Gas Fired Thermostat is burnt

[Namcy]

Quite possibly. The "anticipator" is just a resistor that heats up and fools the thermostat to turn off sooner, how much sooner depends on the heating system. If you have cast iron radiators, for example, you want it to turn off before it reaches the set point because the radiators will keep heating because they take a long time to cool down. If you have forced air, heating is pretty much instantaneous. It heats when the blower is running and stops when the blower stops. In that case you want the thermostat to turn off when it reaches the set point, or run a little longer. But the anticipator is all just a matter of comfort. For a unit heater probably in a factory like this it doesn't matter what the anticipator is set at. Who care if it runs a minute or two longer.

As I said, the "anticipator" is a resistor near the bi-metallic temperature sensing spring. This thermostat has it under it because it looks like that's what burned. This anticipator resistor is in series with the thermostat leads so it heats up when the thermostat calls for heat. Apparently, this "universal" thermostat has settings for 24V and powerpile gas valves which are 750mv. As was said, somebody set it for 750mv and 24V was applied to it causing it to burn up.

Replace the thermostat and read the instructions.

-Hal

Thank you

 

[GoldDigger]

Quite possibly. The "anticipator" is just a resistor that heats up and fools the thermostat to turn off sooner, how much sooner depends on the heating system. If you have cast iron radiators, for example, you want it to turn off before it reaches the set point because the radiators will keep heating because they take a long time to cool down. If you have forced air, heating is pretty much instantaneous. It heats when the blower is running and stops when the blower stops. In that case you want the thermostat to turn off when it reaches the set point, or run a little longer. But the anticipator is all just a matter of comfort. For a unit heater probably in a factory like this it doesn't matter what the anticipator is set at. Who care if it runs a minute or two longer.
....

-Hal

One minor point: with a typical forced air heating system, either gas or electric, the thermostat will turn off the heat input immediately, but the fan will continue running until a thermostat in the heat exchanger or electrical element housing indicates that the residual heat in that part of the system has been reduced. This scavenges the last ounce of heat available, as well as providing greater safety.
On the other end of the cycle, a typical gas furnace will turn the flame on, but not start the fan until a minimum temperature has been reached to minimize cold drafts.

 

[mtnelect]

One minor point: with a typical forced air heating system, either gas or electric, the thermostat will turn off the heat input immediately, but the fan will continue running until a thermostat in the heat exchanger or electrical element housing indicates that the residual heat in that part of the system has been reduced. This scavenges the last ounce of heat available, as well as providing greater safety.
On the other end of the cycle, a typical gas furnace will turn the flame on, but not start the fan until a minimum temperature has been reached to minimize cold drafts.

These are old type thermostats that are not used in modern heating systems anymore including floor furnaces. Modern forced air furnaces are very sophisticated with self-diagnostic capabilities. The first step in commissioning a new furnace is to determine the heat rise by selecting the proper blower speed. Modern furnaces have three to four speeds to make sure you meet the manufacturers specifications, so you don't void the warranty. Also, modern thermostats like the "Nest" have Wi-Fi and can be controlled remotely.

If you have a thermostat that has a heat anticipator or is powered by a thermopile generator it's time to get a new furnace.

 

[ptonsparky]

I don't know if that was the cheapest thermostat available, but I'll bet it was in the running.