# 3HP compressor (for spraying) keeps blowing 13A fuse - help?



## gidon (18 Dec 2007)

Following a very helpful chat with Chris, I've decided to have a go at spraying and have gone the compressor / HVLP (well actually RP) conversion gun route.
The compressor is this one:
http://www.axminster.co.uk/product.asp? ... e=1&jump=0
It comes with a 13A plug but keeps blowing the fuse when starting up. If I empty the tank it will usually start up ok, but that's no good when spraying because the pump will keep kicking in even with the tank full.
Axminster recommended a 16A supply but this isn't possible / practical at the minute.
Is there ANYTHING I can do. It's only the starting current that's the problem. Is it possible to get 16A fuses if that's not silly question (which I'm sure it is!) Could I install a bit of 20A fuse wire in the plug? Or is that just dangerous?
Appreciate any comments / advice.
Many thanks
Gidon


----------



## CHJ (18 Dec 2007)

gidon, in the past I have had 13amp (1" X 1/4") * slow blow* fuses but for the life of me can't remember where I got them from. Using bigger rated fuse wire is not safe as you may be exceeding the rating of the equipement supply cable or connections which could overheat in fault conditions.

As a temporary work around do you have a long extension lead? if so uncoil it and feed compressor through that and see if it causes enough volt drop to reduce surge.


----------



## OllyK (18 Dec 2007)

I have 16A supply in my shop, I'd be happy to take it off your hands for you 

Did it come with the blue 16A plug on it or a standard 13A?


----------



## gidon (18 Dec 2007)

Thanks chaps. Been looking for these slow blow fuses but can't find 13amp 1 inch one only lower amp 20mm ones?
I've tried it on an extension lead but no joy unfortunately.
Olly no it came with a 13a plug. Axminster sent me a blue plug free but don't have 16a supply in my shed . Kind offer - thanks!
Cheers
Gidon


----------



## Digit (18 Dec 2007)

> If I empty the tank it will usually start up ok,



Having serviced a hell of a lot of compressors in my time Gidon that sounds to me as though the unloader isn't working.

Roy.


----------



## gidon (18 Dec 2007)

Thanks Roy.
Come to think of it - it was turning itself back on again before - but now it just turns over really slowly and then cuts out. And this is blowing the fuse.
I temporarily put a 30A fuse wire in the plug oops - and still the same problem. I have to release all the air for it to start again. When it tries turning over it measure 20A(!!) on my tester jobby.
So I'm not sure now what to do - Axminster said it's a problem of electricity supply in my area. And other comments under review on their web site seem to mention this.
But maybe it's just faulty? It it be the oil they supply also?
Anything else I can test?
Cheers
Gidon


----------



## wizer (18 Dec 2007)

This is a worry, that compressor is on my xmas list


----------



## Digit (18 Dec 2007)

If I was still a wage slave Gidon what you're telling me would have me checking the unloading system.
The statement by Axminster is suspect. The current at start up, (tank empty) should be exactly the same as with with a more or less full tank.
_That's what the unloader is for!_

Roy.


----------



## gidon (18 Dec 2007)

Thanks Roy - anyway _I _can check the unloader?
Maybe the ones reported not to work just have faulty unloaders?
Could the cold weather be a problem? I'm leaving it running just now with the air coming straight out and will see if I still have the same problem.
Cheers
Gidon


----------



## Digit (18 Dec 2007)

Do you really want to Gidon? 3HP seem an expensive way to do some spraying.
I just checked the Axminster pic, you see the pipe that runs from the tank to the cylinder head?
If the thing's been in stock for some time and has been doing this from new it's logically either stuck or wrongly assembled. If it's new and you dismantle anything you could blow the guarantee, if it's stuck, clout the top of the cylinder where that pipe enters the cylinder head with a rubber mallet or similar and see if that will free it.

Roy.


