Gary68

Just another point for reference, we have a not very well built or insulated 190sqm house from 2003, heat loss was calculated at 7kw and have an 8.5kw Ecodan and it was fine at -6C last winter.

What is calling for 'heat', you may find that you need to increase the temperatures on your thermostats to call for heat which will tell the heat pump to turn on and then cold water will circulate round the system. That's how it works with my air to water heat pump.

Its an Ecodan, flick DIP switch SW2-4 to on, reboot system, cooling now available in heating menu select flow temp and away to go.

Mine is set to 48C and I can just about hold my hand under it continuously, so it sounds like you are a lot lower than that if the bath is just warm enough, at 50C you get burnt in 5 mins. Also depends where the temperature sensor is in your tank if its not towards the bottom a lot of the tank won't be at 52C

The Melcloud app is easy to program, just choose your unit, go to timer, I add in the start of the off peak time and till it to run at a fixed flow during the winter. The flow temp can only be set from the main controller not the app. Then at the end of off peak I tell it to run change back to WC. In spring and autumn, I still run it at night but only in WC mode so 32C rather than 45C in winter. At this time of year it probably won't come on till the next off peak period, so no peak use.

Agree with Johnmo I have an ecodan I had an extra ufh pump fitted and a wiring centre with actuators and zoned thermostats. 5 years later it’s all redundant never needed in the first place all the actuators are disconnected all zones open all the time ufh pump is turned off water flows round quite happily when the heatpump is on. Probably £500 of waste if it was designed correctly in tne first place

£200-£300 is typical in southern England

3kw is exactly what most immersions pull that would my first check if you have one. The switch for ours is in the understairs cupboard and my in-laws turned ours by accident had me puzzled for a while.

For a rough estimates divide by 2900 so yours would be 6.3kw so your looking for a 7 or 8kw heat pump

If you have the MELCloud app you could do it. There is a timer function and you can set it to heat or cool at any time or day.

Post a screenshot of the front screen of your controller and your heat curve sounds like either the heat curve is wrong or you are running at a set temp and not weather comp

It defrosts less at -7C so increased running time at higher flow temps

My heat loss was calculated at 7.7kW and they installed a 8.5kW Ecodan, it works well at the -2C design temp it has to run 24/7 to keep the house at 21C but works right down to the -7C temps we saw this winter with no noticeable impact to internal temp. I believe this is because the MCS heat loss survey is probably conservative so we have a bigger buffer (no pun intended) in the heat loss than calculated. The bigger issue with Ecodan's is that if you have the Mitsubishi preplumbed cylinder then they come with an awful LLH and a whole host of pumps and to maintain warranty they have to be filled with glycol. The other issue with Ecodan is that the primary pump is not located within the outside unit, its installed internally within the house so depending on the location can cause a noise nuisance, especially at night. The Ecodan also cannot modulate the flow rate itself to maintain delta T. In saying all that its run flawlessly for 5 years, has a reasonable COP of 3.5. Would I buy one again, no, I would give Vaillant or Daikin a go if I had to change.

Just to clarify the Melcloud app doesn't calculate COP. Its shows an estimate of power consumed and heat generated on a bar chart that you can estimate COP from but its not particularly useful, as there is no data other than the bars and its an estimate. Where the app is useful is seeing what the flow and return temperatures are doing for the last 24 hours so you can see how its cycling on and off. You can use it to turn the ASHP on and off remotely and change room temperature if you are using the main controller to control temperature. You can also set a schedule for heating and hot water and change from fixed flow to weather compensation modes but you can't change the flow temperature specifically.

There is an installation video online there is only 1 place it can go, turn off power to FTC, remove cover (4 screws), plug in, put cover back on.