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!
System pressure dropping on my Ecodan ASHP system
I have an Ecodan ASHP, due to some building works the hot water cylinder was relocated and some legs have been run for 3 more radiators which have yet to be fitted.
Hot water has been fine since the relocation of the cylinder around 4 weeks ago. This weeknd I put the heating on, all was fine but next morning when the hot water cycle ran before the heating comes on there was a U1 fault which I believe is a low pressure fault.
So I filled the system to about 1.7bar when heating was on and bled the radiators. I manually put water cycle on and cylinder had hot water.
Next morning after heating had been on before same problem. It seems that when I fill the system within about 30 mins pressure drops to 1 bar or less, however all rads are nice and hot.
Any ideas? Thanks.
@spacebiscuit - this is an interesting question, why does an ASHP circuit need to be pressurised in the first place? I can't be, as it is with a traditional car radiator system, so the water can get to a higher temperature without boiling, since ASHPs don't get anywhere near those temps. I have a very very small leak, at least I assume it is, in my primary circuit, that causes the pressure to drop very slowly (over days if not weeks) and yet the system seems to run the same whatever the pressure, as long as the circuit has fluid in it, which it does. Maybe the pressure is there to stop negative pressure that would perhaps allow air to enter? Does anyone know the answer?
Midea 14kW (for now...) ASHP heating both building and DHW
Hello i am an ASHP Engineer and new to this group. Ecodan U1 code is said to be high pressure fault,which is cause by abnormal water flow on the primary circuit. I recommend get ASHP engineer to come have a look.
- 27 Forums
- 2,811 Topics
- 66.5 K Posts
- 2,933 Online
- 7,217 Members
Join Us!
Installer Finder
Degrees of Separation
Latest Posts
-
RE: How much of your renewable and home setup would still work if the internet went down?
Agree but remember to retain your isp router as they wi...
By JamesPa , 9 minutes ago
-
RE: The Changing Jet Stream Could Challenge UK Air Source Heat Pumps
@susannasaunders Reluctantly I think i agree with @r...
By JamesPa , 15 minutes ago
-
RE: Why don't people choose heat pumps?
It's swings and roundabouts - during off-peak periods t...
By Temperature_Gradient , 1 hour ago
-
RE: Adding data centre electricity costs to domestic energy bills?
never ceases to amaze me.. Keeping steel works going ...
By Batpred , 8 hours ago
-
RE: Electricity price predictions
great session Reminds me why some politicians can be ha...
By Batpred , 9 hours ago
-
RE: Boiler Upgrade Scheme funding reduced by circa £750 million in 2026 budget
Absolutely agree. The massive Hager CU my vaillant requ...
By Batpred , 9 hours ago
-
RE: Octopussy cosy 6 experience
People who have a Cosy appear generally to be happy wit...
By JamesPa , 13 hours ago
-
I thought the cr*p came first and the biofuel came afte...
By Majordennisbloodnok , 16 hours ago
-
RE: Aerotherm and weather compensation
@jamespa I replied yesterday with detailed readings whi...
By DavidB , 2 days ago
-
RE: Marvel Heating liquidation
@editor This is an important point. each winter, you...
By davidnolan22 , 3 days ago
-
RE: Solar Power Output – Let’s Compare Generation Figures
Very nice. we’ve been super soggy here, but rather m...
By Papahuhu , 4 days ago
-
RE: DIY powerflushing tutorial
Interesting! I toyed with the idea too. But I installed...
By bobflux , 4 days ago
-
RE: 15kw pump for 225m2 1990's house - over kill?
@seaviews Agree with the others on sequence: loft first...
By mk1234 , 4 days ago
-
RE: Vaillant ecoTEC Plus - Flow Temp and Set Up
Heating been on for 4 weeks now, continuous. It's 6C o...
By trebor12345 , 5 days ago



