Pentair MasterTemp 125,000 BTU Gas Heater Thermal Regulator | 474989

Figure 1 is a diagram of the heater showing how it operates.
Precisely matched orifice plates meter the air and gas into the mixer.
The blower draws the air and gas through the mixer and forces it into the burner’s flame holder. A sealed heat exchanger surrounds the flame holder, discharging exhaust gases out the flue.
Two inch PVC water piping connects directly to the manifold/header on the heat exchanger using 1.5” PVC slip unions provided with the heater.
The outer manifold remains cool; no heat sinks are required. A thermal regulator and an internal bypass regulate the water flow through the heat exchanger to maintain the correct outlet temperature. The heater operator control panel board assembly is located on top of the heater.