Two gas appliances into one chimney


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Old 05-29-14, 01:49 PM
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Two gas appliances into one chimney

At my cottage I have a squat old cast iron NG boiler which exhausts into the chimney on the other side of the block wall. The hole into the chimney is about chest height. I want to add a NG HWH and need to know if the proper vent is to punch a new hole through the wall higher up and combine both flues with a "Y" into a single pipe (seal the original hole or cover it for use as a cleanout), or leave the boiler flue alone and just add the HWH flue above it?

I'm pretty sure you're not supposed to have 2 connections to a single stack but since both appliances have draft hoods I'm not clear why.
 
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Old 05-29-14, 02:37 PM
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Presumably, there is a metal flue pipe from the boiler that connects directly to the liner located inside the masonry chimney shell? There is a liner inside the chimney shell, right? If not, all bets are off.

Normally, there is a wye installed in the large flue pipe between boiler exhaust and the chimney shell and thence to the flue liner. The hot water heater's flue connects to the smaller diameter leg of the wye.

There are several important NFPA code requirements that apply, unrelated to your draft hoods. Post photos. Probably the safest thing is to have a qualified person install the water heater and take care of the flue. Since you are increasing the flue gas, you will need to have the chimney inspected based on prevailing NFPA code requirements.

No, you can't break open a hole in the chimney shell. The flue gas isn't vented into the chimney shell, only into the in side liner.
 
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Old 05-29-14, 04:36 PM
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I think an important point to note is that the boiler is venting into the chimney at " chest height " and of course you need that to be higher in order that the water heater vent doesn't have to go DOWN to meet the flue pipe into the chimney. Gil, I think you might have missed that.

I doubt there's a liner..................
 
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Old 05-30-14, 06:18 AM
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I doubt there's a liner.....
There will be. Currently there isn't and I've been getting moisture through the chimney block that leaves behind the telltale efflorescence.

I assume with a liner it's not even possible to have 2 entries at different heights? Which leaves the wye connection. Is this DIY-able?
 
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Old 05-30-14, 07:36 AM
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Is this DIY-able?
I don't see why not... just make sure you've got required permits, etc.
 
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Old 05-30-14, 08:57 AM
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Often times the installation manual for a boiler/water heater will include venting guidelines/instructions. Might be worth checking out.
 
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Old 05-30-14, 09:59 AM
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Not in the case of the Bradford White unit I bought. The Venting section only has a couple pages of general requirements with no specifics, no diagrams, etc.

A link to a more useful one would be appreciated...
 
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Old 05-30-14, 10:57 AM
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I think an important point to note is that the boiler is venting into the chimney at " chest height " and of course you need that to be higher in order that the water heater vent doesn't have to go DOWN to meet the flue pipe into the chimney.
Yes, but many gas water heaters come in both tall and short models. For example, A.O. Smith offers a 30-gal, shorty which is 46" high.
 
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Old 05-30-14, 12:51 PM
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Per gas code as I know it the masonry tile inside the chimney needs to be measured. Then calculate the ft from the appliance. You need to do this to be sure the chimney can support the added BTU.

Follow the charts in the gas code chart and it will tell you. I can look it up when I have time or you can. The codes are in a sticky at the top of this forum.

Whats the BTU of the boiler?
Whats the BTU of HWH?
Whats the diameter of the chimney?
Whats the height of the chimney?

Additionally you can add a tee to the boiler such as a 5x4x6 Y. 6" going into the chimney, 4" for the HWH, and 5" for the boiler ''''if the boiler is 5"'''...

Last if you do tie the HWH separate from the boiler, by code, it will need to tie in 6" minimum above the boiler...

This is code as I know it, and use everyday from the national fuel gas code......
 
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Old 05-30-14, 09:10 PM
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Last if you do tie the HWH separate from the boiler, by code, it will need to tie in 6" minimum above the boiler...
So this is still allowed? My first house had this setup and is the reason I'm conSidering copying it. As with that house I have a 100kbtu boiler and a 40kbtu hwh into a 9x9 clay-lined chimney.
 
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Old 05-30-14, 09:14 PM
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... but then again I can't visualize how I would do that with a liner in there.
 
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Old 05-30-14, 09:39 PM
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You have plenty with a 9x9 from my memory. ( But check)...

So this is still allowed?
It used to be no distance. We put the HWH right above the boiler. But that changed a few years ago... Its been a while since I did separate so check. I may be wrong as it may be 12"..... ( Dont have time these days to check code)

Adding a new appliance as you state you need a permit. Ask your local authority. They are your best resource...

And please take out the permit for your protection.............

