Moisture in DC Lines

[Jim DeLaney]

Anybody else encounter this problem?

My dust collector sits in the far corner of the shop, with the lines (all 4" PVC) running up into the unheated attic, and across the trusses to ceiling drops for the bandsaw, router table, planer, etc.

Well, it's been a bit cold here lately - nothing drastic, just in the 20's. Yesterday, I started to run the router table, and could hear a funny noise in the flex hose drop. When I disconnected it, about a quart of water - and gummy chips and dust - poured out of it. Apparently, the cold air has caused that much condensation in the lines, and the droop loop in that flex line was the low point in the system, which collected it all.

Gummy mess in the line, and of course, reduced efficiency in the collection. I'm also a bit concerned that sucking that much moisture and wet sawdust into the DC may lead to mold and mildew in the collector bag.

Right now, the drops are disconnected, to drain and dry. Ayybody else got this problem. Any suggestions for mitigating it, other than bringing the lines back down into the heated portion of the shop?

[Greg Funk]

I would suggest insulating the lines the same way HVAC ducts are insulated. Google HVAC insulation and you should find lots of options.

Greg

[Kyle Kraft]

Are you humidifying the shop air??? My shop is so stinkin' dry the shavings stick everything....and all my DC piping is grounded steel.

[Jim DeLaney]

Are you humidifying the shop air??? My shop is so stinkin' dry the shavings stick everything....and all my DC piping is grounded steel.

Kyle,
No, I'm not. I thought the shop itself was (is) dry, too. That's why I was so surprised about the condensation. Also, I have no idea how long it took for that much water to build up - days? weeks?...

BTW, the shop is heated with gas radiant. 65° daytime, 50° overnight. The attic stays at whatever outside ambient is. I have 12" of fiberglass batts up there, and 5½" in the walls, so it's pretty well insulated.

Some, maybe most, of the moisture may be coming from the radiant heat. Ambient humidity around here is somewhere between 45% and 75%, except of course, when it's actually raining. The past month was pretty rainy, btw, until this past week, when it's gotten colder - 17° as I'm typing this.

I've thought about using insulation wrap on the pipe, but I still do need to be able to relatively easily disassemble it if I need to clear a clog or something. Maybe just laying some more batts over it will help.

[Kyle Kraft]

Jim,

If your radiant heater is an unvented type (no chimney, combustion by-products go directly into the room), this could be your whole problem. Anytime you burn gas, large amounts of water vapor are emitted, along with other chemicals and gasses such as CO2 and CO. I had an unvented "blue flame" type heater in the basement of my first house and it caused the cold concrete block walls to sweat, as well as the windows. I never ran a humidifier in that house, as the small, 18kbtu heater produced more than enough moisture to keep the rest of the house comfy!!

Basically the DC pipe in the attic is acting as a dehumidifier with no drain, sucking humid air into a cold pipe then recirculating the drier air back into your shop.

Sound plausible?

[Jim DeLaney]

Jim,...Basically the DC pipe in the attic is acting as a dehumidifier with no drain, sucking humid air into a cold pipe then recirculating the drier air back into your shop.

Sound plausible?

Kyle,
Yeah, that sounds very plausible. The radiant heater (35K Btu) is unvented. Funny thing, though, is that this is its third Winter, and I've never had (or at least, noticed) the problem before.

I'm pretty much at the point of thinking that adding insulation batts over/around the ducting may alleviate the problem. Of course, if I procrastinate a bit, Spring will be here and the problem will solve itself...:D

[Chris Padilla]

Start procrastinating tomorrow, Jim! ;)

[Jim DeLaney]

Start procrastinating tomorrow, Jim! ;)

Yeah, there'll always be time to do it later...

[Ron Brese]

I'm afraid that even if you insulate the ducts in the attic space there will still be enough difference in temperature to cause some condensation, and besides as long as they are up there you will be cooling the warmer air pulled from your shop in to the attic ducts. This will cause the condensation and hurt you heating efficiency.

Ron

[Jim DeLaney]

I'm afraid that even if you insulate the ducts in the attic space there will still be enough difference in temperature to cause some condensation...

Ron

Yeah, I was sorta thinking that, too. Hence the procrastination.


... as long as they are up there you will be cooling the warmer air pulled from your shop in to the attic ducts. This will cause the condensation and hurt you heating efficiency.

Ron

I think that's less of a problem. With the air velocity as high as it is in the DC, the air cycles from the shop, thru the ducting and back into the shop in a matter of a second or two. There is certainly a bit of loss, but I doubt it's a great cause for concern at this point.