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  • Propane shop heaters

    I work a lot of nights at my shop and it has been getting rather chilly. I purchased a 30-55,000BTU propane heater which does a good job of knocking the chill down. The 350P does a good job as well. On the propane heater, how much outside ventilation is required so the carbon monoxide doesn't become a hazard. I plan on getting a CO alarm from Wally-world, $20bucks seems like cheap insurance. Shop is 975 sq ft.

    Thanks

    Scott
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  • #2
    I thought I had read somewhere a spec on "you need X square inches for Y BTUs", but now I can't find it.
    The International Fuel Gas Code says do not exceed 20 BTUs per cubic foot for unvented appliances. It has all sorts of specs for sizing chimney pipes. I suspect you need a lot more vent area when it's just a window opening and not a tall hot chimney stack.
    The NFPA58: Liquified Petroleum Gas Code only says things about venting LP distribution buildings.
    Seems like they've missed an important point!

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    • #3
      scott, i'd like to know this as well. my shop is only 500' but have been afraid to go the propane heater route for the reasons you have already states. I just deal with the cold. sucks.
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      • #4
        Originally posted by jimmy_pop View Post
        scott, i'd like to know this as well. my shop is only 500' but have been afraid to go the propane heater route for the reasons you have already states. I just deal with the cold. sucks.
        I will usually run it 15-20 minutes at a time. If I am welding a lot, I end up turning it off. A few layers of clothes and some good socks go far
        Miller 350P
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        callouses and burns a plentysigpic

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        • #5
          Strength and Power,

          I have the same heater (2 of them, the Mr Heater #MH55FAV) and I run them both as much as needed without any problem with carbon monoxide.

          Generally, in the AM, if really cold, I'll fire them both up and let them run until the shop starts to warm up. Then, I'll generally shut one of them down and turn the other to a lower setting.

          My shop is pretty well insulated (8" batts in the walls and ceiling (16') and pretty well sealed but I've never had a problem.

          I actually feel that the propane heaters are safer than the old kerosene salomaners that we used on construction sites for years.

          The carbon monoxide detector will provide another level of security. Let me know if you set it off. I suspect you won't.
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          • #6
            Here in southern Michigan I have 100,000 BTU torpedo style, Kerosene fuel. What I do is put at the roll up door raise the door up and hold it just above units top bar. It is a 9 foot wide door by about 32" off the floor. And run it till it get to hot, then unplugged it till it gets cold again. Never have had a problem. As it is sucking air in for the forced draft fan for the heater and it is blowing air out of the shop under the door.

            But the detector is probably, a good idea will have to make a point to swing by Wally world and pick one up!
            glen, If your not on the edge, your wasting space

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            • #7
              You should be fine with a proper propane heater. A properly functioning fuel heater will not generate CO. Complete combustion yields CO2 instead.
              I'd get a CO alarm for safety, but I use a kerosene torpedo and it has never set off my CO alarm.

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              • #8
                Propane? Not for me thanks!!! I've had all kinds of problems because of a propane with my tig.If you dont heat your shop all the time and you use propane,the bi-product of propane combustion is water vapours and it can get bad enough to cause condensation inside my Dynasty to the point of messing up the HF arc starts badly!I've switched to electric heat and never seen the problem since.Propane would just get the humidity levelway too high in my shop,Frank
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                • #9
                  Propane Shop Heaters

                  I know this is not what you are making reference to, but have you ever tried electric (oil filled) radiator heaters? If your shop doors are closed most of the time and you are just trying to get rid of the chill so it is comfortable to work in, I have found these small space heaters to work very well.

                  I hesitate using electricity for heating purposes, but since I set mine on the lowest settings, I find that I don't have a spike in my electric bill. Some of these units come with 24 hour timers and could be set to come on a couple of hours before you start work.

