Problem with Horstmann electricity meter.


I have had my Mk2 PV Router up and running for 18 moths now. It was operating well until a few days ago when the program occasionally stop running and then started again. This was traced to a faulty connection to the RFM12B. This was repaired and the unit now appears to be running well.

I previously checked the electricity meter by making sure the readings did not increase when power was being diverted. After reading the forums I realised that a red light on my meter should flash to indicate consumption.  I have now located this light but it is not very bright and impossible to see in daylight, as the meter is situated in an outside cupboard.. When I shaded the meter I saw that the red light did in fact flash occasionally.

The meter is a Horstmann series 2 model NU 076-1M economy 7. I am running Robins code V5c in anti flicker and remote has priority mode. I decided to change the energy bucket size (SWEETZONE_IN_JOULES) to see if this would stop the red light flashing. This made no difference, and the light continued to flash,even when I took it down to 100.

I turned off the diverter and the light continued to flash even when no electricity was been used in the house, but I did noticed that the flashing rate increased as the PV generation increased. The flashing only stopped when I turned off PV generation.

Could it be that the meter is recording PV generation? Does anyone know if this is usual for this meter or have any ideas to solve the problem please?


Many thanks.

dBC's picture

Re: Problem with Horstmann electricity meter.

I'm not familiar with your meter, but I guess it's possible it's erroneously counting PV generation, or it may be that it's not counting it, but still flashes the LED regardless of power direction.  On a sunny day, where you're producing more than you're consuming, and with the diverter OFF, does the kWH reading on the meter climb or remain at the same reading until the sun goes down (or some big loads come on)? 

Robert Wall's picture

Re: Problem with Horstmann electricity meter.'s possible it's erroneously counting PV generation...
It may not be erroneous! I believe some meters deliberately count export as import as an anti-fraud measure. It was of course sensible before private generation became a reality. All you can do in the circumstances is check the register(s) when you know you are exporting energy. The import register of the meter (if it has a register dedicated to import), or the register if there's only one, should not change when you are exporting. The rules are here:

dBC's picture

Re: Problem with Horstmann electricity meter.

According to Horstmann it shouldn't decrement at least:

Forward energy registers do not decrement if reverse energy is passed through the meter (for all Horstmann models). 

They also claim to indicate when reverse energy has been detected via the LCD display, so you could possibly check for that too:

There is an indicator on the LCD display to indicate that reverse energy flow has occurred. This can only be reset by communicating with the optical FLAG port

And to count it separately:

Reverse energy measured by the meter is stored in a Reverse Energy Register.  In the case of Import/Export meters independent registers are used for import and export energy.

solar's picture

Re: Problem with Horstmann electricity meter.

Many thanks for the replies.

The display on the meter does show a left pointing arrow with the word RED next to it, so perhaps that is an indication that the meter is receiving exported energy.  I have a feeling that the meter is counting exported energy as consumption if the PV system is generating more power than the diverter loads can absorb or it is turned off. I therefore need to prove this one way or the other. I will update this thread as soon as I can as other meters may be similarly affected.

Once again, thanks for the help.


calypso_rae's picture

Re: Problem with Horstmann electricity meter.

Our supply meter slowly toggles between the Consumption reading and "rEd".  This occurs regardless of the state of the LED or anything else.  As I understand it, the presence of the "rEd" display is simply to show that at some stage in the meter's life there has been some reverse flow.  That must have been before our Mk2 system went live :)

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