Need advice installing a propane shop furnace

[ponytug]

So if I got a different or newer furnace with sealed combustion chamber I'm OK with my 125 gal of diesel fuel 50 ft away?

There is no way I'm cutting a hole in the roof for a vent. Sidewall is OK but not roof. That's just asking for trouble.

The newer sealed combustion versions allow horizontal venting, usually at a downward slope to let the combustion water drain easily.

All the best,

Peter

 

[CH4Ohio]

If you decide to go with a DIRECT VENT unit that takes all its combustion air from outiside, you'll see that they are much more expensive to purchase. If you're going to go that far, you might want to just look at mounting a horizontal high-efficiency furnace (Category IV) up high on a platform or suspended from the ceiling. I believe you can buy a 90+ forced-air furnace as cheap as a Category III Direct Vent hanging heater. With the furnace you'll get better efficiency (90%+ vs ~82%) and also be able to vent it through the sidewall with much cheaper PVC.

If your building is really tight, this makes more sense. If you have quite a bit of air infiltration around garage doors, etc., a standard Category III horizontally vented heater is what most people would install.

Might be worth pricing it out. I need to go through a similar exercise prior to next winter.

 

[pmsmechanic]

If you are going to buy something different look at a radiant tube system. They heat objects rather than air and are supposedly more efficient.

By far the majority of large open area buildings are heated with radiant heaters in this area. If you goggle "radiant tube heater" you'll get an idea of what they are.

 

[sixdogs]

If you decide to go with a DIRECT VENT unit that takes all its combustion air from outiside, you'll see that they are much more expensive to purchase. If you're going to go that far, you might want to just look at mounting a horizontal high-efficiency furnace (Category IV) up high on a platform or suspended from the ceiling. I believe you can buy a 90+ forced-air furnace as cheap as a Category III Direct Vent hanging heater. With the furnace you'll get better efficiency (90%+ vs ~82%) and also be able to vent it through the sidewall with much cheaper PVC.

If your building is really tight, this makes more sense. If you have quite a bit of air infiltration around garage doors, etc., a standard Category III horizontally vented heater is what most people would install.

Might be worth pricing it out. I need to go through a similar exercise prior to next winter.

I'm older so not spending the longest dollar possible. The most widely used for the mass market is likely my best bet. I just want to have something to do in the winter, do some maintenance and maybe build something.

I just want something that heats, won't set my diesel fuel on fire and vents from the side of the building. I know I need to spend something but whatever the majority uses sound good enough for me.

Also, the building is insulated really well. They did a great job bt even do I have sliding 18 ft wide doors that will let air in. I'll seal one permanently for the winter and the other should leak enough.

 

[CH4Ohio]

If you are going to buy something different look at a radiant tube system. They heat objects rather than air and are supposedly more efficient.

By far the majority of large open area buildings are heated with radiant heaters in this area. If you goggle "radiant tube heater" you'll get an idea of what they are.

Good point. I got a quote for a couple options for low intensity radiant unit(s). This was just for the heaters and hardware to hang them and equipment ranged from $2500 - $3400. (This did not include venting (which is not cheap), gas pipe, wiring, thermostats, etc. And certainly not any labor!) This price was for a highly efficient unit with well engineered reflectors. Not bad price for the heaters really, but quite a bit more than one or two low-end hanging heaters.

I really like the idea of radiant -- heat the concrete and objects instead of trying to get hot air to stay near the floor.

Main concern for me was the clearances from combustibles and painted surfaces, etc. The radiant heat intensity is such that I was worried that a trailer or taller equipment might be damaged. There seems to be specific warnings about stacking vehicles under or near these tube heaters. (I don't stack vehicles, but it's not hard to have a roof or canopy at almost 10'. I can also see where I might have wagons of hay in one end of the building for a short time -- that would preclude this type of heat in that area.) So even with heaters hanging 12' high it seemed like I'd have some areas where it could be concerning.

If you look at radiant heaters, be sure they're using "low intensity" technology. The sales people or the brochures can explain why. (Doesn't mean the heat is low intensity -- refers to wavelengths of radiation produced.)

Good luck.

 

[CH4Ohio]

I'm older so not spending the longest dollar possible. The most widely used for the mass market is likely my best bet. I just want to have something to do in the winter, do some maintenance and maybe build something.

I just want something that heats, won't set my diesel fuel on fire and vents from the side of the building. I know I need to spend something but whatever the majority uses sound good enough for me.

Also, the building is insulated really well. They did a great job bt even do I have sliding 18 ft wide doors that will let air in. I'll seal one permanently for the winter and the other should leak enough.

