Vacuum Pump Exhaust Setups
Thoughts on how to exhaust a vacuum pump outside the shop, in order to reduce heat buildup. December 2, 2011
Question
I'm just getting comfortable with my first CNC router and the vac pump is creating too much heat in my 1400sf shop, so I would like to duct it outside. Anyone done this before? I don't want to break the bank, and my first idea - car exhaust pipe wrapped in heat tape until it's above the ceiling - turns out not to be all that cheap. Anyone know of a good pipe to use that could withstand the heat and that's insulated enough so as to not burn skin or put off too much ambient heat (it runs past the feed wires to the machine)?
Forum Responses
(CNC Forum)
From contributor L:
We have a 40hp Travaini unit and vented it with #80 PVC 4" pipe and haven't had any problem with heat. There is 24" off steel pipe coming off the top before the plastic connects. The only issue we have is some run back of oil, so we have a catch bucket.
From the original questioner:
The pump/blower I have is a Gardner Denver 11.5 hp. The outlet is 2" female threads. It's quieter than most pumps I've heard running and so far the hold down power has been great. I tried 2" schedule 40; the pipe going from the floor to above ceiling (10') got so hot and soft it bowed and fell down (joints weren't glued). The first 8' of pipe along the floor before that was hot enough to collapse about halfway on itself after we shut it down. This much heat built up after about 10 minutes of running. After seeing that I ruled out PVC as an option.
From contributor J:
If you increase the pipe to 4" you will reduce back pressure and possibly decrease the amount of heat. The pump may have a 2" outlet, but I would step up to 4" as soon as it leaves pump.
From contributor K:
I have a 25 HP Quincy vac pump and I ran the exhaust out the roof, 2" steel pipe 4 ft from the vac pump that increased to 4" PVC the rest of the run and up through the roof. Offset the steel pipe and install a T fitting with a 12" or so nipple with a small ball valve at the bottom. This will act as a water trap. If you don't do this you risk contaminating your vac pump with water that may find its way into the pipe. Also be sure to leave the pipe on the roof higher than your deepest snowfall, maybe 4-5 ft or so. You will also need to anchor the plastic pipe securely to your bar joist or the ceiling somehow. It will expand and contract. I would suggest consulting with a qualified roofer regarding what's best for anything above the roof line.
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From contributor I:
I have 2 Becker 10 hp pumps I ran 2" EMT to the outside. I disconnect in the winter and take advantage of the heated exhaust. I have heard of problems with PVC getting hot and melting.
From contributor T:
Why not mount the pump unit outside and use sch40 PVC to pipe the vac back to the CNC? That's what I did and not only did I put the heat outside, but cut down on the noise inside the shop.
From contributor K:
You would have to heat the enclosure the vac pump is housed in or heat the oil sump.
From contributor A:
We have a 40 hp Quincy in an insulated shed near the shop. 4" PVC in and out. There is an 18" fan on a thermostat to circulate shop air into shed and return to shop through insulated ducts. In warm weather we have an automatic shutter on a 30" fan in the shed wall to the outside. If I was doing it again I'd put a bigger fan and duct work to the shop. I've got a remote alarm connected to a thermostat in the shed in case it gets too hot. My first router had the vac pump in the shop; got really tired of listening to it.
