Hi Guys
My friend recently had an 80% draft induced forced air gas furnace installed. The furnace shares a b-vent with a natural draft gas water heater. The water heaters vent connector is installed correctly above the furnaces vent connector. I read on the nachi site that natural draft appliances should not share a vent because of the pressure that draft induced furnace creates. The furnace and water heater are in enclosed room ,but they do have sufficient air supply. Should he worry about this or are their new guidelines permitting this installation
Thanks
Jeff Prince
Safe At Home Inspections,Inc.
Darien,IL
A draft inducer is mounted in a furnace. Modern furnace heat exchangers are narrower plus have multiple passes through the heat exchanger and require a draft inducer to pull the vent gases through the heat exchanger. Once the vent gases exit the furnace natural drafting takes over.
Older furnaces that are natural draft, without inducers, have wider passages that allow the natural drafting of vent gases through it.
A power vented system is a system that has a powered drafting fan at the termination of the vent pipe. Properly installed on a call for heat the power venter starts. Draft is proved and then a control signal is sent back to terminal W onthe furnace to start the furnace ignition process.
All of the 80 percent efficiency furnaces that were side walled vented with the recalled HTPV (High Temperature Plastic Vent) were replaced with a barometric damper, double wall B vent and a side wall power venter.