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Furnace and fireplace flue seperation


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What is your opinion on the furnace venting so close to the fireplace flue. The rusted chimney cap is a given. I've never seen this before. What would you say about this. I'm still working on the report my rough draft reads as follows

"Employ a chimney sweep and/or HVAC contractor to evaluate, and correct as neded, the furnace and fireplace flue termination. I believe they are to close and not in accordance with building standards. The fireplace flue should terminate 2 feet higher than anything within 10 feet?.. "

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Mark,

I would not use that language for this condition. I would be very brief because there are many defects and the best way is to be direct. "The sheet metal top of the chimney chase is rotted. the deterioration is caused by improper placement and installation of the two flues. have a hvac tradesperson replace top and correctly install flues." or something like that. short, sweet and to the point.

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Okay thanks, short and concise it is.

For my benefit and the benefit of others can we list (discuss) what is wrong with this situation. I've looked a thousands of these framed chases with the sheet metal tops. It is not uncommon to find them rusted. What I have never seen is a furnace flue coming out the top of one. Also I've never seen a furnce and fireplace flue so close together.

1. The corrosive nature and high moisture content of the furnace exhaust is causing the sheet metal to rust.

2. The two flues terminate too close to one another.

3. ......?

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I do 'single system' lists only on houses that don't give me enough to show a decent return on the client's investment in me. If I have enough major failures, I keep such lists to a minimum, using language such as what Les suggested.

This touches upon one of several dimensions of HI reports - How detailed to make the report.

Marc

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Mark I am on my phone so can't see photo so good. One thing I did note was how does a rust streak appear on the left side of chase and the water not appear somewhere down stream? How much restriction is created by the left flue (B vent?) being close to metal? is there a brake line in the top pan? has the left flue settled? and anecdotally, I would not have written the being close. I see that all the time and unless there is evidence of a problem, it would not be written. I would want to carefully walk around this chase.

Hope other contribute.

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The primary issue is not the proximity of the furnace vent termination to the fireplace flue outlet. There are many, many masonry chimneys that have gas or oil equipment flues terminating just a couple inches from fireplace flue openings at the same elevation. There would have to be other issues for this to actually be a problem.

The first issue is the B-vent for the furnace is supposed to terminate at least 12" from the top of the chase.

Both vent pipes are supposed to be properly flashed at the chase cover, including storm collars.

The sheet metal chase cover (if it was even galvanized) is overdue for replacement (with stainless steel and drainage slopes).

I would also advise that someone get inside the chase to find the other likely installation errors.

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The primary issue is not the proximity of the furnace vent termination to the fireplace flue outlet. There are many, many masonry chimneys that have gas or oil equipment flues terminating just a couple inches from fireplace flue openings at the same elevation. There would have to be other issues for this to actually be a problem.

The first issue is the B-vent for the furnace is supposed to terminate at least 12" from the top of the chase.

Both vent pipes are supposed to be properly flashed at the chase cover, including storm collars.

The sheet metal chase cover (if it was even galvanized) is overdue for replacement (with stainless steel and drainage slopes).

I would also advise that someone get inside the chase to find the other likely installation errors.

Thanks Bill, that was a learning experience.

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Bill pretty much covered it. Denray, there is no code addressing recirculation of flue gases per se. If that's happening, fix the depressurization. In general, you want the most noxious exhaust taller than surrounding terminations and separated if possible.

Note that when terminating factory chimney through chase tops, such as for woodstoves, most require a ventilated flashing to reduce chase temps.

If you find shrouds over vent terminations, they must be listed for all appliances. I know of NO shrouds that are listed for multiple brands and fuel types within the same shroud so call that out if you see it. It's all too common. Also, often you'll see two square-type fireplace flue terminations but one fireplace. Check the other and you'll often see it's a shroud over an oil or gas vent and thus illegal. Dummy terminations are common, too so don't assume.

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Denray - I have seen the opposite happen some times where the smoke from the fireplace will get drawn down a combined furnace/water heater vent. The fire is drawing air from the home, and if the home is too tight, the home draws make-up air back down the water heater vent, and you end up with smoke in the area of the water heater which in the two cases I looked at, was the basement. When the people tried a fire and slightly opened a window on the floor where the fire was located, no problem.

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