High Rise Flue Stacks - Part 2

[boze]

Looking for a design source, guidelines, etc for vent stack systems installed 20 - 30 years ago. Need to modify an existing system. Have discussed with several local code departments

Part 1 raised the question regarding design guidelines for multiple insert gas fireplaces in a multi story high rise that used a common vent for alternate floors. Thread 403 182301, 3/26/07
One response advised that the common vent for the inserts was no longer in code.

Part 2 ---Have problems with an existing 18 story apartment building, with fireplace inserts connecting into a common flue.

Owners are looking for solutions to reduce some of the problems that are created by this type of installation.

Power exhaust fans, roof mounted, have had multiple replacements. Have done a number of calculations for correct sizing of fan, but am not comfortable.

So many variables - primarily the diversity factor- (how many units are firing, ---stack effect is so dependent on the common vent temperature, which is dependent on the location of the "fired" units (lower floors vs mixture of upper floors).

Cannot find any source that relates to the "design" rules that were used 30 years ago. Would appreciate a source. Have some old ASHRAE books, but not enough help.

 

[chilled]

In my part of the world such a venting arrangement is highly illegal and was never allowed.

I'm not trying to be sarcastic, but if you are going to tackle such a project, be sure your liability insurance is up to snuff, carbon monoxide poisoning almost always goes hand in hand with a lack of fiduciary responsibility.

 

[lilliput1]

How about using variable speed to maintain a negative static pressure at the top.

 

[walkes]

Try exhausto, they can do the draft calculations on the system to properly size the fan. The fan would have the ability to vary to maintain the correct pressures in the stack.

See

http://us.exhausto.com/NewSite/Index.htm

 

[willard3]

NFPA codes cover fireplace venting and do not allow multiple units on different floors with a common flue for the very reasons you have enumerated.

Fix the bugger, don't put on a band aid that won't work either.....you're going to have to get the client to realize this is a serious problem.

 

[boze]

Appreciate all of the input.
I will be filing a report to the client within several days with the awful truth that they will have to face.

Each of you provided substantial help, which is a great assist to convey the message to the client.

My attempt was to make a last ditch attempt to discover if others had found a magic solution.

Boze