Yeah -- I would think a sliding door would leak some.

Diesel or kerosene stored properly isn't a concern. It doesn't vaporize like gasoline. Code requires that a gas burner in a garage or shop be at least 18" off the floor. The thinking is that even gasoline vapors lay on the floor. So a ceiling mounted forced air propane heater is not a safety concern if installed properly.

Even "sealed" combustion units aren't "sealed" to the point that you could install them in a flammable atmosphere. I wouldn't worry about the diesel.

It's not the high tech NASA solution, but look at the unit I mentioned from Menards -- just to give you a starting point. Hang it, pipe it, vent it out the sidewall. Might even need two but it's cheaper than buying one large 175K BTU or larger unit.

 

[sixdogs]

In doing my research on this, I called a local farm company that sells and installs furnaces like this. My goal was to find out what a new one would cost and to ask some questions about the old one and venting the exhaust.

My biggest question was can the vertical exhaust be converted to horizontal. I got some maybes there but he's doing further checking, talking with an older installer and maybe calling a tech at Lennox. He said he thinks--and is pretty sure the vertical exhaust can he angled to horizontal but not positive.

Here's the pic of the back again showing the vertical vent.


We also spoke about the newer furnaces with enclosed flame and I do like that. The question now is on the vertical to horizontal exhaust and what I can learn. CH4--can this exhaust be vented horizontal in any way?

 

[2manyrocks]

I suggest looking for the installation manual. What I remember about direct vent water heaters is they used a fan and had different sealing than the heaters that were vertically vented.

 

[ning]

In doing my research on this, I called a local farm company that sells and installs furnaces like this. My goal was to find out what a new one would cost and to ask some questions about the old one and venting the exhaust.

My biggest question was can the vertical exhaust be converted to horizontal. I got some maybes there but he's doing further checking, talking with an older installer and maybe calling a tech at Lennox. He said he thinks--and is pretty sure the vertical exhaust can he angled to horizontal but not positive.

Here's the pic of the back again showing the vertical vent.
View attachment 3422004

We also spoke about the newer furnaces with enclosed flame and I do like that. The question now is on the vertical to horizontal exhaust and what I can learn. CH4--can this exhaust be vented horizontal in any way?

The manual will typically provide a graph showing how much horizontal is allowed; typically some is, but whether it is immediately or not varies.

Power Venting indicates that kits are available to convert to side venting; my bet is that they're pricey.

 

[CH4Ohio]

I'm not sure you want to hear this, but here's my opinion . . .

If some engineer at Lennox tells you how to do it, or what to modify in order to do it, you can do it. You'll need to hang onto his written approval just in case you need to assure someone or some insurance company later. Anything can be done if it's specially engineered. I'm pretty sure you won't get an engineer to put anything in writing.

Barring that . . . Note the designation of "Category I" near the top of the rating plate on your unit. That means this unit is non-condensing and uses a "negative pressure" vent. In other words, it does not produce sufficient positive pressure to vent horizontally and it depends on its HOT flue gases to create a chimney effect in a vertical vent. That's the ANSI rating plate and the ANSI standard that this furnace was designed to. Even though it has an "induced draft" fan, this simply establishes air flow through the heat exchanger and is not powerful enough to create positive pressure sufficient to vent horizontally. It is NOT a "power vent".

A Category III unit has a positive pressure vent and can be vented either way. (It could look almost exactly like yours.) However it's still "non-condensing" meaning it has "hot" flue gases and must still use special sealed high-temp vent material -- whether vented up or out. Most of the new units are using metal vent but older units were required to use expensive high-temp plastic materials. This would be the cheapest solution.

A Category IV unit has a positive pressure vent but is condensing (higher efficiency, cooler flue gases, has a secondary heat exchanger). That's why these high-efficiency furnaces have a condensate drain teed into the PVC exhaust vent. These units can be vented up or out horizontally and can use cheap PVC because heat is not an issue.

There are units, especially from the mid-80's, that are listed as BOTH a Category I and III. BUT it's right on their rating plate. They are designed such that they can be vented either way, if instructions are followed. They require the expensive high-temp sealed vent material if vented horizontally. Their design limits are right on the edge and the way that it's ultimately vented determines whether there is positive or negative pressure in the vent system.

Based solely on the rating plate, your heater is a Category I heater and must be vented vertically using natural draft.

