Two question - Disable RF and AC inputs

I would like to disable the other transceiver on this board as I am only using the esp wifi for my needs, is that possible to disable it? Even if its removing the chip.

Second question, what voltage range can be used for the ac sensing? Most residential HVAC systems in the US use a 24vac little transformer that powers the thermostat and relay controls. It would be ideal to tap off this as the voltage source, as well as power. Any thoughts on that? I assume I can get a small ac to dc supply to run the 5v input, but what about the voltage monitoring part?

Welcome, Jason, to the OEM forum.

I know next to nothing about the Heatpump Monitor, however I’ve had a look at the drawings and the what I think is the core section of the software.

First, the easy one: The energy monitoring part is designed to accept a nominal 9 V a.c. signal. The type of transformer used is always specified at full load, whereas in this application the load is almost non-existent, so the actual voltage that it expects to see is around 10 - 12 V. If you can change resistors on the circuit board, then the actual minimum voltage is about 1 V (rms), anything above that up to the voltage rating of the connector (probably about 25 V without checking) could be used with the appropriate resistor change. However, to measure real power accurately, the transformer needs to have a relatively undistorted output and it’s not referenced to GND, so sharing the voltage from some other equipment could give you problems, either with the heat pump monitor or with the other gear, or both. You definitely cannot use the same transformer for both power and voltage sensing.

Looking at all the source files I can find, the RFM module (the 433 MHz ISM Band) is disabled in software - the relevant line is
#define RFM69_ENABLE 0
in all but “HeatpumpMonitor_AutoTemp”, where it is enabled (1). To disable it in there, you need to change that to RFM69_ENABLE 0; save the file, recompile and reload it.

If this doesn’t help, post again and I’ll find someone who knows for you.

it was a real pain to flash the software, is the software you are referring to on the atmel chip or on the esp8266? I would rather just cut a trace if I could that powers that transciever.


The RFM module is driven by the sketch in the Atmel ATMega 328P, so it is that which you need to modify.

You should be able to find the CAD files for the p.c.b. on Github. There are png files, which you might be able to use, if not you might want or need to install Eagle CAD (free).