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Ecodan Cascade System Problem: DHW Heating Stops UFH & Pool Output

 
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Air Source Heat Pumps (ASHPs)
Last Post by F1p 8 months ago
30 Posts
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 fosterl2
(@fosterl2)
Active Member Member
Joined: 9 months ago
Posts: 16
Topic starter 04/02/2026 1:17 pm  

@f1p Just checked again (with different glasses on!) and they are sliders, not rockers, and set correctly.

Looks like separating the cascade will be the way to go.



   
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 fosterl2
(@fosterl2)
Active Member Member
Joined: 9 months ago
Posts: 16
Topic starter 24/02/2026 9:16 pm  

The issue seems to be solved: I found that the plumbers had routed the flow return from ASHP1 into the flow return of ASHP2, hence the whole system was behaving very badly.

I had to get the cascade removed to work it out, as there was only 1 set of thermistors - once the flow and returns of each ASHP could be monitored independently, it was pretty clear that there was a plumbing issue. Now the DHW ASHP is getting its proper flow return, the tank heating time has changed from not always being able to heat to target in 2hrs, to getting to 50 degrees in about 45 minutes!

I think the hardware supplier got the hump when asked to remove the cascade wiring (they took the master controller away...) so don't think I'll be asking for it to be put back in - with matching settings, the two ASHPs seem to be playing nicely, but the pool and pool room rads are not yet connected. 



   
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 F1p
(@f1p)
Estimable Member Member
Joined: 1 year ago
Posts: 129
24/02/2026 9:24 pm  

@fosterl2 operationally that's a great outcome!

I wouldn't be too pleased them taking away the master FTC7 with a retail price around £940 though!



   
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 fosterl2
(@fosterl2)
Active Member Member
Joined: 9 months ago
Posts: 16
Topic starter 24/02/2026 9:26 pm  

@f1p Indeed - I am just waiting to see if I get sent a bill for removing the cascade, but intend to either ask for a refund, or a return of my property and have it as a cold standby!



   
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 fosterl2
(@fosterl2)
Active Member Member
Joined: 9 months ago
Posts: 16
Topic starter 24/02/2026 9:31 pm  

The next challenge will be getting 60mCu of water warmed up! - I assume for the initial heating, take the weather compensation off, fix both flow temps to perhaps 40 degrees and run it during the day to maximise efficiency.

Any thoughts on how long that volume of water would take to around 25 degrees?



   
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 F1p
(@f1p)
Estimable Member Member
Joined: 1 year ago
Posts: 129
24/02/2026 9:43 pm  

@fosterl2 with a hysteresis of 5C probably around 6 days non-stop

If you do fixed flow of 40 and the  only in the day it might be similar? 

Guesswork!



   
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