chimney sizing for staged boilers sharing same

grumbug

gentelmen
I need some hard copy on sizing flue & thinble sizing
for multiple boilers sharing common the same


Grumbug

Unknown

What Category are these

boilers? What Make and Model number are the boilers? We need to start there and then we can go on. I also need some information on the BTU input of each, chimney or vent height, lateral run (how far from chimney or vent), what is the flue size on the boilers?

What are you using the thimble for? Are you passing through combustible material?

jeff_51

dig out your UMC

Around here in Minnesnowta chimney size is based on total BTUH and of course horizontal run can only be a certain percentage of the overall vertical height. All of that should be in you UMC. We of course have a couple of addendums because {we} in Minnesnowta are smarter than everybody else and have to do it differant

grumbug

chimney sizing for staged boilers sharing same


Thanks, For the reply

Here,s the facts

2 buderus G115-28 Riello F40-F3 burners 112,000.

Chimney Height 26' 8x12 flue 8" thimble, The project
Manager thinks the 8" thimble is inadaquate wants 10"
So thats why I need printed data to resolve this

Also am planning to use a true 8" crotch to tie them

together.


Grumbug

kevin coppinger_12

is that chimney....

inside the house/build. or on the ouside/exposed side of the building. reason being the flue gasses on a buderus can be so "cold" that it will have a difficult time going up a large exterior flue. kpc

John Mills_5

NFPA54

Get a copy of the National Fuel Gas Code, it will tell you everything you need to know about flue sizing. Many mfrs reprint it in the installation instructions too.

Michal

careful how you twin them in

to start Like mentioned before use the code books, second be aware of your elbows, turns, stack temperatures (because buderuses fue gasses can get low, they can condense in the flue, corrion will occor) and finally your height. You can go onto the selkirk-metalbestos website and get ideas and calculations. Also I would not twin the boilers together with pants ( I am assuming crotch as you have called it) You should run a horizontal header and twin them into the header individually. 8 inch might be fine if you have the correct height

Bob Harper

NFPA 31 limitations

No sizing charts in '31 for dual appliances common vented the way '54 does in detail. One solution would be to install a priority switch on one appliance then common vent them into one stainless liner sized for the largest single appliance. At under 1 gph and 26 ft. you're in the 5-6" liner range. I always get the boiler techies to rig the priority switches so I don't have all the poop on parts and techniques but it does work well when you have multiple appliances sharing an inadequate chimney.
Having said all that, getting some good vent rise off the top, nice smooth runs with minimal elbows helps. Manifolding is an art with some science as I'm sure Jim Davis would tell you. I'd like to hear Jim's take on this.

Always eager to learn, too.

Steve M_2

venting

Here's a link that will tell you everything you need to know. Check with your local juridiction as well.

Steve M.

http://www.hvactechsupport.com/Dwnlds/Car-Bry_Lit/GAMA.pdf