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!
New Mitsubishi system, several concerns but just a newbie…..
@carpenterstation happy to try and help but can you post screen shots of what you have set in the timer menus. Assume you realised there are 2 seasons that you have to set up?
The heating and hot water should display the timer symbol next to them if they set to use the schedule.
Just checked the schedule timer some photos all taken at the same time
it looks like schedule1 is set Jan to Dec and schedule 2 is inactive - but both schedules are set per image 3.
image 1 shows current state - water at 35degrees I think. Nothing calling for heat. So why is the system pumping? Image 4 (now 18:00 and Elex is 35p per kWh plus vat)?
I’d appreciate any help but short of putting a timeswitch on the whole system I seem powerless to stop it needlessly operating?
@carpenterstation In the screenshot of the main controller the hot water temp is the 35C reading as you thought.
You have the clock symbol by the tap so that shows its using the schedule, it also has the square by it that shows its inactive which at 17.50 is correct per your schedule.
If the purple section in the solar chart is showing house usage of around 3-4kW between 5-6pm thats not due to the heat pump heating the hot water.
Under the tap symbol you have the house heating symbol, your system is set up for 2 zones. Its displaying that zone 2 is paused but that doesn't mean that zone 1 wasn't running, if you flick it to zone 1 by pressing the button underneath the z1/z2 then it will change to display zone 1, if you have a play symbol then the heat pump is heating zone 1.
The other thing that is could be is that the immersion assuming you have one is heating the hot water is that something you can check?
This is exactly my point. There is literally nothing running in the house except a fridge freezer and the house is burning 4kw - and the heat pump is definitely ON even though it is not supposed to be. I have checked z2 and there is nothing loaded there. The immersion (if it was running) is only there for the legionella cycle, and it wouldn’t drive the pump (image 4). But as the hot water is not budging from 35 degrees it can’t be that either !!
sorry but I am really confused. I seem to be spending money on nothing!
Have you been outside and you can actually see the fan running on the heatpump?
You said you have checked zone 2 was this a typo as it’s zone 1 you need to check.
if the fan is running turn off the main controller by holding down the power button and go and check the fan again.
Has it stopped? Can you check that the power draw for the house is now back to normal.
I would some basic checks to prove it’s the heat pump running.
i would also find the switch for the immersion and turn it off and check power draw again .
@gary thanks very much Gary. I genuinely appreciate the help. I will try all that tomorrow at 18:00 ish again and will let you know.
thanks again.
Got home from work today. Same scenario. Nothing calling for heat. One of the cascade pumps is running - again burning high cost electricity ? What for? Water isn’t heating? Rooms are above thermostat temp? UFH is not pumping ? So why is the unit burning electricity?
You can see from picture 1 that the ASHP kicked in at 17:30 ( 16:00- 1900 is 35p / kWh and I really don’t want to consume electricity at this rate) pic 2 you can see that the unit on the right is whirring away. (Unit on the left is not running).
luckily it was sunny today so I have only used some of the battery rather than than import from the grid - but I still need to know why it is running? I don’t think it was a defrost cycle. It’s 5 degrees outside - but it wasn’t doing much from about 16:00 - so I can’t imagine that it needed to defrost?
I think you need to get your installer back, something isn't set up correctly, you have ruled out all the obvious causes.
- 27 Forums
- 2,811 Topics
- 66.6 K Posts
- 3,621 Online
- 7,223 Members
Join Us!
Installer Finder
Degrees of Separation
Latest Posts
-
RE: Why don't people choose heat pumps?
Absolutely nothing in the regs prevents this, nor does ...
By JamesPa , 1 hour ago
-
RE: Air-to-Air Heat Pumps & Air Conditioning: UK Heating and Cooling Q&A
@jamespa I agree, the efficiency of Cosy Cooler ought...
By Rob of York , 2 hours ago
-
RE: How much of your renewable and home setup would still work if the internet went down?
I think you're right! 🤨
By Transparent , 14 hours ago
-
RE: Renewables & Heat Pumps in the News
ECO4 muddies the water somewhat, and then some. I thi...
By cathodeRay , 14 hours ago
-
RE: Vaillant ecoTEC Plus - Flow Temp and Set Up
If there is a drain nearby that's exactly what I would ...
By JamesPa , 15 hours ago
-
RE: DIY powerflushing tutorial
This is what bacterial growth in UFH loops looks like. ...
By Pirate Rich , 22 hours ago
-
I think that CCGT plant in Lingen is more likely to suc...
By Transparent , 2 days ago
-
RE: Heat Geek installations: share your experiences
@l8again fwiw my experience (Valiant but not with heat ...
By JamesPa , 2 days ago
-
RE: How Can I Prove Coal Was My Main Heating Source Without Receipts?
@etchedpixels thank you for the advice paid cash all...
By Chilli304 , 3 days ago
-
RE: The Changing Jet Stream Could Challenge UK Air Source Heat Pumps
@susannasaunders An interesting conversation to have ...
By Rob of York , 4 days ago
-
RE: Electricity price predictions
@rob-of-york sounds like a term that Heidegger would...
By Papahuhu , 4 days ago
-
RE: Adding data centre electricity costs to domestic energy bills?
never ceases to amaze me.. Keeping steel works going ...
By Batpred , 4 days 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 , 4 days ago
-
RE: Octopussy cosy 6 experience
People who have a Cosy appear generally to be happy wit...
By JamesPa , 5 days ago
-
RE: Aerotherm and weather compensation
@jamespa I replied yesterday with detailed readings whi...
By DavidB , 6 days ago












