Can Stoker and Propane Boiler Share Chimney?

Wallknight wrote:What I still need to understand is the physics of why both cant be on that chimney. And why the coal must be on top. Makes no sense. I think yall are making this up!

The gas burner will put a large volume of waste gas out when running as it has a forced draft with a good size blower. That large volume will lift the coal appliance waste gases if it is above the gas appliance. What do you think will happen if the gas appliance flue is above the coal? Like sting says, you can prove it doesn't matter but you won't be able to crow about it 'cause you'll be dead.

rockwood wrote:The pipe isn't big enough

Wallknight wrote:BTW- that pipe is probably 8". Definitely larger than the Alaska exhaust.

What I meant is the 8" pipe isn't big enough to handle both appliances operating at the same time while connected to said pipe.

the coal appliance must be the highest because it is the appliance with the largest draft requirement. a coal stoker will want to pull -.02 min and probably more, a hand-fired stove will like -.04 to operate and -.05/6 to operate well. The propane furnace has almost no draft requirement - simply enough draft to evacuate the flue gas volume from the top of the appliance and no more, this is why it has a draft hood - it virtually eliminates any draft that the chimney is pulling and prevents the appliance from ever "seeing" it.

You do not want to "T" into the the furnace flue for three reasons: 1. Improper draft and volume/capacity for both appliances. 2. Flyash buildup will occur and potentially cause a problem should you wish to switch to propane. 3. The pipe is TOO CLOSE to the floor joists of your home and should never have been installed that way initially, that IS a fire hazard. Also make absolutely sure that you don't "dead end" the chimney, there must be another hole knocked in the stack below the lowest flue connection for a cleanout, otherwise flyash will buildup at the thimble of the lowest appliance and cause a very significant risk of death from CO. Most of us aren't trying to scare you, we're trying to be honest about the risks of not doing something safely.

Wallknight wrote:Single-flu brick chimney- center of house, inlet in basement- Roughly 40' tall. I'm almost certain at some point it had a coal stove in it. Now, it has an old propane boiler exhausting through it. I just got a Kast Console II (goodbye Surdiac!). Can I share the chimney with the propane boiler? Both would be in the basement.

Call Burnham boiler in the morning and tell them you bought a used Woodlander SFB-101boiler and if they could send you a manual for it (they will ). That manual shows in Figure 11 the proper installation of a solid fuel appliance and gas/oil appliance using one flue. It requires a damper be installed on the gas/oil appliance that TEEs into the coal appliance stovepipe.

coaledsweat wrote:It requires a damper be installed on the gas/oil appliance that TEEs into the coal appliance stovepipe.

Wouldn't a damper be dangerous if when closed the oil burner or gas burner fired? It seems to me there would have to be some sort of safety switch to prevent this in the event it was neglected to open it manually or if the oil or gas fired automatically.

franco b wrote:

coaledsweat wrote:It requires a damper be installed on the gas/oil appliance that TEEs into the coal appliance stovepipe.

Wouldn't a damper be dangerous if when closed the oil burner or gas burner fired? It seems to me there would have to be some sort of safety switch to prevent this in the event it was neglected to open it manually or if the oil or gas fired automatically.

The stack damper opens as soon as the boiler powers up and closes at shutdown. It would mount on the gas appliance.

http://www.fieldcontrols.com/pdfs/46352700.pdf

Berlin- Thank you for your KNOWLEDGEABLE explanation. How much higher does the coal need to be?

Also: What is code for the LP pipe? I've got 5.5" to the nearest joist. Not much I can do with it. The draft hood could only be lowered 1" according to the stamp on the side. Probably been like since well before I was born.

Power Venter fan: Why in the world would I drop $400 on a venter to upgrade a boiler that should have died decades ago? You must be the type to put turbo boosters in '84 Yugo's. My original plan was to rip the whole thing out and replace it with a totally different system, but decided to first check to see if there was a more elegant solution.

