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Old 01-26-2011, 11:11 AM   #1
Dragster Racer
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Default Hanging heater efficiency

I heat my 40X40 insulated shop, and need to push my propane usage down a bit. I set it at 45 normally and kick it up to low 50's when I am out there. I have a hangine Reznor heater that is quite old.

I have caught this heater when it cycles making a rushing noise, which I would guess means the burner is firing oddly, probably due to being dirty. So I can clean and try to adjust it to see if that helps.

However, I have yet to see efficiency ratings for hanging heaters like they do with home furnaces. I don't know if figuring it is as simple and dividing the output btu number by the input btu number.
I was just wondering if there are hanging heaters on the market now that are higher efficiency than what the old ones tend to be. i don't know if the radients are actually any higher efficiency, but I could go that way if the savings was worth it.
What do you guys know on this?
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Old 01-26-2011, 11:16 AM   #2
lametec
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Default Re: Hanging heater efficiency

Yep, output/input = efficiency factor.
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Old 01-26-2011, 09:32 PM   #3
trythis
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Default Re: Hanging heater efficiency

I have looked at old and new hanging heaters and they are always either 80% or 85%. I cant remember which.
I had a HVAC guy bid on some work and he was looking at a 1940's or older one we had and suggested I replace it for a more efficient one. It had no rating, but the math on input and output BTU's was the same as the newest highest dollar one available today. So I think they are all the same.

I installed a tube style radiant heater and it was mucho more comfy than the blower style I had.
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Old 01-26-2011, 10:56 PM   #4
Charles (in GA)
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Default Re: Hanging heater efficiency

Radiant should be very efficient as all the energy is going to heat and little or none (depending on design) is going outside.

Charles
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Old 01-27-2011, 02:40 AM   #5
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Default Re: Hanging heater efficiency

I have a 24x34 3 car with 11' sidewalls. Walls are R19, Ceiling R28-30, and 3 so-so insulated garage doors. I heat with a 45000 btu Hotdawg type heater that is 80% efficient and it's more than enough (I'm in St Paul, MN). I keep it heated to 45 unless I'm working and then 55-60. I have been monitoring the gas use for just the garage since the first week of December 2010. I just looked tonight and I've used 94 therms of gas so far @ $.80 per therm, so just over $75. I'd say that over 75-80% of the time it's been kept at 45 degrees.
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Old 01-27-2011, 12:56 PM   #6
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Default Re: Hanging heater efficiency

We have several of those old reznor's in our warehouse at work.

Good thing is, they will last forever.

Bad news is, they will last forever.

The ones I've checked have been rated at 80% efficiency, but when I look at the flue size...I can't believe they would be rated at that by today's standards. I'm not sure if they did it differently years ago or not. I'd be interested if anyone knows for sure.

When I bought my house in the early 90's, it had a 1960 furnace rated at 200,000 BTU input, 160,000 BTU output (80%) and the flue was 6" diameter I think. The replacement furnace was 120,000 BTU's and (I THINK) had a 3" diameter flue.

A 6" flue is 4 times the size of a 3" flue. Doesn't seem they'd have the same percentage of heat going up...but I don't know for sure. The new one did have a combustion air motor...so who knows?

Phil

p.s. It has nothing to do with the thread, but I replaced that 80% furnace a few years later when gas got really high (2000). Went to a dual stage high efficiency Rudd and like it a lot.

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Old 01-27-2011, 07:40 PM   #7
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Default Re: Hanging heater efficiency

I spoke with my propane supplier, and he educated me a bit.
He said that all of the shop heaters for the most point are 80-83%, and that is the best they can be. That's because they can't be better without lowering the flue temp past the point where moisture will fall out of the air, and nobody wants a shop heater that has to be drained or winterized. Makes sense.
He said that the efficiency of the radient heaters is the same, but in operation they seem to be much more efficient, costing much less to operate. Especially if the doors are ever opened, since you don't loose all of your heat with all the items being warm. Not sure I can afford to convert right now, but may be the way to go down the road. He also gave me some things to check on my current heater to make sure it is operating correctly. Nice guy.
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Old 01-27-2011, 08:07 PM   #8
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Default Re: Hanging heater efficiency

I don't know if this is relevant but my Lennox shop heater died and the parts to fix it would have cost between $350. and $830. depending on the source. I replaced it with a home style forced air furnace that I had. It is a universal design that can be used either vertically in either direction of horizontally. It has a rating of 80%. I know that there are some out there rated as high as 96%. Before I spend anything on a more efficient furnace I plan to install a couple of solar collectors on the south face of the barn and see how that works.
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Old 01-27-2011, 08:30 PM   #9
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Default Re: Hanging heater efficiency

