Propane fired forced air heater mantainance. Do it!
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  1. #1
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    Propane fired forced air heater mantainance. Do it!

    I have a small (Mr Heater brand I believe) 40K BTU forced air heater in my garage. My garage is only 20'x 22' and it get quite dirty when I have a lot going on. Anyways, I hadn't ever done any real deep cleaning on it since I put it in in 2009. I've blown it out, but never took the side cover off and blew out the heat exchanger.

    Yesterday, I was about out of propane and the heater started sounding different than normal. Figured it was because I was like almost out of propane. Got the cylinder refilled and now the burner won't fire when I tried to turn it back on. Being I know almost nothing about this kind of stuff, I went to YouTube and watched some vids on what could cause the furnace to do what it did. Grayfurnaceman has some excellent troubleshooting vids and sounded very knowledgeable about HVAC stuff. Even tho none of the videos had anything even remotely specific on my particular heater, the principles were the same and it was quite informative all the way around.

    The led on the board was flashing a code indicating the high limit/flame rollout switch had tripped. The diagram on the inside of the cover had a code chart and flow schematic. Found the switch and reset it. This was actually the first thing I looked at when I took the side off the heater. Afterwards, it reset and allowed the burner to light again. Then, I got a good look at what the burner was doing. Yea, classic flame rollout. Just like in the videos. Dude said a blocked flue or dirty heat exchanger was likely the main cause, barring cracks.

    I blew the exchanger out, and a huge cloud of black soot came billowing out of it

    Guess that was the problem lol. I went ahead and took the heating chamber apart because the insulation inside it was pretty nasty. It was sagging, filthy and had some rips from blowing it out with compressed air over the years. Practically disintegrated when I touched it. Plan on replacing it today. After blowing everything out well, it worked perfect.

    Guess the whole point of this is to make a habit of regularly checking and cleaning your garage heater if you have one like this and you get a lot of dirt and dust in your work area. Prolly should have done this a few years back, but sometimes you just don't think of this stuff until it happens. I'm more happy than anything that I was able to figure it out without a lot of dicking around or having to call somebody to do it.

    If you haven't cleaned yours out in awhile, might be a good idea to take a look at it.

    IMHO of course
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    Last edited by 7A749; 01-08-2017 at 10:12 AM.

  2. #2
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    Re: Propane fired forced air heater mantainance. Do it!

    Good to hear it was a eazy fix. Stuff like that usually gets neglected ,then it turns into a wtf moment. I imagine there is an incredible amount of crap that enters the furnace, and then builds up. You probably also avoided a potential fire situation.

  3. #3
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    Re: Propane fired forced air heater mantainance. Do it!

    Yea, for sure. A fire would be very, very bad. As dirty as my little shop gets, I should have been doing this a lot more often. That's why I figured I would make a thread about it. Hope my experience might save somebody some money and trouble if the same thing happened to them. I had my house furnace checked out by an HVAC guy I know just a few years back. It's old but still chugging along. I was gonna call him if I couldn't get it sorted today. I don't really like screwing with stuff like this lol.

    Went to menards last night, but I forgot they close at nine durning the winter lol. Gonna go back here in a bit and get some insulation for the inside. Hopefully I can find something that will work. No way I was leaving that old stuff in there the way it looked.
    Last edited by 7A749; 01-08-2017 at 10:29 AM.

  4. #4
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    Re: Propane fired forced air heater mantainance. Do it!

    Menard's should have something, like the stick on water heater insulation. If not, a good contact adhesive should work, with a foil back and face insulation. Be a good idea to check on the heat rating tho.

  5. #5
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    Re: Propane fired forced air heater mantainance. Do it!

    I had a natural vent propane furnace in my garage back in the 90's
    Non-power vent, low efficiency old style.

    One day as it lit, some fire puffed out the front.

    Same problem as yours - blew out the heat exchangers and black, oily soot everywhere.
    Big chunks of black stuff too.
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  6. #6
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    Re: Propane fired forced air heater mantainance. Do it!

    mice and lots of other little critters love to make there home in a warm heater , along with every engine driven piece of small equipment you may have, its amazing how they build there house under the heat shields of lawnmower engines...and if the grass and junk they plug the air vents with is bad enough, then they chew through the wiring...

  7. #7
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    Re: Propane fired forced air heater mantainance. Do it!

    Good info. I haven't cleaned mine out since I installed it 7 years ago. Thanks for the reminder.
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  8. #8
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    Re: Propane fired forced air heater mantainance. Do it!

    Unless you heater is right up against the ceiling, I wouldn't worry about the insulation. It not like you are going to loose any heat for it is all in your shop. If you do replace is, it does have to have the foil back to it, and be generous with the contact spray glue, plus make sure everything is really clean or it will just fall down again, and burn up the heat exchanger.

  9. #9
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    Re: Propane fired forced air heater mantainance. Do it!

    Quote Originally Posted by Baloo2327 View Post
    Unless you heater is right up against the ceiling, I wouldn't worry about the insulation. It not like you are going to loose any heat for it is all in your shop. If you do replace is, it does have to have the foil back to it, and be generous with the contact spray glue, plus make sure everything is really clean or it will just fall down again, and burn up the heat exchanger.
    I kinda figured that was the deal with the insulation. To keep heat off the outside of the furnace. I bought some roll crap from menards. It was like $19 but there will be plenty extra for whatever else. This is that foam stuff with a foil facing in a roll. I have some 3M 90 spray glue, that should do it. I just wanna put it back as close to the way it was as I could.

