big maxx 45k horizontal vent size

[icefisherman]

I know this was posted a while ago but I talked to Brad from mr. heater service today and he said the directions are not real clear on size , but it is suppose to be 4" when venting horizontal and it can be tipped down a little for condensation to run outside. I already ran 3" so its a little late now. I have had mine for a year with no issues. Anyone else using 3" venting on a 45k heater? If you are any issues? He told me to put a 90 degree elbow than a 12" straight piece than a rain cap on it. It will help if its really windy outside.

 

[flatheadguy]

Getting ready to install my Mr Heater 75K unit. I am under the impression that the flue size for 45K is 3" and the 75K 4". You might want to research a bit more. After all, I never make mistakes. (well, only once in a while....like daily.....smiling)

 

[sshewchuk]

45k is 3", Slope inward not out! Mine failed inspection because of this and the heater is now mounted 6" lower to compensate

 

[ggcdad]

What is the reason for an inward slope down? I would think that you would want the outside end lower so any rain water that gets in would not drain into the garage?

 

[toyotadriver]

I am interested in installing one of these in my future shop. I checked the install paperwork and it said that for a 45k btu unit, for venting it horizontally you should use 4 inch and for vertical venting you should use 3 inch. Obviously, you have 3 inch and it's working properly so I wouldn't worry about it.

I think the instructions also said to slope the pipe down inside the building but that really doesn't make any sense to me either.

 

[sshewchuk]

Well at first it didn't make sense to me either but the heater is designed to put the compensation through the burner. Very very minimal rain gets in. Another way to look @ it is if you vertical vent what direction does the condensation/water fall?

 

[bd8134]

I installed my horizontal vent pipe so it had a downward slope to the outside as my instructions said this was correct. There are installation manuals available here.
http://www.sterlinghvac.com/sterling-gas-product-literature.asp
For the vertical install they have what looks like a trap on the bottom. If you require a length of horizontal also, the slope is towards the heater.
They also said it depends on the gas code. I believe with these 'high' efficency burners and using propane the condensation might be high. I would think it would be best to not angle the vent pipe into the heater, hence the drip tee. See below.
http://www.littlegreenhouse.com/accessory/heater-pipe2.shtml

 

[Lambo nut]

I installed my horizontal vent pipe so it had a downward slope to the outside as my instructions said this was correct. There are installation manuals available here.
http://www.sterlinghvac.com/sterling-gas-product-literature.asp
For the vertical install they have what looks like a trap on the bottom. If you require a length of horizontal also, the slope is towards the heater.
They also said it depends on the gas code. I believe with these 'high' efficency burners and using propane the condensation might be high. I would think it would be best to not angle the vent pipe into the heater, hence the drip tee. See below.
http://www.littlegreenhouse.com/accessory/heater-pipe2.shtml

I installed my 75K Mr Heater the same way you did your Sterling, slope to the outside as I did not want anything coming back to the heater. Now your instructions are correct for your Sterling, but the Mr heater instructions clearly state the slope is back to the heater. 1/4 per foot to be exact.
http://www.northerntool.com/downloads/manuals/172645.pdf
Mine worked fine all last year so I am keeping it that way.

Kevin

 

[dave67fd]

Horizontal Category I/III Vent System Determination
• Horizontal vent systems terminate horizontally (sideways).
• A vent system that terminates vertically but has a
horizontal run that exceeds 75% of the vertical rise is
considered horizontal.
Most horizontal vent configurations are Category III. For
residential installations, this requires the use of an agency
approved (UL1728) Category III stainless steel vent system.
Additional requirements, including those for commercial and
industrial installations are covered in “Section C –
Horizontal, Category III Vent System Installation”.
If the application is residential and specific vent dimensions
and termination limitations are followed, the use of a less
expensive Category I vent system may be used.

See Table 7.3 Horizontal Category I Vent System Limitations in the modine manual, page 8
http://www.modineheaters.com/Modine-HD-Manual-After-5-07.pdf

The Mr. Heater manual states the same info but is vague and not discriptive enough for each application. The difference in the vent system classifies it as catagory I (negitive vent pressure non-condensing) or catagory III (positive vent pressure, non-condensing)

So if category I is used you must follow the proper dimensions, lengths, slope, number of 90's etc..

 

[BwBrown]

I too am installing two 75k units. My gas installer said:

If using single walled horizontal vent pipe, the exhaust should slope 1/4" to the foot inward and requires a condensate trap and drain.

If using insulated horizontal vent pipe, the exhaust should slope 1/4" to the foot outward.

Since his signature is required to hook things up, I'll be doing it his way. I guess each area has it individual code guy with his own interpretation.

The exhaust kit ordered with the heater from Northern Tool includes 3' of insulated 4" vent pipe. It also includes the correct through-the-wall clearance thimble. Insulated pipe requires 1" of space between it and a combustible material.

The instruction that came with the 75k heater spec'd 3" vertical and 4" horizontal.
I believe the 45k units can use 3" either diretion.

 

[Lambo nut]

I too am installing two 75k units. My gas installer said:

If using single walled horizontal vent pipe, the exhaust should slope 1/4" to the foot inward and requires a condensate trap and drain.

If using insulated horizontal vent pipe, the exhaust should slope 1/4" to the foot outward.

Since his signature is required to hook things up, I'll be doing it his way.

Yep, I used the insulated pipe on my horizontal sloping down to the outside, no trap. Gas guys looked it over, said it was good to go, then filled my 250 gallon tank.

Kevin

 

[toyotadriver]

I just installed my Mr. Heater Big Maxx 45k btu. I vented it horizontally with 3 inch double wall B vent pipe. The venting has a 90 degree bend, 4 foot vertical pipe, 90 degree bend, and a 2 foot horizontal pipe. The vent termination is about 1 foot from the wall and there is no soffits to worry about. I debated on 3 vs 4 inch but decided that since it uses a fan to vent the combustion gases, I couldn't see a downside to using 3 inch vs 4 inch.

I also sloped it down to the outside.

I checked the temps of the pipe with a non-contact thermometer. Temps were all safe.

Mine works fine.

 

[KCarGuy]

It could simply be, because if any Condensation builds up and flows outward (outside your building) and pools at a 90...If your heater is turned off and the water freezes, it could turn your 4" to a 3" or worse...a 3" to a 2" exhaust.
I am not sure, but thats the only thing that I can think it could be.
Just a Thought!