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Rank 6
October 25, 2021
Solved

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

  • October 25, 2021
  • 81 replies
  • 18264 views

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)

 

Best answer by Speps

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.

 

81 replies

juliamc
Rank 20
Rank 20
January 31, 2024

Sorry, I can’t help there as I don’t know the controller. I hope Friday’s visit will sort it out.

Finger’s crossed !! That ECO is a good sign at least.

Newcomer
January 31, 2024

That's ok, you've been a great help and so have the others.  It is greatly appreciated 🙏 

Yes I'm happy to see eco!  My heating just kicked in....I was feeling bit nippy too so good timing there! 

Oh and I'm happy it's over two days and I only used 12.5kwh over that time.  Still on flexible tariff though, I thought I'd already gone on cosy, maybe its tomorrow,  new month and all.

 

I'll let you know what happens on Friday. 

 

I best go give lots of attention to my chinchilla now, or he'll get upset with me lol.

Newcomer
January 31, 2024

 

Emmanuelle_OVO
Retired Moderator
Retired Moderator
February 1, 2024

Your Chinchilla is so sweet! 

 

Please do keep us posted if you can, with the engineer visit. It may be helpful for other Community Members @Auds 🙂

Renewable Energy? Big Fan.
Newcomer
February 1, 2024

Emmanuelle Pippin says thank you and yes he fooled everyone 🤣🤣  no he is a sweetie 90% of the time lol. 

Yes I will do.

 

Annoyed again as I've not long got back from shops and damn hot water come on!!!  It went down to 43 this time....makes no sense!   That will all be changing tomorrow! 

 

 

Newcomer
February 3, 2024

Hi all, well this guy wasn't great....he zoomed through the whole walk through and controls, he basically changed some and didnt show me how...I think he went into service and entered pass code, as cannot get into the water temps.  But he reduced my water temp which was stupidly set at 60!!!  So no wonder it was too hot, its now at 50.  He also changed the legionnaires which was set to come on at midday, now 1pm!  Length to heat was 120, now 1hr, it's every seven days I noticed, and he upped the running time from 5-10 mins! I questioned it he said needs time to kick anything off...I said do I actually need this setting he said yes so.  He reckons I should see how I get on with it on constant now as it best way...but I can ring them anytime to change it to timer.   So it was ok in some ways but not so much in others.  When it gets serviced I'm going to ask that person go through it properly and let me record his fingers as he does it lol.  The hot water didnt come on this evening, thank god,its at 41 now so it will come on in the night and fingers crossed it always does....if not I'm going to ignore his words and put it on a timer! 

Thanks again everyone.   If anyone knows how to get into the service part let me know? Thanks 😊 

juliamc
Rank 20
Rank 20
February 3, 2024

🙄 If there’s one thing worse than mansplaining it’s not-splaining.

Newcomer
February 3, 2024

Well the water being a lower temperature is great, not burning my hands and it isn't turning on at peak hrs.  It's not cooling as fast....so now to see the cost.…

Oh yes something else the guy said, was to only have one big appliance going in summer at a time, as in my air con only, not washer too....as the solar won't cope....how does he figure that?  Is this right?  Seems weird 😕 

Newcomer
February 3, 2024

@Speps  thank you so much for your comment on how to get to the hot water temperatures and legionella settings, I am so happy to know now! Thank you! 

Quick question my legionella is setup hot water temp 60  frequency  7 days   duration max temp at 10mins.....do I leave it like this or can I change max duration and frequency to say 5mins and 10days.  Bare in mind I have an electric shower, so hot water is only for washing up and hand washing.

Thank you 😊 

Newcomer
February 3, 2024

@Auds i understand the risk of legionella is when there are airborne droplets you breathe in, you can safely drink water contaminated with legionella - so showers are highest risk activities with all the water vapour created.

 

Given that you are only filling sinks a cycle every 2 weeks should be appropriate - I think this is fairly common practise even in installations with showers from the cylinder. 

 

Heat geek and HSE will be reputable sources to make your own assessment.