shared flue issue?

[John Dirks Jr]

The picture shows a natural draft water heater flue. It's almost totally horizontal to begin with. However, my major concern is that is shares a flue (to the right) with a forced draft furnace.

This is wrong isn't it? I just want to make sure.

Thanks.

Click to Enlarge

43.22 KB

Click to Enlarge

57.09 KB

[Bill Kibbel]

I can't see it, but I'm guessing your "forced draft furnace" is actually a category I appliance with a fan-assisted combustion system.

If not, then the joints on the flue connector should have been sealed too.

[John Dirks Jr]

OK, if it is a fan assisted combustion system, can it share a flue with a natrual draft water heater?

On the furnace, there was a blower just inside of the cabinit where its vent pipe connects.

I missed getting a picture of that part

[John Dirks Jr]

I'm getting cat IV forced draft mixed up with cat 1 fan assisted combustion I guess.

So forced draft would be a high efficiency condensing furnace, right?

[Bill Kibbel]

John,

A "fan-assisted combustion system" in a cat I or II furnace pulls combustion byproducts through the heat exchanger. It is not a forced-draft system that creates positive pressure in the flue connector or vent.

Sharing a vent with a natural draft water heater is typically permitted, but it can change the equation for the vent and water heater flue connector sizing.

[hausdok]

What you've got there is a Category 1 draft induced furnace and, despite it's induction fan, is considered a gravity appliance just like the water heater and can share the same flue.

ONE TEAM - ONE FIGHT!!!

Mike

[SonOfSwamp]

Let me gently suggest that you call the manufacturer and get explicit info regarding how the furnace should be hooked up.

Or, maybe better, tell the customer to call an HVAC tech and get whatever needs fixing fixed.

WJ

[John Dirks Jr]

Thanks for setting me straight. I'll be looking much closer next time. I called out the horizontal connector. Let them figure it out.

I said, among other things,

"Calcultate the mesaurements. If the venting needs adjustment, fix it"

[Jim Katen]

Thanks for setting me straight. I'll be looking much closer next time. I called out the horizontal connector. Let them figure it out.

I said, among other things,

"Calcultate the mesaurements. If the venting needs adjustment, fix it"

But you spelled the words correctly in the report, right?

There's nothing wrong with venting a natural draft water heater into the same vent as an induced draft furnace. When you do this, though, the water heater *will* backdraft during the furnace's purge cycle. During that time, when the furnace's draft inducer is running but before the burners have ignited, the fan will push cold air into the vent and the water heater will spill at the draft diverter. It's no big deal, but some people freak out when they learn this. After the furnace fires, the water heater goes back to drafting normally.

When you vent these appliances together, there are a couple of rules to keep in mind. The vent connectors should join together in the same room but at a point that's as high as possible and the appliance with the greater BTU/hr rating should enter below the appliance with the lesser BTU/hr rating. The minimum slope for the vent connectors is 1/4" per foot.

In your picture, the wye should have been placed up near the ceiling.

- Jim Katen, Oregon

[Darren]

John;

These may help explain:

http://www.pmmag.com/Articles/Column/22 ... 32a8c0____

http://www.pmmag.com/Articles/Column/e1 ... 32a8c0____

[John Dirks Jr]

But you spelled the words correctly in the report, right?

Ms Word catches the misspellings.

Thanks for the extra info everyone. I enjoy learning. I hope it never ends.

[Chad Fabry]

Ms Word catches the misspellings.

I consistently mistype "plumbing" and leave the b out. Sadly, "pluming" is a word and I let a report go with about 20 references to to pluming. Since then I use spell check and I force myself to read my own documents, just to be sure.

[Tom Raymond]

Ms Word catches the misspellings.

I consistently mistype "plumbing" and leave the b out. Sadly, "pluming" is a word and I let a report go with about 20 references to to pluming. Since then I use spell check and I force myself to read my own documents, just to be sure.

I proof read each section of my report as I complete them, then proof the entire report for spelling only. If I reread any more than that I end up spending as much time on editing as I did writing it in the first place. I find that the MS Word dictionary is missing many common construction words, and the words that I have added still get flagged occasionally. I don't completely trust it, if I'm gonna look dumb for misspelling a word I'd rather it be me than my software.

Tom

[Terence McCann]

One thing to remember too John, with this type furnace, if it was installed in an older home, as a replacement, typically the chimney needs to be lined.

If these appliances are installed in a small closet be mindful of the combustion air requirements.

