Honeywell thermostat going blank

Chris Bain

A few times per day, my digital Honeywell round thermostat, controlling my steam boiler, goes blank. There's no readout whatsoever, even when I turn the dial. Then awhile later, the diplay comes back. Is this normal?

Nron_9

thermostat

there not supose to go blank if it takes batteries change them if not the high limit maybe turning off the power to the thermostat get your system checked for problems soon

Chris Bain

It is a battery-less model.

Bill Nye_2

Sometimes

You need a 24 volt circuit to power the t-stat . "Power stealing" it is sometimes called. The t-stat needs just a little current to power the LED display. When you have no call for heat for an extended period of time the screen goes blank. When you turn up the temperature and the circuit "makes" it will re-energize the LED.

You may need some type of relay to keep power to it. I have the same t-stat in my entry way for my radiant zone. In the summer when I turn the heat / off switch to off , I lose my clock display.

Do have a gas or oil burner? Maybe Bill from Honeywell can help if he sees this post. Maybe a diode or resistor can help. Electronics is not my strongest subject. Hope this helps. Bill N

Steamhead

Does the screen go blank

after the boiler has been running for a long time? If so, it's probably the Pressuretrol stopping the burner on pressure. On most steamers this will also cut power to the thermostat circuit as well. The same thing happens on oil-fired steamers if they go out on safety.

An ordinary circulator relay such as a Honeywell RA89 or R845 will cure this. It has its own transformer that will maintain power to the thermostat, while switching the burner's "Thermostat" circuit as needed.

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