sanity check - direct vent propane shop heat

[DividedAttention]

Looking at my options for heat this winter in my shop - the space is a well insulated 300sf "room" in the corner of a 30'x46' pole barn. The greater pole barn is not insulated and IMO, well vented with 9" opening to the soffits the entire length of the building as well as a continuous ridge vent. I did not spec the pole barn, it was on property when I bought in last year. I'm in CO, so ambient humidity is always very low.

I'm looking at various direct vent propane fired furnaces (like a small Rinnai) to heat the small shop. I'd rather NOT have the unit on one of the 2 exterior walls due to location of machine tools already in the room. The sanity check part of this is, am I nuts considering venting into the pole barn? I'm thinking it's not exactly a well sealed space...

 

[The Cobbler]

I doubt it would be permitted by code , or even documented in the manufacturers literature as an acceptable method .

 

[rlitman]

In a word; yes.

 

[sberry]

A heater the size to heat that bity room wouldn't have a problem in a drafty building.

 

[rlitman]

A heater the size to heat that bity room wouldn't have a problem in a drafty building.

I beg to disagree. A ventless heater might be appropriate, as they burn more efficiently than vented heaters (from the perspective of CO and NOx emissions). A good ventless heater will also have an oxygen depletion sensor.

But CO is not the only issue. A vented heater's exhaust stream is likely to set things on fire. Ventless heaters are much less prone to doing that.

 

[dfiler2]

I may know a person who vented their hanging heater in just the way you describe. That person put in two carbon monoxide alarms in the cold storage area and has never had one go off. That person also has access to more sophisticated air testing equipment and has seen no problem.

The termination is a long way from any combustibles.

 

[DividedAttention]

A heater the size to heat that bity room wouldn't have a problem in a drafty building.

I may know a person who vented their hanging heater in just the way you describe. That person put in two carbon monoxide alarms in the cold storage area and has never had one go off. That person also has access to more sophisticated air testing equipment and has seen no problem.

The termination is a long way from any combustibles.

Thanks for the replies so far. It looks like I'm only 50% crazy to consider this. With no disrespect to the letter of the law, my thinking is along the lines of the responses above.
I'm looking at the Rinnai EX08CP which has a maximum BTU of 8000. I'll be happy if it can retain 60° during working hours. The setback feature is most appealing because it can be adjusted to a minimum of 38°.
Last winter after getting the room built and functional, I got by with one of those Kero-Sun heaters. I was much more worried about emissions from that thing being in the same room.

 

[sberry]

it will be a lot cleaner than a ventless. 8k is really small, the exhaust is really minor, wouldnt hurt a building that size if it wasnt drafty

 

[finn]

Another case of "just because you can (get away with it), doesn't mean you should ".

Darwin is at work here.

 

[thickhead]

If you have power, wouldnt it be simple to just run a small electric heater?
Maybe rates are higher in your area?

 

[rlitman]

it will be a lot cleaner than a ventless. 8k is really small, the exhaust is really minor, wouldnt hurt a building that size if it wasnt drafty

8k is really small, and the air quality may be better than with a ventless.

But the condensation will be awful on the cold side. Also, a vented heater is expecting a stack draw to pull through it. Without the vent, it can overheat and burn up.

I still think this is idiotic. If you want a ventless heater, just get one.

 

[Jackfre]

The Rinnai Direct vents, with the exception of the 08, can accommodate SS vent extensions that can in some configurations allow installation on an interior wall. The 08 due to its very low btu input and to prevent condensation in the flue cannot handle the extensions. The 11 (modulates from 5500-11000 btu) is the same physical size and can handle 13' of vent extensions, but as you are in CO, you are limited to a 5' max rise. Can you clear your machine tools with a 5'rise and a horizontal run to the outside wall?

I agree with your sizing on the 08, but it is very restricted in venting options, as in, there are none. Go to www.rinnai.us and look over the installation manual for more info.