                  Steve

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                  • #10
                    Originally posted by SundownIII View Post
                    Strength and Power,

                    I have the same heater (2 of them, the Mr Heater #MH55FAV) and I run them both as much as needed without any problem with carbon monoxide.

                    My shop is pretty well insulated (8" batts in the walls and ceiling (16') and pretty well sealed but I've never had a problem.

                    I actually feel that the propane heaters are safer than the old kerosene salomaners that we used on construction sites for years.

                    The carbon monoxide detector will provide another level of security. Let me know if you set it off. I suspect you won't.
                    Good catch on the Mr. Heater. When not in use, I keep mine next to Mr. Bandsaw and Mr. bench grinder

                    My shop has no insulation in the warehouse(welding area). The front office/storage has a drop ceiling with insulation on it.

                    We have a kerosene heater at work, didn't care for the smell which prompted me to get propane. And 5 gal of kerosene was $38.00 which seemed high.

                    I will let you know how the CO alarm goes. It will probably cause a warm front and I won't need the propane heater until next year, which I am totally OK with
                    Miller 350P
                    Miller Econotig
                    Milwaukee Dry saw
                    Evolution Dry saw (for sale)
                    Scotchman 350 cold saw
                    7x12 bandsaw
                    1910 ATW 14 x 72 lathe
                    fridge full of adult beverages
                    Sirius radio

                    www.snpequipment.com
                    callouses and burns a plentysigpic

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                    • #11
                      Originally posted by SBray View Post
                      I know this is not what you are making reference to, but have you ever tried electric (oil filled) radiator heaters? If your shop doors are closed most of the time and you are just trying to get rid of the chill so it is comfortable to work in, I have found these small space heaters to work very well.

                      I hesitate using electricity for heating purposes, but since I set mine on the lowest settings, I find that I don't have a spike in my electric bill. Some of these units come with 24 hour timers and could be set to come on a couple of hours before you start work.

                      Steve
                      My neighbor a cabinet maker bought an oil filled radiator heater. Then asked to borrow my propane heater as it wasn't cutting it even with the doors closed.

                      I usually leave the bay door open some what for weld smoke/fume extraction. I don't think the radiator would keep up. Plus it is nice to feel a warm breeze, makes it feel warmer than it actually is.

                      I definitely respect the guys who weld outside in the low temps who are probably shaking their heads at this thread. I have snowboard jacket and pants that would be great for this type of weather but am afraid they wouldn't last long with sparks getting slung at them as they are nylon/polyester.

                      Thanks to all who have responded

                      Scott
                      Miller 350P
                      Miller Econotig
                      Milwaukee Dry saw
                      Evolution Dry saw (for sale)
                      Scotchman 350 cold saw
                      7x12 bandsaw
                      1910 ATW 14 x 72 lathe
                      fridge full of adult beverages
                      Sirius radio

                      www.snpequipment.com
                      callouses and burns a plentysigpic

                      Comment


                      • #12
                        Since diesel engines do not produce carbon monoxide I highly doubt that a kerosene fired torpedo heater would either. I use the kerosene heater in my shop because it's what I have on hand. In an ideal situation I would be using a wood heater for both my home and shop. I'm talking about the ones that look like a storage shed behind the house and you circulate hot water from the wood heater into the house and shop. You can also use the hot water to dry your clothes and heat the water in your water heater as well. You can bank some of them up to 40 hours and they only take about 2 1/2 years to pay for themselves in savings over the electric or gas heat you're using now. Of course in the perfect situation I will not be living in this frozen tundra much longer
                        Blondie (Owner C & S Automotive)

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                        • #13
                          Originally posted by STRENGTH AND POWER View Post
                          My neighbor a cabinet maker bought an oil filled radiator heater. Then asked to borrow my propane heater as it wasn't cutting it even with the doors closed.

                          I usually leave the bay door open some what for weld smoke/fume extraction. I don't think the radiator would keep up. Plus it is nice to feel a warm breeze, makes it feel warmer than it actually is.