----------



## mailee (18 Dec 2007)

Aw my God! :shock: This is exaclty the same compressor I have but under the Sealey label. I bought mine brand new and it also did exactly the same thing, well in that it wouldn't switch off. (Mine didn't blow fuses) I sent it back under warranty and they sorted it out. Apparently it was a faulty valbve in the head or so they stated. It was about a week in repair but now works fine. Looks like there is a batch with some faults.


----------



## Digit (18 Dec 2007)

That valve, Mailee, is the unloader valve. A compressor attempting to start up against the tank pressure would need a much larger motor and a lot more current to do the job, the unloading valve is a means of getting around that difficulty.

Roy.


----------



## jonny boy (18 Dec 2007)

Gidon, if you don't want the hassle of installing a fixed 16 or 20 amp supply, then i'd say try to get Axminster to swap it for a 2hp which should run on a standard 13amp outlet. Fault or no fault with the compressor, a three horse one will draw too much on start up for a 13amp outlet really.
cheers,
jon.


----------



## gidon (18 Dec 2007)

Digit - tried that - thanks. Didn't work (the clouting that is). Well i use the compressor for other things too - the 3HP ideally gives me the ability to do spraying without having to buy another box .
Mailee - interesting - thanks. There's a SIP machine too which looks similiar: http://www.worldofpower.co.uk/acatalog/ ... ssors.html (the 3HP one)
I think I'm going to swap it either for another Axminster or the SIP/Sealey. Reassuring that it doesn't blow 13A fuses. Do you use your for spraying? Is it up to it? What gun do you use with it?
Jon - I want the 3HP to run a conversion spray gun - 2hp won't do it. I already have a 1.5HP compressor (an Italian made Cosmo one). But I think I will still need to sort something with the fuse.
Cheers
Gidon


----------



## jonny boy (18 Dec 2007)

What do you mean by conversion gun?
jon.


----------



## Digit (18 Dec 2007)

Fair enough Gidon, if you don't know what you need nobody does.
You can get around the 13amp problem if you wire into a switched spur or cooker box and connect to a twenty amp MCB.
Perfectly safe and legal, no insurance problems either.

Roy.


----------



## jonny boy (18 Dec 2007)

If you do go with the cooker box, you must get the motor rated class 'c' MCB.
jon.


----------



## Digit (18 Dec 2007)

Jon's correct and you should be able to get one from any local electrical supplier to the trade. They are not expensive and if you have any problems the counter staff are usually most helpful.

Roy.


----------



## Jake (18 Dec 2007)

A 3hp motor is around 2.2kW, it should be fine on a 13A plug if it is working properly.


----------



## Digit (18 Dec 2007)

> A 3hp motor is around 2.2kW, it should be fine on a 13A plug if it is working properly.



Absolutely! But if it's trying to start against a load then 13amps may be insufficient, which of course brings us back to the unloading valve. Why Axminster supplies it with a 13amp fitting then seem to imply that a 16amp circuit is required seems a little odd.


----------



## gidon (19 Dec 2007)

Jon - a conversion gun is a low pressure gun that fits to a compressor.
The wiring for the cooker box to a 20a MCB - does that have to come off the main fuse box? Or can that just be done in the shed of the exisitng wiring? I really need to get some knowledge on electrics! The part p has made me more lazy than I would have been even.
Thanks for all the advice - really appreciated.
Cheers
Gidon


----------



## OllyK (19 Dec 2007)

Not sure if these are any use:
http://www.maplin.co.uk/searchtemplate. ... LOW%20FUSE, near the end of the page showing as "Time delay" fuses.


----------



## mailee (19 Dec 2007)

Hi Gidon. I also use mine for spraying and my nail guns. I use an Iwata HVLP spray gun and find it just handles it nicely. I think I am correct in assuming that your compressor also produces 12 CFM which is sufficient for most HVLP guns. I have had no problem running mine on a 13 amp plug although a friend of mine has a similar machine for spraying and says his does tend to throw the thermal cutout in the cold weather. Mine is kept in the workshop which has background heat so no problem there. I have to add that I was very impressed with the service I got from the company I dealt with as they took it back under warranty even after I had had one of the valves apart and also added a clarke's regulator to it. It was returned to me within a week all palleted up with no cost to myself. HTH. :wink:


----------



## andycktm (19 Dec 2007)

Gidon,
I had the sip 3hp belt drive compressor very quiet and run on 13 amp fuse
no problem  

http://www.worldofpower.co.uk/acatalog/ ... iven_.html


----------



## Digit (19 Dec 2007)

> does that have to come off the main fuse box? Or can that just be done in the shed of the exisitng wiring?



