Resideo Q313A1188/U 35 in 750 mV Thermopile with Push-In Clip and Split Nut

The Q313A1188 is a 750 mV thermopile from Resideo (Honeywell Home), 35 inches long.

A thermopile is a stack of thermocouples wired in series. Where a single thermocouple makes about 30 millivolts — just enough to hold a pilot safety valve open — a thermopile makes around 750, which is enough to run the whole control circuit.

That is what a millivolt system is: a gas appliance that needs no electrical supply at all. The pilot flame generates the power, the thermostat switches it, and the gas valve opens. The appliance keeps working through a power cut, which is why millivolt controls are still specified on fireplaces, wall heaters and standing-pilot unit heaters.

A thermopile that has aged puts out less voltage before it puts out none. The symptom is an appliance that lights and runs but drops out when the thermostat calls, or one that will not restart once it has cooled — the output is enough to hold the pilot but not enough to pull in the main valve.

Supplied with a push-in clip for the pilot bracket.

Supplied with a split nut.

Thermopiles power the control circuit, so they pair with millivolt thermostats such as the T827K1009.

• Brand: Resideo (Honeywell Home)
• Manufacturer Part #: Q313A1188/U
• Type: Thermopile
• Output: 750 mV
• Length: 35 in
• UPC: 085267066297
• Category: Thermocouples & Thermopiles