Vent wood stove through faceplate over zc fireplace?

[jimychelita]

We have a 20 year old Superior FR3870 zc fireplace that we have not used in the 6 years we have been in the house. It appears to be in good shape.

Now my wife and I are wanting a freestanding wood burning stove for the hearth.

Idea is to set up like the Regency H2100 "hearth heater", namely observe clearances for combustibles from the back of the stove, and go into the zc fireplace with horizontal connector, then up with 6" ss liner. Want to cover the face with a tiled backerboard.

Max height above the hearth for the top of the flue collar is 26 inches. There is a 2x4 header across the top of the zc fireplace, which could be replaced with steel, if necessary.

I have mixed signals from installers/sweeps on this installation. Hearth.com has a sort of general statement, but ends with "contact a licensed installer" or something similar. Any suggestions? Dangerous or no?

Thanks.

 

[jimychelita]

Well, even after looking for a long time before posting, I still didn't find an answer to my question. Then, of course, after I posted I found several threads with answers, including some references to Hearthstone Homestead.

 

[Gooserider]

Certainly it takes a review from an installer that can actually eyeball your situation - we can't be totally certain about what we can't see and that's a problem we can't really work around.

That said, part of the question is EXACTLY what you have. You say it's a ZC fireplace, but that can be hard to tell sometimes. There are also metal "heat form" fireplaces that look like ZC units, but act more like traditional masonry fireplaces, and which can have stoves put into them with minimal problems.

The key issue is the chimney. ZC fireplaces generally come with a special manufacturer designed and specified chimney, usually air cooled, that matches up ONLY to the particular models it is tested for, and the ZC fire box is only intended to be installed if used with that specific chimney - the two are a system that must be used together. The firebox and chimney are engineered together to provide (barely) sufficient cooling and thermal protection in order to allow the system to be installed next to combustibles without all the clearance and other construction requirements of a conventional fireplace and chimney. Because of the specific engineering to reduce the clearances, any modifications to the chimney risk changing it's thermal characteristics so that you risk overheating the nearby combustibles, and therefore are not allowed.

Note that there are a FEW cases where specific ZC stove models have been tested and approved for use with certain stoves, when installed in a specified way, but this is not common, and requires that you have an exact ID on the make and model of the ZC unit, probably from a data plate.

A "heat form" type fireplace may have a metal box, and might even be engineered to be installed with reduced clearances, but is normally connected to a standard clay tile flue, masonry chimney or a "generic" Class A pre-fab chimney that was designed for use with any appliance. These units can be fitted with a stove as long as it's done properly using normal NFPA blessed materials and techniques.

The trouble often lies in figuring out just what you have, which is where the "profesional eyeballs" come into play.

Good luck and welcome to the Hearth,

Gooserider

 

[jimychelita]

Thanks for your thorough reply.

The chimney question is one that vexes me. If I run 6" ss liner up the chimney is that a modification? or is the new liner operating pretty much independent of the existing larger diameter pipe?

It has been a bit of a bad dream trying to get a wood stove into the house. What looked like a simple case of using an existing fireplace as a channel to vent through has become a real tar baby. Even when I think I have a fix, like Hearthstone Homestead, which fits perfectly into the opening, I discover that the plenum on back of the Homestead needs to have nothing below it but 4-6 inches of air, followed by hearth. At least it appears so. In our fireplace the back plenum would be resting close to the fake firebrick. Got to go see a chimney sweep again (7th or 8th visit).

I've had wood stoves before, so I believe this quest will be worth it...someday.

 

[elkimmeg]

Instalation into ZC do present problems the first of which what is the UL listing of the current ZC
There are some inserts that only can be installed in a certain UL listing

Homesaver does make a tested and listed liner system that can convert a ZC venting systyem to code compliance for a wood stove application

Finally the stove/insert has to be listed for ZC installation

I also think if you have a wood header that close and the entire opening built out of wood this seems like a situion that has to be addressed

Another way most resort to, is by ripping out the Zc and starting fresh with a corect ZC enclosure and venting system

 

[webbie]

Elk has it.

In my way of thinking, there is NO stove made that it is OK to install in front of a prefab and pass the pipe through a plate, etc.

The two options are:
1. Approved ZC insert which sits IN the fireplace, not in front
2. Rip it all out (chimney and fireplace) and install built-in high efficiency unit or freestanding stove and new class A chimney.

That's the simple answer. As you will see by some other threads, we have dealers here who have done what you suggest....and say it is common in their part of the country and passes inspection. Take my word for it - that does not mean it is an approved installation, it isn't!

 

[wg_bent]

Elk has it.

In my way of thinking, there is NO stove made that it is OK to install in front of a prefab and pass the pipe through a plate, etc.

The two options are:
1. Approved ZC insert which sits IN the fireplace, not in front
2. Rip it all out (chimney and fireplace) and install built-in high efficiency unit or freestanding stove and new class A chimney.

