Venting a Mod Con

Larry (from OSHA)

Getting very close to changing out the old boiler for the new. Side venting is not an option. My hope is to use the existing 7" diameter b-vent as a chase for both the vent and intake, but obviously this is a close fit for 3" PVC.

If they both fit down the old chimney, is it OK if they are in contact with each other and the old chimney? My new Knight and I want to know. Concerns would be expansion and contraction noises and any code concerns.

Thanks,

Larry

hot_rod

Do you need 3\"?

The new Knight wall hung 50, 80, and 105K vent with 2".

Two 3" inside a 7 will be a tight fit. Hope there aren't any offsets or screws sticking in

hot rod

Larry (from OSHA)

no offsets

but I'm sure that any screws sticking in will be in the worst spots! If the wall mounts vent with 2", do you think the factory will allow 2" for a floor model (80M)? Unfortunately, I don't have a good wall space for one. Are they even out yet.

Thanks,

Larry

hot_rod

Maybe

but it probably has more to do with with their listing and approvalsl.

I know HTP once had a table for combining a pair of 1-1/2" together. This allowed you to replace hydro pulses with Munchkin.

The actual connection on the Knight intake side is 2". They use a 2X3 increaser fitting at the boiler.

hot rod

Dr Pepper

Press the factory for info...

the installation guide should have that information but to many do not. W-M has a separate booklet, sometimes it's like pulling teeth. Boiler or furnace their is a length in feet and each elbow counts as so-many feet. Most will also list a maximum number of elbows. Also, you want to know exactly what the discharge configuration is, (example: flue straight up 10"+ above the CAI which requires 2 elbows,and must be installed within 4' of each other.)
Good luck...

Floyd_43

2\" all the way...

will probably work just derates the boiler which may not be a bad thing.

Floyd

Larry (from OSHA)

thank you

Floyd, Hot Rod and Dr. Pepper, thank you for the perspectives. I hope to hear from the factory with some options, but considering how the boiler is listed and approved, they may be reluctant to step outside of those listings.

In any event, I'm quite anxious to get this puppy up and running. Before and after pics will follow eventually.

Larry

Tom Hopkins

What size boiler?

Just remember, that the exhaust passing through 2" tubing will be much more audible than with 3" and the boiler itself will be very quiet. This exhaust noise is all dependent on what your real heat loss load is of course. I'm not sure is a 50 is quieter on 3" than 2" at the lower end. You certainly don't want to be hearing it when your indirect is calling, then again maybe you'll like the sound? ;-)

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Larry (from OSHA)

good point

Robert, that is an interesting tidbit. The boiler is an 80 and I had not really given any thought to that. It may be a moot point, if the factory won't put their blessing on using the 2 inch. I'm hoping to keep the install as easy as possible, but if we need to rip out the existing chimney, I suspect that my contractor will be able to.

The last I heard from the factory was a suggestion to use cpvc all the way up. I've suggested a few alternatives for them to consider and we'll see what they say.

Thanks for your thoughts.

Larry

Mitch_5

I was talking to WM once about a similar project

they said they were coming up with spec for running a 3" up the chimney and using the chimney itself t pull the combustion air down. Just talk then I have seen no official spec but it is a thought.

Mitch S.

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Perry_3

Vitodens Cocentric Vent...

Solved this problem long ago...

I should also note; that for side venting I had to run the vent up into a closet on the first floor and then vent out the side of the house in order to be above normal heavy snow in this area (2 ft above normal snow line).

I note that I believe I have one of the few houses in the area with a retrofit that actually meets this code requirment.

Perry

Perry_3

Vitodens Cocentric Vent...

Opps! Double post. Double post.



I've deleted text.

Please disregard.


Perry