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Mitsubishi Ecodan 11kw Defrosting Issue.

 
Air Source Heat Pumps (ASHPs)
Last Post by ThunderMink 3 days ago
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 ThunderMink
(@thundermink)
New Member Member
38 kWhs
Joined: 7 days ago
Posts: 3
Topic starter 28/11/2024 8:12 am  

Hello, i am new here and also a newbie on air to water heat pumps.

I recently bought a Ecodan / Zubadan split system manufactured 2019 and installed 2021, it was too cheap (500€) so i could not help my-self from buying it and try to get it working. Outside unit is Zubadan PUHZ-SHW112YAA with the pre plumbed inside unit EHST20C-YM9CR2.UK. 

I installed it in June and found lots of small problems, outside unit dip switches configured wrong and also some settings in the FTC5 controller that made it run really inefficiently, when i first got it running the COP was about 2.0 or worse even tho it was summer and warm weather. Then made some changes to the settings and got the COP up to about 3.2 and that was not too bad, now when the weather has become colder the real problem started to show.

When the outside temperature gets below 0 degrees C the defrosting seems to have some weird issue. I saw that the unit had frost on it so i waited until a defrost cycle started and it worked fine, but then when it got even colder to about -4 to -6 degrees it defrosted many times every day and i noticed that the defrost cycle is much to short so it just starts to melt the ice then stops and resume with the heating causing the unit to freeze completely in a day or two.

 

My first guess to the problem would be the 4-way valve but i really cant see how that could be the issue when it clearly do go in to defrost mode but mostly seem to "finish" the cycle in well under 10 minutes which seem to be a very short defrost cycle.

So now with the colder weather the outside unit is frozen and the COP goes down under 2 and won't completely defrost until the ambient temperatures are just below 0

 

Here are some Melcloud and SD card graphs.

internal temperature
Enery usage
21.11 temperature history

 

operation mode
Defrost zoom
SDcarrd

Could this be a sensor problem or something else? Grateful for any advice on this issue.

 

And greetings from Finland.

 

 


   
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Ecodan Zubadan Defrost
 Westkent
(@westkent)
Trusted Member Member
253 kWhs
Joined: 1 year ago
Posts: 22
28/11/2024 10:06 am  

I had a problem with my ecodan unit freezing up having to literally put a hot air gun on Christmas Eve at 10pm 2 years ago.

Took various engineers over a month to sort out.

Low and behold after all the headaches it mounted to a dodgy temperature sensor mounted at the outside or the outside unit at the rear.

Basically it was sending the wrong signal.

good luck 


   
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 ThunderMink
(@thundermink)
New Member Member
38 kWhs
Joined: 7 days ago
Posts: 3
Topic starter 28/11/2024 10:14 am  

@westkent Thank you for the info, this was exactly what i was thinking about. i have a Beamex temperature calibrator and a dry well temperature generator at hand so i will check the service manual what kind of thermistors they use and then check the temperature curve and compare with the manual. Best to check them all as they seem prone to failure / drifting.


   
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 ThunderMink
(@thundermink)
New Member Member
38 kWhs
Joined: 7 days ago
Posts: 3
Topic starter 29/11/2024 4:26 am  

I did not have the time to check the thermistors Yesterday but i am now almost certain that's the problem. I enabled the cooling function on the heat pump and manually "defrosted" the unit by cooling the home. Worked great, had it on about 12 minutes and all the ice was gone. 

At least the 4 way valve should be ok, worst case there is low refrigerant but would not bet on that as the pump both heat and cool very good.

Also i noticed that when using weather compensation i got really bad COP, then when using room auto adapt i got much better COP which also points to the outside unit thermistors. 

This weekend i will test ALL thermistors and hopefully find a faulty one.


   
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Topic Tags:  Ecodan (22) , Zubadan (1) , Defrost (1) ,

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