LED to trigger Stopwatch

[poolpro]

Hello, I would like to rig a stopwatch to a pool thermostat. When the unit calls for heat, an LED lights up and the boiler fires up.

I want to rig a stopwatch to the LED light so it will start when the LED goes on (boiler fires on) and then the stopwatch stops when the LED goes off (boiler turns off).

This will allow me to keep a running time on the actual BTU's expended so I can calculate the overall cost of heating the pool.

Please assist.

 

[kinarfi]

That seems complicated, just hook an electric clock up to the boiler so it only run when the boiler is on. If necessary, hook a relay to the gas valve, assuming gas fired, so you know how long the gas valve is open.
Kinarfi

 

[Reloadron]

Maybe just use a pretty standard run time meter the types of which can be found here as an example. That would provide an accumulated time the boiler has run.

Ron