I forgot one more thing that the propane guy told me. The new draft induced furnaces aren't any more efficient, but....they don't allow warm room air to escape through the flue when the heater isn't running.
He said that he gets a lot of calls from customers who want to use a high effc home furnace in their shop. His first question is are you going to heat it all the time? If no...then don't use it. The water is the problem. If heated all the time...no problem
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Old 01-27-2011, 08:30 PM   #10
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Default Re: Hanging heater efficiency

I'm totally hip to the solar project. I have a south facing wall that is begging for a passive solar panel.
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Old 01-27-2011, 08:44 PM   #11
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Default Re: Hanging heater efficiency

Quote:
Originally Posted by Dragster Racer View Post
I spoke with my propane supplier, and he educated me a bit.
He said that all of the shop heaters for the most point are 80-83%, and that is the best they can be. That's because they can't be better without lowering the flue temp past the point where moisture will fall out of the air, and nobody wants a shop heater that has to be drained or winterized. Makes sense.
He said that the efficiency of the radient heaters is the same, but in operation they seem to be much more efficient, costing much less to operate. Especially if the doors are ever opened, since you don't loose all of your heat with all the items being warm. Not sure I can afford to convert right now, but may be the way to go down the road. He also gave me some things to check on my current heater to make sure it is operating correctly. Nice guy.

wouldn't it take alot longer to heat up the shop with radiant?
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Old 01-28-2011, 12:41 PM   #12
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Default Re: Hanging heater efficiency

If you are talking about starting from dead cold to operating temp, probably yes. Not a great choice unless you are heating all the time. But, if you are heating all the time, and open a door, the recovery is really nice because all the items that are in the shop including the floor somewhat are radiating heat. And the comfort is decent because the heat is radiating on your body, keeping you comfortable.
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Old 01-28-2011, 12:52 PM   #13
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Default Re: Hanging heater efficiency

Quote:
Originally Posted by foss View Post
wouldn't it take alot longer to heat up the shop with radiant?
Nope!!!I worked in a shop that had radiant heat........got warmer faster than with a hanging furnace..........much faster......Jim
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Old 01-29-2011, 07:31 AM   #14
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Default Re: Hanging heater efficiency

Quote:
Originally Posted by Dragster Racer View Post
I heat my 40X40 insulated shop, and need to push my propane usage down a bit. I set it at 45 normally and kick it up to low 50's when I am out there. I have a hangine Reznor heater that is quite old.

I have caught this heater when it cycles making a rushing noise, which I would guess means the burner is firing oddly, probably due to being dirty. So I can clean and try to adjust it to see if that helps.

However, I have yet to see efficiency ratings for hanging heaters like they do with home furnaces. I don't know if figuring it is as simple and dividing the output btu number by the input btu number.
I was just wondering if there are hanging heaters on the market now that are higher efficiency than what the old ones tend to be. i don't know if the radients are actually any higher efficiency, but I could go that way if the savings was worth it.
What do you guys know on this?
Someone is making a 92% forced air efficient unit heater. Might want to look into that.

If you have the ceiling height, the tube style radiant heaters are a lot more cost effective to operate than forced air. Plenty of info on the web if you look for it. The combustion efficiency isn't any better, but the radiant style heat delivers the btu's used better than heating air.
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Old 01-29-2011, 09:07 AM   #15
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Default Re: Hanging heater efficiency

A couple of years ago I experimented a bit. Over a 2 year period I found that I used (within a few gallons) the same anount of propane running at 50 degrees and raising it to 55 when working as I did keeping it at 55 degrees and raising it to 60 when working. When I asked my propane supplier abouty this he mentioned that bringing the temp up 5 degrees from a colder temp requires more propane. So mine is at 55 degrees right now.
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Old 01-29-2011, 09:37 AM   #16
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Default Re: Hanging heater efficiency

The HVAC company I work for sells a lot of heaters and these days it is uncommon to install unit heaters anymore, radiant is the way to go. More efficient to heat whats in the shop than just the air. Like a previous member said, open the door once and you are starting all over again because your warm air just left. Ceiling height is a consideration tho, as you could end up bubbling the paint off your car if its too close.
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Old 01-30-2011, 09:47 PM   #17
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Default Re: Hanging heater efficiency

How much is the initial cost of a radiant heater compared to a forced air unit?
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