Venting a Bosch Therm 330PN into an Existing Chimney

The Bosch Therm 330PN is a naturally drafting gas tankless water heater and must be vented to the outside using a minimum of a 4" diameter galvanized type B gas vent.  Under no circumstances should the vent pipe be reduced in size.  There must be a minimum of a 12" rise off the top of the heater before any 45's or 90 degree elbows.  If there is to be a horizontal section before going into the chimney then try and keep it as short as possible.  The maximum horizontal run allowed is half of the total vertical vent height.  45's, 90 degree elbows and any horizontal length is not to be considered in the total gas vent height.

The Chimney the Bosch 330 PN tankless water heater is venting into must be the only thing going into the chimney.  The galvanized type B gas vent must run all the way up the chimney to an approved rain cap.  The minimum vertical vent height is 6 ft and any horizontal vent connectors or elbows are not to be considered in the total gas vent height.  All gas vent sections of pipe must be screwed together with sheet metal screws and properly supported.  The Bosch 330 PN may be vented into the chimney alone as long as it is lined with the correct tile or metal ling.  Consult local codes for proper lining of chimney.  You may not vent any other fuel burning appliances into any free space remaining in the chimney.  Please see the illustration below for venting into the chimney and always follow the instructions listed in the installation manual for the heater.

A = Minimum of 6 ft. rise
1.  Listed approved Rain Cap
2.  Horizontal vent connection rising 1/4" per ft.
3.  Establish a 12" rise before any elbows

Bosch Therm 520HN & 520PN Installed at Elevation

The Bosch Therm 520HN and the Bosch Therm 520PN can be installed at elevations for people with homes or cabins in Colorado, New Mexico, etc.  The Bosch 520HN & 520PN are natural drafting units and require a 6" galvanized type B-vent and must vent vertical for a minimum of 6' to the rain cap for all elevations over 2,000'.

Gas pressure is dependent upon the gas type whether it is Natural Gas (NG) or Liquid Propane (LPG) and also the length of the gas line.  See sizing charts in the installation manual for the heaters.  The Bosch 520HN & 520PN can be installed above 4,500' elevation but the unit would have to have the gas pressure adjusted using a manometer to compensate for the air and gas mix at the high elevation.  Please see the insert below for more details.

Cutting the gas pressure back as per the chart above is called "de-rating" the burner.  Elevations above 2,000 ft require the Bosch tankless water heater to be de-rated 4% for every 1,000 feet.  Basically you will loose 4% of your heating capacity for every 1,000 ft.

Bosch 5" B-Vent Vertical Vent Kit (H/P VVT)

The Bosch Vertical Vent Kit (H/P VVT) is a 5" Galvanized, Type B Vertical Vent Kit. This vertical vent kit includes a 5" x 12" pipe, (2) 5" flexible 90 degree elbows, a 5" fire stop support, a 5" roof flashing, a 5" storm collar, and a 5" rain cap. The HP VVT Vertical Vent Kit is manufactured by Selkirk and is used only for the Bosch Therm 520HN and 520PN naturally drafting heaters.  The H/P VVT vent kit will also work for the older retail models 1600H and 1600P.

The venting system must be designed and constructed so as to develop a positive flow adequate to remove flue gases to the outdoors.  Consult the National Fuel Gas Code if the vent will have elbows or share venting with another natural draft appliance.  The vent system must have at least a 12" rise off the top of the heater before any elbows or vent connectors.  

Selkirk 5 Inch Type B Venting Double-Walled Galvanized

GlobalTowne stocks 5" Selkirk Metalbest Type B Double-walled Galvanized vent pipe for the Bosch AquaStar 1600H and 1600P tankless water heaters.

The Selkirk Metalbestos 5" Type B vent pipe will connect up directly with the 1600H and 1600P tankless hot water heaters and will also connect up directly with the Bosch H/P VVT vertical vent kit.

The Bosch H/P VVT vertical vent kit contains all of the venting parts needed to vent the Bosch 1600H and 1600P heaters through the roof except for the straight pipe.

Our customers have found that ONLY the Selkirk Metalbest vent pipe will mate up with the H/P VVT vent kit piping, so this is the 5" Type B venting that we stock.

Steve