                          I definitely respect the guys who weld outside in the low temps who are probably shaking their heads at this thread. I have snowboard jacket and pants that would be great for this type of weather but am afraid they wouldn't last long with sparks getting slung at them as they are nylon/polyester.

                          Thanks to all who have responded

                          Scott
                          You'll melt your snowboard stuff up in a mad minute welding in them plus you don't want that nylon melting on your skin it leaves a nasty burn. If you want to wear warm weather gear go and get something made of duck twill such as Carhart or Berne coveralls or bibs and jacket. I use the bibs and jacket because they allow me more freedom of movement and don't need help getting in and out of them as I do coveralls. Another thing if you can avoid steel toe work boots as they make your feet colder opt for insulated leather boots with no kevlar on them make sure they have a leather tongue on them. I had the misfortune of having a hot glob hit my foot and it melted through the kevlar and put 2 nasty 3rd degree burns on my foot which took 6 months to heal and I usually heal pretty quickly.
                          Blondie (Owner C & S Automotive)

                          Colt the original point & click interface!

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                          Victor O/A torches
                          Lincoln SP125
                          Too many other tools to list

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                          • #14
                            Originally posted by Blondie_486 View Post
                            Since diesel engines do not produce carbon monoxide I highly doubt that a kerosene fired torpedo heater would either.
                            Diesel engines produce around 0.5-1.0 grams of carbon monoxide per brake horsepower per hour. This translates to thousands of ppm CO.

                            A few hundred ppm CO will kill.

                            That said, I have never measured more than 11ppm CO running the kerosene turbine heater. But mechanical problems can cause large quantities of CO to be created. The only way to know it's there is with a detector.

                            BTW the complete combustion products of any hydrocarbon are CO2 and water.

                            Assuming decane (C10H22):

                            C10H22+15.5O2->10CO2+11H2O

                            molar weight C10H22=142g

                            1 Gal=7.3lb=3.31kg=23.3mol

                            O2 req =15.5*23.3=361mol (@32g/mol)=11.6kg (@22.4 l/mol)=8.1m^3 (286cu ft)(20% concentration in air means 5 times this volume of air (1430 cu ft)is required

                            co2 produced= 23.3*10=233mol (@44g/mol)=10.3kg (

                            H2O produced=23.3*11=256mol (@18g/mol)=4.6g (10.2lb or 1.2 gallons)

                            Every gallon of kerosene you burn (7.3lb) makes 1.2 gallons of water, 22.7lb CO2, and requires 1430 cubic feet of air.

                            Food for thought.

                            If anyone spots any math or stochiometric errors let me know.
                            Last edited by Bodybagger; 01-09-2010, 11:53 PM. Reason: mixed a number up

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                            • #15
                              Air requirements are going to be similar per BTU for hydrocarbon fueled heaters,

                              As previously discussed, you need 1430 cu ft air per gallon of kerosene just to feed combustion.

                              At 19,000BTU/lb kerosene (139,000BTU/gal), you need 1430 CFH for 139,000BTU/hr.

                              1430CFH=23.8 CFM per 139,000 BTU/h = 1.7 CFM per 10,000BTU/h

                              So for your 55,000 BTU/hr heater, it will consume 9.5 CFM of air.

                              For a tight building, you get about 0.5 air changes per hour from infiltration alone. You said your shop is 975 sq ft, so if you have 8' ceilings, worst case is you have:

                              975*8*.5=3900CFH = 65CFM of infiltration.

                              Far more than the required combustion air. I think you're set. But use a CO detector anyway.

                              80% of failures are from 20% of causes
                              Never compromise your principles today in the name of furthering them in the future.
                              "All I ever wanted was an honest week's pay for an honest day's work." -Sgt. Bilko
                              "We are generally better persuaded by reasons we discover ourselves than by those given to us by others." -Pascal
                              "Since we cannot know all that there is to be known about anything, we ought to know a little about everything." -Pascal

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