Results 1 to 16 of 16
  1. #1
    Bobbyblackcloud is offline Aluminum
    Join Date
    Jul 2007
    Location
    ontario
    Posts
    145

    Post

    i have been looking to put two of the box type garage heaters 45000 to 75000 btu "hotdawg" in my shop.prices seem to be allover the board.local heating supply quoted 1400 and i see princess auto has them on sale for 599.00.Wondering what models guys have and if they are happy with them and what kind of prices they paid

  2. #2
    Jerry Leskovec is offline Aluminum
    Join Date
    Jul 2007
    Location
    New Philadelphia ,Ohio
    Posts
    111

    Post

    I also want to heat my attached garage / work shop with propane.

    In the coldest winters my garage stays at 40 deg. ( no heat ) In size it's one big open area 30ft X 34ft X 9 Ft high.

    I just want to have it at about 50 Deg when I'm not in there and 6o would be nice when I am out there .

    Is there a way to figure out about how much gas I will use ? I guess I could read the literature on the box etc from the manufacturer.
    I am hoping to maybe get away with a 60 lbs tank a month ??

    Would it be better to use a radiant heater or a convection ?

    Thanks guys and all replies
    Jerry

  3. #3
    gar
    gar is offline Stainless
    Join Date
    Feb 2005
    Location
    Ann Arbor, Michigan USA
    Posts
    1,336

    Post

    Jerry:

    What keeps your garage at 40 deg F. when the outside temperature is -10 F. ? Is it buried in a hill?

    The amount of power, rate of expenditure of energy, to maintain a given internal temperature is a function of the outside temperature and the thermal resistance to the outside. Thermal resistance will not be a constant because of wind variations. There also may be some thermal gain from solar radiation on the outside surface.

    All the above is difficult to calculate.

    Note: if you building is mostly in a hill then you might be mostly heat sinking to ground temperature.

    You can experimentally determine energy required with some electric heaters. On your coldest day with high winds run the electric heaters to maintain 60 deg F. As a guess maybe 5 to 20 KW worth of heaters. Use a KWH meter to measure energy over a days time. This will give you an average energy requirement for a worst case day.

    Another way is to use a torpedo type kerosene heater and measure the fuel used over the 1 day period.

    Electrical heat has 100% efficiency, combustion heaters have less efficiency. There is data available on the energy content of various fuels, and there are conversion factors between different units of energy measurement. Thus, you can make measurements with one means and compare with a different one.

    In my garage which is about the size you are describing and with fiber glass insulation filling 3.5" in the walls and mostly heating a 22 x 15 area 5 kw on continuously wiil heat to about 60 deg F. with outside about +0 to 10 deg F.

    1 KWH = 3413 BTU. So my requirement is about 17,000 BTU/HR. 134000 BTU are in 1 gallon of kerosene. 21548 BTU are in 1 pound of propane.

    At 100 % efficiency I would require about 0.12 gallons of kerosene, or 0.79 # of propane per hour.

    Our electrical rate is about $0.11/KWH and our natural gas is about $0.04/KWH. If fuel oil is $3/gallon, then its cost per KWH is about $0.08 . Note these are 100% efficiency.

    The difference between your heat sink temperature (building outside) and the internal temperature in combination with the thermal resistance from inside to outside determines the amount of energy require to achieve the internal temperature. If you double this difference then you double the energy required.

    If I required 0.79 # of propane per hour and we use 24 x 30 for the hours per month, then I would require 568 #/month for the 60 deg F. internal at 0 to 10 deg F. outside.

    Would our temperature be 0 to 10 F. for a continuous month? No. Averaged over a winter it is more in the range of 30 F.

    Your area is larger than mine, but your average required temperature difference is much lower.

    When you look at costs you may find that added insulation would be cost effective.

    For improved efficiency, but at a high capital cost, you might look at a ground based heat pump.

    Is your estimate of 60 #/month realistic? I have no idea. You need more information than what you have provided so far. But it won't be 600 #/month.

    .

