Hot water heater - atmosphere question

[kdog]

Currently have electric HW and new condensing gas furnace

Want to install 50 gallon gas HW which calls for 3 or 4 inch vent

House has a unused 30ft 6 inch Galvanized stack, which was used for old oil furnace, it was built 10 yrs ago so it is good shape.

Stack center is 57 inches high in basement. The HW vent is 53 inches high and would be less then 5 ft away.

Oil furnace worked fine for years, so should be enough air in basement for HW.

Oil furnace was vented with 6 inch galvanized pipe, there was 6 inch clearance everywhere.

Should I use 4 inch galvanized pipe (26 gauge) from HW to 4 x 6 adaptor or would a short run of 3 inch first be better? Elbow on top of HW will be fairly close in order to keep 1/4" rise per foot, so I was thinking maybe a 3 inch would be better???

Any other concerns?

 

[frodo]

if you have a 6" vent and yo want to add another vent 4"
the vent size shall be at the minimun 9''

since they do not make 9'' you step it up to 10''

not down to 8''

where are you located are you under ipc or upc code

 

[kdog]

Sorry if it was confusing. The six inch is currently not used at all, so the only device connecting to it will be the new HW. After the oil furnace was removed, the stack was capped at the wall. I will uncap it and connect HW to it. My question was more on the best way to do that. I am under NSPC

 

[Mr_David]

If the Wtr Htr has a 4" draft hood then you need a 4" vent connector. If the WH only requires a 3" vent then you can use a 3" connector

 

[frodo]

set your heater do not hook up water yet.

put your draft diverter on the top of heater..look at the 6".

hell, post a picture. easier that way

basically. your gonna have to take a section of the 6" down so you have rom to offset to the heater
you will need 2 4" double wall adjustable 45 bends and a 6x4 reducer

its very important yo look at old vent. for the name brand Ameri-vent? the parts youbuy must be the same name brand to fit correctrly

 

[Mr_David]

set your heater do not hook up water yet.

put your draft diverter on the top of heater..look at the 6".

hell, post a picture. easier that way

basically. your gonna have to take a section of the 6" down so you have rom to offset to the heater
you will need 2 4" double wall adjustable 45 bends and a 6x4 reducer

its very important yo look at old vent. for the name brand Ameri-vent? the parts youbuy must be the same name brand to fit correctrly

Check your local authority You don't need double wall Ameri-vent for connector. as long as you have 6" clearance from any combustibles like drywall or wood.

Check the spec on your heater. Depending on what you get most residential htrs have 3" draft hood.
but for example the Bradford White Htrs if over 40K BTU then they use a 4" vent

 

[journeyman]

i think it might be a bad idea to go from 3 inch to 6 inch. the gases are just going to waffle around in the vent and not escape properly. i would pull 6 inch out and use either the 3 or 4 inch pipe. you want to make sure the heater will draft properly