Horizontal Vent for Mr Heater Big Maxx

[theKiwi]

I've just had a new barn built for me - 24 x 40 x 12, and bought a 50,000BTU Big Maxx heater for it. I was planning to vent it horizontally out through a side wall with the 4" Category III vent, but looking in the installation instructions it mentions that the termination must be 4' below or 4 ' horizontally from any vented soffit - of which the whole side has it.

So one idea is to run the pipe out through the wall at least the required minimum of 12", 2' below the soffit, and then put a 90° bend facing downwards, with 2' of pipe under that and then a T termination, so that the outlets on the T would be at least 4' below the soffit.

See my crude hand drawing below.

Is that permissible, or does a horizontal vent have to remain horizontal for its entire length (apart from the ¼" slope per foot)?

(I do have a call in to our local building inspector about this too).

Thanks

Roger

 

[allinon72]

I don’t think that would fly as flue gas doesn’t really flow downhill. You’d probably be better off just living with the 2’ clearance from the soffit, or extending it out further. Can you lower the heater at all to get you closer to 4 foot?

 

[TractorJeff]

You sure its 4 feet?
Mine is 24" from the Vented Soffit with a horizontal TEE to stop the North wind from blowing into it.

 

[Twodawgs]

I believe you can do this with category III vent piping, but only with a appliance that has positive flue pressure.

 

[theKiwi]

I don’t think that would fly as flue gas doesn’t really flow downhill. You’d probably be better off just living with the 2’ clearance from the soffit, or extending it out further. Can you lower the heater at all to get you closer to 4 foot?

I don't want to lower it that far - I have a 12' ceiling, but wanted the heater up out of the way at say 10' above the floor.

Roger

 

[theKiwi]

You sure its 4 feet?
Mine is 24" from the Vented Soffit with a horizontal TEE to stop the North wind from blowing into it.

The instructions in both the heater manual, and the manual for the Saf-T-Vent flue say 4' horizontally or 4' vertically from vented soffit.

I do have a T termination for the end of the flue.

Roger

 

[theKiwi]

I believe you can do this with category III vent piping, but only with a appliance that has positive flue pressure.

Yes, I'm using Category III pipe, and yes, the heater has an exhaust fan blowing the exhaust down the flue.

Roger

 

[theKiwi]

UPDATE

I spoke with our township's building inspector, and he gave me the contact details to the company who does our township's mechanical inspections. I described the problem to him, and he said all I need to do is get out clear of the edge of the soffit by say 4-6 inches. So 16-18" out from the wall. He seemed more concerned with which wall this was on in terms of the prevailing winds here and when I told him I had a T for the end he said I'd be fine.

So if I do that, and he comes to inspect it, then it will pass it seems.

Thanks Everyone

Roger

 

[Showkey]

Never got this prevailing winds concern........the wind can blow from any direction with any speed. If the furnace can not handle the winds at all time, every time, that would be a problem.
Power vents seem to be immune to wind issues.

 

[allinon72]

Never got this prevailing winds concern........the wind can blow from any direction with any speed. If the furnace can not handle the winds at all time, every time, that would be a problem.
Power vents seem to be immune to wind issues.

Certain areas are known for winds that come in one particular direction. If the wind blows down a horizontal flue it could significantly impact performance or cause the heater to lock out.

 

[Showkey]

Certain areas are known for winds that come in one particular direction. If the wind blows down a horizontal flue it could significantly impact performance or cause the heater to lock out.

Guess that’s why they put end caps of various design.

 

[allinon72]

Guess that’s why they put end caps of various design.

The prevailing winds concern isn’t conjecture, it’s listed in the manual of nearly every manufacturer’s manual. Maybe it’ll be OK, maybe it won’t, but it is to be taken into consideration.

 

[TractorJeff]

That is why I put a TEE on my Horizontal pipe! So the North wind will not blow into it. It is positioned East/West on the theory of venturi effect from the West wind.

 

[Showkey]

The prevailing winds concern isn’t conjecture, it’s listed in the manual of nearly every manufacturer’s manual. Maybe it’ll be OK, maybe it won’t, but it is to be taken into consideration.

The point is winds are variable in strength and direction.

If this a big problem heaters, furnaces and water heater would lock out and cause problems all the time. Go on vacation for week to come home/shop to frozen pipes because the wind blew in the wrong direction.....does not sound like a reliable heat system. Seems any power vent heater can handle 60-75 mph winds with no issues. 20- 30 mph winds might a weekly condition in many areas.

As for being practical vent pipes are very rarely out the front of a building , windows and door win over the chance of wind direction which can not stopped or predicted.

If I was concerned ........snow drift over the inlet or outlet would be far more common. Obviously there’s a standard pipe placement and height regarding snow.

 

[theKiwi]

That is why I put a TEE on my Horizontal pipe! So the North wind will not blow into it. It is positioned East/West on the theory of venturi effect from the West wind.

I have a T for the end of the pipe and was going to place it vertically so that all wind would in effect be going past the ends of it (well except for a good downdraft or updraft I guess.

Roger