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Ecodan unable to hit legionella target temp - what's the consensus?

 
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Air Source Heat Pumps (ASHPs)
Last Post by ASHP-BOBBA 4 months ago
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 9jwr9
(@9jwr9)
Active Member Member
Joined: 7 months ago
Posts: 9
Topic starter 17/12/2025 12:37 pm  

@majordennisbloodnok ah! Yes, I did see this video. As per my reply to @rhh2348, we don't have that controller unfortunately. We have an older one, which has no legionella settings available.. If we had the one in the video, I think we'd be sorted!



   
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 rhh2348
(@rhh2348)
Estimable Member Member
Joined: 2 years ago
Posts: 102
17/12/2025 12:46 pm  

MITSUBISHITECH.CO.UK "http://www.mitsubishitech.co.uk/Data/Ecodan/Controls/PAC-IF031B-E_FTC2/FTC2_IM.pdf"

mentions dipswitches to control legionella - one of the options is every 15 times DHW?



   
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 benson
(@benson)
Reputable Member Member
Joined: 2 years ago
Posts: 300
17/12/2025 4:00 pm  

@rhh2348 ...maybe this option is what you want?

Alternatively the immersion heater may be controlled separately. If direct control is not required then DIP switch SW1- 4 should be turned OFF and the immersion can then be controlled via its own weekly timer as with FTC1.

 



   
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 9jwr9
(@9jwr9)
Active Member Member
Joined: 7 months ago
Posts: 9
Topic starter 27/12/2025 12:27 pm  

UPDATE: Thanks everyone who commened with suggestions here - all really appreciated. For those interested, the issue was with the immersion thermostat itself, as some people suggested. The thermostat had been calibrated (for reasons unknown) to max out at 60 degrees, which meant it was physically impossible for the water temp to go beyond that. I broke the little plastic restricter off it, turned it an extra quarter turn, and the tank then succesfully heated to 65 degrees, satisfied the legionella cycle requirement and we're all good now! 🙂



   
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 ASHP-BOBBA
(@ashp-bobba)
Honorable Member Member Professional Installer
Joined: 1 year ago
Posts: 440
28/12/2025 7:41 pm  

@9jwr9 Hi, yes this is the issue with every (stand alone Ecodan) when mixed with an alternative cylinder, we set them all to 60 Deg C and just make them keep that heat level longer to cover the burn. If you use a Mitsubishi cylinder they do not have a control stat on the element only an overheat and all of the control is done through the contactor. What happens with the stand alone Ecodan and an alternative cylinder is the contactor is still used but has another stat inline as part of the element.


AAC Group Ltd covering the Kent Area for design, supply and installation of ASHP systems, service and maintenance, diagnostics and repairs.
Professional installer. Book a one-to-one consultation for pre- and post-installation advice, troubleshooting and system optimisation.


   
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