Originally Posted By: chorne This post was automatically imported from our archived forum.
Hi all,
I inspected a boiler and gas water heater where the water heater
vent was installed into the boiler vent pipe below the barametric
damper. Should the water heater be vented above the damper?
I saw somewhere a NACHI tip of the day where the water heater
and the boiler are both going into a chimney and the water heater
needed to be above the boiler.
Originally Posted By: jmyers This post was automatically imported from our archived forum.
Carla,
The vent pipe for the water heater should not be installed into the vent pipe for the boiler, whether it would be before or after the damper.
Typically, when they have limited space in the chimney structure for vent pipes they add a saddle to the chimney allowing the extra space so the two vent pipes can be properly spaced apart, with the water heater on the top which I like to see 12 inches above the heater vent pipe.
I am pretty sure there is an IBC code that would cover that but since I don't own the code books, I would suggest that someone else here would have to offer that information to you.
Originally Posted By: chorne This post was automatically imported from our archived forum.
Thanks Joe,
I also forgot to mention that the 8" boiler vent was a direct vent
with a power vent
The listing realtor called me and said she wanted an explanation
because the seller did all the work on his boiler because he went to
school for this. What a joke!
anyway, I did not think that the water heater vent stack should
go into the boilder stack.
Originally Posted By: jmyers This post was automatically imported from our archived forum.
Regardless of whether it is a direct vent or not, the water heater pipe should not be attached to the stack for the boiler. The power vent for the boiler is a nice feature but it would still allow flue gases from the water heater to enter into the boiler rather than start a draft up the chimney as it should when the power vent is not running. I am again of course assuming that it is vented into a chimney and not directly outside.
Even given both were direct vents, when the boiler was not running it would allow the water heater to vent the flue gases to the heater instead of allowing it to draft up the chimney and vice versa.
You are certainly welcome, I am always willing to share my two cents worth. You should be warned however, that since I just started doing home inspections last week you should not construe my words as gospel. No offense intended Will. 
Originally Posted By: Lew Lewis This post was automatically imported from our archived forum.
I see the water heater flue and boiler flues run together all the time. This is a standard installation if the chimney is a b vent rather than a masonry chimney. Also, if a masonry chimney flue is relined, the two appliance flues have to be joined together before the chimney. I have no problem with it, as long as they are drafting OK.
I've never heard of a 12" separation between the two flues into the chimney. Most older houses don't have enough basement headroom to accomodate the 12" separation.
Originally Posted By: jmyers This post was automatically imported from our archived forum.
Lew,
I did not say that could not be run on the same chimney, whether it would be type B vent pipe, or a masonary chimney. Is what I said was that the water heater flue pipe was not allowed to be tapped into the flue pipe for the boiler.
In the case where you have both running off the same chimney without the 12 inches a saddle would have to be installed to allow the 12 inch seperation.
Originally Posted By: roconnor This post was automatically imported from our archived forum.
Quote:
M1801.11 Multiple appliance venting system
Note 3. Connectors serving appliances operating under a natural draft shall not be connected to any portion of mechanical draft system operating under positive pressure. [Also IRC G2426.3.3 Mechanical draft system, Note-3 is similar]
Quote:
IRC G2424.10 Connections to exhauster
Appliance connections to a chimney or vent equipped with a power exhauster shall be made on the inlet side of the exhauster.
Quote:
IRC G2425.2 Connectors required
Connectors shall be used to connect appliances to the ... vent
Quote:
IRC G2426.10. Two or more appliances connected to a single vent
Where two or more appliances are vented through a common vent. chimney flue or single-wall metal pipe, the smaller connector shall enter at the highest level consistent with available headroom or clearances to combustible construction.
-- Robert O'Connor, PE
Eagle Engineering ?
Eagle Eye Inspections ?
NACHI Education Committee
I am absolutely amazed sometimes by how much thought goes into doing things wrong
Originally Posted By: jmyers This post was automatically imported from our archived forum.
David,
A "saddle" is an extension pipe, much like a flue pipe, which extends out of the hole in the chimney for the purpose of allowing multiple appliances to be vented from the chimney when you don't have enough room to place both on the existing chimney.
Originally Posted By: chorne This post was automatically imported from our archived forum.
Hi guys,
The boiler stack is direct vent (not into a chimney) that vent pipe
was to code but the gas water heater vent pipe enters the boiler
vent pipe below the barometric damper and then the power vent
is located after that just before it exits the building. I hope that is
more clear. I can't wait until I can send pictures. Just got a new
digital and I need to figure out how to send pictures to the forum!
Originally Posted By: jmyers This post was automatically imported from our archived forum.
Blaine,
I am pretty sure I have heard them called crickets too, although around here it is more common to hear the term "saddle".
Neal,
No, they extend out of the chimney structure, just as a flue pipe would and they are actually made of the same material a flue pipe is made of. I have also heard of the term thimble and you are correct, they are made of terra cotta. They look just like the standard terra cotta flue liner only they come in a variety of shapes, most are angled in one way or another.
Carla,
If the power vent fan was located just before it exits the building, that means it would have to serve both appliances. Sounds like one of those home made jobs.
It would still be incorrect to place the water heater flue before the damper, because when the water heater started it would force the damper to open and allow flue gas into the house.
Originally Posted By: cbottger This post was automatically imported from our archived forum.
Sure I will jump into this. You should determine what your State and city code requirements are before you start writting. The state Of Ok does allow furnaces vents and hot water heater vents to be combined. Not all cities have adopted the National Code book for residential dewellings.
Originally Posted By: roconnor This post was automatically imported from our archived forum.
Charlie … actually the current national model codes allow it too, with certain restrictions that really make sense to me from a safety point of view. While it is always good to know what the local code provisions are, a home inspection really is not about code compliance. Plus, the local codes at the time that was constructed (which is what really applies) may be different. So, as I indicated above, many HI’s just use the model codes as a guide.
Just my 2-nickles
-- Robert O'Connor, PE
Eagle Engineering ?
Eagle Eye Inspections ?
NACHI Education Committee
I am absolutely amazed sometimes by how much thought goes into doing things wrong