Hot water and heating control with my Mitsubishi Ecodan Air-Source Heat Pump (ASHP)?

Hi. I have the same system as you, let me see if I can help you out, as I had some similar issues and have got to a happy place through help from this forum and some trial and error.

First on the melcloud app. I don’t think you can use this to change any settings, its more to get the charts like the ones you post. The one thing I do occasionally use it for is to manually force the system to heat the hot water tank.

Like you, my initial setup was that the tank was set at 50C and once the temp fell to 40C is kicked in and reheated. The issue I have with this is that the thermostat that measures the temp in the tank is right at the bottom, where it fills with cold water as you take hot water out the top. So the tank is reheating almost everytime you run a hot tap. This is also keeping you awake i think.

I changed this by setting two hot water on and off times. For me its 4am to 5am and 4pm to 5pm. This means it only heats the tank during these hours. To do this you need to use the ecodan control panel thats should be on the wall next to your hot water tank. I think this video shows you how to do that.

So I’m guessing for you, you would want the HW to fire up the hour before you go to bed, and then maybe as your alarm goes off in the morning!

I don’t know if its just the HW that makes the noise for you, or if its the central heating too. You are a bit stuffed if its the CH too, as with a heat pump this will need to be on a lot of the time during cold weather (maybe 12 hours day). And unlike a gas boiler, it will need to be running for some of the night. I have mine set to 20.5C during the day, and 19C at night. If it doesn’t run overnight, the temp will drop too much in the house (say to 17C) and it will take the system 6 or 7 hours to get the house back to 20.5C ie not until mid afternoon. I also think its more effcicient for the pump to be maintaining a more constant temp 24 hours a day.

Hope this helps. Let us know

James

i have an ecodan too. firstly about the noise, youve said it comes from the tank. Need much more info to give you an answer on this. Is it a pre-plumbed unit? What is actually making the noise? A pump or movement of water through pipes? Have you checked the app when it is making noise to see what mode is active?

If you start changing settings before being sure what is making the noise, you will likely cause another issue. But, adding sound insulation to this room sounds like a sensible idea anyway given its proximity to your bedroom and likelihood that in the dead of winter, it will be ticking over at night (at least it should be).

Re: the MEL cloud app, this lets you do scheduling, look at reports and manually reheat hot water - there is little else to this so all settings are controlled by the wired controller.

Now on to your hot water question, you said it is only reading 35 degrees after you ran a bath and isn’t reheating. This has been discussed elsewhere, but to cut a long story short the measurements on that app are not taken from the hottest part of the tank, particularly when its been half used. So there is probably enough hot water still in the tank not to trigger the reheat threshold.

As for setting the threshold, its going to be specific to your tank size, hot water usage, how hot you like showers, how much energy you want to save etc. Rule of thumb if tank has been sized correctly, tank set at 50 +/-2 in the winter and a few degrees lower in the summer, with 10degrees drop to activate reheat. 

Thank you @James_N and @Spepsyour replies are a great help.

For reference this is my Water tank installed, do you think the installer should have lagged these pipes or is that down to me?

The outdoor install isn't much better with bare sections, gaps and gaping on the bends.

Should I try and get the installer back to sort these issues?

Yes, i think all that interior pipework should be lagged

Just a little update on our noise issues, Hafod Renewables came back, this time with 2 different engineers who told me they actually subbed out the install to a plumber.  Within an hour they had improved the lagging outside and given me a guided tour of the Eco Dan Settings.

Both water pumps were set to run at 5 (max) and now with them both set to 3 the noise level is greatly reduced and their is no whoosh of water when they start, so we aren’t woken when anti freeze kicks in (he also dropped the anti freeze temp to 3 from 5). We have a large 11.2 kw ASHP for our 4 bed house but he said a smaller 8 kw ASHP would need to run at 5 to keep a 3 bed house warm.

The water tank was incorrectly set as medium size when we have a large which has 2 temperature sensors not one like the medium.  This sorted the issue with a huge temp drop which didn’t cause the water to come on.  So pretty much all sorted and happy now thanks.

I do have one other question about insurance cover.  I’ve just had a weird conversation with my contents insurer who told me a gas boiler and presumably a ASHP is covered under buildings insurance because its fixed to the house and wouldn’t fall out if the house was turned upside down (their analogy not mine).

So did anyone else let their insurer know they now have a heat pump or was it the buildings or contents insurer?

No, we didn't tell our insurer about our heat pump. Any installed equipment will be automatically covered under your buildings insurance.

What size hot water tank do you have? I’m wondering if mine has also been set up only using the bottom thermostat

The water tank is a large which has 2 temperature sensors not 1 like the medium.

The controller was set to work with a medium so didn't heat the water when expected or possibly just showed the wrong temp on the screen leading us to think it should be heating when it wasn't.

Hi, does this look normal to you guys. Our hot water drops considerably within a few minutes of running our mixer shower.  Any help would be great. Thanks