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Ecodan U4 error code

 
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Air Source Heat Pumps (ASHPs)
Last Post by spacebiscuit 2 years ago
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 spacebiscuit
(@spacebiscuit)
Active Member Member
Joined: 2 years ago
Posts: 11
Topic starter 17/06/2024 2:42 pm  

I've cleaned that solder joint up and resoldered it, looks good now. But today no matter what I've tried the machine will not spin up. I've tried wiggling the wires connectors, thermistors on the pipes but nothing! I'm all out of ideas.



   
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 spacebiscuit
(@spacebiscuit)
Active Member Member
Joined: 2 years ago
Posts: 11
Topic starter 18/06/2024 11:17 am  

I discovered that there are some dip switches (SW2) that can be set on the unit's controller board which will indicate the exact thermistor at fault. In my case it was the water inlet thermistor that was showing a wrong resistance which I missed when I was testing each thermistor for general operation not actual readings.

Part ordered and hopefully that will be it fixed!



   
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 Gary
(@gary)
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Joined: 4 years ago
Posts: 350
18/06/2024 12:58 pm  

@spacebiscuit could you detail what switches you changed maybe useful for someone else in the future thanks



   
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 spacebiscuit
(@spacebiscuit)
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Topic starter 18/06/2024 2:25 pm  

On SW2 switches 1, 4 and 6 need to be on - this will then return a number corresponding to a thermistor. Although in my case it returned '3' which could be one of two. So I then had to try 3,4,5 on which gives the temperature of the inlet - mine was read '102' which is not achievable and so indicates a bad resistance reading and therefore TH32 being the faulty thermistor - I hope!

See pages 74 and 76 here:

RENEWABLEENERGYHUB.CO.UKRENEWABLEENERGYHUB.CO.UK "https://www.renewableenergyhub.co.uk/uploads/products/1628/product_brochures/Ecodan_ATW_PUHZ-HW140VHA2-BS-PUHZ-HW140YHA2-BS_Service.pdf"

 



   
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 Derek M
(@derek-m)
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Joined: 6 years ago
Posts: 4425
18/06/2024 3:06 pm  

@spacebiscuit

Page 55 shows the resistance range for TH32, which could be measured if you have a suitable multimeter. You could also test the circuit board by connecting a suitable resistor in place of the thermistor.



   
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 spacebiscuit
(@spacebiscuit)
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Posts: 11
Topic starter 18/06/2024 4:05 pm  

Oh I didn't see that - so I'm getting 300-320 ohms on that thermistor....



   
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