B vent sizing question

[jborge]

I live in a townhouse that has a 20 year old cheap condo sandpan type gas fireplace. I am planning renovations and I have been looking at my options for replacing the fireplace.

I am researching the B vent. I have not opened up the wall yet, but I have removed the louvers and measured a 4" bvent coupling.

So I am assuming a 4" Bvent or possibly a 5" Bvent pipe to the roof.

The bvent pipe length is about 30 feet to the roof straight up with no horizontal runs.

4" bvent is limiting for what I can choose for a fireplace that looks nice. I am still researching. I found a useful bvent application guide from Duravent that has educated me quite a bit.

Would it be possible to couple a 5" collar to a 4" bvent using a reducer? That would give me at least some options for upgrading the fireplace. The new fireplace will be no more that 24000 BTU. So looking at the Bvent tables even a 4" Bvent would be adequate for a 30' vertical rise.

I realize that the size of the vent is also a function of maintaining a proper draft.

Unfortunalty most of the nicer Bvent fireplaces are 6", but FMI seems to make a nice one from the Vantage line that is 5" Bvent.




Thanks for your advice in advance.


Jan.

 

[DAKSY]

Why B-Vent? Just curious, since a Direct Vent will work just as well, if not better. You won't have to worry about ANY draft. The DV units draw whatever combustion air is required from the outside & as long as the glass is sealed, there's no issue with CO.

 

[FanMan]

But he's already got the B-vent piping in place...

 

[DAKSY]

But he's already got the B-vent piping in place...

OK. MIssed that. I'd STILL go DV. Sounds like he's tearing the fireplace out anyway...

 

[jborge]

Why B-Vent? Just curious, since a Direct Vent will work just as well, if not better. You won't have to worry about ANY draft. The DV units draw whatever combustion air is required from the outside & as long as the glass is sealed, there's no issue with CO.

Valid points on the DV.

This is a corner installed fireplace. I can direct vent out the back wall, but I would have to get permission from the Strata (townhome) to add the vent, also it would stick out on a narrow balcony area.
One of the key reasons for me on pursuing B vent is I am looking for the openness of a B vent fireplace which is part of the renovation plan.

There are many beautiful direct vent options out there, but the glass front kills it for me as I am looking for a direct view of the flame. The fireplace is not a primary heat source, and I am aware that BV is not as efficient as DV.


I am just trying to figure out my options with the 4" bvent sizing. It goes up in a straight line 30 feet.

Jan.

 

[DAKSY]

All the B-Vent units that I've ever seen ALSO have glass fronts on them. If they didn't, you would end up with the same NO HEAT condition of an open fireplace. Waste of money, IMHO, as all your heat goes up the flue...

 

[Ironhorse74]

I am with Daksy on this one. If you are going to the expense of tearing out an ineffective old B-vent unit do it right and install a direct vent. You should be able to open up the chase the B-vent goes through and install direct vent. You do realize direct vent does not have to terminate horizontally,

Peace

Brad