For a vent free the Rinnai 510 will modulate from 5-10 kbtu and would work well, but be aware that anything that is airborne will go thru that heater and it will absolutely come out smelling worse than it went in. The 510 & 824 Rinnai's are the only low NOX vent-frees. Your point of low humidity is noted and in some cases the moisture from a vent free can be a benefit, but that will vary or can vary substantially due to the weather. If you can go DV, do so. I can answer any questions you have on the Rinnai DV's. I've sold close to a quarter million of them

 

[Bretny]

Why not just get a hanging unit heater? Run the chimney up and out.

 

[DividedAttention]

Another case of "just because you can (get away with it), doesn't mean you should ".

Darwin is at work here.

Thanks for that bump in your post count.

If you have power, wouldnt it be simple to just run a small electric heater?
Maybe rates are higher in your area?

Yes, around here the utility cost hierarchy puts natural gas at least expensive and electric at most expensive. Propane is in the middle. I don't see the payback in trenching a gas line to the shop.

8k is really small, and the air quality may be better than with a ventless.

But the condensation will be awful on the cold side. Also, a vented heater is expecting a stack draw to pull through it. Without the vent, it can overheat and burn up.

I still think this is idiotic. If you want a ventless heater, just get one.

I don't want a ventless heater because of the condensation in the room. The rinnai has a vent, I have 2 choices - vent to the pole barn or re-arrange and run the vent outside. If I'm to expect an awful lot of condensation coming from the vent, does that mean expect dripping water? I figured the inherent moisture would be airborne. I don't really want to manage a frozen drip catcher on the pole barn side.

The Rinnai Direct vents, with the exception of the 08, can accommodate SS vent extensions that can in some configurations allow installation on an interior wall. The 08 due to its very low btu input and to prevent condensation in the flue cannot handle the extensions. The 11 (modulates from 5500-11000 btu) is the same physical size and can handle 13' of vent extensions, but as you are in CO, you are limited to a 5' max rise. Can you clear your machine tools with a 5'rise and a horizontal run to the outside wall?

I agree with your sizing on the 08, but it is very restricted in venting options, as in, there are none. Go to www.rinnai.us and look over the installation manual for more info.

For a vent free the Rinnai 510 will modulate from 5-10 kbtu and would work well, but be aware that anything that is airborne will go thru that heater and it will absolutely come out smelling worse than it went in. The 510 & 824 Rinnai's are the only low NOX vent-frees. Your point of low humidity is noted and in some cases the moisture from a vent free can be a benefit, but that will vary or can vary substantially due to the weather. If you can go DV, do so. I can answer any questions you have on the Rinnai DV's. I've sold close to a quarter million of them

From my preferred location, I don't think 13' would get me outside. I'd have to route the vent over one of 2 doorways. So now I'm looking at moving stuff around which will get the unit on an exterior wall. At that point it would be easiest to just use the short vent that comes with the unit. Is there a negative aspect to using the short vent vs. longer? For a couple hundred bucks, I think you have me sold on the EX11.
Last winter on Kerosene demonstrated why I don't want a vent free. Once the Kero-Sun was shut down and the overnight temp drifted down I quickly learned about dew point on my mill table.

Why not just get a hanging unit heater? Run the chimney up and out.

My primary goal here is that I'd like to be able to keep the temperature above freezing all winter so I don't have to relocate items that might freeze overnight when the heat is off or days when I'm not out there at all. Working at a comfortable temperature is nice too. Overnight freezing is a reality where I'm at for a solid 6 months - I'm at 9000ft.
AFAIK, all standard thermostats have a low set point of 50°. I'm cheap so I'd rather not pay for 50° and 30,000+ BTU in a 300sf space. Same $ buys a Rinnai and it will maintain 38° when I'm not out there.

 

[Fueler]

You stated the payback for running a gas line was not sufficient.
None of the fuels will get any cheaper than now and electricity will always go up.
Are you only planning on only one winter and then move?
Never, ever planning on expanding, improving or using the rest of the shed?

 

[rlitman]

...I don't want a ventless heater because of the condensation in the room. The rinnai has a vent, I have 2 choices - vent to the pole barn or re-arrange and run the vent outside. If I'm to expect an awful lot of condensation coming from the vent, does that mean expect dripping water? I figured the inherent moisture would be airborne. I don't really want to manage a frozen drip catcher on the pole barn side...

