Question
I would like to heat my finishing room (500 square feet) separate from the rest of the shop. I only need to maintain about 60 degrees with the fan on. I looked into air make-up units last year and discovered that the unit alone would cost $10,000. How can I heat this space in a more conventional manner?
I looked into infrared heaters, but don't know if they will affect the finish or if they are safe. The one I looked at had a closed combustion system.
Our finish room has 13' ceilings, a spray booth with 8' x 7' filter wall, a 24" fan, a 1 ½ HP motor with AC inverter, and plenty of fresh air available (3- 24" x 48" windows). We can slow down the fan with the inverter while parts are drying. We typically only run the fan fast enough to get the over-spray out during the winter. We also steal a bit of heat from the shop through two 2' x 3' filters in the door.
I am located in northern New Jersey, where it gets very cold sometimes.
Forum Responses
I had a used gas furnace for my spray room. It was outside the spray room but still in the shop. A duct ran through the wall for the hot air. It wasn't diffused very well, so it created a lot of turbulence. Would it be possible to install a furnace outside the shop? This would act as a low budget exchanger, and with the exhaust fan at a low speed, it would pressurize the room to keep dust out.
Radiant systems are not cheap to purchase and install, but are quite a bit less than air makeup. Operation cost of radiant is pleasantly low, at least here in Kansas on natural gas. Radiant heat warms objects, which then in turn warm the room. It keeps our finishing materials at a good working temperature in spite of the fact that in winter we are bringing in cold outside air to supply our booth fan. It gets a little uncomfortable for the operator when the fan is on for long periods, but when the fan is turned off, the room warms up quickly.
I am in no way saying that radiant heat provides a solution as good as a heated air makeup unit. If you can afford air makeup, don't consider anything else. A properly sized and installed makeup unit provides just the right amount of air so the booth draws optimally and your operator has maximum comfort and safety.
With radiant heat you’ll still need to bring in supply air to your booth, and you’ll need to do it in a way that your booth will draft well. If supply air is inadequate, negative pressure is created in the building, which causes all sorts of problems. If you have any sort of common forced air or overhead heaters operating anywhere else in the building, they will not vent themselves properly. They will also be using air for combustion that is probably contaminated with whatever you're spraying. This leads to rusted out flues and heat exchangers on a constant basis.
The existing gas line should handle a radiant tube heater. The booth fan never has any affect on our forced air system in the shop. I am very concerned about the infrared heat because our finish room is so small. I think we would end up with pimples! I like to leave all newly finished products in the spray room with the fan on low so the shop doesn't stink. We often cram whole jobs in there. I am in trouble if I can't store work in a 5' wide area under the heater. I was thinking of mounting the heater along the back wall and angling the deflector out into the room. This may create a wider danger zone for "pimples"?
You may also be able to shield your work if it is too close to the tube. For instance, we have racks for doors and other flat things. We put a rather large piece of plywood on the top space and this shields the whole rack so we can heat the danger zone.
I draw fresh cold air through an open doorway at one end of a 25'x50' room. We use a screen door to catch larger debris and bugs. It gets cold for the operator standing directly in the air stream. It is tolerable, though, at least here in Kansas. Our booth fan is on intermittently, probably 60% of an average workday. So even after an extended period of drawing cold air into the room until it feels cold, the room recovers its heat quickly once the fan is shut off. This is because everything in the room is relatively warm even though the air moving through it has been frigid.
The fine assistance I received from my area's rep for Combustion Research was crucial to my being satisfied. There are many variations on these systems, and some systems (like mine) need to be configured specifically for your installation.
I plan to increase my output. A larger finishing facility is in the works. I'm thinking about in-floor or in-wall radiant heat. With enough area and a modest temperature the heat would be omni-directional, lack hot spots, and be most comfortable. The cold air moving through should still have minimal effect on drying, if it is intermittent. The room would be reheated by the large thermal mass of the warm walls and floor.
This system doesn't use big gulps of energy in short periods of time, but moderate energy consumption over extended periods. Your gas supply may be adequate. Additionally, there would be very little hardware taking up space in the finishing room, the boiler being outside and the radiant tubing behind wallboard or under floor.