Need more info Gidon. Do you have a consumer unit in your workshop?

Roy.


----------



## gidon (19 Dec 2007)

Olly - thanks - I found those too but they are 20mm no the normal 25mm.
Thanks mailee - that's a fancy spray gun. I've bought a second hand Sata RP but having some troubles with it at the minute - Ebay - arghh!
I'm sending the Axminster compressor back and have ordered the SIP version- so we'll see how I get on with that. Who did you buy yours from then? Good to get some service. I prefer to stick with Axminster but they have a fairly limited range of compressors.
Andy - that's stretching my budget a fair bit - lets hope the direct drive version is ok too.
Roy - no consumer unit. Just a 60 ft run of cable from the house consumer unit.
Cheers
Gidon


----------



## Digit (19 Dec 2007)

What's the size of the cable Gidon? If you don't know in amps capacity try and measure its width and let me know. 60ft of cable can result in a serious drop in voltage at start up on motors, the motor responds by increasing the current drawn, so when 13amp fuses are working near their limit the increased current can push them to failure.
But panic ye not, there are ways around these problems.
A proper consumer unit and RCD is definitely a good move in any workshop though Gidon and you should consider upgrading accordingly.

Roy.


----------



## gidon (20 Dec 2007)

Thanks Digit
The cable's 10mm wide, about 4mm thick.
I have had an electrician check it out once - he seemed to think it was ok - but that the cable should be replaced with armoured cable. Having said that that electrician turned out to be a bit hopeless to be honest.
I'm planning to knock the shed down so not worth getting it rewired properly.
Thanks again
Cheers
Gidon


----------



## Digit (20 Dec 2007)

That's large enough Gidon. Any time you're in doubt about cable size plug a table lamp, or similar, in in your workshop then start the machine you're concerned about.
If the cable is too small the lamp will dim quite badly, must be a carbon filament lamp by the way.

Roy.


----------



## gidon (20 Dec 2007)

OK thanks Digit - much appreciated.
So can that wire just be connected to a fuse box in my shed then?
Maybe I should wait and see if this new compressor works without any workarounds!
Cheers
Gidon


----------



## Digit (20 Dec 2007)

Sorry Gidon, that should have read, 'that's not large enough'. Typed over my breakfast cereal. 
If you are running the compressor on its own, and no other large machines you should be okay, but the compressor is working the cable at about its limit on start up.
The info you've given me still indicates that the compressor unloading valve is defective so that the compressor is starting under load, and that, plus the voltage drop on 60ft of cable will undoubtedly push the fuse to its limit.
It won't be doing the compressor's motor much good either.
You could try the the compressor on a household socket if that's feasible, if it performs ok then it is definitely the cable limitations. If it still blows fuses it is definitely the unloading valve.
Keep me informed.

Roy.


----------



## ivan (21 Dec 2007)

When the compressor cuts out because the tank is up to pressure, you should hear a pretty lould "PSSSH". This is the unloader releasing te pressure in the pipework, so the motor does not have to restart against a 140psi load. The tank itself does not loose any air as the pump pressurises it through a non return valve.


----------



## dickm (21 Dec 2007)

Jake":pyfrvjwo said:


> A 3hp motor is around 2.2kW, it should be fine on a 13A plug if it is working properly.


That's been my experience with the 2.2kW motors on my old Lurem. But these are quite old motors, and really BIG beasts compared to more modern ones. Could this make a difference? (I wondered if there being more metal present means they are more efficient, and so take noticeably lower start/run currents?)


