Shop Heater Question- Hot Dawg Type - Woodworking Talk - Woodworkers Forum
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post #1 of 6 Old 01-07-2016, 09:06 AM Thread Starter
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Shop Heater Question- Hot Dawg Type

Need your help guys. I am having a heat pump put in and at the same time I asked the guy to hook up a Modine style "Hot Dawg" gas tube heater. It is a Lennox but works, functions, and looks almost identical. I have been having some problems with this contractor already and now I am having one with this heater that he hooked up yesterday.

My shop is a 21' x 31' basement garage under the main garage. The house is surrounded by dirt on 3 sides. Only exposed side of my shop is the garage door which is insulated. The basement is cinder block. Th e heater he sized and got running yesterday is 30K btu and it is not cutting the mustard. At 7pm last night before I cut the heater on it was 52 degrees in the shop. It wasn't going up very fast so I checked it at midnight and the temperature was 55 degrees. With the heater on all night I checked it again at 6am this morning and it was 59 degrees.

I am not sure about you guys but I wouldn't have paid $1300 to raise my shop temperature 7 whole degrees. Ideally I like it around 65 in there.

In contrast, I had a heater that worked on the same principal but ran off my hot water boiler in the same shop and it heated the shop to whatever temperature you wanted in about 30 minutes.

I did another test with my salamander type forced air 55k btu kerosene heater and it heated the shop from 52 degrees to 70 degrees in 26 minutes.

I fully understand the new heater is 30K btu and it will take longer, roughly 2x as long to heat if btu's work that way, however, to raise it from 52 to 59 in a matter of 11 hours is unacceptable to me. I told the guy about it this morning and he said "well run it longer and see if it comes up and holds" and I told him I don't want to run my shop heater Mon-Fri to be able to use it on Saturday.

I told him I would pay the difference on a higher btu unit. He has not got back with me about that. What btu do you guys think I need or do you think it is something wrong with my unit. I am highly frustrated mainly bc this isn't the first thing with this guy.
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post #2 of 6 Old 01-07-2016, 10:25 AM
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Something is wrong with that heater.

What was the BTU of the hot water boiler unit? Most of those are around 30-45K BTU. The hanging type, right? Those forced air hanging type heaters are supposed to heat as fast, if not faster than the other types of heat. I had one in my old shop which was 26'x36' 9' ceilings, well insulated and If it was 50 degrees in the morning when I walked in I had 72 in about any hour. 12'x8' overhead door, lots of windows, etc.
So, that guy needs to come back and see what's up. If you look from the back can you see that the entire burners are lighted? Maybe something is plugged in the burners. It just sounds to me something is not firing properly.
Good Luck,

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post #3 of 6 Old 01-07-2016, 01:22 PM
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This will not help but just for reference I heat my attached 2 car insulated garage with 10.5 ft ceilings to 50 - 55 degrees in freezing (15 - 30 degree) weather with a 1500 watt electric heater. If I turn it on in the evening it's warm by morning. Not sure but I think 1,500 watts is equivalent to 5,000 btu so I would think 30,000 would warm that up pretty quickly unless you have a lot of outside air infiltration. I do have to keep after the side seals on my garage doors.
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post #4 of 6 Old 01-07-2016, 01:49 PM Thread Starter
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I am going to do some more looking tonight. I got home late last night and couldn't mess with it a whole lot.

Now that you say it about the hanging hot water heater it probably was in the 30K btu range. Now it really makes me wonder if something isn't right about the new heater.

One obvious thing that came to mind is they needed to convert the heater to Propane from Natural Gas. I saw the conversion kit in the box but don't know if it got done. Is there any way to tell? Also would the symptoms I'm having with it be indicative of the conversion not being done? (Running propane through a system that was still tuned for natural gas)
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post #5 of 6 Old 01-07-2016, 04:16 PM
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How are you venting the heater, are you above 2000 ft. altitude? In many cases the heaters are set up for either NG or LP at the factory. NG has a larger orifice. Do you have a fresh air intake source?
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post #6 of 6 Old 01-07-2016, 04:17 PM
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The biggest problem if they didn't install the propane orifice is going to be incomplete combustion and your heat exchanger is going to get crudded up bad. It will stink and probably smoke - probably at the exhaust.

Propane (higher pressure) going through a NG orifice (bigger hole) actually means more heat at the exchanger(and a dirty burn). Problem is that the heat exchanger gets too hot and the unit cycles on it's own limit switch rather than the thermostat that it should.

It's easy to confirm the "cycling on the limit switch" problem. Just crank the T-Stat up as high as it goes and wait. If the unit shuts down before it's actually 85 degrees (or whatever), then it's likely cycling on the limit.
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