What are Best Practices for Venting High-Altitude Installations?

High-Altitude Venting Considerations

When sizing and venting propane tankless water heaters at high altitudes, it’s crucial to account for the lower atmospheric pressure. As altitude increases, the air pressure decreases, resulting in a lower draft. This can lead to backdrafting, where combustion gases are pulled back into the appliance, reducing efficiency and potentially causing safety issues.

Vent Pipe Sizing and Length

To ensure proper venting, the vent pipe should be sized according to the appliance’s manufacturer recommendations and local building codes. A general rule of thumb is to use a vent pipe with a diameter of at least 3.5 inches for propane tankless water heaters. The vent pipe should be sized to accommodate the appliance’s exhaust gas flow rate, which can be calculated using the appliance’s CFM (cubic feet per minute) rating. Additionally, the vent pipe should be sized to extend at least 2 feet above the highest point of the roof or 2 feet above the highest point of the surrounding structure.

Freeze Protection and Demand Requirements

High-altitude installations also require careful consideration of freeze protection for the propane tank and water lines. This can be achieved by installing freeze-resistant pipes and using a propane tankless water heater with built-in freeze protection features. It’s also essential to calculate the demand requirements for the installation, taking into account factors such as water usage, temperature, and appliance efficiency. A general rule of thumb is to size the propane tankless water heater to provide at least 3.5 gallons per minute (gpm) of hot water at a temperature of 104°F (40°C) or higher.