----------



## Digit (21 Dec 2007)

To an engineer HP is the output, which Dick correctly equates to 2.2Kw, but electric motors of the mass produced kind are about 60% efficient, so the full load current, (FLC) is about 16 amps at 230 volts.
Normally the design of a motor driven device will use a motor that only uses 80-85% of its FLC, about 13 amps in this case. The problem here is that the start up current of a motor is dependent on the load imposed, even running free the motor has to accelerate its own moving parts and therefore the SU current can be many many times the FLC.
A 13 amp fuse should run at 13 amps as its rupture current is about 50% higher than that, but fuses 'tire', the more times they are subjected to a heavy load the sooner they will fail. I've probably replaced 1000s of fuses that had 'blown' when there was no fault in the circuit, the fuse was simply 'tired'.

Roy.


----------



## andycktm (21 Dec 2007)

The fore mentioned compressor i had run at 6.5 amp's according to
the plug in meter


----------



## Digit (21 Dec 2007)

On or off load Andy? When the tank is empty the motor is effectively running off load, as the pressure builds the motor must work harder.
Roy.


----------



## andycktm (21 Dec 2007)

All the time mate ,except for startup which i could not measure.  
one other thing tho'; i knew Gidon did.nt have a consumer unit in the 
shed,because i've never had a 13amp fuse blow yet.The 16amp rcd always trip's first.
I went for a type "c" rcd ,but the shop had a type "D" in so 
i thought what the hell ( i believe type "D" are no longer available)
Anyway the gas space heater once burnt through the cable and the rcd didn't trip the 40 amp went in the house first :shock:


----------



## Digit (21 Dec 2007)

RCD? MCB surely? Depends on the pressure the compressor was working at Andy. The higher the pressure the harder the motor must work.'

Roy.


----------



## andycktm (21 Dec 2007)

Yeah mcb sorry  i pluged the compressor in and start to finish it said 6.5 amp's  
although the meter takes about 5 seconds to register
so it's under way before i got a reading.


----------



## Jake (21 Dec 2007)

Digit":1psyygas said:


> To an engineer HP is the output, which Dick correctly equates to 2.2Kw, but electric motors of the mass produced kind are about 60% efficient, so the full load current, (FLC) is about 16 amps at 230 volts



And after the marketing folks have been at it? 

Jet are very unusual in the world of woodworking equipment for giving their specs in terms of output power, and the compressor world seems even worse for specsmanship.


----------



## Digit (21 Dec 2007)

About the same as Estate Agents and Labour Ministers I'm afraid.

Roy.


----------



## gidon (21 Dec 2007)

Thanks Digit - yes I have that problem - I can only run the p/t'er on it's own. If the heater or table saw is switched on it trips the switch on the main fuse box in the house. And now I guess the compressor. Not a biggy for me.
Anyhow I've now got the SIP compressor. It has very slightly higher spec (10.5 cfm free air vs 10 cfm of the Axminster), pneumatic tyres, two outlets (one unregulated but handy for permanent air nozzle), and a more thorough manual.
Seems quieter too and hasn't blown a fuse yet!
Does anyone who knows about these things know how there appears to be 3 different compressors with similiar spec - an Axminster, a Sealey and my SIP yet they all manage to achieve differing free air delivery?
Out of interest I measured the Axminster and the SIP and the quoted figure for FAD is fairly accurate (depending on what range on the pressure gauge you measure it).
Cheers
Gidon


----------



## Digit (21 Dec 2007)

Many years ago Gidon there was a programme on the steam radio called 'Around the Horn' and they used to come up with such pearls as, 'are exits on the way out?' or 'how much is a four penny loaf'.
Believe me, the way some things are measured these days is about the same.
To have accurate figures you need to know how the measurements are taken, and that is very rarely specified.
The orientals don't use the same horse power that we do, neither do the yanks, so without knowing the standard used you can't even make comparisons.
So 'when is a horse power not a horse power?'
I'm off back to my cuppa!


----------

