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

[gidon]

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]

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]

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]

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]

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]

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]

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]

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]

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]

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]

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]

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]

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]

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]

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

 

[Digit]

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]

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]

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]

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]

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.