EmonHP Electric meter

Good evening all,

Following a somewhat eventful heatpump swap from the tentacled beast my electric meters are now not showing any reading in my local emonhp.

The outdoor energy and power feeds show under the inputs however the emonhub shows the following error:

2024-01-10 23:15:02,216 ERROR    SDM120     Could not read register @ 72: No communication with the instrument (no answer)
2024-01-10 23:15:02,317 ERROR    SDM120     Could not read all registers
2024-01-10 23:15:02,317 INFO     SDM120     Connecting to Modbus device=/dev/serial/by-id/usb-FTDI_FT232R_USB_UART_AQ03GQBP-if00-port0 baud=2400 parity=none datatype=float

I have checked and it is ID1 (as expected and has a baud of 2400 and parity of n.

The only thing they have done today with this meter is remove and re run the cable due to it being run from inside, via the heatpump and back out to the outdoor CU where the rcd is located.

The r485 port seems to be wired correctly on both ends and I will be digging out the multimeter to run a continuity test on all three wires tomorrow, is there anything else I can check or review before that as now that I have the EDLA08E2V3 I am keen to actually see the performance and if it is finally running as desired.

If this was bought as the HP Bundle, I believe this is sold with online support so I’d contact the shop.

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Just following up to confirm the cause of the issue to hopefully help others.

During the electrical installation the Electrician overtightened both for the SDM120M meters modbus terminals, this caused the above error.

To correct this I purchased a new meter and had it installed and all is now working.

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Now you understand why the Field Services manager at my last firm referred to those people as " hairy ar$ed 'tricians".

It doesn’t beat the mechanical fitter who used a lump hammer to fit an optical encoder into its mounting.

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These days torque settings are specified for electrical terminals and they can be quite high. I was surprised how much effort was needed to get the right torque on MCB treminals after I acquired a torque screwdriver…

A decent electrician should have a torque screwdriver and use it.

FWIW the SDM120 specifies 2Nm for the power terminals and it feels a lot for the flimsy nature of the device.


I am aware of the need to torque the power terminals. but power and the data terminals (only data were damaged) have different values associated (2nm vs 0.5nm). Regardless it was late due to a delivery issue and he just wrenched on both with a Philips screwdriver (not a torque driver or wrench both of which even I as a diy’er have in my kit), thus breaking the data terminals.

Only added the info about what happened and why to the post in the hopes it helps someone else with troubleshooting in the future :slight_smile: