no more fuses blowing ;)

I can better that.

Where i used to work there was a fairly large tub grinder with a 48" diameter magnetic table and one morning it was 'whats that smell', it turned out to be that the windings had melted down in the magnetic table of the tub grinder as the machine had been left with the main breaker in and the table energised when the shop closed the day before. Upon investigating why the cartridge fuses had not blown it was found that they had been replaced with 1 1/4" diameter bright mild steel bar!!! the shop owner had at some time been giving this machine some serious grief and the fuses kept failing, so he went for the non blow type.

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