What does MV stand for on a gas valve?

These are usually a PV (pilot valve), an MV (main valve), and a COMMON wire. In the redundant valve one coil allows gas into the onboard regulator where you can set the output pressure and the second coil allows the output of that regulated gas to the burner manifold. Both have to open for the valve to allow gas out.

What does th and Tr mean on a gas valve?

TH – The 24v hot leg from the thermostat on a call for heat (R+W closing) to the gas valve (TH terminal) to open the solenoid to allow gas to flow. This is assuming that the transformer is good and the high limit is closed. TR – The 24v common/return side of the transformer.

What is millivolt control on gas logs?

Millivolt Gas Valve This small amount of electricity provides enough of a current to control an electromagnet that pulls the valve open against a spring; if the current isn’t present, the valve will snap shut and turn off the gas.

How many volts do you need to open a gas valve?

24-volt
Modern gas valves typically have a printed circuit board in them that receive a 24-volt signal to activate the valve inside of it.

How many millivolts does it take to open a gas valve?

on/off switch. Thermopile Output- MAIN BURNER ON: 110 mv minimum required for system to operate consistently. If lower than 110 mv, conduct valve operating head test.

What is th and TR?

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Is th or TR common?

TH/TR is a common connection, but that doesn’t explain much in itself. TR – The 24v common/return side of the transformer.

What does MV millivolt mean?

one thousandth of a volt
a unit of electromotive force equal to one thousandth of a volt. Abbreviation: mV, mv.

What is a 750 millivolt thermostat?

Millivolt systems are not very common and are primarily used in direct- or top-vent wall furnaces. Millivolt thermostats use very low voltage, usually 750 millivolts (mV) or 0.75 volts. Unlike low-voltage systems, they do not require a step-down transformer and are not connected to the household wiring system.

How do you test a Honeywell gas valve with a multimeter?

How to Check the Furnace Gas Valve With a Multimeter

Turn off the furnace at the wall control.
Take out the bolts in the service panel on the side of the furnace using a nut driver.
Pull the wires off the gas valve terminals.
Turn the test control on the multimeter to “mV,” which stands for millivolt.