Wallknight wrote:What is code for the LP pipe? I've got 5.5" to the nearest joist. Not much I can do with it. The draft hood could only be lowered 1" according to the stamp on the side. Probably been like since well before I was born.

Single wall pipe should have 18" of clearance. There are plenty of installations that have less, but 5.5" is pretty tight. You could use double-wall pipe (needs 6" clearance), or install cement board on the joists with 1" spacers. Since you can't lower the draft hood more than 1", your options are limited.

Wallknight wrote:Power Venter fan: Why in the world would I drop $400 on a venter to upgrade a boiler that should have died decades ago? You must be the type to put turbo boosters in '84 Yugo's. My original plan was to rip the whole thing out and replace it with a totally different system, but decided to first check to see if there was a more elegant solution.

A power venter was suggested because it would solve the problem of different draft requirements for each appliance, and allow you to install a thimble for the coal appliance with the proper clearance from the joists. As it stands right now, you can't drop the propane flue pipe enough to get a second thimble installed, and installing a tee in that pipe still leaves the fly-ash issue.

Wallknight wrote:My original plan was to rip the whole thing out and replace it with a totally different system, but decided to first check to see if there was a more elegant solution.

If you can afford it, a stoker boiler installed in-place of the LP unit would be a great solution.

Berlin wrote:Lisa, I have no problem at all with different options being presented or different "points of view". What I don't like is for someone to be unnecessarily scared away from doing something that is not unsafe. It was acceptable for years to have two appliances in the same flue if the one thimble wasn't too much higher than the other (same story for example). It is STILL acceptable and extremely commonplace for more than one appliance to be connected to the same flue providing the chimney can handle the exhaust volume, and they burn the same fuel. All the concerns about flue gas exiting the the draft hood on the other appliance could happen in most homes in america today - because most have more than one appliance connected to the same flue, often two gas furnaces or a gas furnace and water heater. these scenarios don't change whether or not one of those appliances happens to be a coal stove..

Gee Berlin,

Obviously I don't know your engineering back ground but I always pay attention to what you have to say because it always makes sense and you have this incredible body of knowledge I want to tap into but the building code is the building code and no matter what your or my personal feelings or experiences are is going to change that. Failure to compile with that code will have consequences if things go bad. It won't matter if it's been done that way forever or done by millions of other people. You can continue to deny that the insurance company doesn't care but I know different, They are in it for the profit and their shareholders. I know that the county will fine the owner for any work they discover that was installed not up to current code. Been there, paid a hefty fine to the county. No, they won't come looking for code violations but if they see them on other visits, they will make you change it and they will fine you for any work completed after the code was updated. They don't care that it's always been done that way. Ask me about my gas water heater sometime.

That was always my point and it still is. I'm sorry that you are having an issue with it. I said it because I believe its an important point and now it's up to whoever reads it to act on it or not. I'm not trying to scare anyone away from doing things themselves but they asked for input and I gave mine. End of story or it should be.

As a side note, I just picked up a wood burning insert for my sister in GA who because of finances will not be able to install with the recommended full chimney liner. Thankfully, that's not the current code, only a recommendation. We will meet the current code and we will pull the permit because it's important. Current code says that the exhaust pipe must extend up the chimney past the 3rd tile or about 3 to 5 feet. Thanks to you and others on here on the forum my son and I can handle that and help her deal with her "necessarily skyrocketing" energy bills. Lisa

coaledsweat wrote:

franco b wrote: Wouldn't a damper be dangerous if when closed the oil burner or gas burner fired? It seems to me there would have to be some sort of safety switch to prevent this in the event it was neglected to open it manually or if the oil or gas fired automatically.

The stack damper opens as soon as the boiler powers up and closes at shutdown. It would mount on the gas appliance.

http://www.fieldcontrols.com/pdfs/46352700.pdf

This is the easiest, safest, solution without spending a lot of money. Not recommended if there is a steady pilot light for the gas burner. There still remains the problem of getting the pipes lower, so insulating the overhead and the pipe is the only way to go.

Pilot light.