Connecting an air compressor

[d6monk]

So I have no experience with air compressors, but I was thinking about buying a large one for sandblasting (80 gallon, 7.5hp, 2-stage) and was wondering how you guys hook it up for use with a sandblasting cabinet. I was trying to figure out what is needed by reading some automotive etc. forums but all I found was a bunch of stuff about running 100' of copper or galvanized pipe around your shop with all kinds of drops for air tools etc. and I didn't think it would really apply to me. Could I just directly connect the compressor to the pressure pot with a length of high pressure rubber hose? Do I need any special kinds of connectors etc.? It would be a lot easier than something like this: http://www.tptools.com/StaticText/airli ... iagram.pdf. What do you guys do?

Oh, and as far as 240v go I was probably just going to hardwire it in with 10 gauge wire. Do you guys do that or do you use a plug etc.?

Thanks again guys, I know I have a lot of questions, but I really appreciate the help.

[ToddJohnson]

You're using a pressure pot? Are you using a cabinet as well? Is it siphon feed? Usually with a pressure pot, you need far less air pressure and an 80 gal. 7.5 hp. compressor would be like dropping an enormous anvil on a very small fly. Nonetheless, whatever you're connecting your compressor to, you'll want to run 1" PVC from the tank to the cabinet and include a moisture trap, pressure regulator, and a ball valve with a 90 degree down pipe to dump the condensation that the moisture trap doesn't get. For a compressor this large, the best thing to do is hard wire it into a separate switched breaker box. That said, mine is not, so do what you need to do. Hope this helps.

Todd

[KurtHuhn]

There is nothing wrong, and everything right, with Todd's setup. And here's another set of options as well.

Mine is on a dedicated 30A/240V breaker in the subpanel, run to a twist-lock receptacle over 6 gauge wire, and the wire from the compressor to the receptacle is also 6 gauge. I use 6 gauge because it's what I had, and is more than sufficient.

Between my siphon cabinets and compressor (no pressure pot here) I have, in this order:
- fittings to take it from 1/2" FPT to 3/8* MPT
- regulator
- moisture trap
- shutoff valve
- female 3/8" quick-connect fitting

These are all directly connected to the compressor tank.

From there I run the typical 50-foot black airhose with 3/8" MPT ends, onto which I've installed 3/8" quick-connect fittings - female for the cabinet end, and male for the compressor end - as per normal for airhose in any given workshop.

I also install a male 3/8" quick-connect fitting on the cabinets, since mine did not come with, though they did come with a 1/2" FPT ball valve (you need a reducing bushing).

This way I can swap between cabinets, or run more hose out to the driveway to run air tools when working on the vehicles, or into the house on the rare occasion I need it in there.

[ToddJohnson]

I just have a T coming off my compressor so I can use various other air tools off the compressor. You'll get more pressure (and less condensation) at the gun running through PVC, but we're really only talking about degrees of sufficiency here. Kurt's way will do the job just fine, mine will do the job just fine, and there are other methods that will do the job just fine. Hopefully we've flooded you with enough information that you can just pick and choose what's easiest.

Also, if I remember correctly, code for single phase 30A 220 is 10-3 with ground. You could also use 10-4, it doesn't matter. Don't need 8, though, unless you've got it laying around. If none of that made any sense to you, though, call an electrician. This sort of voltage--especially when you're coming directly off your breaker box--is enough to "kill you dead" as my grandfather used to say.

TJ

[RadDavis]

The way I have mine set up is the best way to do it.

Rad

[jeff]

Thank you for your typically illuminating response, Rad. You're always so helpful.

[SimeonTurner]

Kurt and todd's explanations were confusing. All of these fancy terms and numbers. Rad's advice was simple. I think I'll follow Rad's way.

[d6monk]

Thanks Kurt and Todd, that really helps a lot.

Also, Rad and Jeff, how do you have your's set up? I would especially like to hear about your setup Rad, I want to set up mine the best way too!

[RadDavis]

Thanks Kurt and Todd, that really helps a lot.

