For Those Who Have A Small Shop And Spray Booth, Heating In Winter?


From original questioner:

Hi guys,
I've got a 1 - 2 man shop and am fed up with our current heating setup. Our insurance agent will only let us go electric. Everything else they figure is too great of a fire risk. There's only a handful of insurance companies to choose from here in this part of Canada. The electric is fine at maintaining temperature until its winter and I turn on the spray booth fan. The fan will create approximately 10 complete air changes / hour, or one every 5.4 minutes to be exact. The electric heat just can't make that up. A heating calculator shows that I'm about 92,000 btu/hr short on ideal heating capacity.
What type of heat are you using in your smaller shop that can keep up with a booth?

From contributor JM

I am in Canada as well, and a 3 man shop. We have an 8' wide open face booth. We pull air from outside for make up air.

We have a gas fired unit heater for our primary source of heat. It does a bad job of keeping up when the booth is running, but it recovers very quickly when we shut the booth off.

We have a VFD on the booth so when we are done spraying, we turn it down to a very low speed to continue evacuating fumes.

In the winter, we need sweaters to spray.

The only way to get around this is to have a gas fired air makeup unit installed. You are looking at about $15k minimum to have one installed in your shop. In case you dont know what an AMU is, it will feed the shop with heated air at the same cfm as the spray boot is exhausting. Very expensive to install, and very expensive to run.

I would find another insurance company, and get some sort of gas heater in. You can get a saled combustion heater so it draws air from outside for combustion so that it does not use air inside the building (spray fumes) while heating.

From contributor Ma

I'm with JM - I have a sealed combustion gas furnace and the insurance company is fine with it. The shop air is not exposed to any open flame.

From contributor PW

See if they'll let you use a sealed gas overhead radiant heater. The radiant may hold better than just heating the air. You might be able to find a large electrical one instead.
One thing we did was to create a "baffle" on our intake hole (an unused door, blocked off with piece of plywood and a hole cut into the top). The air comes into the shop and immediatelty shoots up to the ceiling. The theory (in my head anyway) is that it pushes all the risen hot air at the ceiling level down toward the work area and thermostats. Since we've done it, it seems to keep the shop warmer, longer.

From contributor Mi

I gave up trying to keep my spray room warm to a level of comfort, as it was expensive and just really always made the entire shop too cool when the fan was running. Our winters here are not as cold as yours, but can still be very uncomfortable. Our spray room can be closed off from main shop, with air being pulled through a side door when we are painting. I have a coupe of infrared heaters I bought 8 or 10 years ago, that will warm a person, but not the air in the room. One is wall mount shop type unit, the other is a floor stand unit, but both work off 120 volt current. We leave them out of the main air flow, over in an area right upwind, yet outside the paint room doors. Every 15 minutes or so, we can warm up a bit and keep spraying. I like these heaters even in the main shop area as they allow us to keep a cooler shop, yet we stay warm when the heaters are on in the main work stations.

From contributor oz

usually your local building inspector and fire marshall should tell you how to do, Insurance comp comes after the specs, We all create the laws and regulations for safe working environment.

From contributor ri

Do you own the building? Have you thought about an outside wood fired boiler? All you will be doing is pumping hot water to the shop. It would be a huge radiator in the make up unit, but I would consider it for the main heating of the shop. Can't imagine your electric bill!

From contributor St

Thanks guys for the input on this. I'm not shooting for 70F, but if I could keep it at 45 I'd be doing great. I start to get concerned about the stability of the water based lacquers I'm spraying when the lacquer and wood gets too cold, plus its just plain uncomfortable. I've sent a letter off to my insurance company outlining where things stand, what I need, and what they could do for me. I have asked for permission to used a sealed / direct vented gas heater and / or a direct vented solid fuel furnace (pellets, or coal, or something of the like). I'm hoping that by giving them an option they'll decide to pick gas as the lesser of two evils. I also pointed out that if they toured commercial shops they'd see gas heaters in 90% of them.

I like the wood boiler idea, and might consider going that route. I lease the building, but my landlord is great. I try to be careful to not make too many permanent tenant improvements that I couldn't take with me if I need to move. The boiler I could probably take and just leave the piping in the ground.

I'm going to see if I can get some numbers on what the boiler heat exchanger would look like in terms of size for it to produce at least 50,000btu.

From contributor Ga

I heat with a wood boiler and love it. Don't overlook the labor of making firewood. It is a lot of work but I really enjoy it.

I have a fairly large make up unit as well as in floor heat that both use the boiler. The make up unit should be bigger but it's what we have for now.

