Another Garage Heater Thread
 

I have converted the bottom of my barn into a garage. The size is approximately 35'X70'. Ceiling height is 10'. It has a cement floor. Three of the four walls are 18" thick stone walls, but the interior walls and ceiling have been framed, insulated and pannelled. Because of the layout, I can't really run a vent or chimney. I live in the mid/northern atlantic. Temps can get down to 0, but the coldest days rarely go below 20 degrees.

What would you guys recommend for heat?

Lew,

From page 594 of McMaster-Carr
www.mcmaster.com

About Choosing the Right Heater
There are several factors to consider when choosing a heater: the power source, the type of heat transfer that best suits your environment, and the heat output of the heater, measured in watts or Btu/Hr.

Power Source— Electric, gas, oil, hot water, or steam.
Electric (594-599) heaters are easy to install and operate, but can be costly to run and may be best suited for spot heating smaller areas. Note: When choosing electric heaters, match the voltage of your power supply with the voltage of the heater and the amperage of the heater to the amperage of your circuit.
Gas (598-600) and oil (599) heaters are economical to operate, but can be costly to install permanently. If permanently installed, they can be used as a primary heat source in all climates. Gas and oil heaters may be limited in their indoor use to areas with good ventilation, or where permitted by local codes.
Hot water and steam (600) heaters work by transferring the heat of heated water to the air. Although costly to install, hot water and steam heaters are economical to operate. Typically used as a primary heat source in all climates, they provide warmth without the low humidity associated with systems that directly heat air.
Heat Transfer— Radiant (infrared), convection, or forced-air heat.
Radiant (594-595, 597-598, 600) heaters transmit heat waves through the air, warming objects and people in their path instead of warming the air. They are excellent for spot heating, and if properly arranged can also be used to heat an entire warehouse. Unaffected by drafts, they are good for heating open areas such as loading docks.
Convection (594, 597-599) heaters offer excellent circulation and produce even warmth. Initial warm-up is gradual; however, they continue circulating warm air long after they're turned off. Ideal for maintaining even heat levels in areas that are well insulated and have few drafts.
Forced-air (594-597, 599-600) heaters use the force of a fan to distribute heat quickly for instant relief from the cold. Like radiant heaters, they make good spot heaters, and if properly arranged for maximum circulation, can also be used to heat an entire warehouse. Forced-air heaters also cool off quickly. Best suited for well insulated areas, and to quickly restore heat to an area that gets occasional exposure to the outdoors.

Heat Output Required— A heater should be large enough to replace the heat lost through the floor, walls, and ceiling of the space you are trying to heat. The amount of heat lost depends on how well an area is sealed and insulated. Follow these steps to estimate your heat requirement:
Step 1: Determine the surface area of your floor, walls, and ceiling in square feet:
(2 x length x width)+(2 x length x height)+(2 x width x height)
Step 2: Estimate your heat loss factor by choosing the description that best fits your building:
Very well sealed and insulated = .25
Well sealed, but not insulated = .75
Not well sealed or insulated = 1.25
Step 3: Decide how much you want the temperature to rise in ° F:
If you don't currently have interior heat this would be the difference between the outside temperature and your desired temperature. If adding to existing heat this would be the difference between your current temperature and your desired temperature.
Step 4: Multiply the results from steps 1-3 for your estimated Btu/hr. requirement. You may need to consider more than one heater to meet your total requirement.
Step 5: If you are sizing an electric heater by watts, multiply the result in Step 4 by .293.
For Example— Your 20-ft. x 20-ft. area has a 12-ft. ceiling and is well sealed and insulated. Your current heat source can only maintain 50° F, yet you want your area to be 65° F.
Step 1: Your surface area is: (2 x 20 x 20)+(2 x 20 x 12)+(2 x 20 x 12) = 1760 sq. ft.
Step 2: Your heat loss factor is .25 since your room is well sealed and insulated.
Step 3: You need a 15° F temperature rise (the difference between current 50° F temperature and desired 65° F temperature).
Step 4: Multiplying the results of steps 1-3 determines your heat required: 1760 x .25 x 15 = 6600 Btu/Hr.
Note: Your result in step 4 is the minimum requirement to reach your desired temperature. If this result is between two heater sizes, you should select the larger size.

Thanks Tom!

You might be the right guy to ask my other question:

Should I mount my air compressor above my workshop (I have plent of room on the second floor) or should I mount it at shop floor level? I thought that if I mounted it on the second floor and ran pipe through the ceiling with a line drain/moisture trap at the lowest point of the line, it might be a good way to keep water out of the air flow.

How large are the individual rooms? That will determine a lot about what type and size of heaters you will need for the space to be heated.

I just reread your post and realize you have a single room. A room this size will require probably 2 unit heaters hung from the ceiling with fans in them to circulate the heated air. They would need to be pointed so they create air movement around the perimeter of the room, so one fan pointed down a wall clockwise fashion and the other heater in the opposite corner pointed in the same clockwise direction. A good thermostat will control them but with 2 heaters at 230V- 30 Amps you will need the Thermostats to control a contactor to turn them on and off. Separate Thermostats can be used but they won't be as precise for control. You would need to place the Stat in the middle of the room between the two heaters probably on the wall where you have the most heat loss- probably at the doors.
I install these heaters quite often for customers and they are fairly efficient and will heat a room very quickly. I'm an electrical contractor. Just be sure you have enough Electrical power to run all your planned equipment and these two heaters. If it were me, a shop this size would have it's own Electrical panel and possibly a separate metered service rated at least 150 Amps/240 volts.

I would put the compressor in the upper floor just to avoid the noise, but you will still need additional water traps in the line. I've heard about every 50 feet of line needs a trap, plus at least one at a spray gun if you are painting.

Bob

Another thought might be a pellet furnace,I heat my garage with a pellet stove and it is fairly economical however the garge is not as large as yours.

Also you may want to take into account the local building codes as well on what they allow for your building.

Marc

A geothermal heat pump could be a good solution if you're willing to do some of the installation and you have room for the ground coil. While the initial cost can be a little high, they are extremely economical to operate and you have the added benefit of air conditioning in the summer.

I have a 50 x 50 basement that is insulated. With no heat on it stays around 55 deg, installed a propane fireplace with built in thermostat that will put out 25,000 btu. Also have a ceiling fan. I turn both on, shut the door and within 30 - 40 mins the place is sizziling warm. The best thing is you don't need to vent it to the outside, all the heat goes into the room so nothing is wasted. I use a 100lb tank to feed it which I just filled up yesterday for $67.15. I only use it on the weekends in the winter and the tank lasted one year. Plus its nice to look at, I have a corner model.

Compressor thoughts
 

Compressors have been known to start fires. Think about this prior to deciding where you want to place your compressor.

If you pull the intake air from outside the building it greatly reduces the noise. Your neighbors might not like the noise however.

The compressor will heat up the room it is in. (good in the winter, bad in the summer). This is another reason to have the intake plumbed to the outside. (Your compressor will be more efficient)

You need to have water drains and traps. What you don't want is the outlet of an air line to be the lowest point. You want to have a water trap with a valve (to let out the water) at the lowest point.

Spend the extra money and get ball valves. They are much easier, quicker and reliable than gate valves.

You should have an air dryer.

A vertical (vs a horizontal) tank saves a lot of space.

For the most part, the bigger the tank the better.

Three phase (if you have it) is better than single phase.

Two stage compressors are better than a single stage.

Screw type compressors are more efficient and quieter than reciprocating compressors. They are also more money. We have a screw type at the shop and we are very happy with it.