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New Mitsubishi system, several concerns but just a newbie…..

Carpenterstation · 2025-02-01T08:53:39Z

We have just installed a 17kw cascade ecodan system. Seems too big to me - but the installer insisted based on property size (450 m2) despite our LPG historic usage being less than 30MW per annum which would suggest a 12kw system (and therefore not a cascade) not 17! We have 10kw of solar panels and 15kwh of battery storage it is not possible to monitor energy consumption via Melcloud (as it is a cascade system) and apparently Ovo won’t be able to tell how many kWh we have used either - so we can’t use their tariff. But I can’t believe that this is really the case? How is journey to net zero (etc) being measured if the API can’t cope with cascade systems? the Ovo tariff isn’t available at the moment in any case - so we are with Octopus Cosy. Because of the cosy tariff we do not want to heat water at peak electricity cost times - so I have configured this. But even though this is off from 16:00 to19:00 and no heat is being called the system still kicks in? Any idea why! Is the water heating timer somehow disabled (even though the controller is suggesting it is enabled?) and the final point… we are using less energy than with LPG - but the cost per kWh is at least 25% higher on the cheapest tariff - and up to 350% higher on the most expensive. We need a very high SCOP just to break even. Why is gas (even LPG) so cheap compared to electricity?

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Air Source Heat Pumps (ASHPs)

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Gary

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04/02/2025 3:00 pm

@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.

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Carpenterstation

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Topic starter 04/02/2025 6:05 pm

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?

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Carpenterstation

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Topic starter 04/02/2025 6:09 pm

And here is the solar tracker showing that I am burning 4kw - that can only be the heat pump.

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Gary

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04/02/2025 6:24 pm

@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 post was modified 11 months ago by Gary

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Carpenterstation

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Topic starter 04/02/2025 6:55 pm

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!

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Gary

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04/02/2025 7:30 pm

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 .

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Carpenterstation

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Topic starter 04/02/2025 9:11 pm

@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.

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Carpenterstation

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Topic starter 06/02/2025 6:23 pm

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?

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Gary

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