We have two 24" diam. 6000 cfm paint booth fans running most days. My stove is rated at 800,000 btu. It can keep up on all but the coldest of days.

A 50,000 btu outdoor wood stove/boiler is tiny. I don't think anyone makes one that small or that it would be big enough anyway. Consider going too big rather than too small. Make sure it has a big enough firebox so you don't have to fill it so often or have to work the firewood into small pieces to get into the stove.

It normally isn't done but you can put the water lines above ground in a site built insulated chase. Maybe local building code won't allow it but I have seen it done.

From contributor St

Thanks Gary,
I like the sounds of that. The additional 50,000 btu was a hypothetical minimum. If I replace my electric heat I will need a minimum of about 150,000btu, as a minimum. 200,000 would probably be comfortable. I should also talk with my 2 neighboring shops, maybe they would be interested in going in on a single larger unit. It might make the initial cash outlay a little more manageable. Looking at units online, it looks like I should expect to pay about $10k to get up and running with an outdoor boiler and the lines and internal heat exchanger?

From contributor Ga

$10,000 is a very realistic number. If you are going to have addition shops on the same stove it is even more important to size it correctly, possibly requiring a larger stove.

The salesman should be able to size the stove properly for you're needs.
It is important to have all the components including the water line sized properly also.

I like the idea of sharing the stove with neighbors but everyone has to do their part so be careful. It's a partnership and many partnerships don't work out.

Will everyone make their share of firewood? Pay for repairs and operating costs? Do end of heating season maintenance?

Again, don't underestimate the time or space making firewood involves.

From contributor Bi

You can get boilers that run on pellets, it's more cost effective than cordwood unless you cut and split it yourself.

From contributor da

We have a boiler with radiant heat in a concrete floor. It doesn't help when the fans are on but it keeps your feet warm and the make up is quick when the fans go off. we only do that in the booth. the prep areas can get chilly but who cares?

From contributor St

Thank you everyone for your thoughts and help on this topic. I put a proposal together and had my agent send it in to the underwriting co. They still didn't allow any sort of gas device, but they said yes to the pellet stove. It's more labour intensive than propane, but at half the cost per btu, it has its own advantages. I have got one that can be thermostat controlled and produces a "real" 55,000BTU/hr. Its not the 90,000 that was ideal, but I think its going to be a big help and with the stove and electric both running when needed, we're going to be able to be much more productive in the winter months and not have to shut the finishing down during the cold spells.

Thanks guys.

From contributor Sc

Not sure where you are located, but most areas won't allow a spray booth unless you have a make up air unit that is matched up with your spray booth. You need to replace all the air that is removed by your spray booth. If you don't have this then you will create a negative pressure in your building and your gas appliances like your furnace and water heater won't vent properly and you will fill your building with carbon monoxide.

From contributor La

I use water base products. Target Coatings. All of that went away.

From contributor St

Same here, I'm a water based only shop.

The pellet stove is going in with an outside air inlet and a fan forced exhaust, so no shop air will be involved with the combustion process.

From contributor sc

Why does it matter that your spraying water base? You still need heat for it to flash off or cure properly. I would be scared to send out a project that I sprayed when it was cold.

I would check with your insurance company before you install a pallet stove, a lot of insurance companies will not allow any kind of a stove in a woodworking shop. Even woodworking dust can cause an explosion .

From contributor St

Scott, it's all in the posts above.

From contributor Ju

For heating in the winter in our paint shop, we use infrared heaters. Reason being is that it doesn't blow air around and whisp up the dust, so the paint jobs are much smoother since they are dust free. Hope that helps.

From contributor La

With water base products the danger with solvents is no longer part of the consideration.
I have two issues now. One, with HVLP also, is enought draft and filter to keep any overspray off the drying parts. Two is enough heat during winter to dry adequately. The air dosent have to be exhausted from the building. It can be filtered and recirculated.

From contributor Jo

I am looking for something to heat my shop for the winter and I have a spray booth so I bring in cold air. what should the temperature be at while spraying in the winter to have doors turn out good?

From contributor Za

Two Radiant Heaters. Cheap. You can get them used on Craigslist or at garage sales.

From contributor da

We also have a boiler with radiant heat in the floor. We also have a radiant ceiling unit in the prep area. We pull our makeup air through a tunnel. On the south side, we have a 40' long tin roofed tunnel that at least gets somewhat warm from the sun. It's free and it really helps. They use portable propane heaters in the prep area too. The biggest factor, in my opinion, is dust not vapor. Control your dust and flame won't hurt you.