Hey - I imagine this is a strange question this time of year, especially since it will e 90+ degrees in some parts of the country. At any rate, I am in the process of researching how to install a direct vent gas fireplace. I have heard from one fireplace store that the higher the vertical vent goes (within reason), the nicer the flames will be. I have also heard that this makes the fireplace more energy efficient as the intake air has time to heat up. Another store told me that for my planned run through the existing chase (where the wood fireplace once vented) of roughly 18-20 foot, I would need a reducer otherwise the escaping hot air would move too quickly, draw the intake are in too fast, and result in a poor burn pattern as the flames would be blown about.

My question here is, which is correct? I do have the option of just going up about 4 foot and then out horizontally (about a foot of horizontal travel after a 90 degree elbow). Otherwise, I can do my first plan which is 2 45 degree elbows followed by about 18-20 foot of vertical rise. Note both are valid according to the install manual for the Mendota fireplace I am looking at.

If this is the wrong place for this question, please let me know.

Thanks!
Rob

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Originally Posted by dmrlook

Hey - I imagine this is a strange question this time of year, especially since it will e 90+ degrees in some parts of the country. At any rate, I am in the process of researching how to install a direct vent gas fireplace. I have heard from one fireplace store that the higher the vertical vent goes (within reason), the nicer the flames will be. I have also heard that this makes the fireplace more energy efficient as the intake air has time to heat up. Another store told me that for my planned run through the existing chase (where the wood fireplace once vented) of roughly 18-20 foot, I would need a reducer otherwise the escaping hot air would move too quickly, draw the intake are in too fast, and result in a poor burn pattern as the flames would be blown about.

My question here is, which is correct? I do have the option of just going up about 4 foot and then out horizontally (about a foot of horizontal travel after a 90 degree elbow). Otherwise, I can do my first plan which is 2 45 degree elbows followed by about 18-20 foot of vertical rise. Note both are valid according to the install manual for the Mendota fireplace I am looking at.

If this is the wrong place for this question, please let me know.

Thanks!
Rob

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This question is answered in your install manual for the unit. All other answers are just guess work and illegal. All units must be installed as per its listing in the install manual. This is UL and CSA standard.

Thanks HVAC1000 - I am not asking for guess work - would not be safe to rely on a guess. As both options I discuss are allowed per the install manual, I know both are a safe and effective means of venting the fireplace. Obviously, going ~20 foot vertical will cost quite a bit more in materials than 4 foot up and a foot horizontally. So my question is really one of aesthetics and efficiency. If vertical venting 20 foot would provide a better looking fire with higher efficiency (as one salesman told me), it may be worth the extra cost of materials. On the other hand, if the benefit is very small, or non-existent (as implied by another salseman at a different store), then I should just go the 4 foot vertical, 1 foot horizontal route and save on material cost and installation time (and safety as I won't need to climb on the roof).

Thanks again,
Rob

I have seen them installed both ways and never noticed a difference in what the fire looked like. The length of the flue/discharge pipe should make no difference at all with a gas fired unit as far as what the fire looks like.

Many units we installed years ago were done with the short pipe system then the carpenter would build a false chase to make it look form the inside like there was a chimney going to the roof.

A gas fired unit is preset for BTU output so the flames will be the same no matter what you do for a chimney or flue. Now there are some logs that look more real than others and I would try to find a unit that has the best looking fire.


Good luck with your install.