Is it ok to route copper compressor piping outside?

sbarton · Dec 8, 2008

I have my compressor in a closet in my garage. I'm thinking about adding a zig-zag portion of pipe to get some extra piping to let the air cool. Originally I was thinking about putting this next to the compressor, but have concerns about space as well as heat from the compressor.

Would it be ok to route the copper pipe outside and do the zig-zag. This will allow me to use whatever length I want and the ambient outside temps will always be cooler than the compressor closet temps.

My concern is freezing. Since the point is for this section of piping to cool and condense the water to drain, freezing may be an issue as temps get as low as the 20's or even teens.

Here is what I would like to do. It would require having a drain (ball valve) outside.

Is freezing something I need to worry about? Will it condense enough water to be a problem? Do I have to worry about the pipes freezing/cracking, or just the valve sticking, or what?

-Scott

kbs2244 · Dec 8, 2008

There are a lot of variables here that you don’t mention.
Size of the compressor and air volume at heaviest use being the most important.
I wouldn’t do it your way because of the freezing concern.

A vertical length from the floor to the ceiling of 2 inch with the kind of fins they use for hot water heat pipes and a drain at the bottom will be enough for most home shops.

You want to have a large dia so you have enough room for the moisture to flow down, against the air flow.

If you are a real large volume user, go with 2 verticals and a connecting manifold at the top and bottom.

TRDon · Dec 8, 2008

I would be concerned about condensation and freezing, especailly where temps get cold.

2LTim · Dec 8, 2008

If the lowest point of your cooling loop is higher than the inlet on your tank, nd you din't have any low spots for the water to collect, you souldn't have any problem with the condensate freezing. Remember why you want to cool it in the first place, because it is hot. This heat will keep the moisture from freezing, and it will drain back into your tank.
If you use too small of a pipe for your cooling loop, the air will pass through so fast, it will not have time to cool. Unless you use a lot of it.
Tim

Torque1st · Dec 9, 2008

Let the compressors come out of the closet before they die from the heat. Your tank will cool the air like it is supposed to also. Pipe the inlet away somewhere if you don't like the noise. Of course if you have one of those direct-drive compressors the only solution is to replace it with a belt driven model.

sbarton · Dec 9, 2008

Torque1st said:
Let the compressors come out of the closet before they die from the heat. Your tank will cool the air like it is supposed to also. Pipe the inlet away somewhere if you don't like the noise. Of course if you have one of those direct-drive compressors the only solution is to replace it with a belt driven model.

Hi Torque. Unfortunately taking the compressor out of the closet really isn't an option for me. I plan on putting a vent fan to the outside in the closet and possibly a box fan over the tank/compressor and run them when I use the compressor.
I have an 80 gal 5.4hp belt driven Craftsman compressor.

-Scott

buening · Dec 9, 2008

While it's true that the hot air from the compressor may keep it from freezing, that does not mean the condensate will not freeze in the water traps when the compressor is not running.

Torque1st · Dec 9, 2008

Muffle the air inlet or run it somewhere away from the area just like I said in your other thread. Then you can take the doors off and use that space. Openings for vents will just let the sound out anyway. Making an enclosure to cut the sound out is difficult at best. Always attack the source of the noise. I have made machines that functioned even to European factory noise standards. When the tank is cool you probably won't need any lines outside.

sbarton · Dec 9, 2008

2LTim said:
If the lowest point of your cooling loop is higher than the inlet on your tank, nd you din't have any low spots for the water to collect, you souldn't have any problem with the condensate freezing. Remember why you want to cool it in the first place, because it is hot. This heat will keep the moisture from freezing, and it will drain back into your tank.
If you use too small of a pipe for your cooling loop, the air will pass through so fast, it will not have time to cool. Unless you use a lot of it.
Tim

I have 14' of 3/4" copper tubing I plan to run outside (5 rows of 34")
The only place water would collect and freeze is in the drain. See diagram in my post above where the drain is. I plan on putting the first regulator (3/4") after the zig-zag comes back into the closet to regulate the pressure from 180psi down to ~150psi or less.

Right now all I will be using it for is small air tools, like ratchet, scraper, impact gun, drill, cut off tool, etc. Some of these I may use continuously though. Eventually I will be getting a media blast cabinet as well as possibly doing some painting. I'll take extra measures for those lines when I get to them though.

-Scott

Torque1st · Dec 9, 2008

Yikes! Regulators waste all the energy that was used to compress the air. If you need closer to 150PSI turn down your pressure control. If all you are running is air tools that require ~90PSI air then you can turn down the control even more.

sbarton · Dec 9, 2008

Torque1st said:
Yikes! Regulators waste all the energy that was used to compress the air. If you need closer to 150PSI turn down your pressure control. If all you are running is air tools that require ~90PSI air then you can turn down the control even more.