Do it once and do it right!!!!!!!!!!


Liner? You dont have a liner so what? Do you want a liner? Depends on your local autority. We are still doing no liners here............( As long as tile is intact) ( Or that equipment does not require) ( or the chimney is too large, which is often with HE equipment)
 
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Old 05-31-14, 06:34 AM
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Yes I think I need a liner. See previous post. I keep a minimum temp of 45-50 in the winter while I'm away and there doesn't seem to be enough flue heat to dry it out.
I can't Find the code sticky but if I understand the intent then a 6" Liner will work.
 
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Old 05-31-14, 07:08 AM
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... but then again I can't visualize how I would do that with a liner in there.
No expert on liners here... but during my research when I installed mine I learned a bit from this site:

Chimney Liner Depot - Buy Flue Liner and Save Big, DIY Chimney Repair

I imagine that you would use two of these:


Chimney Liner Depot - Rigid 304L Chimney Liner Tee - 6in

one above the other. Of course you would have to make a new hole in the chimney to accomodate the second entry.
 
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Old 05-31-14, 07:11 AM
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I keep a minimum temp of 45-50 in the winter while I'm away and there doesn't seem to be enough flue heat to dry it out.
Does the boiler not make it over 150F water? What type of heat emitters?
 
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Old 05-31-14, 07:22 AM
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Old 05-31-14, 09:29 AM
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If the tile dia is 9x9 then thats 81 sq inches. We need to know the total height of chimney..

quick look was last chart here link below......

But lining is best as you are going to go that route, but 6" may not be needed. Possibly too big. Maybe 5" will suffice..

What was the flue size out the boiler?


Towards bottom chart here shows masonry. or find single liner for sizing..........


Chapter 5 - Chimneys and Vents
 
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Old 05-31-14, 01:15 PM
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Great liner link Trooper--I had no idea something like that existed to allow you to drop the liner down into the tap. So with some careful measurements I CAN have 2 wall penetrations and CAN use rigid liner. I don't know if I can swing the expense but the traditionalist in me likes the rigid pipe. Is SS the only option? I thought galvanized and aluminum were still OK for low-efficiency gas appliances?

And thanks Mike for the code links. I'm pretty sure my boiler has a 5" exhaust. I will check that next weekend when I return there. Chimney height from thimble to cap is about 20 feet. I need to verify that, too.
 
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Old 06-01-14, 08:11 AM
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Is SS the only option? I thought galvanized and aluminum were still OK for low-efficiency gas appliances?
I think the others are OK also... I found them when dealing with oil, so needed to use the SS myself, and didn't research other materials. I'm sure the same system is available for other types.
 
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Old 06-09-14, 06:15 AM
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I was at the cottage over the weekend and unboxed the water heater & set it where I want to install it. Is it too tall to join the existing boiler vent? Boiler is 5" and HWH is 3".
I think there's room for the elbow and correct pitch but I've read it's not good to drop an elbow right on top of the hood--some vertical rise is needed to keep the exhaust moving fast. I'm not clear whether that's a "must" or a recommendation, or how much is enough.
What do you guys think?


 
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Old 06-09-14, 06:26 AM
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The HWH needs to be piped 4" per codes as I know it.. Unless it was stand alone,,,

Yes a short piece of straight pipe. I believe supposed to be 12"..

Last I dont think you can fit a Y on there and be able to reconnect boiler? Cant see really. Why is the chimney open like that where the flue goes through? Should be cemented..
 
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Old 06-09-14, 06:56 PM
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I need to upsize the flue because it's going into a wye?Install manual makes no mention of that.

Or that.

?
Are you mistaking the thimble for a huge gap?


Sounds like I'm back to 2 holes in my chimney. ..
 
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Old 06-09-14, 07:11 PM
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No you have to upsize the water heater to 4" because that is code as I know it here in NJ. If its here in NJ it will be everywhere else sooner or later. There is a whole story involved in that. The inspectors make us do it. Although the draft hoods from the manufacturer are still 3". ( We do install 4" aftermarket hoods)

Actually that draft hood is beveled and will fit 4" which we do...

And the code is stupid because the internal flue in the HWH with the baffle is only 3"...

I dont see a thimble. Is that still a tile chimney?


Just saying is all....
 
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Old 06-09-14, 07:27 PM
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I may have my terms wrong. I thought the collar an appliance flue passed through is the thimble. Anyways the dark donut is metal sleeve and cap and cemented in place. Chimney is clay lined.
 
