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

  • 25 October 2021
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Hi there,

 

I’ve been looking at some of the data coming from my EcoDan system. 

Something you can see here just looking at the tank temp maroon line at the top (chart is last 24 hours of time). At around midnight the HW temp falls to about 40 degrees which triggers the pump to bring it back up to 50. The temp then falls back across late night / early morning. Given I know no one is going to use the HW until 7am, is heating up at midnight a waste? It seems like that intially, but then you have to factor in that the tank temp would still fall further if not reheated at midnight. 
 

Wondering if I could / should stop the HW heating up at midnight? (Of course if I had a nighttime elec tariff this could be a better strategy)

 

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Best answer by Speps 29 October 2021, 10:55

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The report posted by @jason.lewis in the COP thread doesn’t mention much about hot water heating but does suggest schedules can be used to good effect. I’ve changed my to a schedule but that’s partly because I have my immersion connected to my solar PV and any excess electricity gets dumped to the tank. My water COP isn’t good but I’m also not heating my tank very often. 
Does the Mitsubishi system allow a schedule and reheat option? On the Daikin you can set this up so that it’ll run a schedule, say 48C at 10pm, which only kicks in if the immersion hasn’t heated up the tank or we’ve used the hot water.  Then we have reheat during the day if water temp drops low, in the Daikin case 10C less than what you set it at, so my day time reheat temp is 45C, so if tank temperature drops to 35C it boosts it back up to 45C. 
I don’t personally see the benefit of an eco7 type tariff. The hot water demand isn’t enough of overall electricity usage to warrant the increase peak rate you pay when heating is required, at least through the winter.

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You can do two things to stop this.

Firstly is to look at and adjust the reheat temperature, which is the temperature below the set point that the tank will heat up. These graphs don't tell the whole story but it looks like yours is very aggressive, 5 degrees or less? Try 10 or even 12 degrees.

Second thing you can do is to adjust the hot water timer so it doesn't go on overnight.

I use this timer to stop the hot water from reheating in the morning, as otherwise a few morning showers will stop the central heating and interferes with the heating schedule. But I would not suggest this for your fix as there will be times you empty the tank before bed and need it in the morning.

I've attached my graph of the same. By chance it also shows a leigionella boost. Its strange your graph doesn't show the boiler set point? 

Another warning not to take these graphs as 100% accurate for temperature, as I had a shower last night and it was definitely warmer than the 20 degrees it says my tank was.

 

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thank you @Speps . Another question seeing as we seem to have the same system. Do you know how to navigate the menus to adjust the legionaires cycle? Mine is set at 7 days and i wanted to extend it to 10 days

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@James_N yes on the controller hold the bottom left button until the menu options change colour. From there click hot water, and the pencil icon on legionella. Try to resist changing other settings but do have a look what your tank set and reheat temperatures are.

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Thanks @Speps   Mission accomplished. Hot water is set to 50 degrees with a temp drop of 10 degrees 

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@James_N @hydrosam and @Speps, would anyone object if I moved this topic into the public Smart homes forum category? I think this might be helpful to heat pump owners even if they’re not on the trial…..

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No objection here. The original question was about how to control this on the Mitsubishi system. I don’t whether it’s worth mentioning that? The Mitsubishi Ecodan does appear to have more flexible controls and an easier to use interface than the Daikin. 

Userlevel 7

Good point, @hydrosam - I’ve now specified the Ecodan in the title and tags so this thread is nice and specific now. 

 

I’ve also spotted a very nice summary of the settings available. posted by @Speps on this private Smart trials thread:

 

“The ecodan has 3 options for heating: fixed flow temperature (always the design temperature) , weather compensation mode (variable on air temperature and following the weather compensation curve) and target room temperature mode.

 

I understand the target room temperature mode uses the indoor temp sensor and the outdoor units temp sensor to calculate the real time heat loss, and adjust flow temperature from there. The building’s rate of heat loss is variable but more consistent than the air temperature, so should be most efficient way for the heat pump to maintain room temp.”

 

I feel like this is a big subject, with lots of variables that influence which option to go for. So it’s nice to have somewhere specific for the Ecodan. 

I’m already kinda of relieved to find this forum / post because I too have an Mitsubshi EcoDan ASHP fitted 3 weeks ago and the installers have pretty much fitted it and forgotten us.  I was rushing to get the RHI in before the end of the month and I’ve already let them of the hook by paying but I don’t think there isn’t much that can’t be sorted out without some education.