The output of the compressor is 180psi. It's not adjustable afaik.
For some reason I thought the 1/2" regulators I was looking at needed a maximum of 150psi inlet prerssure, but I just checked and I was wrong. So I won't actually need to put a regulator after the zig zag.

-Scott

buening · Dec 9, 2008

Torque1st said:
Yikes! Regulators waste all the energy that was used to compress the air. If you need closer to 150PSI turn down your pressure control. If all you are running is air tools that require ~90PSI air then you can turn down the control even more.

Not to try to argue with you, but care to explain? It would be pretty dumb to buy a large compressor and keep the tank at 90psi when it can put out 180psi. A quality regulator at the outlet should not affect the system enough to really notice, and keeping the compressor tank at it's peak output will (in this case) double the air reserve. The elbows or tees and any ball valves in the system will create more losses than a regulator will, assuming this is what you are referring to.

Uncle Buck · Dec 9, 2008

Torque1st said:
Yikes! Regulators waste all the energy that was used to compress the air. If you need closer to 150PSI turn down your pressure control. If all you are running is air tools that require ~90PSI air then you can turn down the control even more.

You cannot forget to take into account the pressure drop from the compressor through the lines as measured at the tool. Ninety pounds at the compressor would be less at the tool depending on the line size, and the distance of the run.

engnerdan · Dec 9, 2008

Because this tube will be outside and under significant air pressure I would recommend painting the tube to protect it from the elements. I know it generally takes a long time but copper is subject to embrittlement from the elements and most significantly bird droppings. The last thing you would want is an high pressure air line rupturing.

-Dan

2LTim · Dec 9, 2008

IMO, Scott has his finger on the pulse of what he needs. A regulator does just what the name implies, regulate theair pressure, at a preset level. If you try to use the pressure switch of the compressor to do that, you will constantly be figting pressure fluctuations up and down from your upper limit to the cut in pressure of the switch. If his cut out pressure is 180, his cut in pressure is most likely 155 - 160. With a regulator set at 150, he will have a constant pressure to opperate his tools. And, unless his regulator has a leak in it, he will not "Waiste" any of the energy used.
Tim

ron in sc · Dec 9, 2008

I'm running copper outside underground from attached garage to detached garage; freezing is not an issue. I made a very small tank to collect water at the lowest point. I can drain by means of a ball valve on the bottom. The tank is underground.

sbarton · Dec 9, 2008

Thanks guys. The informaton is very useful.

I'm still not sure if running the pipe outside will be a problem with freezing. If I drain it regularly with every use, then I really shouldn't have a problem with water in it anyway, correct? How much water would you expect that I collect there?

I think what I would do is at the drain location go from copper to black iron at the lowest point in the vertical section for a few inches before the ball valve. Doubtful a little water would break the black iron, and the worst that could happen is the ball valve would freeze and be inoperable while frozen. Doubt it would ruin it right? If need be, I could take a torch to warm the valve up and open it?

-Scott

Torque1st · Dec 9, 2008

buening said:
Not to try to argue with you, but care to explain? It would be pretty dumb to buy a large compressor and keep the tank at 90psi when it can put out 180psi. A quality regulator at the outlet should not affect the system enough to really notice, and keeping the compressor tank at it's peak output will (in this case) double the air reserve. The elbows or tees and any ball valves in the system will create more losses than a regulator will, assuming this is what you are referring to.

Buening, I am surprised at you. I seem to have to constantly repeat myself but the energy to compress air is well known in most engineering circles and can be calculated. Check the fluid power design manuals. The elbows and tees etc will cause pressure losses but they are unavoidable. The pressure loss thru a regulator is avoidable. It is not dumb to buy a large two stage compressor and run it at a low pressure. A two-stage compressor is more efficient than a single stage compressor (Check the design manuals). His two-stage compressor can also be turned up when he needs higher pressure for a specific task like sand blasting.

Most air tools are rated at 90PSI but any air tool or machine should operate at anywhere from 70-90PSI. Designing a system with large enough air lines to minimize pressure drops is the goal of any air system design.

Most pressure switches can be adjusted within certain limits. Pressure switches are available with wide control ranges and narrow differentials (cut-in/cut-out for some of you).

Torque1st · Dec 9, 2008

2LTim said:
IMO, ... And, unless his regulator has a leak in it, he will not "Waiste" any of the energy used.
Tim

Your "opinion" is wrong. Try checking engineering manuals for scientific information.

buening · Dec 10, 2008

My apologies, but most here may not have understand your reasoning and regulators are prevalent in many professional shops. I wasn't trying to make you repeat yourself, just explain further. While I'm not a hydraulic engineer, I have had numerous hydraulic courses and know enough to get by (but I could be wrong in this case!). I'm well aware of the energy formulas and how losses are calculated. I think the your concern about the energy loss through a regulator is correct but the loss is relatively small in 99.9% of the cases on this website. Also keep in mind that most of the pipe networks on this website are quite small, and likely only involve a couple regulators. If we are talking a large system of pipe and numerous regulators, then I can see the concern of losses....as they would add up quickly. The roughness of the pipe should also be a concern if we are going to this depth of design. A rough wall pipe like galvanized or black iron will create more friction losses than, say a smooth wall like aluminum or copper.

