Hi Everybody!
I’d like to switch from an electric hot water heater to a gas heater. I already have a gas furnace. Can the two share an exhaust stack? How would I determine the size?
Thanks!
Hi Everybody!
I’d like to switch from an electric hot water heater to a gas heater. I already have a gas furnace. Can the two share an exhaust stack? How would I determine the size?
Thanks!
Learn more about the benefits and compliance details for the DOE's new water heater energy-efficiency standards.
"I have learned so much thanks to the searchable articles on the FHB website. I can confidently say that I expect to be a life-long subscriber." - M.K.
Get home building tips, offers, and expert advice in your inbox
Fine Homebuilding
Get home building tips, offers, and expert advice in your inbox
© 2024 Active Interest Media. All rights reserved.
Get home building tips, offers, and expert advice in your inbox
Become a member and get instant access to thousands of videos, how-tos, tool reviews, and design features.
Start Your Free TrialStart your subscription today and save up to 81%
SubscribeGet complete site access to expert advice, how-to videos, Code Check, and more, plus the print magazine.
Already a member? Log in
Replies
Careful...there are really strict requirements for flue size, type, and configuration...for the good of both appliances and especially the occupants as carbon monoxide poisoning is no joke and it's awfully easy to get the flue sizing etc wrong . You'll have a hard time getting this information second-hand.
The only sure, safe way to do this (without the knowledge of a pro) would be to run a separate flue spec'd out per the WH manufacture.
I you really want to DIY, at least hire a licenesed HVAC guy to do the design work..if you can find one that will do it.
"Can the two share an exhaust stack?" Yes, most likely. If both appliances are gravity vented, both can and in most common installations, do share the same flue. If either of the appliances is a forced draft, induced draft or power vent type, I (and most Code officials) would recommend against combining vents/flues.
"How would I determine the size?" The easiest way is to rely on the professional that you are paying to install the vent to size it proerly based on the specifics of the installation and the appliances involved. Most manufacturers of the common "b-vent" products have tables to properly size the flue.
A very common installation combination includes a GWH at 40,000 btuh input and a gas furnace at 80 to 100,000 btuh input, both non-condensing, vent through a 3/4/5 type of setup. 3" connection to the water heater, 4" connection to the furnace and 5" combined vent size through the roof.