Power Vent, or moving flue

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Old 02-12-20, 06:21 PM
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Power Vent, or moving flue

Folks,

We are considering a major renovation of our 1970s ranch that will hopefully include taking down a brick chimney measuring approximately 9' 6" by 32". It has three flues, two of which now service two propane-fueled fireplace inserts. The 3rd flue services the oil-fired hot water boiler. The propane fireplaces will not be replaced. A wood-burning something or other will be built in anther part of the renovated area about 20' away.

One problem is that the flue servicing the boiler is located in just about the worse place that it can be. It will interfere with the view from the kitchen table of the window that gets all the hummingbirds and the nice sunsets. How far can a flue be offset from where it leaves the boiler? And what is the smallest boxed-in sized that we can expect? I believe that the masonry in the basement will remain, as it's tied into the framing of the first floor, although I assume it can removed if we want to pay for it.

What are folks' thoughts about "power vents"? I know little about them, except that they exist. Can they do anything for me in this situation?

Thanks for past assistance, and for any that you can offer me here.

Nick
 
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Old 02-12-20, 06:29 PM
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Maybe I'm missing something.... you are taking down the entire chimney ?
 
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Old 02-12-20, 06:37 PM
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Yes--it is expected that the chimney will be removed, up through the attic and roof. It slims down to what looks to be about 3' by 3' above the roof-line. (Obviously some roof work to be done . . . )
 
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Old 02-12-20, 06:51 PM
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So you are asking about a power vent for side of the house venting as opposed to building something new for the oil fired boiler. One thing to consider..... is your house close to another ? You don't want to be blowing oil fumes at a neighbor.

That is a question I cannot answer. I'm the furnace guy. Hang tight.... others will stop by.
 
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Old 02-12-20, 07:12 PM
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We are on 1-acre lots. Nobody across the street and there's a river out back. My boiler is about 95' from the closest neighbor's attached garage--another 20 feet or so to the occupied part of his house.

If I can relocate the flue a couple of feet, the problem is solved. If a power vent can work, so much the better, but not an issue if the flue can be moved.
 
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Old 02-12-20, 09:23 PM
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I don't see an issue moving the flue.
As long as the pitch is maintained from the boiler to it everything should be ok.
How would you move the flue ? Build a new chimney ?
 
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Old 02-13-20, 05:24 AM
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Moving the flue, and figuring out how to do it, would be a job for the architect and builder.

At the initial general discussion with them here at the house, it was indicated that taking the chimney down could be done. Whether he would take the entire chimney down and do a new chimney and/or flue pipe, or carefully take down 2/3 of it, leaving the existing boiler flue--I have no idea. Not yet at that level of detail. I wouldn't mind if he took the entire chimney down to the basement floor so I could pick up the extra square footage. One side of the chimney faces my workshop/utility section and the other side faces the finished "gym" part. But as I mentioned above, taking it all the way down would require new structural support of some sort.

If he took the entire thing down to just below the level of the 1st floor floor, and perhaps routed the boiler exhaust into the existing middle flue, rather than the flue at the west end of the chimney where it is now, what would the minimum dimensions of the new, replacement chase need to be? The flues are about 3 feet apart, and moving the flue 3 feet would make a huge difference for us.

Can he route the flue all the way out to an outside wall of the basement, and up the outside of the house? Or is that where a power vent would come in?

Thanks.
 
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Old 02-13-20, 01:32 PM
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power vent

Hi- I have a power vent (Tjernlund), and it was installed when the home was built. It works OK, but if you could install a flue without a lot of work, that would be my recommendation. The power vent adds noise, another thing to clean, and if it quits you're out of action. My boiler guy recommended I buy a replacement motor and keep it on hand, since they're not always stocked by the local parts places. I followed his advice and - knock on wood- haven't needed it (yet). One thing I've read is that with a regular flue, there is some heat loss up the flue from the residual draft. Not so much with the power vent. But I'm a "keep it simple" kind of guy, and if I was here when this house was built I would have gone with an outside chimney. Steve
 
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Old 02-13-20, 02:40 PM
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If you can do natural draft do so. Power vents are nothing but trouble on oil fired equipment. I've had the displeasure of having to work on quite a few over the years.
 
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Old 02-13-20, 03:16 PM
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My preference would be to do natural draft.

I'm hoping someone can tell me how far from the boiler they can run the flue, and what the minimum dimension is apt to be for the chase. I'm working on a 3d drafting program so I can get an idea of what the views will be like. The architect is a little backed up, and we can start zeroing in on some of what we want to do if I have an idea of where I can put the flue, besides where it is now.
 
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Old 02-13-20, 06:02 PM
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Hi, that flue should probably be designed by the furnace mfg. specs.
Geo
 
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Old 02-14-20, 06:36 AM
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I'm sure that the experienced contractor, whoever it will end up being, will do the job properly. All I'm asking for is an approximation of what would be possible so that I have something to work with in the early design stage.

Am I not on the right forum for that sort of information?
 