Another factor one should think about is the cost of startup each time the compressor cycles. If you have a compressor with the pressure switch set at 90psi, it will cycle much more than one at 180psi because it has less air reserve. Efficiency of the pump may likely go down as the pressures increase though, this I'm not sure of. That would be more on the mechanical engineer side

Let me know your thoughts on that, not my specialty.

If you happen to know what the losses are through a regulator compared to a ball valve or an elbow/tee (relatively), let me know as I'm really curious. I don't have a good feel with regulators. I have a charts and a ball valve contributes much more losses than an elbow, but the chart doesn't include a generic regulator. This may be dependent on the regulator manufacturer though. The Norgren B73G is the model I'm using. Again, just a simple discussion but if you don't want to continue then no need to reply. I agree with what you are saying, but I believe the magnitude of losses will be small on these size networks.

timgr · Dec 10, 2008

Another suggestion - cold air is dry air. If you have access to the outside wall, I'd suggest you take cold outside air for the compressor inlet. As well as quieting the compressor (a lot), this will reduce the amount of moisture in the tank and reduce the temperature of the air after it is compressed.

Torque1st · Dec 10, 2008

buening -I posted the general formulas and a small section of a table in another thread here but I can't find it at the moment. For a complete explanation, tables, and formulas check some fluid power texts or handbooks. The loss thru a regulator is orders of magnitude greater than the loss thru a fitting and is easily calculated.

sbarton · Dec 10, 2008

I'm confused. Let's you have a 50' run of 3/4" black iron pipe with (6) 90* elbows and (3) tees (or whatever, just an example).

If you set the compressor to 90psi, by the time it gets to the tool, wouldn't it be signifigantly less?

Now if the compressor pressure is set to 180psi, and it goes the 50', and there is a regulator going down to 90psi, at the end right before the tool. Wouldn't the tool see much closer to 90psi?

Also with the compressor set at 90psi, as soon as you start using air, the pressure will drop. This means the tool will see various pressures. But if you have 180psi at the tank and then regulate it down to 90psi right before the tool, the tool would almost always be seeing 90psi? Having a constant pressure at the tool would make it much easier to work with.

Would having a lower tank pressure and therefore lower reserve also lower the SCFM output of the tank/compressor? Wouldn't that negatively impact large use items like a media blast cabinet, etc?

Also with the compressor cut off at 90psi and cut in at 70psi, wouldn't the compressor be running more often since there is less reserve? And if it is running more often, it won't have a chance to cool in the tank?

While there may be more losses with a regulator, it seems that the advantages of having a larger reserve and constant pressure at the tool with a regulator, outweigh having a lower reserve and fluctuating pressure at the tool by trying to avoid a regulator, no?

-Scott

Matti · Dec 10, 2008

I would run the compressor to it's max rated pressure and regulate to minimize cycling. If the condensation cannot be routed back into the garage it will freeze. If it is run back inside it's a guess as to whether it will freeze or not before coming back in.

malibu101 · Dec 10, 2008

timgr said:
Another suggestion - cold air is dry air. If you have access to the outside wall, I'd suggest you take cold outside air for the compressor inlet. As well as quieting the compressor (a lot), this will reduce the amount of moisture in the tank and reduce the temperature of the air after it is compressed.

X2 on piping the intake outside of the building. It quiets down the sound ALOT.

timgr · Dec 10, 2008

A regulator is just a variable orifice that changes size based on the downstream pressure. There are some frictional losses associated with putting an orifice in the air pathway.

There are some advantages to running the air tank at a higher pressure. The tank acts like a reservoir. The amount of air stored in the tank is larger, so you can potentially do some jobs with the reserve air that you could not do before, without having to wait for the tank to refill. There's a cost in electrical power at startup - the electrical efficiency is higher with fewer motor cycles. Plus with a pressure set point close to the operating pressure of the tools, it makes the compressor motor run very often for short durations.

I believe what Torque1st is claiming is that these frictional losses are a much worse penalty than the advantages you get with maintaining a high pressure in the tank. It's possible, but then why would the manufacturers supply their compressors with large reserve tanks, if it's more efficient to run the compressor frequently with a low set point? You may as well use an on-demand system, where the compressor runs constantly while the tool is being used, and the speed of the compressor changes in response to air demand.

The conventional wisdom says to use a big reserve tank at high pressure and regulate down to the demand pressure. The conventional wisdom may be wrong in this case, but most times it isn't.

Is it ok to route copper compressor piping outside?

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