That's the simple answer. As you will see by some other threads, we have dealers here who have done what you suggest....and say it is common in their part of the country and passes inspection. Take my word for it - that does not mean it is an approved installation, it isn't!

Sorry Web, but your wrong on this one. Hearthstone Homestead has a version that is designed to be installed exacly as desired here. Look it up. On the other hand, I do agree with your suggestions overall. I personally did #1. If I had to do it again... I'd do #2.

 

[webbie]

Ah, there are exceptions to every rule. The Homestead manual does indeed address this, and I must say it is the first instance of such an installation I have ever seen in a modern manual. They must have tested it this way...

BUT, look at the list of caveats enclosed, and you will see that it takes a lot to make it safe. Add to this the fact that the homestead requires a R 6.6 (how many layers of wonderboard is that?) when used with it's shorter legs, and you'll start to see why this exception is very rare.

 

[jimychelita]

Thanks for the inputs Craigi and all. Not that I feel any more confident that this is going to be possible. However, option 2, rip out and make a standard zc stove installation, has some appeal at this point. Except that the depth of the chase is not enough to accept any unit zc unit I've seen so far. So, "tear out" might mean to tear out the entire side of the two story house to make a larger chimney chase. Life is grand!

Does anyone have any experience with alcove installations. The shallow chase wouldn't make any difference, if I could rip out the stove and chimney (Or use the metal chimney???) and frame an adequate alcove. Frankly, that is another appealing option, since it would involve a simple, straightup flue installation. Does this sound like an option that makes sense?

 

[webbie]

You may want to look into option 1.....

With #2, you cannot use the chimney in any way. You must install a new generic class A (or, if using a built-in whatever is approved for it)....

If the chase is not large enough for built-in ZC new fireplace, then a good option is a close clearance stove set in front of the wall - some can go as close as 6" or so, and then vented into a new class A chimney installed (this WILL fit) in your chase.

But if a smaller stove will do, option 1 is worth looking into - it will cost much less.

 

[jimychelita]

Your suggestion of a wall with a close-clearance stove in front of it, vent through the wall and up a new class A chimney is by far the most feasible thing I have heard. I also have a fair idea of the cost. Only question remaining, would you suggest

1) ripping out the existing zc unit and reframing the chase which contains it and reframing the wall which the vent will pass through,

or

2) vent through a cover plate over the existing zc to a T inside the existing zc, with class A going up the existing chimney the full 25 ft to the top. I think this may actually be my original question


I think we are homing in on the best, though not least expensive, solution.

 

[webbie]

I'd rip it out (in that case)- for a number of reasons.

Main reason being that the value of the house would seem to be better with a perceived "new" installation, than some kind of retrofit. When you went to sell the house, it could be tough to explain the whole "chimney in chimney" routine, plus there is the issue of perhaps someone removing the unit, etc. and whether or not the fireplace would still be safe (after modification).

There is also the issue of stove choice. Why limit yourself to the few with very low rear vents? With the "new" option, you could use a lot of different stoves, including some with top vents (using double wall interior pipe).

So the least expensive is still the approved ZC insert, but the "best" may be a rip-out.

 

[dmt5000]

I have seen statements in other posts that installing an insulated 6" liner in a prefab. fireplace chimney will bring it to the 2100* standard. If that is the case, then why couldn't any wood stove be connected to that chimney, as long as all other required clearances are met?

 

[webbie]

In theory it would be ok.

However, reality is a whole different matter. Just the flue height itself rules out 90% plus of all stoves. Then add the hearth requirements and the other clearances, and you rule out most of the others.

So, I would look at it like trying to make a sailboat out of a Boston Whaler. You could do it....and it might work once you installed a keel, a sail and lots of other stuff. But in reality, no one does it - or at least no one does it right!

So, all in all, my answer is this: NO, unless the installation is addresses specifically in the owners manual for the stove.

That's my opinion and experience and I'm sticking to it!

 

[Gooserider]

I have seen statements in other posts that installing an insulated 6" liner in a prefab. fireplace chimney will bring it to the 2100* standard. If that is the case, then why couldn't any wood stove be connected to that chimney, as long as all other required clearances are met?

The chimney is only PART of the problem - The other issue is the ZC firebox itself. You can stuff an insert or a free-standing stove into a conventional fireplace with minimal concern about clearances other than the exterior trim and hearth pads because you know that the fireplace itself and the clearances that it was required to be installed with will offer you enough protection for the combustibles inside the walls - thus you have a safe install.

OTOH, a ZC is very carefully engineered to add extra airflow and do other tricks that are only promised to work in a stock installation such that they are allowed to be installed MUCH closer to combustibles than a conventional fireplace would be. By the time you get done with the modifications needed to get a stove into the unit, you can't guarantee that those protections are still going to be functional, especially since the stove is going to provide a different heat distribution than a normal fire would. Bottom line is you end up with a firebox that has unknown insulation values located way to close to combustibles

Gooserider