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Old 02-14-20, 07:37 AM
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This is something which would have to be done by someone who could see your house, where the boiler is, etc. Trying to design something like this without at least pictures & measurements is begging for trouble.
 
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Old 02-14-20, 10:19 AM
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Grady,

Thanks for the response, but I'm not suggesting that someone recommend a design. A simple indication that a chase could be as small as 12" x 12", or will need to be at least 24" x 24" inches would be helpful. That it could go into the vertical flue/chimney 2' from the boiler, or 4 ' or 5' from the boiler. All would be helpful to me.

Obviously I understand that I could move the boiler to get what I want, but I'd rather not, since I will need a new flue/chimney either way. Anyway, thanks to all those who have responded . . .
 
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Old 02-14-20, 12:15 PM
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I don't really understand what you are asking. What is going thru this "chase"? By "flue" do you mean the pipe between the boiler & chimney?
Are you going to be using the existing chimneyi? If not, will the new one be masonry or metal all-fuel?
 
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Old 02-14-20, 01:23 PM
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As I indicated earlier, as part of a home renovation, we want/expect to remove the huge 9' 6" by 2' 8" chimney, which has 3 flues within it. We will be doing away with the 2 propane fireplace inserts which use 2 of the flues, but will still need a flue for the oil-fired boiler. I am not an HVAC person, but have some general "DIY" knowledge of construction.

I consider a chase to be the space within which various utility supply/exhaust/drainage lines/activities are enclosed. I also consider a flue, in this instance, to be the exhaust "pipe" of the boiler. Presumably a flue will be enclosed in something, but I am not knowledgeable about, for instance, if there exists flue-pipes/lines (or whatever) which DO NOT need to be enclosed, which might thus have a smaller footprint as it runs through my kitchen and out the roof. I am guessing that the existing chimney within this 1970s ranch has 3 clay-lined flues, or liners, or whatever they are called. There are 3 clean-outs in the basement, and 3 "appliances" using the chimney.

Lastly, as I also indicated before, I would like to have the replacement boiler flue traverse the kitchen in a different location from where it does so presently. Minimum size and distances that it could possibly be moved are what can help me design, roughly, the new layout--in advance of having the architect and contractor fine-tune it.
 
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Old 02-14-20, 01:48 PM
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I think the simplest answer is that if you are only looking to vent your boiler by natural draft the standard clay liner is 8 x 8 which is all you need for your boiler.

What the fial dimensions would be depends on how you enclose the flue liner. Obviously it comes off the boiler which is an exposed pipe and goes into a flue line or metal chimney to a point above the roof determined by code or high enough to pull a draft.

If you use a metal liner or chimney is has to be only as large as your exhaust pipe coming off the boiler. Most oil boiler flue pipes are 6" but they do go as small as 5 or as large as 7 depending on the make of your boiler.

As far as moving exhaust pipes or flues, as long as you can pull a proper draft which you can determine with a draft gauge there is no set rule. I worked on one where the furnace was 15 ft from the chimney and it worked fine much to my amasement.

Hope this helps a little.
 
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Old 02-14-20, 03:24 PM
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Thanks Spott--most helpful.

Are steel liners and clay interchangeable? Is one preferable to the other. The architect thought that 2' x 2' space coming up from the basement would be a fair approximation to start with, until the contractor gets more specific. Knowing that it might a little less, but more importantly, that it might be able to be moved without moving the boiler helps a lot, and is a relief.

Right now, the steel flue coming off the boiler looks to be about 6 1/2" to 7" in diameter. The boiler is about 13" away from the masonry chimney and the flue pipe goes into it about 30" above the top of the boiler.

 
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Old 02-14-20, 04:33 PM
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The difference between using a metal liner as compared to a clay line is that the stardard clay liner size is 8" x 8" for a residential heating unit so no matter what size your smoke pipe is coming from the boiler it will fit. With a Steel liner you can match the smoke pipe size off the boiler so if you have a 6" you can get a 6" liner and so forth for a 7 or 5 or whatever.

That 8X8 is just the size of the clay liner. What you enclose it with such as bricks would have to be added of course to the dimensions. As far as interchangable goes you can use either or to vent your boiler. The smoke pipe coming from your boiler is 24 gauge instead of reg. 30 gauge you would use for heating ducts so it is thicker. The liner you would use for a chimney is stainless and much more expensive. Personally if possible I would go with clay.

Just my thoughts.
 
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Old 02-14-20, 05:16 PM
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Thanks again.

Below is a picture of the offending chimney. I had just removed the first course of bricks of the "bump-out"--which as now been totally removed. We'll be happy when the whole chimney is gone.

https://drive.google.com/file/d/1m96...rt3zx0ubc/view
 
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Old 02-14-20, 08:06 PM
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The pipe between the boiler & chimney must be left accessible for removal & cleaning. Six inch all fuel chimney is 9" outside diameter & requires only 1.5" to combustible materials. Metal Fab is one manufacturer. https://www.mtlfab.com/
 
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