Underground Air Supply

[Thane Duncan]

So Folks-next problem:


I have a basement shop. When I built it I ran a circuit, 10 gauge 220 so can carry 30 amps, to the back of my house to a AC style box. I also ran a piece of iron pipe through the ceiling out to the back of the house. I want to locate a compressor in a shed that is 25 feet from the back of the house. Plans are for a 5hp Quincy with a starter and an automatic drain. Then I will put a filter to further dry the air in the shed and then pipe it with copper rigid and flexible half inch pipe back to that stubbed out iron pipe on the back of the house. It will need a dielectric union on both ends as I plan to plumb the basement with copper. This will allow me to turn on the compressor when I head to the basement, close the shed, its about 150 square feet, insulated not heated. I can run the electric circuit in a trench with the copper line to the shed to supply the compressor. Then at night I can turn off the feed to it which is in the basement and has a cut off switch already wired to the circuit. If the automatic drain is working I thought this would work, no worries.

My questions are two fold. First what about the compressor in a unheated space and no AC. Second, the copper run from the shed will go out of the wall, underground and then up to band joist height to join the existing stub-out running into the basement. 1. will this ground loop be a problem with moisture, if I trap it prior to the loop and, is the fact that the pipe is exposed outside a big issue? I could insulate the pipe I guess or sleeve it with something? Give me your input, I thought it would be great to get the compressor out of the shop but after reading some of the threads and online discussions I have concerns.

Thanks in advance.

[Larry Edgerton]

I wouldn't do it without haveing the line fron the shed to the basement have a 1/8" to a foot fall, and a drain where it comes in to the basement. For me trapped water freezing would be the issue, but you do not say where you are from so I have no idea what your conditions would be. I would put the water seperator in the basement and an automatic drain on the compressor. Again, I don't know your climate so?

[Jimmy Coull]

I agree whole heartedly with Larry. Have an auto dump on the compressor and have it angled to where you can drain it conveniently. From experience, you will always have some moisture in the line with this set up, so either have traps at the end of the line (definitely if spraying), or make sure that you blow out your line prior to use.

Good luck,
Jimmy

[Thane Duncan]

The problem is, the basement wall is 10 inches of concrete, covered in stone and that wall on the interior is covered in cabinets. If I ran it downhill it would come into solid concrete and also be a break in the waterproofing. I am in Memphis. We have a lot of water so sealing that line might be a problem (the reason I brought it in high) and it would break the integrity of the membrane waterproofing. Humidity is a big problem here. Doesn't get too cold for long but we have freezing weather for weeks at a time at night. Lows at minus 5 rarely. Highs in the 90's for months in the summer, it is already hot and humid.

[Bob Wingard]

I don't think freezing of any condensate in the lines is much of a problem .. .. so what if a shallow layer of ice forms in the pipes ?? It will thaw out and go away in time. Unless the pipes are FULL of water, there shouldn't be any issues with bursting.

If you really want the lines empty, why not form them up with a belly in the middle and have a drain valve installed at the low point, blowing any condensate into a small dry well. You could either pour a small concrete vault to house the valve, or simply get a stainless one, leaving a stub just under the surface to slip a handle onto. Possibly even install something like a cheap Wilkerson automatic drain valve that's setup to blow for a few seconds every time the pressure changes by about 20# up or down. It works off of line pressure and requires no pilot air or electric power to operate. I have one installed on my tank in the basement of the shop that blows out through a small hole in the wall and into the French drain, and another that is outside, mounted at the end of a drip leg which is the low spot of my system, and it blows out onto the ground.

[Thane Duncan]

Thanks Bob, probably a good suggestion, what happens to these valves if they freeze? Not sure where I would locate as the midpoint is at the swale which drains runoff from the back yard, not a good place for a valve unless it can work underwater. Could possibly locate at the end of the run but this point is still higher than the midpoint, might drain it before it went back up into the air above ground. Wish I had run it differently to start with, behind the rock face and entered at a different site, but as we say live and learn, anyone else think this is a crazy idea or would you go for it and see what happens? The real question is whether it will likely work as large compressor purchase in question, twenty five foot to trench by hand etc.

Thane

[David G Baker]

I would dig the trench close to the depth of the frost line if you live in cold country and cover the pipe with foam insulation and PVC pipe. The slope towards the inside of the building is a must and an automatic drain is a good idea. I do not know how the compressor will take being in an unheated building. A friend of mine has an oil pump compressor that he can't get started in his unheated pole barn in the Winter. He has to warm up the building and compressor before he can use it. If you run the air line through the wall and then down into the ground, the exposed area is subject to cold weather issues. The compressed air when it leaves the compressor is warm and when it hits the pipe that is outdoors in colt temp you will probably get condensation. You can cover the pipe as it leaves the shed with foam insulation and PVC, or you could cover the pipe with larger PVC pipe and spray in the expanding foam for insulation.

[Keith Outten]

The 80 gallon 3hp compressor for my workshop is located in an adjacent unheated building that is about 15 feet from my shop. I buried PVC pipe just below the frost line and ran an air hose through the PVC to the shop. This setup has been working fine for about 5 years.

Surprisingly there is almost no condensation inside the piping, I open the ends of the pipe inside my shop and let the air blow down every few months just to make sure. The second floor of my shop is my shop office and I have my laser engraver hooked to the air supply for vector cutting and I have never had any condensation issues.

I don't know if this helps...it works for me and I enjoy not having to listen to the dang air compressor run. Shortly my dust collection pump will be outside of my shop as well.
.

[harry strasil]

There is a car dealership body shop next to my Blacksmith Shop and their large compressor is outside in the open air and also the main dealership compressor across the street that serves all the mechanics is outside in the open air and they have no problems and its gets down to -10 plus here in winter and also it gets in triple digits in summer.

[Jerry Bruette]

Thane,

I live in N.E. Wisconsin and where I work all of our compressors are located in buildings, some heated some not. All of our air is run through a dryer, some driers are dessicant some refrigerated. We will have condensate freeze in the lines where the lines leave the building to go outside to the baghouse type dust collectors.

I think if you insulate the lines good enough to lower the dewpoint inside the lines you might be okay. Otherwise you could heat trace the lines along with insulating them, and turn off the tracer line in warmer weather.

Good Luck
Jerry

[Thane Duncan]

Jerry

Pardon my ignorance but what is trace the lines. Last time I did that I was in first grade with Ms Taylor.

Thane

[Jerry Bruette]

Jerry

Pardon my ignorance but what is trace the lines. Last time I did that I was in first grade with Ms Taylor.

Thane

Thane,

A heat trace is an electrical wire that is wrapped around a pipe or run down a down spout, etc. to keep it from freezing. Up here some people even run them on the eaves of their houses to prevent ice dams from forming.

You can get fancy ones that are thermostatically controlled or the cheaper ones are just turned on and off when needed.

Jerry

[Rod Sheridan]

Jerry

Pardon my ignorance but what is trace the lines. Last time I did that I was in first grade with Ms Taylor.

Thane

Regards, Rod

That was funny, I believe the person was referring to electric heat "tape" that's wrapped around the pipe to heat it.

[Jimmy Coull]

Heat tracing uses an electrical heating wire that you attach to the length of your pipe that might freeze up. it can work off a thermostat or you can turn it on and off by yourself.