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Old 06-10-14, 09:12 AM
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I don't want to do this job. I just want to know enough about what I need to not get screwed or unknowingly accept a substandard job.. My place is out in the sticks and there are no "chimney experts" for at least an hour drive. Probably going to have to use a local plumber--they seem to be the "jack of all trades" there.
 
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Old 06-10-14, 09:41 AM
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either do this and put 6" above boiler flue.. ( Use 4" pipe for HWH)




Or do this. Srry not better pics. But you see the two flues were seperate. I combined them with a 6x5x4 Y. See I have the HWH side of the tee rolled down for pitch..

http://www.doityourself.com/forum/bo...ue-issues.html

Last thing is get a powervent heater and pipe PVC to an outside wall. ( Or go electric)
 
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Old 06-10-14, 12:24 PM
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I remember that thread...and your frustration at finding out you might have to line the chimney even though the boiler is an 85% unit. I didn't see what you ended up with. Did you go with your gut that running the heaters hot would be fine into a clay chimney?

My boiler is an older one but still in great shape since it's so rarely fired up. I'm probably fine exhausting into clay but last winter I did have a fair amount of efflorescence on the outside of the chimney. I don't know if that's because of the record-setting cold, the 50* thermostat setting, or a leak. I need an inspection--but then there's that issue with rare qualified tradesmen. I'm adding a garage (unheated) and that chimney will then be internal. Not much difference in temps but it will be a big change in the wind the thing has been exposed to.

I'd still be more comfortable with a liner but my budget might not permit it this year.
 
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Old 06-10-14, 12:28 PM
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Now the guy wanted an es2 burnham. They need liners.

This is just a regular $1200 boiler per my link... Utica... Inspectors have no issues with the clay liners/ masonry chimneys as long as all the tiles are intact. ( here in NJ)

Ill have to re read that thread...
 
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Old 06-10-14, 05:34 PM
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Have you ever knocked a new hole in a clay-lined chimney? What's the process? Just use a bfh & bash away at the cinder block & whatever layers until you break through and then keep chipping away at it until it's more/less round?
 
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Old 06-10-14, 06:09 PM
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Yes break the main block till you get to liner. Then I use a long flat blade for the tile in firm strokes to break cleanly...
 
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Old 06-11-14, 09:02 AM
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OK--so it sounds basic enough that I can trust a backwoods plumber or GC and not have to worry that I won't wake up.
 
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Old 06-11-14, 09:31 AM
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Cement around the pipe when done and make sure the pipe is not stuck in so far. maybe 1-2" or so into the clay liner..( I have seen guys stick it in so far that it hits the back of the liner and the appliance then does not draft)

I use a lump hammer for the block. And large chisel to make smooth edges.. For the clay liner I sometimes use a masonry bit and drill a series of holes in a circular pattern. Then whack it out with the chisel.
 
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Old 06-12-14, 06:59 AM
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Thanks Mike--I really appreciate all the tips. I'll tackle almost anything if I can learn enough about it first. I was browsing Youtube videos and even though 90% of them are self-promotion and don't offer any real instruction, I did find a couple good ones that gave me a good sense of how my chimney is built.
 
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Old 06-25-14, 09:18 AM
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Update:
I just got back from my cottage and while there I took apart the boiler flue to inspect and see how deep the chimney clay liner is from the wall surface. I found that my chimney thimble is badly rusted. I suspect the heat & moisture leaking into the block that surrounds the liner is why I have been seeing efflorescence on the exterior the past 2 winters. I've backed off from trying to do this myself and have made an appointment for next month with the only "chimney guy" within 50 miles.

I have a thimble question: I recently watched some Youtube videos to get a better understanding of chimney construction and watched a series from a guy that calls himself "chimneyking" where he makes a thimble from 6" round fireclay and muds that in tight through the block & into the clay liner. His definitely won't rust out over time. How common is that kind of masonry thimble vs. galvanized?
 
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Old 06-25-14, 03:55 PM
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How common is that kind of masonry thimble vs. galvanized?
Not common around here.

Galvanized steel should be OK unless you are getting condensation in the flue - which evidently you have been. Even with the masonry thimble, it presumably will still need to transition to steel for fit-up to the boiler, right?
 
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Old 06-26-14, 06:58 AM
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Originally Posted by gilmorrie
will still need to transition to steel for fit-up to the boiler, right?
Yes. At the end of that video I was left wondering how the flue attaches? I assume the flue would be crimped to fit inside the tile thimble with a bit of high-temp sealer to secure it? He didn't leave the thimble proud to use a cap to fit over it so inside seems the only option. "Chimneyking" seems to be a bit of a nut but the final result looked very nice and much more professional and "right" than a sheetmetal plate with a hole in it (what I now have).



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