Thread: Questions about my new compressor

[quote=Arron;1529480]Hi. I have just purchased a new compressor and have a few questions about it. Its 2.5hp, 50 litres and 14 thingees of free air delivery. I will be using it mainly for spraying lacquer - mostly small objects. Anyway:

1. No hose came with it. I'm using one of those thin coiled hoses, which came off a smaller compressor. Is this an issue, should I be using a wider diameter hose of some sort ??[QUOTE]
Those cheap coil hoses are crap because they tangle so easily and the leak and break too easily. In terms of air flow they are ok if the length is kept short.

2. Does hose length matter ? At some stage in the future I'd like to use a long hose and move the spraying into the (powerless) shed at the rear of the yard.

It certainly does matter especially if you use the thin hose. Minimum I'd used over 10m is the 1/2" (garden hose size).

3. There is a sticker on the motor that says I should not use an extension cord with it. Is this just a case of manufacturer being overly cautious ? I limited myself to 2.5hp because I wanted to use it in the back yard where there is only a 10 amp outlet, and if I cant use it with an extension cord then it really isnt much use.

How long are you looking at? It should be OK if you use a cable rated for a 15A power plug

4. I keep the compressor in an outdoor cupboard (used to be a toilet, outdoor but attached to the house). Is there any problem actually running the compressor inside the cupboard - mainly to keep the noise down ?

Yes there is. Compressors need good circulation of air around them - it would probably be good to vent the cupboard with an extractor fan. My compressor enclosure has a 100 cfm fan wired it parallel with the compressor motor - when it fires the fan also switches on.

Originally Posted by BobL

It certainly does matter especially if you use the thin hose. Minimum I'd used over 10m is the 1/2" (garden hose size).

This answer and the previous one implies that pressure drop is more of a problem in a thin hose then a thick hose. Is this right ? I intuitively thought it would be the other way round.

Originally Posted by BobL

How long are you looking at? It should be OK if you use a cable rated for a 15A power plug

3 metres would be OK. Also, I dont have a 15 amp circuit at the back of the house - so do I simply buy a 15 amp cable and change the plug to a 10amp one ?

Originally Posted by BobL

Yes there is. Compressors need good circulation of air around them - it would probably be good to vent the cupboard with an extractor fan. My compressor enclosure has a 100 cfm fan wired it parallel with the compressor motor - when it fires the fan also switches on.

This is to prevent overheating, right ?

thanks for your replies.
Arron

Originally Posted by Arron

This answer and the previous one implies that pressure drop is more of a problem in a thin hose then a thick hose. Is this right ? I intuitively thought it would be the other way round.

Pressure drop is greatest for narrower hoses because the flow rate of a fluid through a pipe is proportional to r^4 so small pipe has MUCH smaller flow (think about clogged arteries).

3 metres would be OK. Also, I dont have a 15 amp circuit at the back of the house - so do I simply buy a 15 amp cable and change the plug to a 10amp one ?

Yep - that would do it. Also keep the extension cord full unravelled and uncovered when you use it.
I have my 2.5HP compressor on it's own 15A circuit because when it was connected to the old shed circuit that was a 10A circuit connected to the house, depending on what else was connected to that circuit at the time it would sometimes trip the breaker. You might have to try it and see how it goes.

This is to prevent overheating, right ?

Yep - I even have a thermocouple in my enclosure so that I can monitor the enclosure inside the shed. Even with the fan it heats up my little enclosure by up to 10ºC above ambient.

Ok
Thanks very much for your answers
arron

As far as the power cable is concerned.

Yes they are "concieling their donkey" (covering their ass), a very short extension should not present too much of a problem, but of course some idiot will try running on a 50 meter cord...seriously lots of builders run on a 25 or 30meter 15 amp cable with 10 amp plugs.

I have the polocy of replecing the mains cord on most machines with 5 meters of 15 amp cable.....this removes the need for extension cords much of the time.

How much the hose size matters depends on how much air you are flowing.

Builders regularly use 30 meter pluss lengths of 1/2 inch air hose. Hell I have sprayed right down the back of my lawn on 45 meters of hose no problem.

Spray guns realy are not a high demand item.

As for the ventilation
there are tw good reasons why you ventilate a compressor.
First is to keep the motor cool....but it has to be a small cupboard to be a problem.
Second, the coller you keep the actual compressor and its tank the better it will perform and the less water you will get in the air lines.

One of the first things you should buy is an off machine filter reguator.
Seperate this from the machine by at least 3 meters of air hose.

the filter regs on many machines if the come with one are pretty poor and being on the compressor will rattle then to bits.

cheers

In the ideal world, you would set up an area for spray painting and put a small pressure regulator on the wall there, it allows the compressor to charge up to 100psi and then delivers even with pressure drop etc for small hoses 70 - 80 psi of pressure at your spray area, you can then regulate it here down to 30 psi for a hvlp gun.

There is a formula for pressure drop over distance for size of line carrying the air, a internet search should come up with something.

My HVLP guns have a regulator attached to the gun.

If you are spraying away from your compressor, you want a regulator near where you are spraying for a number of reasons.

cheers