Big Maxx Heater

[Dave Norris]

Hi Everyone,
I just installed a Big Maxx 75,000 BTU garage heater by Mr. Heater. I actually bought the heater last year, and it has been sitting around for a variety of reasons. I have 28 x 32 uninsulated shop, and probably 16 feet to the peak of the roof. The temp today was about 30 degrees, and it took almost two hours to get the shop to 50 degrees. I was expecting it to do a little better than that, so I wanted to ask folks who may have some experience with the Big Maxx for some input if possible?

How hard does the fan blow the air out the front of the heater? I would say that mine blows with mild to moderate force, and I was expecting the air to come out with some force, and also to be hot. The air that comes out the front of mine is warm, but not at all hot.

Also, on the corners of the heat exchanger where they bend back from the front get literally red hot. Does anyone else's do this?

Finally, the flue/exhaust pipe gets super hot as it exits the unit. I would expect it to be hot, but it seems to REALLY hot to me. Not glowing like the heat exchanger, but definitely really hot. I actually thought about putting a small fan to blow across the pipe to further extract some heat from it before it goes outside.

As an aside, to anyone thinking of buying one of these, the thermostat they sell with it is a very basic unit, and you could certainly pick a thermostat up at the hardware for well less than half what you will pay for the recommended one.

Thanks for any thoughts or support anyone could offer.

[Jim Andrew]

Not familiar with your heater, but if you own the property, insulation is very cheap, especially considering the cost savings in fuel. If you have a Menards store near, they have insulation on sale most of the time. Fiberglass is the least expensive, although itchy, and I would recommend doing it in cold weather, when you can wear gloves and a hoody, and a dust mask. Glasses also, if they don't fog up from the dust mask. Taking a shower after finishing working with the stuff is also a very good practice, as it seems to wash off easily. I especially spend time washing my eyes in the shower. Hate insulation, but love what it does for your buildings.

[Chris Damm]

"I have 28 x 32 uninsulated shop"
Until you insulate your shop you are fighting a losing battle! My 26' x 26' x 9.5' shop is very well insulated and I heat it with a 5200BTU electric oil filled heater. I'm in MI near Lake Michigan and it really gets cold here. The thermostat goes to 9 and with it set at 2 on the low setting (750 watts) it will keep my shop at 50°.

[Dave Norris]

Thanks Guys. Uninsulated certainly is not the optimal operating situation, but for now I have to play the cards I'm dealt in that regard. My question is more about whether my heater is operating correctly though.

Insulation is still a way on down the road.

[David G Baker]

An example of how good insulating is; I had a 20x12x10' one car garage that had insulation on the outside wall but none on the ceiling and was cold and damp during the Winter months. I installed an electric wall mounted infra-red heater that I would use while working in the garage. It took a while to warm the work area and would keep it warm as long as I kept it on. I found a bunch of two inch Styrofoam sheets at a garage sale and fastened it to the Sheetrock ceiling and added fiberglass to the wall that I built between the work area and the garage door. Over my work bench I had a hanging 150 watt flood light that helped light my work area. I would start out working wearing a sweater but after 10-15 minutes I would have to take the sweater off because I was getting too warm. My only source of heat was the 150 watt flood light. This was during the cold damp Winter months. This took place in Northern California where it doesn't get near as cold as it does here in Mid Michigan but it can be very uncomfortable. Any further insulating I do will be with the dense spray foam.

[Jim Andrew]

Your savings on fuel will pay for the insulation. If you can't afford the wall material to close it in, just put strips on the wall and ceiling for the insulation to rest on.

[Ray Newman]

I would call the manufacturer and explain your concerns.

Could be that unit is defective or some other problem with it.

I have a Modine Hot Dawg of about the same size and it really moves the air, which is hot.

[David Hostetler]

Not familiar with your specific unit, but it sure doesn't sound right. Call Mr. Heater and get them to help you out...

You already know about the insulation issue, so I am not going to pile on, just going to encourage you to jump on it as soon as you can. MUCH more effective than trying to pump heat into a leaky building...

[David G Baker]

Ray N,
I have a 75 K Hot Dawg heater in my pole barn. It does a great job of heating the building because it is well insulated. My problem with the unit I have is the foil liner is coming off in small pieces and blowing all over my shop. I tried to contact Modine and they told me to contact a local HVAC company, I did that but never got an answer to what caused the problem and what to do about it.
As for not being able to afford the insulation price, as has been written, the insulation will pay for its self in a very short time especially if an electric heater is used. This may be something that has to be learned through experience.

[Chris Damm]

Thanks Guys. Uninsulated certainly is not the optimal operating situation, but for now I have to play the cards I'm dealt in that regard. My question is more about whether my heater is operating correctly though.

Insulation is still a way on down the road.
You only pay for insulation once but you pay for fuel ever time you use the heater!

[John Lifer]

Your issue is that the hot air is going to the ceiling that you say is 16ft up. What's your wall height? 10-12feet? You need to either insulate or drop a ceiling with insulation. Sounds like the heater is working, only rated for 1000sf garage. And assume they expect some insulation in that rating. As others have said, spend it now or spend it ongoing...

[Ken Fitzgerald]

My shop is 30'x24' with 10' ceilings. I insulated the walls with R-19, the ceiling with R-30, a 4-mill vapor barrier, caulked around doors, windows, and electrical boxes. Used spray insulation (low expansion) around the doors and windows. My wife bought me a 75,000 btu Lennox hanging gas (NG) furnace and it loafs heating my shop. I keep the thermostat at 64ºF when I am working and will turn it down to 58ºF when I don't have a project. When finishing, I will turn up the heat to 70ºF 3 days before I start finishing so the project has a chance to stabilize before I apply finish.

The gas is run through the same meter as our home and we saw very little increase in our heating bills when I started heating the shop.

Insulation pays for itself in very short order. I wish I had built the house so I could have done similar things to it!

[Carl Beckett]

I am in the process of shop insulation.

In my area, there are rebate programs covering up to 75% of the cost. That makes it pretty compelling.....

[Glenn Kotnik]

Insulation is of course essential, but it sounds to me like something is not right with your Big Maxx. The vent pipe shouldn't be nearly that hot and the air coming out the front should be very warm. You don't say if you are using propane or NG. Most of the Big Maxx units are sold set up to run on NG. There is a conversion kit sold to convert to LP. There have been recent changes in the gas regulator so that not all of the conversion kits work with the most recent heaters. You need to change both the orifices on the burner and the spring in the regulator. If you are sure your heater is set up for the fuel you are using, you need to check the gas pressure with a manometer as described in the instructions. The manometer is very easy to make yourself, but be sure you adjust the regulator to the proper pressure. You can't assume it is correct from the factory. Another thing comes to mind, you said the heater has been sitting around for a year. If it was not in the box, consider the possibility some small furry animal built a nest in it and is blocking things off.