Furnace monitoring

Question - How can I used existing furnace wiring connected to a sensor to monitor if the furnace is not firing on a “regular” basis.
Currently there is a wire that runs from a Riello 40-F5 burner to a Gem-400 Alarm panel (zone 4). I assume it was used to monitor if the burner was firing or something similar as it also had a primitive low temperature sensor on zone 3. I should note this was a second home to the previous homeowners so they were not in the house at all times.

While I have smart thermostats to know if the temperature in rooms are OK, I do not have a way to know if the boiler is firing regularly during warmer months to keep the water in the hot water tank hot.

Has anyone done this? Can I just take the wire from the alarm panel from the furnace and connect it to a Mimolite?


You can use a current sensing relay with the output going to something like a mimolite or cheaper a EcoLink contact sensor. In your boiler should be something you can put the sensor around that draws power when its running.

Now if you want to get fancy and actually know the heat is firing you can use a old school mechanical thermostat, set it for a temperature like 80*, and place it on the boiler or somewhere that gets hot when it fires. It simply will make or break the contact at the temperature you set.

if hot water is the question then it could be useful to actually monitor the pipe temperature. I would not care about an actual water temperature, so it would be useful to strap either a regular wireless temp sensor to the pipe, and insulate around it (or not). Or strap a remote bulb like DS18B20 + Fibaro FGK-101 . Pipe temp would be close to water temp anyway.

You said furnace AND boiler so not exactly clear which. I do like to monitor furnace temp which is even easier to drop a temp sensor into any discharge duct.

One nice thing about temperature is, it is not on/off, so it should update and change with some freshness. That with battery monitoring, should allow supervision of the device health.

It is a boiler. Sorry about that had to have someone explain the simple difference to me.

yup. And boilers don’t boil water. Language is a fuzzy thing

They do if they arn’t setup right and the safeties have a paperclip in them…

(unfortunately speaking from experience)