  4. #4
    gbent's Avatar
    gbent is offline Diamond
    Join Date
    Mar 2005
    Location
    Kansas
    Posts
    4,996

    Post

    I have a supplier with the Hot Dawg heaters listed at 45,000 btu at $545.70, 60,000 btu at $561.25, and 125,000 btu at $716.75. These are vented heaters, not unit heaters. They have a more horizontal profile that will use less head room.

    Only 30,000 and 45,000 btu are ups sized. Larger must go truck freight.

    The pricing looks to be slightly cheaper than standard shape power vented heaters. I wonder how much efficiency you give up for the low profile shape?

  5. #5
    Jerry Leskovec is offline Aluminum
    Join Date
    Jul 2007
    Location
    New Philadelphia ,Ohio
    Posts
    111

    Post

    Hi Gar
    Not sure if my first reply went out ?

    My house / garage is not into a hill side ( I wish it was )
    I bought this place about 4 years ago. It was totally remodeled and updated in 1999. I was not the owner at the time . The attic and walls are stuffed with insulation. the house itself holds heat incredibly well.
    The garage is attached and they didn't make access into the attic above it . The walls are dry walled . ( have peeked into them they are stuffed . The door is aluminium and insulated .

    I have 2 different thermometers and they both read the same . My winter temps usually average from 15 deg ( usually night time --- to 40 deg day time )
    I have never seen the inside the garage temp go under 40 deg. ( except when it dipped to 5 deg for few days and then it stayed at about 35 deg . water did not freeze .
    There are no heat vents of any kind . I have a large freeze and a large fridge out there so some heat comes off them .
    When I have started my torpedo heater up and let it get to 65 for 3 - 5 hours , after I shut it down , it takes about 6 - 7 hours before the temp drops back off to 40 deg.

    What I want to do is get a heater that will keep it at about 50 deg when I am not out there and when I am out there bring it up to about 60 - 65.

    Thank you for your formulas and input to this subject. I was able to get a really great deal on a Mr.Heater propane Blue Flame with a built in fan...it's rated at 20,000 BTU on hi.... I know that this is a bit small but all I am looking for is a few deg. rise in Temp....I also got a deal at same time on a 40 Lb. New Tank. If I have to I will get a 80 or a 100 lb tank.
    So far all I have sunk into it is 100.00.

    I guess 60lb per month is way out !!! I will be happy if I can get by with 120-160 lbs .
    I guess I will see what it all does soon as it gets chilly.

    Again thanks guys ....JerryK

  6. #6
    aboard_epsilon's Avatar
    aboard_epsilon is offline Titanium
    Join Date
    Mar 2003
    Location
    North Wales GB
    Posts
    2,379

    Post

    views

    right

    if you don't heat it 24/7 to a consistent temperature ...
    then you're going to get condensation on all your machines.

    propane does produce water vapour ...but the effects of it are very much lessened if all the surfaces in the room are at the same temp all the time ...and are not being brought up to temp in fits and starts ..


    so if you want dry machines ...then that heater should be on a stat ...and the room heated 24/7

    heating a cold room with a propane heater or diesel or kero will bring the temp up of the air quickly ...and machine will be slow to gain that temp and will sweat...because of the dew point.

    all the best.mark

  7. #7
    gar
    gar is offline Stainless
    Join Date
    Feb 2005
    Location
    Ann Arbor, Michigan USA
    Posts
    1,336

    Post

    Jerry:

    If there is little insulation between your garage and house this is probably the reason for the 40 deg F. My garage is essentially detached because it is separated from the house with a breezeway.

    Have you considered getting heat from the house furnace.

    Someone in the heating and air conditioning business in your area can probably fairly accurately estimate what you need.

    Do heed the advise of aboard.

    .

  8. #8
    Petersontools's Avatar
    Petersontools is offline Hot Rolled
    Join Date
    Mar 2006
    Location
    Lebanon, Virginia
    Posts
    502

    Post

    Use propane in my shop...a Warm Morning® (don't think these are manfuactured any longer). I use shellacs a great deal--anything other than propane like kerosene reacts and creates horrific aromas--I prefer denatured alcohols in the shellac mixtures for short periods, of course.

