# workshop dust and natural gas heaters



## Holbs (Nov 4, 2012)

i have 100sq ft more of R19 to install to finish off insulating my 2car garage ceiling (early spring, i'll toss up 5/8" gypsum firewall drywall when funds available). but i'm leaving it open to add another circuit for lighting, a future circuit, and gas piping for the Reznor.
i'll be doing a horizontal exhaust with a wall thimble (it's amazing how little information is out there when you have clay tile roofing as compared to asphalt shingles), B vent pipe extending 12" (or 24") past wall (or roof eave… i have to find out which is code). this will all be under city permit & inspection.

my question: since the combustion air is coming from a powered fan on the backside of my Reznor UDAP60, does woodshop dust become a concern? i'll have a grizzly air cleaner running as well. i imagine, regular cleaning maintenance is necessary. is this the type of theory similar to dust collection ducting and a spark in dust buildup? that it should never happen if preventive maintenance is performed?


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## wapakfred (Jul 29, 2011)

I doubt you will have a problem. My last shop had a direct vent gas furnace, and i used it for over 8 years with no problem (LP gas). That furnace was a vertical wall mount furnace (could fit between the stud cavity) and vented through a wall thimble.That was also how it drew in outside air for combustion. My current shop has a ceiling mount (Modine type) direct vent heater, and after 4 years it's not had a single problem. This one vents though the roof, and draws combustion air from the attic.


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## Holbs (Nov 4, 2012)

my combustion air would be coming from the workshop. unless i need to have a reason to change that thought.
or maybe i do not understand how the combustion air is received into the udap. i assumed, the fan on the backside draws the combustion air in. but then, maybe combustion air is drawn thru the outer section of the b pipe.
nope  just re-read the installation manual. combustion air comes from the fan & workshop. the UDAS is the higher end model that has the ability to draw air from outside the workshop.
I could consider placing a air filter behind the fan to ease my concerns.


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## wapakfred (Jul 29, 2011)

Even so, about the worse that could happen is that dust settle on some parts that shouldn't have dust. You will never have enough dust in there to cause an explosion (if there was, you wouldn't be able to be in there). If you have electronic ignition it's probably shielded in some way, but if not there may be an occasional cleaning on it.


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## shawnmasterson (Jan 24, 2013)

no there should be no problem. I heat with wood now, but I used to use a kerosene salamander (115,000 btu). I never had any trouble and I spray water, and oil based finishes.

just for fun


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## a1Jim (Aug 9, 2008)

I have used my gas heater for 10 years with out problems but I would be mindful of having the air filled with dust like running a planner without dust collection.


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## teejk (Jan 19, 2011)

I think your biggest problem is going to be more frequent maintenance (burner nozzles etc.). I heated with a kero salamander for years also and it was a little fussy when it was time for a cleaning. Sounds like you have the owners manual open so you know all about clearances and stuff. My new shop is radiant in-floor with a power vented hot water heater. Apparently new rules require a totally sealed combustion chamber (no open flame).


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## MarkwithaK (Sep 12, 2009)

DO NOT put a filter on the combustion air inlet. Air being pulled through there is what keeps the flames going into the heat exchanger and not rolling out.

I've repaired and installed more Reznor's then I care to think about. Which model are you installing?

Typically speaking on unit heaters I almost always recommend using outside air for combustion when possible. Saw dust will not usually clog up the gas orifices (it can accumulate though especially during off-seasons) it will most certainly be pulled into the heat exchanger. You have to keep in mind that you will have a negative pressure at the burners/heat exchanger. Sealed combustion chambers can eliminate this though.

Another thing to take into consideration is maintenance and yearly start-up. That exchanger can get a build up of fine dust that should be cleaned out before you run the unit for the first time each year. Otherwise it will most likely burn off but in worse case scenario it can start a fire.

Side wall terminations can be tricky. If not capped correctly any winds blowing against the termination can put a positive pressure on the flue which will most certainly cause either roll-out or force the pressure switch to close. Either one will shut the unit off on a safety switch.


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## Holbs (Nov 4, 2012)

mark.. ok, no filter at inlet 
the unit is a Reznor V3 series UDAP60.
I would do an outside air vent, but i would have to do another hole thru the stucco exterior of the garage wall. not something i would look forward to.
side wall termination will be face my neighbors house 20' away which blocks the normal direction the wind is coming from


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## hookfoot (Jan 23, 2013)

I have had a Reznor (54000 BTU) for 15 years in my wood shop(dusty). it draws its air from the room and exhausts up a chimney. If I am doing something that haises a safety concern I just turn the furnace off for a while. I clean it very thoroughly every fall. All I have had to do to it is replace the igniter about 3 years ago.


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## MarkwithaK (Sep 12, 2009)

Ahhhh the V3. I remember the V3, not fondly, but I remember them. I had a few of them in service in a diesel shop and they were finicky little things. At least the ones I serviced were, but those were in what could be called a rough service environment.

Again I would urge people to utilize outside air for combustion. If my memory serves me correctly the inducer housing shares the same compartment with the electrical and the microprocessor based control is just an open circuit board, if I recall correctly, and that concerns me for 2 reasons. One being that I worry about airborne contaminants damaging sensitive components. The other being that those live voltage terminals mixed with a combustible material like sawdust can spell disaster.

In the end it's your shop, your install and your call. But speaking as an HVAC professional I would think long and hard about that combustion air intake.


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