Venting of on-demand water heater through roof

Ralph Buzard

I have a Bausch propane on-demand water heater vented through the roof. When the temperature outside gets to -15 the heat exchanger starts to freeze up. Is there a dampener that will stop the cold air from coming down the draft and thermally open when the heater comes on? This water heater has no pilot light and fires when the water is turned on. What is available to remedy this situation?
Thanks in advance.

Ed_26

Bosch heater

This condition usually indicates lack of make-up air in your building. That is... your building needs air & it is aquiring it thru the chimney. You need to supply air to the building from another source. IE: a make-up air duct from outside to the area near the heater.

JackFre

Your unit has a 5F

freeze protection rating. You could probably put in an Effical stack damper but you would have to get direction/approval from the factory on the application and wiring. Given the time it takes the damper to open you will further delay the delivery of hot water by that much every time you open the tap. BTW, the Rinnai unit has-30F freeze protection on it. In cold climates especially, I prefer the side wall vent option for On-demands. Install the vent so the invert of the vent termination just above the unit is above the top of the temination pipe outside and it prevents any gravity flow of cold air back to the unit, thereby reducing energy consumption. Just a thought!

Scott Gregg

not a Bosch fan but...

you might have somethig else going on as stated. If you have a new unit, I would start by taking it back and getting a higher quality product like Noritz, Rennai or Takagi. Also you need to make sure any of these are vented properly. Venting straight up through a roof without allowing for a condensate drain will have you replacing the heat exchanger or the whole unit in less than 2 years.

No kidding...I've seen it happen.