# Universal controller for heat pump and air conditioner **URL:** \ **Category:** Hardware\ **Tags:** mqtt, dashboards, emonpi, emonhub\ **Created:** [9 November 2021 18:14 UTC](https://community.openenergymonitor.org/t/universal-controller-for-heat-pump-and-air-conditioner/19008 "2021-11-09T18:14:15Z")\ **Posts on this page:** 1\ **Showing post:** 2
**Author:** ![moojuiceuk](https://community.openenergymonitor.org/user_avatar/community.openenergymonitor.org/moojuiceuk/32/7513_2.png) [@moojuiceuk](https://community.openenergymonitor.org/u/moojuiceuk)\ **Post date:** [10 November 2021 18:57 UTC](https://community.openenergymonitor.org/t/universal-controller-for-heat-pump-and-air-conditioner/19008/2 "2021-11-10T18:57:58Z")
OpenEnergyMonitor heat pump board can monitor energy usage an existing heat pump - think temperature probes, heat meter, flow rate, running current etc, but it’s not a drop in control solution for a heat pump with no controller. There is already a DIY open source Heat Pump controller project here: > **[Arduino Powered Heat Pump Controller Helps Warm Your Toes](https://hackaday.com/2021/09/08/arduino-powered-heat-pump-controller-helps-warm-your-toes/)** > > Heat pump heating technology is starting to pop up more and more lately, as the technology becomes cheaper and public awareness and acceptance improves. Touted as a greener residential heating syst… The issue with this arduino project in your case, is that it has been designed for fixed speed compressor setups. Whilst it is probably possible to alter the code (maybe running it on a more capable Arduino micro for the additional IO and memory), and with suitable RS485 interface, talk Modbus to the inverter you already have, it is a non-trivial exercise and not one to be undertaken without in depth refrigeration knowledge and a full specification of the compressor operating envelope, operating parameters and full Modbus command set for the inverter. I should hasten to add, you should also be F-gas refrigerant qualified if you are going to break into refrigerant lines or make any alteration that could pose a risk of refrigerant leak. I have touched on some of these points in a previous forum post here: > [@COP temperature relationship](https://community.openenergymonitor.org/t/cop-temperature-relationship/18456/13): > > @HUGHG Not a problem to write out a long message as I don’t mind sharing my thoughts on this sort of thing. Average humidity in the UK can vary quite a bit according to this site: [Average Humidity in the United Kingdom - Current Results](https://www.currentresults.com/Weather/United-Kingdom/humidity-annual.php) If it’s a foggy day, you have to assume it’ll have a very high humidity and on a hot summers day with no rain in weeks, fairly low. It’ll vary quite a bit all over the country. Given the defrost cycle is going to have a negative impact compared to milder days a… which include example documents from Copeland who make inverter driven scroll compressors. You’ll find that there are example start up procedures for their compressors (what speed to start the compressor, how long it should be maintained), minimum run times, max and min running frequencies, superheat control rules (to avoid flooding the compressor with liquid refrigerant and smashing up the bearings and scrolls, or running with too little vapour and risking overheating the compressor windings) and rules around ensuring correct oil movement to ensure oil does not migrate out of the compressor crankcase. Do you have this sort of documentation from this Chinese inverter manufacturer and for the compressor itself? In terms of commercial based controllers, Carel in Italy make industrial refrigeration controllers which can be custom programmed to suit various applications but I believe the cost of their software licence to develop on their platform is not cheap, neither is the hardware. I would strongly suggest getting hold of the exact replacement controller for the original heat pump that is already pre-programmed to talk to your existing inverter and heat pump set up, unless you are really confident you can write something from scratch and have a really sound refrigeration background. --- _[View the full topic](https://community.openenergymonitor.org/t/universal-controller-for-heat-pump-and-air-conditioner/19008)._