Low cost on/off mains sensors?

We have an underfloor heating system (UFH) with on/off mains thermostats connected to mains thermoelectric actuators for a number of zones. Heat is supplied from an air source heat pump (ASHP).

We would like to monitor the operation of the UFH system. It would be really handy to be able to monitor when the mains connection to an actuator (or the pump) switches. Don’t need to measure the current or anything else, just whether the power is on or off. Would need to be low cost as there are a number of zones and operate without interfering with the existing wiring.

A search for “1-wire hall-effect” didn’t produce any obvious solutions. In case it isn’t obvious this is a software engineer asking a hardware question. Please be gentle.

Any suggestions?

Hello John

What is driving the actuators? could you use a photodiode on the zone indicators perhaps? E.g on the LED’s that light up on the controller?:

Could be connected to spare digital inputs on a Pi perhaps?

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Thanks, @TrystanLea, excellent suggestion. This is what we have:

I have been told by a colleague on-site that the LEDs behave as expected.

We also have a heat meter on the UFH so no zero flow can at as a proxy for the pump being energised.

Will leave the electronics to someone more knowledgeable.

Hello @JohnConnett

One option could be to use our pulse counting sensor on each LED Optical Utility Meter LED Pulse Sensor - Shop | OpenEnergyMonitor. If you remove the RJ45 connector and wire that up to spare digitial inputs on a raspberrypi that could work. It’s not an out of the box solution that we offer but if you have someone there that can do the electronics and software it might work?

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