    Maintain a comfortable 68 degrees all winter. Have a 500 gallon propane tank. No moisture problems--and helps decrease static charges when moving sawdust in vacuum system.

    Southwest VA is not as cold as it was 26 years ago, so the propane is great here...

    Joe

  9. #9
    gbent's Avatar
    gbent is offline Diamond
    Join Date
    Mar 2005
    Location
    Kansas
    Posts
    4,996

    Post

    Mark, the Hot Dawg BBC is asking about is a vented heater. The water vapor from combustion is piped outside. The 15 degree temp changes are unlikely to cause condensation in this case.

  10. #10
    Bobbyblackcloud is offline Aluminum
    Join Date
    Jul 2007
    Location
    ontario
    Posts
    145

    Post

    thanks gbent really don't need a lesson in thermodynamics been there done that.Thanks for your post that was what i was looking for!

  11. #11
    bryan_machine is online now Titanium
    Join Date
    Jun 2006
    Location
    Near Seattle
    Posts
    3,253

    Post

    Stupid Question - all of those torpedo propane heaters need to be vented somehow, right? So don't you have to have a hole of the exahust that would otherwise let cold air in? Is there some non-obvious trick to using them without getting CO poisoning?

  12. #12
    Bobbyblackcloud is offline Aluminum
    Join Date
    Jul 2007
    Location
    ontario
    Posts
    145

    Post

    typically torpedo types are for open sites ie.constuction. i do have one and have used it in the shop with a window or two open they are lowd and stinky and will kill you if you are in an air tight space not to metion they are a huge fire hazard with an open flame shooting out the end.The reason they work well at heating these spaces is the fact they deliver large amounts of heat

  13. #13
    AAB
    AAB is offline Banned
    Join Date
    Jul 2006
    Location
    Melbourne,Australia
    Posts
    618

    Post

    Bobby,

    Is this the type of thing ?




    This thing really works well, has a range of about 10 ft radius,

    The timber wedges ( under the base, on the uneven floor ) are to keep the unit vertical, otherwise she shuts down.

    Regards from Melbourne,Australia,

    AAB
    [img]tongue.gif[/img]

  14. #14
    Bobbyblackcloud is offline Aluminum
    Join Date
    Jul 2007
    Location
    ontario
    Posts
    145

    Post

    no but those are great. we use them for heating the outside patios at the ski hills great to sit under and have beer with your shades on in -15 degrees

  15. #15
    Orrin's Avatar
    Orrin is offline Hot Rolled
    Join Date
    Mar 2004
    Location
    Colton, WA USA
    Posts
    698

    Post

    {quote]What keeps your garage at 40 deg F. when the outside temperature is -10 F. ? Is it buried in a hill?[/quote]

    I know this question was directed to Jerry, but I'll chime in. We can always count on a couple of nights of 0°, or colder, temperatures every winter; but, the temperature in our free-standing garage has never gone below 32° in the ten years since it was built.

    We have a recording thermometer in the garage and I usually keep a container of water as a back-up indicator of freezing temperatures, should they occur. So far, the water has never frozen.

    I cannot explain it, but suspect that the warmth comes from the soil, below.

    Orrin

  16. #16
    gar
    gar is offline Stainless
    Join Date
    Feb 2005
    Location
    Ann Arbor, Michigan USA
    Posts
    1,336

    Post

    Orrin:

    Sure you get heat from the floor of the garage, but I would expect at -10 deg F. outside that you would go below freezing if that outside temperature remained very long.

    If you have a lot of insulation the thermal time constant will be long. The internal temperature is a function of the sources of energy, the initial temperature, and the thermal time constant. You could model this in a simple way with a capacitor, several resistors, and adjustable voltage sources. One resistor and its voltage would be the outside temperature, a second ground energy, and third heat you add inside the building.

    From long ago when I was small our garage was partially in a hill (about 15% of the surface area buried), no insulation, and in the winter the inside temperature was about 10 deg F. higher than outside.

    My current well insulated garage when not heated will go below freezing with sustained cold weather. However, we have one freezer running constantly inside the garage, but that is not much power. That freezer has been running continuously for about 35 years in the garage and 6 years in the house before that.

    .

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •