Modbus wiring

Finally getting around to installing my heatpump monitor.

The Kit comes with a SDM120

The current meter I have is a Rayleigh RI-D35. Which appears to provide RS485 and 2 types of pulse output.

Just wondering if it is possible to to this meter ? (no idea how to wire it in as it provides 6 termainls as opposed to 3 like the 120.

Not a bit issue, I can just install the 120 if needed.


Difficult to tell, but it does say there is a Modbus version, so it should be possible to read that.


Actually, this is pretty clear.


Right I’ll see if I can workout the pin outs.

Got the sd120 in for now.


It’s pins 4and 5, both readers are available from the shop mbus and modbus.

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