Pentair MasterTemp 400 Natural Gas Pool Heater, Low NOx HD

The Pentair MasterTemp 400 is a natural gas pool heater for in ground residential pools, and this is the heavy duty Low NOx version, part number 460805. It sits in the 350,000 to 400,000 BTU range, which is the top of the MasterTemp line and the size most often paired with a larger pool or a pool and spa on the same pad.

Why the HD version

The difference is the heat exchanger. The HD model uses cupro-nickel instead of the standard exchanger, and that matters when the water runs at low pH, when flow rates are high, or when the heater works hard for long stretches. Those are the conditions that eat through a standard exchanger, and cupro-nickel shrugs them off.

Simple to live with

Operation is as plain as a home furnace. Electronic ignition lights the burner on demand, so there is no pilot to keep lit. Temperature is set on a digital panel, and indicator lights show at a glance what the heater is doing. The cabinet is compact and the unit runs quietly, so it does not take over the equipment area or the yard next to it.

Low NOx

This heater meets the low nitrogen oxide emission standard that a growing number of air quality districts require for new gas heater installations. If you are replacing an older heater in one of those areas, a Low NOx model is the one the inspector expects to see.