4 ducts going to chimney, or 1?

Chris Sweeney · 10-10-2012, 12:19 PM

My friend is having me do some work over at his duplex. He needs to reline his chimney, so we're going to do that with a DIY kit that he's getting online. It comes with everything: 6-inch SS flex liner, tee (for coming into the basement from the liner), insulation kit, rain cap, top plate, & high-temp caulk.

Now, the problem is this - Being a duplex, he has 2 furnaces and 2 water heaters. Right now all four of the vent ducts are going into the chimney separately (see picture):

How should we run all of 4 of these into that tee that comes with the liner kit? Can I just run all 4 into one "junction" so to speak, and then out through the tee, or do I have to run them each separately into the chimney like they are now? The first way would look a lot nicer, and I feel it would be just as effective as the latter way. Thanks!

Technow · 10-10-2012, 01:05 PM

How did he determine 6" is the right size?

Draft requirements are very specific and just like ductwork you can't just hookup some pipe and hope it works.

What are the btu inputs of the appliances? How much vertical height, how much horizontal distances??

"Danger Will Robinson"

**beenthere** · 10-10-2012, 04:37 PM

Use wyes to tie each units vent to the liner.

6" liner may or may not be big enough. So ask him how he determined size.

hvac benny · 10-10-2012, 05:57 PM

Unless you're a ticketed gas fitter, you should not be doing this work. I'm all for DIY, even when it comes to gas, but this sounds like a rental to me. Home owners can pull permits where I live, but only if it's their own single family home that they live in, they are doing the work themselves, and aren't paying anyone to do the work (ie. you have a right as a home owner to possibly endanger yourself and immediate family, but no one else). The scope of work is beyond what you can or should do.

COLDIRON · 10-10-2012, 06:18 PM

Looks like a double Chimney setup, why not run two liners one for each house. He's still saving big $$$$.

Chris Sweeney · 10-10-2012, 09:07 PM

Quote:

Originally Posted by Technow

How did he determine 6" is the right size?

Draft requirements are very specific and just like ductwork you can't just hookup some pipe and hope it works.

What are the btu inputs of the appliances? How much vertical height, how much horizontal distances??

"Danger Will Robinson"

We actually didn't determine any sizes yet. We were using 6" as a hypothetical for pricing materials, etc. The vent pipes from the water heaters are 3", and from the furnaces are 5". Vertical runs are about 2 feet for each unit, horizontal about 3 feet.

Quote:

Originally Posted by beenthere

Use wyes to tie each units vent to the liner.

6" liner may or may not be big enough. So ask him how he determined size.

Wyes sound wise

So I'll have the tee coming into the basement, then from there I'll have a quantity of 4 wyes.

Quote:

Originally Posted by hvac benny

Unless you're a ticketed gas fitter, you should not be doing this work. I'm all for DIY, even when it comes to gas, but this sounds like a rental to me. Home owners can pull permits where I live, but only if it's their own single family home that they live in, they are doing the work themselves, and aren't paying anyone to do the work (ie. you have a right as a home owner to possibly endanger yourself and immediate family, but no one else). The scope of work is beyond what you can or should do.

Second unit is vacant. Not sure if that makes a difference or not. But the process seems simple and straightforward. My friend whose house it is said that the questions about size of the liner and what configuration to use to set everything up correctly would be answered by the company that's supplying the liner. I just wanted to get the opinion of some other pros.

Quote:

Originally Posted by COLDIRON

Looks like a double Chimney setup, why not run two liners one for each house. He's still saving big $$$$.

Only one house & one chimney (two units in the house - one above the other), so I could be wrong but I think there's only room for one liner.

REP · 10-11-2012, 04:08 PM

If it were me,I'd use two chimeny liners (one for each unit).Still size is a must and nothing is close enough.
You didn't say how high the chimey is nor what size the inside of the chimey is.

Chris Sweeney · 10-11-2012, 06:02 PM

Quote:

Originally Posted by REP

If it were me,I'd use two chimeny liners (one for each unit).Still size is a must and nothing is close enough.
You didn't say how high the chimey is nor what size the inside of the chimey is.

If I had two liners, I'd still have to vent two units into each liner. What's wrong with four units into one liner (as it is now)? I could be wrong, but it's not like both furnaces and both water heaters will all be running simultaneously, and even if they did, why wouldn't one liner be able to handle it.

Remember, there's only one chimney, so if I put in two liners, they would have to be two smaller liners. So instead of putting in, say, one 6" liner, I'd have to put in two 3" liners. Doesn't really make sense logically to me, not to mention the added cost, but then again I'm no HVAC/chimney expert.

**beenthere** · 10-11-2012, 06:45 PM

It would probably be more like 2-5" liners, if you went with 2.

What is the combined total BTU input of all the water heaters and both furnaces.

You will be surprised how often all 4 run at the same time. Generally only on the colder days.

Chris Sweeney · 10-11-2012, 08:33 PM

Quote:

Originally Posted by beenthere

It would probably be more like 2-5" liners, if you went with 2.

What is the combined total BTU input of all the water heaters and both furnaces.

You will be surprised how often all 4 run at the same time. Generally only on the colder days.

Right, I was just using 6" (or 2-3") as a example/starting point. Not sure of the combined BTUs (I'm not at my friend's house until tomorrow), but I will check. Once I figure out the BTUs of each unit and figure the total combined BTUs, how should I use that in choosing the width of the liner? Is there a formula to follow or something?

**beenthere** · 10-11-2012, 09:57 PM

There are charts. it goes by total BTU, longest lateral, and height of chimney/liner.