Having said all that . . . . You asked if there was any way to vent that unit horizontally . . . You could mount a separate power vent at the outside wall and run standard metal vent to that. You'd penetrate the wall using a special termination kit that comes with the power vent. This would create a negative pressure between the heater and the power vent fan and then it would be sealed from the fan outlet through the wall termination kit. It has to be wired into the gas valve to ensure the unit won't operate unless the fan is operative. (Not difficult to wire in.) This would be an expensive option too. This used to be done a LOT -- No way would I recommend it today.

 

[2manyrocks]

If the combustion is not properly vented, you can get lethal carbon monoxide. Also, must have proper supply air. This is the reason for so many replies to this thread advising you to consult the installation manual. No one wants to give bad advice on this.

 

[sixdogs]

Excellent advice. I'm about to abandon the used furnace idea and return to sender. Stay tuned.

 

[sixdogs]

A guy I know that sells Reznor gave me a number to go on for full installation while another guy that sells Lennox gave me one as well. Lennox was $500 less than Reznor and I figured it would be the reverse. That's where I'm at so far.

 

[sixdogs]

I think this is the one. Reznor. Any commentary?

https://assets.reznorhvac.com/download/70bf0584-5ed1-11ed-ae02-0016e1e579b9

 

[sixdogs]

Not a lot of input here but does anyone know about size of heater for my shop? My shop is 42'x60' x 14" high. I've narrowed it down to either a 125,000 BTO Reznor propane or a 150,000 one.

Heating guy doesn't a long enough history of a situation like this but thinks 125,000 BTU would be enough. He also thinks 150,000 would be OK as well.

Can anyone offer an opinion on this?

 

[ponytug]

Not a lot of input here but does anyone know about size of heater for my shop? My shop is 42'x60' x 14" high. I've narrowed it down to either a 125,000 BTO Reznor propane or a 150,000 one.

Heating guy doesn't a long enough history of a situation like this but thinks 125,000 BTU would be enough. He also thinks 150,000 would be OK as well.

Can anyone offer an opinion on this?

I think that a small difference in air sealing might make a 50% difference in heating needs, so I would not want to offer up a number. Put a different way, if whatever you choose isn't enough, or runs too long, I would see about controlling air flow around doors and around insulation.

All the best,

Peter

 

[sixdogs]

I think that a small difference in air sealing might make a 50% difference in heating needs, so I would not want to offer up a number. Put a different way, if whatever you choose isn't enough, or runs too long, I would see about controlling air flow around doors and around insulation.

All the best,

Peter

It's a new insulation job by Morton and in a Morton building. It's tight except for what you would expect around two 18' sliding doors. They are OK sealed but they are still big sliding doors. There is a little normal leakage around the man door but the walls and ceiling are snug. Now?

 

[ponytug]

It's a new insulation job by Morton and in a Morton building. It's tight except for what you would expect around two 18' sliding doors. They are OK sealed but they are still big sliding doors. There is a little normal leakage around the man door but the walls and ceiling are snug. Now?

I'd ask Morton. Sorry.

All the best, Peter

 

[CH4Ohio]

It's a new insulation job by Morton and in a Morton building. It's tight except for what you would expect around two 18' sliding doors. They are OK sealed but they are still big sliding doors. There is a little normal leakage around the man door but the walls and ceiling are snug. Now?

The only experience I have with sliding doors is the typical wood-frame hanging on a roller-track barn-style door with no weather-stripping, etc. Do your doors have any kind of seal along the bottom? Are the sides sealed with rubber like you'd find on overhead garage doors? I'm trying to picture how much daylight you can see around those sliding doors when they're closed and latched.

 

[5030]

There are versions of these that are sealed combustion and direct vented. I really prefer that in a shop environment

I have a Modine overhead power draft propane fired unit. Hung it from the trusses with pre punched angle steel and direct vented it out through the side wall. It's sealed combustion so no flame (visible) and I have it wired to a remote wall T'stat. Propane is hard lined to the unit in black iron pipe.

Sealed combustion, positive vent. Understand, I heat the shop primarily with in floor PEX heat (propane fired again) and the forced air overhead unit is primarily for bitter cold windy days when the PEX heat cannot keep up with the hear load. I keep the foor heat at 68 and the overghead is set at 65. I much prefer the floor heat however. With me, it's imperative I keep the machine tools at a constant temperature plus floor heat is nice for your feet. I ave lots of combustable stuff in the shop, from lubricating oils to diesel fuel and even some gasoline and I've never had issue one. You just make sure your stuff is contained in containers that don't leak and produce flammable vapors. Been heating and cooling the shop like that for at least 15 years now.