Renewable Heating Hub Heat Pump Forums

Search with Wattson
Forums
Renewable Heating
Air Source Heat Pum...
Mitsubishi Ecodan F...
 
Notifications
Clear all

Joining the Renewable Heating Hub forums is completely free and only takes a minute. By registering you’ll be able to ask questions, join discussions, follow topics you’re interested in, bookmark useful threads and receive notifications when someone replies. Non-registered members also do not have access to our AI features. When choosing your username, please note that it cannot be changed later, so we recommend avoiding brand or product names. Before registering, please take a moment to read the Forum Rules & Terms of Use so we can keep the community helpful, respectful and informative for everyone. Thanks for joining!

Mitsubishi Ecodan F8 error

 
Page 1 / 2
Air Source Heat Pumps (ASHPs)
Last Post by JamesPa 8 months ago
14 Posts
6 Users
4 Reactions
1,678 Views
RSS
 HJD
(@hjd)
Trusted Member Member
Joined: 5 years ago
Posts: 43
Topic starter 08/10/2025 12:58 pm   [#2506]

Hi all - I haven’t been active for a while but still keep an eye on the ever helpful forum.

Just wondering if anyone has experienced an F8 error code with the Mitsubishi Ecodan PUZ series? A neighbour is getting it every time the outdoor temperature drops to below c. 5 degrees and the unit switches off.

Any thoughts appreciated.

Howard.


This topic was modified 8 months ago by Mars

   
Quote
Mars
 Mars
(@editor)
Illustrious Member Admin
Joined: 5 years ago
Posts: 4709
08/10/2025 1:06 pm  

Almost certainly one for @ashp-bobba to put his Ecodan error codes to the test 😉 


Get a copy of The Ultimate Guide to Heat Pumps

Subscribe and follow our YouTube channel!


   
ReplyQuote
JamesPa
 JamesPa
(@jamespa)
Illustrious Member Moderator
Joined: 3 years ago
Posts: 5018
08/10/2025 1:58 pm  

Posted by: @hjd
↑

Just wondering if anyone has experienced an F8 error code with the Mitsubishi Ecodan PUZ series? A neighbour is getting it every time the outdoor temperature drops to below c. 5 degrees and the unit switches off.

Has your neighbour tried googling it to find out what the code means (other search engines also available)?


4kW peak of solar PV since 2011; EV and a 1930s house which has been partially renovated to improve its efficiency. 7kW Vaillant heat pump.


   
ReplyQuote
 HJD
(@hjd)
Trusted Member Member
Joined: 5 years ago
Posts: 43
Topic starter 08/10/2025 4:31 pm  

Yes - its just that the F8 code doesn’t actually appear much in Google searches!



   
ReplyQuote
Majordennisbloodnok
 Majordennisbloodnok
(@majordennisbloodnok)
Famed Member Moderator
Joined: 4 years ago
Posts: 1892
08/10/2025 4:52 pm  

Well the Mitsi error code lookup says F8 means "No input detected at outdoor unit" and that the cause may be "Outdoor board defective". It suggests "Check mains power is ok" as the checking procedure.

That's now the full extent of my ability to add any value here, so over to @ashp-bobba or other more qualified person than me.


105 m2 bungalow in South East England
Mitsubishi Ecodan 8.5 kW air source heat pump
18 x 360W solar panels
1 x 6 kW GroWatt battery and SPH5000 inverter
1 x Myenergi Zappi
1 x VW ID3
Raised beds for home-grown veg and chickens for eggs

"Semper in excretia; sumus solum profundum variat"


   
ReplyQuote
dgclimatecontrol
 dgclimatecontrol
(@dgclimatecontrol)
Estimable Member Member
Joined: 11 months ago
Posts: 72
08/10/2025 5:01 pm  

@hjd It means the outdoor unit hasnt detected an input or the pcb is defective. Needs looking at by engineer or at worst an electrician.



