Pentair Hi-Limit Thermostat, 115 F, for MiniMax NT and MiniMax CH Pool Heaters, 471587

The Pentair 471587 is the 115 F hi-limit thermostat for MiniMax NT gas pool and spa heaters, models 200 to 400, and MiniMax CH heaters, models 150 to 400. It is the genuine Pentair replacement part.

What it does

A high limit is a safety device. Pentair describes it as a switch that opens the electrical circuit and shuts the heater off when temperature passes a set point built into the device. The parts lists for these heaters carry two hi-limit thermostats, this 115 F part and a 150 F part, 471694, with one of each per heater. Pentair's MiniMax NT Low NOx manual places two water high limits on the main inlet and outlet header.

Fit

The 471587 fits the MiniMax NT STD, NT TSI and NT LN in sizes 200, 250, 300 and 400, with either the 6800 dual knob controller or the DDTC keypad controller. It is also used on MiniMax CH heaters in sizes 150, 200, 250, 300, 350 and 400, including the CH 150 IID model.

When to replace it

Pentair lists a defective hi-limit as one cause of short cycling, where the heater turns on and off rapidly. Low water flow from a dirty filter or pump strainer and a faulty flow valve cause the same symptom, so check those first.

Before you order

Confirm the heater model and whether you need the 115 F or the 150 F limit. Pentair calls for installation and service by a qualified installer, service agency or the gas supplier.