The main problem is that the hot water tank is right next to our bedroom so it wakes us up in the night and tends to stay on for a couple of hours. I've worked out most of the controls but despite setting of timer to switch the system off at night it still sometimes comes on for no reason that I can see.

I know we can power off the system to stop it completely but then of course it doesn't give us heat or water until we switch it back on and I'm worried that the anti freeze system I've seen also can't work when it's powered off. Last night it was warm both inside and out, tank temp was high enough and the timer was off until 7:30am yet at 6am it kicked in, no idea why.

I need some help please.

 

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Hey there @christianedward !

I’m afraid I’m not much of an expert in ASHP stuff myself, but I can ask my friends to stop by. I know @hydrosam is definitely an expert here! I’ll see if there’s anyone else I can ask too. Bear with us!

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Ok, I’ve also got @hambrook @M.isterW and @Nicllb down as having Ecodan units, according to the threads in the Smart Home Trials Treehouse. I’ll ask them to stop by, as they might know some tips.

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@christianedward 

some initial thoughts. 
Make sure all internal pipework around the tank and valves is insulated, see photo below. 
Set a schedule for your hot water, don’t use reheat only mode, despite what some installers say, they just don’t want to be called back for a lack of cold water. Use Schedule and reheat. If you are not on a cheap overnight tariff then early/mid afternoon is typically the most efficient time of day to reheat your water. Set it around 48C, with a  reheat threshold around 38C (all depends on how much water you use). 
Set back the overnight heating temperature a couple of degrees. 
The occasional running might be the anti-freeze mode, when it runs but doesn’t add much heat. For example when external temperature is below 5C, the system runs to stop the water in the external pipes freezing. Not much you can do about this. But insulated pipework inside will reduce the noise if this hasn’t been done. 
 

 

Thanks @hydrosam

I haven’t seen reheat mode but I’ll look into the settings.  Once I got the ASHP on the Wifi I’ve been using the MEL Cloud App but there is no way to change the lower reheat threshold and the Heat Now in uses the emersion heater as the fan outside doesn’t come on when I activate but the pumps near the tank do.  I initially thought the night time starts were the anti freeze kicking in and whilst its happening less as the temps have warmed up it still happens.

MEL Cloud App EcoDan Settings

They have left all the pipes in the airing cupboard complete uninsulated and even the pipe outside aren’t as nicely done as yours, but I can look into that too. 

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Great to have another new ASHP’er here seeking advice, @christianedward!

 

Just in case you hadn’t spotted it we’ve got a great collaborative to getting that pipe insulation up to tip-top efficiency over here:
 

 

Really interesting to see a screenshot of your MEL Cloud App too. Not sure if any others here have used this or a similar app to tweak their settings. @hydrosam, @nealmurphy, @hambrook - Am I right in thinking you’ve been adjusting your settings on the Heat Pump itself?

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@Jess_OVO i can only manage settings through the main controller. My older generation of heat pump has no app 😭.

@Speps and @James_N are both Mitsubishi owners and will know there way around the details of the settings better than me. 

Great to have another new ASHP’er here seeking advice, @christianedward

 

Really interesting to see a screenshot of your MEL Cloud App too. Not sure if any others here have used this or a similar app to tweak their settings. @hydrosam@nealmurphy@hambrook - Am I right in thinking you’ve been adjusting your settings on the Heat Pump itself?

The screen shots higher up in the thread are from the same app they are showing "Reports" my screen shot is from the "Control" section.

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Are we ALLOWED to login to MEL Cloud as part of the OVO Heat Pump Trial? What, if any changes, are we allowed to make? @Jess_OVO @Tim_OVO 

Does anyone know if the Heat Pump Pipe Insulation should be installed as part of the Hies guarantee. My indoor pipes have nothing at all and the outdoor ones don't come anywhere near the standards in the guide.

This might be what I need to get Hafod back to finish the work.

 

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@Jess_OVO Unfortunately we weren't given access to apps as part of the trial for some reason, so all tinkering is via the unit itself, though I've stopped short of getting my screwdriver set out!

Surely this isn't right. We ran a bath this morning and the water still hasn't even.attempted to get back to operating temperature (45).

 

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Hi @christianedward. 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

 

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@christianedward 

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?

 

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Yes, i think all that interior pipework should be lagged

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