Welcome to the MitsuRunner Wiki Page. This site collects information about the project MitsuRunner. Feel free to share your information about MitsuRunner here.
If you don't know what Mitsurunner is, please see the introduction page.

• This web page is hosted and maintained voluntarily.
• The maintainers of this web page do not take any responsibility for its content.
• All installation has to be done by a professional electrician following local laws and regulations.
• If you follow any instructions on this web page, you take full responsibility for possible damage.
• Doing these modifications to your heat pump may void its warranty.

Links:

• MitsuRunner on GitHub: https://github.com/VeliML/MitsuRunner
• Discussion on lampopumput.info (Finnish): https://lampopumput.info/foorumi/threads/msz-ln-sulatushuijaus.31223/

MitsuRunner is a device that optimizes the heating cycles of Mitsubishi Electronics LN-series air source heat pumps. Defrosting is performed only when needed, rather than relying on Mitsubishi's clumsy, reactive “fuzzy logic,” which may trigger defrosting every 40 minutes even if it’s unnecessary.

More about the benefits of MitsuRunner

MitsuRunner tricks the air source heat pump's software by temporarily connecting a 33kΩ resistor in place of the pump’s defrost sensor (Defrost Thermistor R61). Normally, this sensor measures the outdoor unit coil temperature. The trick makes the software believe that the outdoor coil temperature is approximately +2 °C — at this temperature, the pump's logic never initiates a defrost cycle.

MitsuRunner continuously evaluates the actual need for defrosting. It uses two temperature sensors to measure the temperature difference (delta) between the outdoor unit coil and the outside air. When the temperature difference becomes large enough, MitsuRunner disables the trick, and the pump performs a defrost cycle (if its defrost conditions are met). By operating this way — without unnecessary defrosts — the heat pump provides significantly better and longer-lasting heating performance.

More on the topic: MitsuRunner GitHub: https://github.com/VeliML/MitsuRunner Original discussion on lampopumput.info: https://lampopumput.info/foorumi/threads/msz-ln-sulatushuijaus.31223/

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