Finish room heating

Safe systems for keeping you, your finishes and your spray equipment cozy. November 22, 2003

I have a room approximately 25 x 13 that I am using for a finish room. The problem is that I do not have any heat. I am in upstate NY and it is getting cold, so I need a solution. I am very concerned about the dangers associated with spraying. I will be mostly spraying pre-cat lacquer and conversion varnish. Any safe heating ideas would be most welcome.

Forum Responses
(Finishing Forum)
From contributor A:
I can't remember its name, but there is a unit that uses a hot water tank and a circulating pump. That works well. I got one larger than I needed so that I can heat the room quickly when spraying and exhausting. Room is 12 by 20 and r40 all round and the tank is outside. I will be getting a boiler system next year.

From contributor B:
While you're debating how to heat your booth, you can wrap an industrial heating pad around your pressure pot. I have used one for many years and have never had any problems whatsoever.

Having an extra one will allow you to wrap one around a one gallon container, so if you need to refill your pressure pot, the material will be just as warm as what was in your pot. I've used this method with all types of oil varnishes, oil based paints, conversion varnishes, pre and post lacquers, nitrocellulose lacquers, tung oils, Watco oils, etc.

From contributor C:
My buddy, a plumber, is coming over tomorrow to lay out our auxiliary heat system for a spray booth. Right now we have forced air heat, which is not enough for those cold winter days. The setup will be a gas fired water heater with direct venting. The coils will be stapled to the floor and we will do a concrete pour on top. This is a sealed system, making it very safe. It is very efficient. Also, the concrete floor meets code for non-flammable flooring. You need to heat finish, parts and air being drawn across to have an acceptable finish. Any one of the three being too cold will adversely affect your final finish and Advil intake.

From contributor D:
If you can afford it, get an air makeup unit. Nothing else will keep up. I had in-floor heat in my last shop and it won't heat the cold air you are drawing through your booth. I live in MN and so I have to deal with this all winter. I put a variable speed drive on my booth fan and turn it way down after I'm done spraying while it flashes off and my forced air heater keeps up pretty good. I just leave a window open.

From contributor E:
Wrapping an industrial heating pad around any paint pots or cans is very dangerous. If you ever do have a problem, I hope you can pray really fast, because you most likely won't make it out of the booth.

The proper way to heat paint is circulating through a paint heater. Try what you want, but you may only be fooling yourself.

From contributor B:
Contributor E, products like this have been around and in use for many, many years. You can even buy one that wraps around a 55 gallon drum if you're heavily into production.

From contributor E:
Make sure your estate is in order.

From contributor F:
If you have natural gas, a radiant tube heater works very well. It is a sealed unit which is about 30 feet long and draws outside air for combustion and exhausts to the outside at the other end. It comes in ten foot sections so you can make any length you want. Ours is 125,000 BTUs for our 1200 sf finish room. The beauty of it is it heats the objects in the room and not the air that is passing through and out the spray booth exhaust. You feel like you are standing in the sun when it is running. The floor also gets warm along with everything else in the room. Even when our bay door is open, it warms back up very quickly.

From contributor G:
I don't know about these industrial heating pads and your warning is noted. Is there any documentation you can refer to regarding the use of these pads?

From contributor E:
Ask your fire department. If a device that heats is not rated class 1 div. 1 explosion proof, it is not suited for this application. Paint heaters are... they only heat the material in the hose set, the 5 or 55 stays ambient. I'm only trying to save someone from a major mistake, maybe their last...

NFPA art. 33 & 37? cover the documentation.

From contributor H:
We had a radiant tube before our make-up air unit was installed. With one caveat it did work well. Since it heats objects as mentioned, the top parts on the drying rack, usually oak because of the open grain, would get bubbles in the finish much the same as spraying when an object was too warm or caught direct sun in the summer. We would put a piece of scrap plywood on the top level to shade the parts.

From contributor I:
In regard to the heating coil suggestion, many shops attach the coil around a can that is partially filled with water, and then place the pot or the container of sealer or clear coat inside the can. This way, you are heating the water, and the water is heating the coatings.

