Atmospheric Vent WH in Garage

[ajohansson]

Hi I have 2 NG atmospherically vented water heaters in my garage.

I plan to put in a split ductless AC system in this summer. I have a question about the vents that are on one wall in my garage. Its obviously going to bring in outside air but the question is how much. They sit about 4" above the bottom plate. I have 3 of them they are about 6" tall by 12" wide. Are those to provide air for the water heater combustion?Curious how mush air infiltration is caused by water heater combustion through out the day.

Wondering if I should enclose my water heaters in a closet and add an outside air source for it. I do have living space above my garage and the The exhaust venting goes up a chase and terminates above the second floor bedrooms.

Perhaps all this doesnt even really matter...

all info appreciated.

AJ

 

[Dana]

The additional cooling load of the higher air infiltration related to having a couple of atmospheric HW heaters in the garage is really "in the noise" of how much air infiltration a random garage door might have. In CA where the latent loads are low or even negative most of the time it's even less of an issue than in locations with high outdoor dew points.

The parasitic draft of the flue chases are probably higher than the combustion air driven infiltration.

Spending the time & money on air sealing the walls & ceiling, and fixing any window/door weatherstripping issue would have higher value than building an isolating closet with a dedicated outdoor make-up air vent.

 

[Sponsor]

 

[ajohansson]

ok thanks.

As far as the water heater goes and adding a split ductless AC unit when I do replace the water heater I am going to put one in instead of two.

Would it make any sense to put in a damper model and also put a damper on the vent pipe. They would fire at the same time is the plan. This would reduce the as you put it "The parasitic draft of the flue chases are probably higher than the combustion air driven infiltration". Basically would this help retain the cooler air I have in the garage when the water heater is not firing? My though thought is when the water heater is not firing air is going up that pipe and out however its the warmer air in the garage. In winter this would keep cooler air from coming in the garage as well. Perhaps this is even too finite to even calculate.

The fear I have with a dual damper system is if the damper on the pipe didnt open and the one on the water heater did I would fill the garage with CO. I do have CO detectors but not sure that is worth the risk of a malfunction like that.

AJ

 

[Jadnashua]

When it comes time to replace the WH, you could look into one that uses closed combustion...those draw their combustion air from outside via a dedicated pipe. They are more expensive, but also tend to be more efficient.

 

[ajohansson]

thanks the vent pipe goes all the bay to the roof of the two story house I wonder how hard it would be to get that type of vent pipe in there that has the two sections. At this point I think im just gonna replace with a regular atmospheric vent which has its own plumbing issues now which I am starting a new thread on.