Jump to content

shared flue issue?


John Dirks Jr
 Share

Recommended Posts

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
tn_200947212855_HPIM5104.jpg

43.22 KB

Click to Enlarge
tn_200947212925_HPIM5105.jpg

57.09 KB

Link to comment
Share on other sites

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.

Link to comment
Share on other sites

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

Link to comment
Share on other sites

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

Link to comment
Share on other sites

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.

Link to comment
Share on other sites

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

Link to comment
Share on other sites

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

Link to comment
Share on other sites

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")

Link to comment
Share on other sites

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.

Link to comment
Share on other sites

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?

Link to comment
Share on other sites

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.

Link to comment
Share on other sites

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.

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

 Share

×
×
  • Create New...