From the original questioner:
Thanks to all. I'll consider the radiant tube heat sounds. I guess I would have two problems with the heating pad. One, it would only take care of heating the material. What about the cold room air for drying, and the fact that the woodwork is cold? It would have to effect the finish. The second problem with the blanket would be my paranoia. I almost burnt my shop to the ground 5 years ago with some carelessly placed oily rags, so any hint of danger gets me running for cover.

From contributor I:

Another option is using hot water baseboard heating.

From contributor J:
What would you guys estimate the cost of the air make-up units? We don't have gas and will be having around a 400sf booth in our new building. Where do you buy them? Where do they install? How large are they?

Most of our spraying (90%) will be outside as we live in the SW, but on cold days in winter we will have to spray indoors.

From contributor K:
I am in the process of converting my shop over to a corn-burning outside boiler with thinwall and radiators for heat.

The unit sits outside the building, so there is no chance of ignition inside and it will cut my heating bills by 66% with the current prices.

I worked in a shop with the radiant tubes on the ceiling and they work great, but we couldn't set sprayed items directly under the tubes or the finish would boil off. That shop had 12 foot sidewalls and maybe the units were too big. Personally, I like the hot water heat/boiler setup.

From contributor L:
Rule of thumb is about a dollar per cfm with a ninety degree temperature rise. I've had a Weatherrite for about 20 years and I like the unit, as it is easy to service.

It's true that those drum heaters are not safe around solvent based materials. I don't care how long they are around, if you boil of a heavier than air solvent and the concentration is right, kaboom!

From contributor M:
Material heaters don't get hot enough to boil the materials.

From contributor L:
The flash point of solvent isn't its boiling point.

By the way, the acro heaters go to 160.

From contributor D:
I am interested in heating my lacquer. I was looking at the wrap around 5 gallon bucket style that Grainger has, which has a thermostat on it. Would it be safe if you kept it at a lower temp and maybe agitated it so the sides wouldn't get so hot? What temp is normal to heat up to?

From contributor N:
Most hot solvent-based finishes are sprayed at about 110 degrees F, but you should have the substrate at a warm temperature also. The main rationale for doing this is to reduce viscosity without reducing solids.

From contributor B:

Keep your spray area as toasty as possible. In the meantime, the units from Grainger work quite well. If you have an air-assisted agitated device in your pressure pot, use it. If you donít, don't worry. The material will not get hot enough to warrant one. The nay-sayers won't be convinced of their value in a shop and I understand and respect their concerns and opinions. For me they work.

From contributor O:
I've been using a 5 gallon pail heater for years with no problems. I use it mainly to heat my stripper. It does have a thermostat on it, so I can control the amount of heat. In the colder climates you need something like this. As soon as I turn the fans on, all the heat goes with it.

From contributor P:
We have a drum heater from Grainger and won't use it.

1. If you use catalyzed products you run the risk of overheating them and making them useless.

2. Check the flash point on your lacquer. It's pretty low. Feel how hot the material can get from the drum heater. Ours can get hot, definitely warmer than the flash point.

3. Sure, you can keep the thermostat turned down. Do your employees always monitor settings and shut down devices after using them?

From contributor I:
The heaters have their place for heating up chemicals. They have been around for decades, and I never heard of one problem being caused by these heaters.

From contributor P:
They are made for chemicals with a much higher flashpoint. Placing them on a large drum (55 gallon) would be safer than a 5 gallon, which can be heated up too fast, too far. Our fire department won't allow them; they have the capability to raise the material temperature over what is safe.

They can raise the temperature to where the offgassing of solvent is shocking. A very attentive individual can make one work. But do your employees always unplug the burn in sticks, unplug the heated glue guns, keep the lubricating oil drips properly adjusted, properly dispose of oily rags, etc? Go with a paint heater.

From contributor M:
The employees who opted not to unplug heated glue guns, or unplug the burn in oven, or properly dispose of oily rags are no longer here in this shop. Those are not employees that you describe, those are liabilities.

Just because your fire marshal won't allow them does not mean each and every fire marshal will frown on them. Could it be that the marshal noticed that your hired help did not unplug the glue gun, and didn't dispose of oily rags in the proper container, or left the burn in oven plugged in all the time?

From contributor I:
These strap heaters are intended to only keep the chemicals warm, and they do a very good job of just that. As I said, they have been used in many finishing and refinishing shops for many years.