Also, Rad and Jeff, how do you have your's set up? I would especially like to hear about your setup Rad, I want to set up mine the best way too!

I've set up mine the best way. If you do that too, then you'll be in fat city.

Rad

[baweaverpipes]

Thanks Kurt and Todd, that really helps a lot.

Also, Rad and Jeff, how do you have your's set up? I would especially like to hear about your setup Rad, I want to set up mine the best way too!

I've set up mine the best way. If you do that too, then you'll be in fat city.

Rad

I have mine set up exactly like Rad. It's the only way.

[jeff]

I'm currently working with UCSD researchers who are developing a way to transmit compressed air without piping or tubing. I have a transmission box attached to globe valve on my compressor, and a receiving box on my cabinet that restores the transmitted waves to compressed air form.

That's what you're using too, right Rad?

[RadDavis]

I'm currently working with UCSD researchers who are developing a way to transmit compressed air without piping or tubing. I have a transmission box attached to globe valve on my compressor, and a receiving box on my cabinet that restores the transmitted waves to compressed air form.

That's what you're using too, right Rad?

What's a globe valve?

Rad

[SimeonTurner]

I believe there is a picture of a globe valve in another thread around here. Something about a motorized hookah...

Lol

[FredS]

I'm currently working with UCSD researchers who are developing a way to transmit compressed air without piping or tubing. I have a transmission box attached to globe valve on my compressor, and a receiving box on my cabinet that restores the transmitted waves to compressed air form.

In one machine shop I worked in, it was tradition to send the new guy to get a wireless extension cord. It usually made for a laugh or two. Now a device simlar to this is - a wireless cell phone & Ipod charger - is actually available.

[RadDavis]

I'm currently working with UCSD researchers

Also, I'm sorry to know that you suffer from UCS Disorder.

Whatever that is.

Rad

[baweaverpipes]

I'm currently working with UCSD researchers

Also, I'm sorry to know that you suffer from UCS Disorder.

Whatever that is.

Rad

Rad,
I believe you suffer from UCS. Is it not Uncontrollable Curmudgeon Syndrome?
Todd would concur that I suffer from this, on occasion.
In reality, Todd and Jeff are afflicted with YWS.

[SimeonTurner]

I'm currently working with UCSD researchers

Also, I'm sorry to know that you suffer from UCS Disorder.

Whatever that is.

Rad

Rad,
I believe you suffer from UCS. Is it not Uncontrollable Curmudgeon Syndrome?
Todd would concur that I suffer from this, on occasion.
In reality, Todd and Jeff are afflicted with YWS.

Young Whippersnapper Syndrome?

[baweaverpipes]

Give Simeon $5 and a stinky rod of ebonite for answering correctly

[d6monk]

Whew, I didn't know what I was getting myself into when I bought the compressor--

After I unloaded it and moved it into my shop by myself I found out I had to install a new subpanel for the circuit breaker since the tiny panel on my 100 year old house was full. I had never taken the panel off before and it is the scariest birds nest in there, I can hardly sleep at night now after seeing all those rotted and moldy frayed cloth covered cords going everywhere.

Anyway, I have a couple more questions for you large compressor owners:

1. How did you bolt it to the ground--did you use the vibration insulating pads like they recommend in the manual? There is a caution in the manual saying that I shouldn't just leave it bolted on the palette--so my preferred method is out.
2. Is it normal for a compressor to lose a little pressure right after it fills up and shuts off? Mine probably shuts off around 170psi, and slowly decreases until it hits 160-165psi. I have checked for leaks everywhere with soapy water and didn't find anything--so I imagine it could just be the air in the tank cooling off and making the pressure drop a bit.

Thanks again for the help.

[KurtHuhn]

1: Mine is bolted onto the pallet, which is fitted with anti-vibration pads to isolate the pallet from the ground.

2: You maybe correct about the air cooling off. Just to be safe though, check the pressure switch that's on the control relay. It may be the culprit if there actually is a leak.