Heat pump Monitoring

For a number of years now I have been working with John Cantor on monitoring heat pumps. John is one of the UK's foremost experts on heat pumps having worked in the field since the early 1980's, he has written a book on heat pumps and is an advisor and consultant on the technology.

Earlier this year we worked on reading heat metering data from a Kamstrup heat meter in order to obtain accurate heat output measurement in addition to system flow temperatures and electrical power input. After spending quite a bit of time adapting existing emontx hardware and often emontx v2 hardware to integrate the additional circuitry required we decided it might be better to try and design a dedicated heat pump monitoring board that would have all the functionality we needed on a single board.

This board is currently going through initial testing.
The design is up on github here:
https://github.com/openenergymonitor/Hardware/tree/master/HeatpumpMonitor

It features:

• MBUS reader for kamstrup heat meters
• CT current and ACAC voltage based electricity monitoring 
• Pulse counting 
• Analog inputs for Vortex Flow Sensor (VFS) option (e.g Grundfos, Sika) 
• 6x individually broken out DS18B20 temperature sensor connections 
• Arduino ATmega328 core 
• Connectivity options: ESP-12 WIFI, RaspberryPI header, RFM69 
• LCD display connector.

The first version of the design uses through-hole technology for faster and easier prototyping. The cost of the board in kit form is likely to be around £60 inc VAT with an emontx v3 aluminium enclosure and esp-12.

Other uses: The heat pump monitoring board could also be used for other uses such as a esp-12 enabled energy monitor or gas boiler and biomass heat metering. It is essentially an emontx with the additional components for heat metering, on-board wifi and a raspberrypi connector. The analog inputs could also be used with other input devices.

Heat pumps
I have been interested in heat pumps for sometime, they are a key part of zero carbon energy plans such as the ZeroCarbonBritain scenario developed by the Centre for Alternative Technology and are also highlighted in David MacKay's book Sustainable Energy without the hot air. They essentially make it possible to provide heating with around 3x less renewable electrical input than would otherwise be required if direct electrical heating was used instead.

I currently live in a small cottage in Snowdonia, North Wales and after several winters of heating my home with a wood stove and direct electrical fan heaters, I installed with John Cantors help an air source heat pump last October. Its been wonderful having a warm home with much reduced electrical input requirement and its given me a good opportunity to test the technology which I’m happy to say is so far performing well, more on this in another post.

The performance of a heat pump can vary greatly for many reasons, most notably the application. e.g some very well designed space-heating systems are showing COPs (or SPFs) in excess of 4, but some that predominantly heat DHW are only achieving 2. Furthermore, some Passiv Haus applications may seem to have relatively low COPs, but the net energy input is intrinsically very low, so fine-tuning the heat pump design may not be a priority. As can be seen, the topic is complicated, and requires thought, without losing sight of the ultimate objective; to minimise the use of energy.

By monitoring a heat pump its possible to see how well it is working, diagnose problems and generally get a better understanding of how a key potentially zero carbon heating solution works, data gathered and shared from well performing systems could help de-mystify heat pump operation and help improve performance by diagnosing any problems early.

Over the next couple of months we will be testing this new board on several heat pump systems, documenting both the testing of the systems, their performance, the use of the monitor and how to replicate the testing yourself.

Interest list
If your interested in the board please get in contact, drop me an email on: trystanlea@openenergymonitor.org and I will add you to the interest list so that we have an idea of how many to have made in the first batch. The first design is through-hole and would be available in kit form. Please indicate whether you would be happy to build it up yourself or whether you would prefer to wait for a pre assembled SMT version.