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.