Clearance between exhaust pipe and wall

[bobj49f2]

I have a 30' 150 BTU LP fired radiant tube heater running down the long length of my 30'x50' pole building. I am exiting the outlet of the furnace tube with a 4" single wall pipe going out about 40" then turning at a 90° elbow and going across approximately 13' to an outer wall. The 13' run will be run along the back wall. What is the recommended clearance between the single wall and a side wall. The wall is 2"x6" stud, insulated with corrugated steel in inside facing the exhaust tube. Where I want to run it it will be about 9" from the wall. I can bring it out another 12" but then the pipe will be under LED tube lights by about 6", I'm concerned the raising heat from the tube will affect the lights.

Once I get it to the outer wall I will have a double walled B vent going through a wall thimble.

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[Jim greengo]

6" normally for s.w flue pipe around here anyway,b vent is 1"

 

[Jackfre]

I would be surprised with that long a horiz. run with single wall if you are not condensing in the far end of the pipe. Do you notice any moisture att the joints.

 

[bobj49f2]

I am in the process of installing the system in my shop.

Going with the installation instructions the pipe had to slant down 1/4" for every foot. So if this would be some condensation it should drain out the end of the pipe outside the building.

 

[Jackfre]

What type pipe are you using? Be aware that the Ph on flue gas condensation on gas is about 3.2. That is pretty hot.

 

[bobj49f2]

Single wall galvanized steel from the end of the heating tube to the wall, through the wall with a thimble and B vent. The furnace manufacturer supplied everything except the single wall pipe. Their instructions are pretty good, it has clearance information about everything except the single wall pipe. It does tell you what pipe to use. Just like Jim said, 6-9". I'll have 9". Cut the holes last night.

I was able to find some information on line about clearance. Amazing once I figured out what words to use.

 

[SGKent]

my guess is that the flue gasses will condense in the exhaust. You'll need some kind of exhaust fan to push the flue gases out. Most furnaces are designed for a vertical flue unless otherwise stated in the manual. Next the flue gases will be acidic and eat the flue. That is an opinion but usually the manual for the furnace will state that or something like it.

 

[The Cobbler]

....... You'll need some kind of exhaust fan to push the flue gases out. .......

it's a horizontal radiant heater . as far as I know, they all have a fan to exhaust

 

[bobj49f2]

Nothing in the manual about using a fan for flue gas. The unit does have a blower at the beginning of the system so I would assume that would do the job. The manufacturer gave me all of the parts I needed except for the single walled tubes.

I had two of these units in my old shop for over either years, set up the same way, and never had a problem with rust in the tubes as far as I know.

 

[Zaxxn]

Yes, they do have a fan at the burner end of the system. Most systems are controlled by a regular low voltage thermostat and the fan will actually stay running for 30 seconds or so after the burner shuts off to exhaust the remaining flu gases. My system actually lists different warranty periods on the radiant pipe if used with a line voltage thermostat (fan can't stay running) vs. a regular HVAC thermostat.

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[brewchief]

What brand/model heater? 30' seems short for 150k. Is there a max vent length listed?

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[bobj49f2]

A better description of my building (my profile picture, at least for now); it is 30'x50' with a mezzanine protruding 10' from the back wall, which makes the major area 40'x30' with a 15' high ceiling, with the area under the mezzanine 10'x30' with 8' high ceiling. The mezzanine is not heated, it is insulated from the rest of the building in the floor and walled shared with the shop space, this is the wall I am running the flue tube along.

The tube heater is from Detroit Radiant Products, Re-Verber-Ray brand. It is a two stage furnace, 100/65K BTU (mistaken about the 150 BTU size). It'll fire at 100K BTU to start, once it reaches temp it will keep the building warm at 65K BTU. I gave Detroit Radiant Product a detailed drawing of the building with how it was built, insulation and windows and doors and how I wanted to use the building. They did a study and came back with this unit being the proper unit for this building.

 

[brewchief]

A better description of my building (my profile picture, at least for now); it is 30'x50' with a mezzanine protruding 10' from the back wall, which makes the major area 40'x30' with a 15' high ceiling, with the area under the mezzanine 10'x30' with 8' high ceiling. The mezzanine is not heated, it is insulated from the rest of the building in the floor and walled shared with the shop space, this is the wall I am running the flue tube along.

The tube heater is from Detroit Radiant Products, Re-Verber-Ray brand. It is a two stage furnace, 100/65K BTU (mistaken about the 150 BTU size). It'll fire at 100K BTU to start, once it reaches temp it will keep the building warm at 65K BTU. I gave Detroit Radiant Product a detailed drawing of the building with how it was built, insulation and windows and doors and how I wanted to use the building. They did a study and came back with this unit being the proper unit for this building.

If I looked up the right unit it gives a max vent length of 20 feet, each 90 counts for 5 feet so you are going to be very close in vent length.

6 inches of clearance from combustibles is right for single wall pipe.

I will try to buy 5 foot lengths of 4" single wall 26 gauge pipe when venting a tube heater like that, less joints and looks better. Most of the time you will need to seal the joints with high temp silicone as well.( manufacturer requirement).

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