Chimney venting question

Jake2010

I have looking into replacing my oil boiler, for my 2000 sf, 50,000btu heat loss house with Weil Mclean 40 gal indirect.  I was deciding on the Burnham MPO 84 or 115, or Buderus g115/21. It has been recommended that I line the chimney with a SS liner.  I just realized my clay lined chimneys interior dimension is about 6.25 x 11.5 in.  I have realized that I will not be able to fit the required 6in SS liner for both boilers down this chimney.  Where do I go from here?  Any suggestions would be really appreciated.

ChrisJ

Ouch

I just recently had to have my 110 year old brick chimney torn down and replaced with a B-vent for the same reason, only my opening UNLINED (no clay) was 4"x7".  I am using a steam boiler so direct vent wasn't an option and I wanted to avoid a noisy power vent. 

During my fun adventure I had learned they do make rectangular liners, my problem was the top half of my chimney had been rebuild square.



Will a rectangular liner give you the necessary venting?  Also keep in mind the venting goes by the liner manufactures specifications, not only the dimensions.

CMadatMe

Direct Vent

Find a boiler that you can direct vent. Viessmann has the Vitorond 100 in the size boiler direct ventable.

PeterNH

Poured Liner

Hello Jake,

Check out Golden Flue.

http://goldenflue.com/index.aspx

I had this done and it is amazing.

Insulating to beat the band.

Cost is reasonable.

MYy 36+ ft chimney 12" square unlined brick,

now has 3 flues, 6 inch for the boile, 4 inch for the gas stove

and a 5 inch spare for possible pellet stove.

Took 2 days and no mess.



Peter

Jake2010

No place to direct vent

The way my basement is situated I do not think I would be able to direct vent.  It would have to be near windows and deck.

bob eck

venting question

why are you using two boilers?

Jake2010

Boiler choices

Those I mentioned were the ones I was considering. I am only using one boiler.

ChrisJ

Chimney liner

Jake,



What is the input BTU rating of the boiler? We also need to know the height of the chimney, this is just as important as the diameter. How long of a horizontal connector from the boiler to the chimney is also important.



in a 2000 sqft house it seems strange that a 6.25"x11" chimney cannot handle a liner big enough. a 6" liner should be more than enough, in fact I would think a 5.5" is plenty as long as its in a 2 story house.



If I recall, I was going to connect a 150,000 btu input boiler to a 5.5" liner x 33 feet and it was going to meet the specifications from the manufacture of the liner. This was for a SINGLE appliance.

Jack

Appendix E in NFPA31

Has reliable sizing info on liners. Being an appendix it is not really a part of the code, but has been an index for almost 20 yrs and the sizing info has proven accurate, from the system I've been involved with and discussions with others. Oil venting requires L vent. In your case, you could look at Dura Vents Dura-liner. Excellent reclining system and I installed the 8" ovel in my fireplace for a wood stove. Works great and comes in sections. When I was in a real pinch on a System 2000 job years ago we actually lined the deteriorated flue with 4" pellet vent, which is L vent. With the very low firing rates you are discussing you can probably do 4or 5". Unfortunately I am unable to look up the numbers for you as I am still missing a lot of my trade books since I moved.

Jake2010

chimney height

Chimney height is about 25ft, it is a two story house. The horizontal is about 3 to 4ft. The Burnham MPO 84 and Buderus g115/21 both have a net output of 74,000 BTU. I called Buderus and was told I definitely need 6in, have not contacted Burnham yet. Theoretically it seems that a 6in liner would fit in a 6.25 x 11.5 clay liner.  However, the T connector that has to go down first is a little bit bigger than the liner.  I have spoken to liner distributors and they have said you really need about an inch more than the actual liner size.  They clay liners are not always exactly straight so you need a little bit more room.  My chimney is in good shape. I just do not want to buy a three pass boiler and have to raise the stack temp to guard against condensation, thus lowering the efficiency and my purpose for spending the money on it.  Any other boiler options could also be considered.

ChrisJ

Tee

When the pros were setting up to line my chimney they busted open the bottom area where the tee was going to go. They were then going to slide the liner down the chimney into it.



I don't think the tee "must" go on first in all cases, there are work arounds.