    That had some other stuff with the fiberglass insulation on a foil face, but it was quite thick. I imagine the stuff I bought should do ok.

  10. #10
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    Re: Propane fired forced air heater mantainance. Do it!

    I have an older Reznor propane heater mounted up near the ceiling in my shop. It takes something like 6 steps to fire it up. Due to that and the fact I only use it 4 to 5 times a year, I don't always remember the steps. I used it twice this weekend with no problem because it was in the single digits outside.
    I tried to turn it on this morning and didn't get the lighter up to ignite the pilot light fast enough and apparently a decent amount of gas built up.
    The gas lit in a woosh and burnt off most of my eyebrows, eyelashes, part of my mustache and beard. I also ended up with a bit of a flash burn.
    Fortunately I was wearing my safety glasses when that happened.
    I had read this thread when it was first posted and was thinking about it when lighting the furnace.


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  11. #11
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    Re: Propane fired forced air heater mantainance. Do it!

    Huge clouds of black soot, mice contributions, and burned hair...sounds like my weekend!

    Mine's an oil burner that I hadn't lit off in two years. Copper fuel supply tube near the tank developed a stress crack and was sucking air. Cut the tube back, replaced the filter, primed the burner and...sputtering nothing from the firebox. After hitting the reset three times, I opened the observation port and just as I started leaning in to give a whiff to see if there was diesel in the air WHOOMP! She lit off with authority and hawked a big ol' black soot loogey out the port onto yours truly.

    Once my heart rate got down below 200bpm, I was watching the fan limit switch because the fan had never really worked right since we got the place. As it started rotating and tripped the start switch there was a humming sound that ramped up to a WHOMPWHOMPWHOMP outta balance sound as the fan spun up. I was about to shut 'er down when all the sudden things cleared up...for a second...then all kinds of mouse house chunks started blowing out of and getting stuck in all the vents. Based on the volume of stuff that shot out of the vents, I'm pretty sure there was a rodent multi-family aparentment/condo in the squirrel cage fan.

    Once I got that cleaned up, then took the fan limit switch apart and reassembled it the right way, she's working like a top. Naturally, last weekend it was in the teens, and this weekend it'll be in the 50s. Ain't that just the way.
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  12. #12
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    Re: Propane fired forced air heater mantainance. Do it!

    Yea, was afraid there might have been rodent activity in the garage furnace but I got lucky.

    I can imagine your experience pretty much sucked lol. Today on the way home from work my car took a complete dump. This was alternator number four. Had to get towed home, took the alt off and sure enough it's junk.

    Good thing I bought the lifetime warranty alternator lol. It was dark, pouring and pretty nasty so I said screw it, I'll fix it tomorrow when it's light out.

    Guess it's going around huh?

  13. #13
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    Re: Propane fired forced air heater mantainance. Do it!

    Quote Originally Posted by psacustomcreations View Post
    I have an older Reznor propane heater mounted up near the ceiling in my shop. It takes something like 6 steps to fire it up. Due to that and the fact I only use it 4 to 5 times a year, I don't always remember the steps. I used it twice this weekend with no problem because it was in the single digits outside.
    I tried to turn it on this morning and didn't get the lighter up to ignite the pilot light fast enough and apparently a decent amount of gas built up.
    The gas lit in a woosh and burnt off most of my eyebrows, eyelashes, part of my mustache and beard. I also ended up with a bit of a flash burn.
    Fortunately I was wearing my safety glasses when that happened.
    I had read this thread when it was first posted and was thinking about it when lighting the furnace.


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    Damn! Mine has a piezo ignition, I heat durning the winter but only leave it on 45 when I'm not out there.

    Glad it wasn't worse. Propane is no joke. I knew a guy that had a heater in a trailer blow up on him and burned off most of his hands. He was in his 70s then, this was in the 90s. He never really recovered from it. He owned a rustproofing and trailer sales business right across the street from my moms ex husband's body shop. He was a real active guy and had worked his whole life. Pretty much the end for the poor old dude.

  14. #14
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    Re: Propane fired forced air heater mantainance. Do it!

    Quote Originally Posted by psacustomcreations View Post
    I have an older Reznor propane heater mounted up near the ceiling in my shop. It takes something like 6 steps to fire it up.
    PSA, glad it didn't turn out worse. Consider it a little "attention getter"....
    Sounds like you need to check the gas valve? Cant imagine why a properly functioning unit would allow gas flow if the pilot light was not lit (and thermocouple up to normal operating temperature)?

    My shop heated by an ancient reznor nat-gas heater, it has worked well for about 60 years. It gets blown out really well each summer, to make sure its 100% ready for Mt winters. I've replaced fan bearings once, and the gas regulator about 10 years ago. Why the regulator? Because it continued to feed gas after the pilot light went out. Replaced the thermocouple, problem continued. Whole system supposed to be "failsafe" and shut down if its not working properly. Obviously a major malfunction. New gas valve, new thermocouple, no problems since. Light the pilot in the fall, unit cycles normally all winter.

    No idea of the specifics of your system, but I'd take a long hard look at the gas valve. Burned eyebrows is a wakeup call. Next time might be a vaporized shop.

    Please post a followup on what happened.
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