   
ReplyQuote
 ASHP-BOBBA
(@ashp-bobba)
Prominent Member Member Professional+
Joined: 2 years ago
Posts: 478
08/10/2025 5:58 pm  

@hjd F8 is uncommon and could indicate incorrect heat exchange due to a lack of flow or a faulty sensor, if you think this is just happening when it gets colder I would suggest all the normal things you chan check for yourself like the filter and valves, if you are not getting an L9 fault then it is probably moving the water above it minimum but when it needs to kick in and exchange a decent amount of heat then it might meet the threshold where it fails.

As this fault could indicate a sensor, flow or heat exchange problem, if you don't see anything obvious in the filters and all valves are open it may be worth getting an engineer to take a look to check if the system is silted up.

Are you able to provide the flow rate for the water in heating? This is a good 1st step.

 

 

 

 


AAC Group Ltd covering the Kent Area for design, supply and installation of ASHP systems, service and maintenance, diagnostics and repairs.


   
👍
1
ReplyQuote
 HJD
(@hjd)
Trusted Member Member
Joined: 5 years ago
Posts: 43
Topic starter 08/10/2025 7:17 pm  

Thanks for everyone’s input. That helps me and my neighbour to do some more investigation.



   
ReplyQuote
Mars
 Mars
(@editor)
Illustrious Member Admin
Joined: 5 years ago
Posts: 4709
08/10/2025 9:14 pm  

@ashp-bobba, do you have a list of Ecodan error codes? If you do, please can you send them to me so I can train Wattson them?


Get a copy of The Ultimate Guide to Heat Pumps

Subscribe and follow our YouTube channel!


   
ReplyQuote
 ASHP-BOBBA
(@ashp-bobba)
Prominent Member Member Professional+
Joined: 2 years ago
Posts: 478
08/10/2025 10:16 pm  

@editor Pages 59-74 for all Error codes and Request codes in the attached link, F8 is not showing as I think it is a shadow code related to P9. We have a log in code for a installers portal that gives us a different kind of access which is on a cloud system so live rather than downloadable but its the same as the manuals.

I think it is worth speaking to tech support as F8 is uncommon and points toward sensors or flow (heat exchange) 

 

https://library.mitsubishielectric.co.uk/pdf/book/PUZ-WZ_50-60-80_VAA_Service_Manual_OCB816#page-1

 

 


AAC Group Ltd covering the Kent Area for design, supply and installation of ASHP systems, service and maintenance, diagnostics and repairs.


   
👍
1
ReplyQuote
Majordennisbloodnok
 Majordennisbloodnok
(@majordennisbloodnok)
Famed Member Moderator
Joined: 4 years ago
Posts: 1892
08/10/2025 10:16 pm  

Posted by: @editor
↑

@ashp-bobba, do you have a list of Ecodan error codes? If you do, please can you send them to me so I can train Wattson them?

It’s errormentary, my dear Wattson.

Sorry, I’ll get my coat….

 


105 m2 bungalow in South East England
Mitsubishi Ecodan 8.5 kW air source heat pump
18 x 360W solar panels
1 x 6 kW GroWatt battery and SPH5000 inverter
1 x Myenergi Zappi
1 x VW ID3
Raised beds for home-grown veg and chickens for eggs

"Semper in excretia; sumus solum profundum variat"


   
🤦‍♀️
1
ReplyQuote
 ASHP-BOBBA
(@ashp-bobba)
Prominent Member Member Professional+
Joined: 2 years ago
Posts: 478
08/10/2025 10:28 pm  

Just to add to the F8 non existing code, in the book is all of the blinking codes and could be worth double checking it not trying to display a P8 which could look like a F8


AAC Group Ltd covering the Kent Area for design, supply and installation of ASHP systems, service and maintenance, diagnostics and repairs.


   
😂
1
ReplyQuote
Page 1 / 2
Forum Jump:
  Previous Topic
Next Topic  
Share:

SPONSORS

Join Us!

Installer Finder

Degrees of Separation

Latest Posts

SPONSORS

Click to access the login or register cheese
Protected By
Shield Security PRO