Where is the temp sensor?

[andreadebiase]

I have a water heater (sorry don`t rememebr the brand) with a Honeywell thermostat where you can set temperatures throughout the day/week. My question is, is this thermostat also the temperature probe? what/where is the device that reads the current temperarure at any time?

[junkcollector]

If I remember correctly, you have a forced hot water system right?

Well, there are two limit controls, one is the thermostat. The other is the boiler limit control. It is called the "aquastat." While the thermostat senses what the temperature in the room and switches the boiler on based on room temperature. The aquastat controls the boiler based on the water temperature. It also keeps it from overheating. One control is dependent on the other. For example, even if the boiler limit is satisfied (it has reached its set operating temperature) the wall thermostat may not be.

To answer your original question, The thermostat is the "temperature probe" for the actual house, the aquastat is the temperature probe for the boiler itself. What that device looks like depends on whether the system is oil or gas fired. The room thermostat is what "reads the temperature."