[thefury8509]

Hello,

I was wondering what the best way to combine my furnace and water heater vents would be. The reason is that I need to install a chimney liner and vent them both into it. Both are 4" vents, and based on what I've read, I should be able to safely combine both into a 5" pipe and chimney liner. 5" also seems small enough that if I have to replace my furnace then I can orphan the water heater and not worry about the vent size still.

Both vents currently run horizontally into the side of my chimney, the water heater vent above the furnace vent by about a foot. Am I able to safely use a 5"x4"x4" wye for this or is there a better way?

I know that the water heater vent needs to go above the furnace vent in order for it to vent properly. The problem is that most diagrams that I've seen for this has the vent running straight up instead of horizontally into a chimney so I'm not exactly sure how it should look or if it's even a good idea.

I'm attaching some very ugly diagrams of what I currently have and hopefully what a potential option is. Water heater is 40,000 BTU. I can't recall the furnace off the top of my head, I need to try to find it. It's a relatively small home though so I can't imagine it's too high. If this is something best left to a pro, that's fine too. Installing the actual liner seems simple enough so I wanted to try to save a little money if possible... but if that's a bad idea then I have no problem leaving it to somebody who knows that they're doing. I really don't want to deal with backdrafts and venting problems.

Thanks in advance!

 

[WhatRnsdownhill]

standard chimney liner is 6 inch stainless steel..you would be better off using 6 inch and this would give you buffer if you increased the boiler or water heater load down the line, then connect with a 6 x 4 x 4 flue Y...

 

[beenthere]

That will work fine. Configuration wise.

 

[thefury8509]

Ok great, that's good to hear, thanks! Does it have to be stainless steel or does aluminum work? From what I've seen the aluminum liners are ok if I'm doing only gas appliances. Also, knowing that I'm only doing gas, do I need to insulate the liner?

 

[beenthere]

Depends how high the chimney is. If too high, the combusted gasses could cool enough to condensate in the liner. Aluminum liners can pit through. If not real high, aluminum is fine.

 

[yuri]

Depends where you live. Where I am you must use B vent and it must match the appliance size/combined BTU's closely. If you have 5" B vent and orphan the water heater it may be OK and not condense inside depending on the furnace size. Cooling the smoke/flue gases down is a BAD idea as it can cause the furnace to run too cool and you can get condensation/corrosion in the inducer fan or collector box. All depends where you live and how cold the chimney can get plus the height.

 

[WhatRnsdownhill]

aluminum not code by me, its junk it will rot away fast, its so thin....the stainless is a few more hundred and will last a long time...

 

[yuri]

I have seen 25-30 yr old aluminum liners. I would be more concerned with condensation and running it too cool. The inside of B vent is aluminum and does not corrode. If aluminum touches dirt from a leaking masonry chimney which goes below grade it can corrode faster.

 

[WhatRnsdownhill]

most liners are going in chimneys that had oil equipment, so the combo of the cement and oil soot will take out aluminum fast..

 

[supers05]

I assume these are 80% or less appliances? I've recently used a chimney liner for a 98% boiler, but that wasn't cheap.

As long as both vent in the cat I range, your configuration works fine. I

PS. When a chimney with a liner is properly sealed, for all intensive purposes, it is B-vent.

Cheers!

 

[yuri]

most liners are going in chimneys that had oil equipment, so the combo of the cement and oil soot will take out aluminum fast..

Hate to argue but Winnipeg where I am had oil from the 1950's to the late 70's. Then we had a Federal Gov't program to replace them and 95% got done. I have seen thousands of oil to gas jobs. However if the chimney is dirty with soot it should be cleaned before installing a liner. Soot is corrosive as oil had sulphur in it. Point being it is a rare scenario IMO and not one I would worry the OP about. Good point to check though.:smile:

 

[yuri]

I assume these are 80% or less appliances? I've recently used a chimney liner for a 98% boiler, but that wasn't cheap.

As long as both vent in the cat I range, your configuration works fine. I

PS. When a chimney with a liner is properly sealed, for all intensive purposes, it is B-vent.

Cheers!

Not really. Where I am it can get -40F/C inside the chimeny. If you have a single wall liner in a 8" masonry or clay tile liner the sheer amount of air that needs to be kept warm is probably 10X that of what is between the liner and outer liner of a B vent. Maybe in Ontario or warmer areas that is not a problem but I have seen them ice up. They also get very cold and are hard to get drafting at startup or will spill. Natural draft water heaters are very bad for that.:wink2:

 

[supers05]

Not really. Where I am it can get -40F/C inside the chimeny. If you have a single wall liner in a 8" masonry or clay tile liner the sheer amount of air that needs to be kept warm is probably 10X that of what is between the liner and outer liner of a B vent. Maybe in Ontario or warmer areas that is not a problem but I have seen them ice up. They also get very cold and are hard to get drafting at startup or will spill. Natural draft water heaters are very bad for that.:wink2:

Last time I checked, northern Ontario gets just as cold as you guys, and they use the same rules as us. (Actually next week even the south will be cooler then Calgary. (I know it's not common, but funny to note) I do get that you guys deal with the extreme cold for longer, so using triple wall venting is needed. (chimney, bvent outer and inner wall) It makes sense, I was just mentioned the semantics of it.