And my point is, that you're essentially turning the pole barn into a dehumidifier.

Instead of keeping the wet exhaust in the conditioned room, where the surfaces MAY be above the dew point, you're exhausting the 100% humidity combustion byproducts into a cold space where every surface is guaranteed to be below the dew point.

Everything in the pole barn will either be dripping, or covered in frost.

 

[Jackfre]

How deep does the snow get against the wall you want to use? You need to terminate the Rinnai vent 12" above the ground (which in CO at 9000' is ridiculous) or 12" above the expected snow level. That means that you will need some vent extension sets. Specs say you can run a max of 5' vertical. That is basically an air density issue which living at 9000' I am sure I don't have to get into. Total vent length can be 13' total with 2 90's. The part #'for vent extensions are: FOT-155, 11-20" telescoping; 156, 21-40"; 157, 40-80"; 158. 90* elbow. The thru the wall portion of the vent is supplied in the box and will adjust from 4.5-9.5" wall thickness. Due to the very low input of the EX-08, it cannot accept any vent extensions.

The Rinnai's built in programmable stat has a feature that allows you to set a low temp as low as 38*. Even if the unit is powered down, if you have set a low of 38, the unit will turn itself on to maintain that setting.

Back to that air density issue. You will have to re-set the gas pressures. I think this will actually be to your benefit as you will loose a bit of input. I do think the 08 is the right size for your space so dialing it back a bit will be good. You will need a differential pressure manometer (two hoses) or you LP company can do it. With a single tap manometer you can try all day to set it and still be wrong.

 

[DividedAttention]

You stated the payback for running a gas line was not sufficient.
None of the fuels will get any cheaper than now and electricity will always go up.
Are you only planning on only one winter and then move?
Never, ever planning on expanding, improving or using the rest of the shed?

I do use the entire building, however, I do most of my work in only 25% of it. It doesn't make any sense to me to spend extra money running 100'+ of natural gas line for a marginal fuel savings 1/2 the year. I'm not even out there every day, so less than half. When I do need to work on something in the greater pole barn in the winter, I generally have the luxury of picking when to do it. Sunny CO days are plentiful and my 14' door faces south. For perspective on my heating demand, last Nov-May the Kero-Sun went through about 15 gallons.
If I ever have the need to heat the entire thing, I'll have a major insulation job on top of considering that gas line.

How deep does the snow get against the wall you want to use? You need to terminate the Rinnai vent 12" above the ground (which in CO at 9000' is ridiculous) or 12" above the expected snow level. That means that you will need some vent extension sets. Specs say you can run a max of 5' vertical. That is basically an air density issue which living at 9000' I am sure I don't have to get into. Total vent length can be 13' total with 2 90's. The part #'for vent extensions are: FOT-155, 11-20" telescoping; 156, 21-40"; 157, 40-80"; 158. 90* elbow. The thru the wall portion of the vent is supplied in the box and will adjust from 4.5-9.5" wall thickness. Due to the very low input of the EX-08, it cannot accept any vent extensions.

The Rinnai's built in programmable stat has a feature that allows you to set a low temp as low as 38*. Even if the unit is powered down, if you have set a low of 38, the unit will turn itself on to maintain that setting.

Back to that air density issue. You will have to re-set the gas pressures. I think this will actually be to your benefit as you will loose a bit of input. I do think the 08 is the right size for your space so dialing it back a bit will be good. You will need a differential pressure manometer (two hoses) or you LP company can do it. With a single tap manometer you can try all day to set it and still be wrong.

Thanks so much for some helpful info! Yes, the size and Set Back feature are most attractive.
It can snow 3'+ at a time here. Last winter, storms only dumped about a foot each. The sunshine over CO does a good job of melting accumulation quickly so subsequent storms rarely pile on top of each other. I'll be sure to keep the vent out of the snow. Thanks for the tip on the manometer too! I was just reading up on that adjustment in the manual last night.