Shop Heater Question

[Kevin Johnson]

I have an opportunity to get a gas heater for my shop at a great price and am trying to figure out if it will work for me. The problem is that the heater is a 125K btu unit and my garage is a 2 car garage. All of the literature that I have read on the heaters like the Hot Dawg is that 45K btu is sufficient for my size shop. So my question is whether the larger unit will make the shop too warm or be inefficient (i.e. burn too much fuel) in a shop my size. Any thoughts? Thanks

[Frank Hagan]

Depends on the design of the heater, but most of the time an oversized heater will "short cycle". It will go on, then off quickly. That can be hard on components like hot surface ignitors or pilot assemblies.

You might check to see if the manufacturer has a "down fired" or 2 - stage version of the heater you can convert it to; sometimes they do, and the conversion can be as easy as a different gas valve and control.

[Anthony Anderson]

Kevin, efficiency is a function of, the efficiency of the Heating unit and the fact if your garage is insulated or not. Look at it this way, the heater will not take as long to get your garage to room temperature as a smaller unit. The thermostat will regulate the temperature in the garage. IOW the temperature in the garage will only get as hot/warm as you set the thermostat. If you were to buy new, I would recommend a smaller unit. But if the price difference is greater than half of the new unit then consider it. Make sure to look at the heat exchanger, as that can be the expensive part that goes wrong. I hope this helps your decision. Regards, Bill

[Keith Weber]

Kevin,

I should give you my mother's number and let you ask her that question. A few years ago their house furnace broke down, so Dad ordered a new one. He decided that more was better, so he ordered one that was twice as big as it needed to be. It heated up the house real quick, but Mom hates it. In fact, all I've ever heard about for the last few years is that $%@$ furnace (as she puts it.) When it heats up, it's like someone just turned a flame thrower on you. By the time the thermostat senses the temp and turns off the furnace, the area in front of the registers is unbearably hot, and the far corners of the room still cold. Eventually, the temperature evens out, right about the time that the blast furnace kicks in again.

I would pass on that furnace and get a 45K one. Heating your garage with a 125K unit would be like using a fire hose to water the house plants. Coincidentally, I'm installing a 45K in my 4200 cubic foot garage tomorrow. I bought a Sterling model that has intake and exhaust vents to the outside, so I don't have to worry about replacing the exhaust air.

Keith

[Al Willits]

Houses and shaops/garage are/can be two different problems, houses generally have to follow codes as to how big a furnace/AC you can install, but even more importantly is the fact most houses are kept in a small range of temps, so raising and lowering a few degree's can be done with comfortably with a smaller furnace.

The shop/garage on the other hand is rarely kept at a constant temp, least wises for us who don't have unlimited funds, so its required to raise the tempayure but a greater range than the house furnace.

To do this in a reasonably short time, a bigger furnace is required, not always good, as stated before it will short cycle and a furnace that is cooling down or heating up between cycles is lost efficency.
Plus you have a much larger blower and like Keith's mother points outs, its not very comfortable.

Most of the people I know opt for a smaller furnace and allow for heating the shop/garage up, I'll go out and turn the stat up, then come back in for a half hour or so, that's enough to go from the 38 I keep it at to mid 40's, warm enough with a sweatshirt till it gets to the 55 or so I like it at.

My suggestion would be to lose the 125k one and use a smaller furnace, under 75,000 btu's maybe, depending on insulation.

Al

[Kevin Johnson]

thanks, I think I will take your advice and pass on the heater. I will spend a few extra dollars and get the 45K unit.

[Bruce Page]

thanks, I think I will take your advice and pass on the heater. I will spend a few extra dollars and get the 45K unit.

Good decision Kevin. I have a 45K in my 2 car garage and it will flat run me out of there if I let it!

[lou sansone]

I agree with most that the 125 is probably way too big, but we don't know where you live. if your working against temps in northern Maine then I think 45k is not going to be sufficient in a typical garage.
lou

[Kevin Johnson]

I just ordered my heater. If anyone is interested, Northern Tool has the 45K Mr. Heater unit on sale for $269.00. Regularly $399. I thought that was a great deal so I ordered one.

[Bryan Lord]

Kevin, I also have a 2 car garage and am using a 75k btu Reznor gas heater. I talked to them prior to purchasing and they told me there would be little difference when operating. The benefit to the larger unit is how fast it can bring the shop up to temperature if I have had the heat off. I live in Colorado and don't heat the shop unless I have a project going on (which is most of the time).

Reznor makes a unit (like mine) that has a contained burn chamber meaning that it pulls air in from the outside for combustion. The advantage is any flammable vapors in the shop do not see an open flame.