Cheers!

 

[WhatRnsdownhill]

Hate to argue but Winnipeg where I am had oil from the 1950's to the late 70's. Then we had a Federal Gov't program to replace them and 95% got done. I have seen thousands of oil to gas jobs. However if the chimney is dirty with soot it should be cleaned before installing a liner. Soot is corrosive as oil had sulphur in it. Point being it is a rare scenario IMO and not one I would worry the OP about. Good point to check though.:smile:

if code in your area allows aluminum then you can use it, the code here does not..and all flue piping out side of the chimney is steel, no aluminum either.. no argument intended...:smile:

 

[yuri]

Yeah, we don't know where the OP lives etc. I always post info for future readers not just the OP.

We have had problems with water heaters that won't draft because the chimney gets so much cold dead air. Couple that with running a exhaust fan and clothes dryer and central vac and you get downdrafting. Plus once that starts it is impossible to generate enough heat to reverse the draft. I have seen 150M furnaces spilling full blast out a draft diverter once the chimney got downdrafting full blast. Can also cause pressure switch tripping. They went with 4" venting on water heaters because of the cold chimney problem. If you want to test furnaces for worst case cold scenarios you go to Winnipeg or Alaska. They test cars in Thompson (Ford etc) plus tires. We know cold in Manitoba.

 

[yuri]

if code in your area allows aluminum then you can use it, the code here does not..and all flue piping out side of the chimney is steel, no aluminum either.. no argument intended...:smile:

That is expensive but in the long run worthwhile. I have seen aluminum liners rot thru and dirt fall thru the missing/ loose mortar in brick chimneys if below grade and fill the liner up to the furnace takeoff. That and when they get pinholes and drafts go thru the mortar and into the chimney on windy days it can cause pressure switch tripping. Aluminum is cost effective but does not last forever. Still better than galvanized. I replace hundreds of miles of galvanized venting on oil furnaces and gas.

 

[WhatRnsdownhill]

That is expensive but in the long run worthwhile. I have seen aluminum liners rot thru and dirt fall thru the missing/ loose mortar in brick chimneys if below grade and fill the liner up to the furnace takeoff. That and when they get pinholes and drafts go thru the mortar and into the chimney on windy days it can cause pressure switch tripping. Aluminum is cost effective but does not last forever. Still better than galvanized. I replace hundreds of miles of galvanized venting on oil furnaces and gas.

a stainless steel liner kit is about $550 in change and an aluminum kit of the same length is about $300 in change....not too bad a difference...

 

[supers05]

We know cold in Manitoba.

Yes, this is true! That's why I like my southern location, away from you snowman... Lol (you know when you're in the north when you use economisers for freezers....)

The last chimney liner we installed was all stainless, rated for cat IV. Had to be custom made, and very expensive. (cheaper then 6" cpvc and a crane to install several lengths though)




Cheers!

 

[yuri]

a stainless steel liner kit is about $550 in change and an aluminum kit of the same length is about $300 in change....not too bad a difference...

Yeah but in a highly competitive market that $200 won't go over well. We are very cheap in Winnipeg. Old Ukerainians who collect coupons. Used to be the gas coupon capital of Canada. They did away with that but people would hoard them and go out of their way to use them. Now we have Canadian Tire money. Our 2nd official currency.:smile:

 

[yuri]

Yes, this is true! That's why I like my southern location, away from you snowman... Lol (you know when you're in the north when you use economisers for freezers....)

The last chimney liner we installed was all stainless, rated for cat IV. Had to be custom made, and very expensive. (cheaper then 6" cpvc and a crane to install several lengths though)




Cheers!

I have seen everything from natural draft furnaces to 350 hp (+) high pressure steam boilers with 24" steel chimneys. Also spent some time at the U of M and they have 2 story 1000 hp steam boilers with superheaters and a steel recovery wheel that rotated thru the chimney and back into the air supply for the burners.

We had a incinerator at the hospital in Dauphin and we had to get a Litz crane in to replace the chimney cap. Big steel job with screens so the ashes would not fly out. Had a pathological burner in for body parts. Yeah I been around the block quite a few times. Interesting trip though.:wink2: