Fireplaces, Heating Stoves, Flues and Chimneys - Gas fireplace into existing chimmney

Is it possible to connect a gas fireplace into a chimmney that also has a gas furnace and gas water heater already connected to it?(all LP) I would like to put some kind of fireplace in our basement living area and I could reach the chimmney pretty easily from one spot in the basement. The chimmney is the standard cement block with square (clay?) liner. Thanks

If these are b-vent appliances each should have its separate flue. If the chimney liner is large you can use separate flue liners inside it as long as each has a continuous liner to the top and has its own termination. Dumping into a common flue has some potential problems including backdrafting which puts exhaust back into the living space. Having each unit with its appropriately sized liner means that the appliance will start drafting quicker and maintain a better draft. B-vent appliances burn room air to exhaust to the outside which means you have to have a source of combustion air coming into the room.

Masonry chimney liners are more massive and take longer to heat up and form a good draft. Most of them were made for wood burning which means you have a larger volume of air going up through the chimney.

Most appliances have a blocked flue switch which is basically a snap switch that kicks out and shuts down the unit. It detects excessive heat from a non-drafting situation and shuts the unit down.

Flexible aluminum liners are often used inside a larger masonry liner. They are cheap and easily installed. In colder climates it is a good idea to check with your local fire marshal or building code person.

If you can get to an outside wall you can often use a direct venting unit. Basically this unit is sealed to the outside. It has one pipe within another. The inside pipe directs exhaust gases to the the outside. The space between the inside and outside function to bring outside air in for combustion. An exterior cap keeps the exhaust and the intake separated and you are not dependent upon bringing in combustion air into the room. Being sealed to the outside means you don't have to worry about back-drafting as well.

Jim

I can get to an outside wall and a direct vent unit would probably work but how would I get the pipe through the wall?As I mentioned before this is in the basement so do you go right through the block wall and use one of those snorkles? You wouldn't want to cut that large of a hole in the rim joist would you? Thanks for the info

P.S. I see alot of homes with the same setup I have with the furnace and water heater going into the same masonry chimmney. Is that just the way they did it in the olden days? Ours has been like that for at least 20yrs and seems to work OK. Our carbon monoxide detector has never gone off.

It is true that there are a lot of them out there and they work okay. Older systems used to combine chimneys and even use barometric dampers. I still don't think it is a very good idea. In addition, there is a lot of moisture produced with gas combustion. That tends to collect on chimneys especially larger masonry chimneys where the velocity is low. This can deteriorate your chimney over time. Some colder climates require insulated liners through chimneys for that reason.

A lot of the older appliances were less efficient and put more heat up the chimney. This caused a better draft. Newer, more efficient units are more sensitive to drafts. Also, a house location (hillsides, trees, etc.) can cause draft problems.

Having a carbon monoxide detector is always smart. Also not a bad idea to have a propane leak detector. A neighbor of ours was extremely badly burned when he went down in his basement to light the pilot light on his water heater. Propane had pooled on the floor. When he went to light it it exploded. The fellow was very badly disfigured and had to undergo years of operations. After that I was always especially cautious around propane.

Snorkels work fine. I have one on a fireplace in my house. Simpson Duravent makes a tall and a short one. I always liked the tall ones better because I figured that the additional height makes for a better draft (we are in a mild climate here with potential for draft problems). They are a little pricey and you have to plan them out for wall thickness but they work fine.

Simpson makes a high wind cap that works better if you have winds around your house. Unfortunately they don't have it (or didn't have it a couple of years ago) in the snorkel. Simpson also will let you call them and talk to an engineer if you have any special concerns.

Many manufacturers specify Simpson Duravent venting. Some manufacture their own. Be sure to look at the installation manual before you buy a unit. Some are very flexible to install. Some are very limiting. I would also advise not buying an older or used unit. Direct vent units have come a long way over the years. Some of the earlier units had problems.

Jim

Do you typically go through the block wall or the rim joist with the venting system?

You could go through either one. Depending upon the size of the rim joist you would have to get clearance to the joists and the underfloor. The specifications on the chimney will give you side and top clearances.

You can also go through the block wall. Clearances would be less of an issue there. The rim joist is typically just serves a capping function over the green plate.

Jim

Jim, Thanks for all the info. Time to go shopping

Let me know how you come out.

Jim