Just a heads up.

[resqman]

Ms Word catches the misspellings.

I consistently mistype "plumbing" and leave the b out. Sadly, "pluming" is a word and I let a report go with about 20 references to to pluming. Since then I use spell check and I force myself to read my own documents, just to be sure.

Decades ago in a previous life I was a software engineer for a major computer manufacturer. Customer called and wanted to know how to remove a word from the standard dictionary that came with the word processing software. I was curious why anyone would want to remove a word from the dicitionary. There was a correctly spelled word that was very similar but a very different meaning from a word they used all the time. The customer was the Public television station and they kept sending out documents from the Pubic television station.

[SonOfSwamp]

But you spelled the words correctly in the report, right?

Ms Word catches the misspellings.

Thanks for the extra info everyone. I enjoy learning. I hope it never ends.

I say don't rely on spell checkers. We have to be smarter than the spell checkers. Since I started using MS Word, I've had spell-check and grammar-check turned off.

I wouldn't want a spell-checker checking my spelling any more than I'd want a spell-checker driving my car.

WJ

[Les]

I do not use spell checker. I did when I used word perfect. I do use grammar checker on everything, except posting on net.

[SonOfSwamp]

I do not use spell checker. I did when I used word perfect. I do use grammar checker on everything, except posting on net.

I respectfully submit that canned grammar checkers suck all the humanity out of one's writing. If a grammar checker could be brought to life, it would come in the form of the crabby old baggy-stockinged grade school teacher that you still hate after 40-something years.

My advice to young wanna-be writers: Learn all the rules, then break 'em.

WJ

[Jim Katen]

Ms Word catches the misspellings.

I consistently mistype "plumbing" and leave the b out. Sadly, "pluming" is a word and I let a report go with about 20 references to to pluming. Since then I use spell check and I force myself to read my own documents, just to be sure.

* Tools

* AutoCorrect Options

* Replace text as you type

Replace "pluming" with "plumbing"

(or "pubic" with "public")

[Bain]

Ms Word catches the misspellings.

I consistently mistype "plumbing" and leave the b out. Sadly, "pluming" is a word and I let a report go with about 20 references to to pluming. Since then I use spell check and I force myself to read my own documents, just to be sure.

* Tools

* AutoCorrect Options

* Replace text as you type

Replace "pluming" with "plumbing"

(or "pubic" with "public")

I type "hosue" rather than house about half the time and Jim's method corrects it for me without fail.

[John Dirks Jr]

One thing to remember too John, with this type furnace, if it was installed in an older home, as a replacement, typically the chimney need to be lined.

If these appliances are installed in a small closet be mindful of the combustion air requirements.

Just a heads up.

Are clay liners sufficient? I think you mean to watch out for an unlined(bricks only, no clay liner)chimney. It this correct?

[Darren]

John,

Read the 3rd paragraph from the bottom on the 2nd link in my post.

[Terence McCann]

One thing to remember too John, with this type furnace, if it was installed in an older home, as a replacement, typically the chimney need to be lined.

If these appliances are installed in a small closet be mindful of the combustion air requirements.

Just a heads up.

Are clay liners sufficient? I think you mean to watch out for an unlined(bricks only, no clay liner)chimney. It this correct?

No, I'm referring to a standard chimney with a terracotta (clay) liner.

The main problem with the old terracotta lined chimneys is that they were designed for furnaces that had a hotter leaving flue gas temperature, it would leave the chimney in a vapor state. Remember that these furnaces were 60% efficient at best. Now with the higher efficiency furnace they squeeze a lot more heat out of the unit so the leaving flue gas temperature is much lower. End result is flue gas condensing inside the chimney instead of leaving the chimney in a vapor form. Flue gas, when condensed into to liquid, is corrosive.

Whenever I see a new furnace that has an induced draft fan I always note the presence, or lack thereof, a flue liner (stainless) in an older home.

[John Dirks Jr]

I read the articles that Darren posted. Its clear to me now that the combination of category 1 fan assisted furnaces and natural drafting water heaters can be done.

The question is, is it done correctly? Theres a great deal to consider when combining the two. There ways to bend rules to make things work the way they should. Tricky.

I see now that issues with condensing of gasses is as important to consider as the drafting of gasses.

Thanks again everyone.

[John Dirks Jr]

I have another question.

When flue gas condenses to liquid it becomes corrosive. Can all types of fossil fuels produce this corrosive liquid?