Mitsubishi 8kW - strange energy use readings
Posted by: @westkentone issue I’m having is that my hot water loses very close to 1 degree an hr throughout the day.
I do have an annual service in a few weeks so I’ll mention it.
Mine loses about 0.6 degrees per hour so a bit less. Is your HW tank outside the house, e.g in the garage? That would make it lose a bit more than in the house.
170L tank in the airing cupboard where the immersion tank was.
pipes arnt lagged that feed off the tank which I’d imagine they should be although I’d of thought that reason alone wouldn’t amount to 1 degree an hour??
It will lose heat through the tank insulation as well as the pipes. The pipes will make a small but significant difference. Your tank is smaller than my 250l one so the pipes, etc., will have a bigger effect. If you're really interested in HW tank heat loss then have a look at this.
Also, what is your HW temperature? The hotter it is, the faster the tank will lose energy. A 55 deg tank will emit more heat (i.e. lose energy faster) than a 45 deg one.
Let us know what the engineer says.
Hot water is timed to come on between 5am to 7am at its maximum 60c at 9.5p/kWh.
Thats ample enough h/w for 2 showers and the washing up.
My upcoming service will be carried out by a contractor from the Housing association not Mitubushi unfortunately so I’m unsure how knowledgeable they’ll be with advice on the settings.
My COP over the last 2yrs is only 2.4.
Iv recently changed my setting from adaptive room to curve although we’ve not really used the heating side since the change of setting.
Posted by: @westkentHot water is timed to come on between 5am to 7am at its maximum 60c at 9.5p/kWh.
Thats ample enough h/w for 2 showers and the washing up.
My upcoming service will be carried out by a contractor from the Housing association not Mitubushi unfortunately so I’m unsure how knowledgeable they’ll be with advice on the settings.
My COP over the last 2yrs is only 2.4.
Iv recently changed my setting from adaptive room to curve although we’ve not really used the heating side since the change of setting.
Based on mine, I suspect your losses from the HW tank are as expected. It's not going to cost much; mine costs less than 2kWh per day to maintain temperature even if I don't use any.
Is that your heating COP or overall?
I moved to auto adapt last winter and found COP went down but overall consumption was the same or a little less. With AA you need to be careful if you vary your room temp because AA bumps the flow up quite high when heating up to a target room temperature.
It seems a shame that Mitsubishi can't or won't explain the misreporting of energy consumed, I wonder whether it is a data recording issue rather than measurement issue. It is noticeable that on days when a hot water cycle runs for 1 hour and the remaining 23 hours have no actual heating generated that the system records 2.3kWh consumed – 100Wh each hour. All the reports out of MelCloud are given to 0.1 kWh or 100Wh – there will be a minimum unit of use that is recorded and if the unit is recording in blocks of 100W then it won't distinguish between 0< and 100W. So the 25W or so it draws is inflated from under 0.6 kWh to 2.3kWh. Though as I also find that when there is no hot water cycle either, i.e. just a continuous 24 hrs of not running the pump at all, this figure rises to around 3kWh then it's either a curious anomaly or proves I am spouting nonsense.
All water tanks will lose heat at a rate that Mitsubishi have measured. For a 170l tank they give a standing loss of 1.63kWh over 24hrs. Which I think is measured from a tank filled at 60°. But that will be a best performance and the tank won't have had heat-conducting copper pipes connected to it when that measurement was done. If I grasp this correctly that rate would equate to the water losing around 8° over those 24 hours. My tank pipework was not lagged initially and it was noticeable how warm it made the space it was installed into, and how hot some of those pipes felt. Even the hot water loop that circulates through the heat exchanger would still feel hot several hours after a cycle suggesting to me that the water in the loop was passively circulating from within the tank as it cooled in the pipe. It is damned fiddly trying to insulate the tank pipework as it is all bends and valves and pumps but you are reducing heat loss from the one part that you are trying to keep really warm 24/7/365.
Mitsubishi EcoDan 8.5 kW ASHP - radiators on a single loop
210l Mitsubishi solar tank
Solar thermal
3.94kW of PV
- 22 Forums
- 2,011 Topics
- 43.9 K Posts
- 21 Online
- 3,184 Members
Join Us!
Trusted Installers
Struggling to find a reliable heat pump installer? A poor installation can lead to inefficiencies and high running costs. We now connect homeowners with top-rated installers who deliver quality work and excellent service.
✅ Verified, trusted & experienced installers
✅ Nationwide coverage expanding
✅ Special offers available
Latest Posts
-
RE: What happens when the outside temperature exceeds the upper WC point?
@ashp-bobba @old_scientist thanks both. Very useful.
By bontwoody , 6 hours ago
-
RE: Are Homeowners Being Silenced Over Faulty Heat Pumps?
@ectoplasmosis I’ve never had an issue naming and shami...
By Mars , 6 hours ago
-
RE: Would You Find Value in a Premium Installer-Supported Forum?
Thought I would be the 1st to give you a thumbs UP Mars...
By ASHP-BOBBA , 7 hours ago
-
-
RE: Grant Aerona fine tuning advice needed
@stopbar We have a 13kw R32 Grant and found running ...
By Uk_pete_2000 , 11 hours ago
-
RE: Grant Aerona3 - Home Assistant control via Modbus
This is true, but I about learning about agentic AI and...
By Grantmethestrength , 12 hours ago
-
RE: A question about battery life
Here's my take on this with some rough maths that might...
By Mars , 12 hours ago
-
RE: Is it KISS or constant – weather compensation vs. set flow temperature?
I had to laugh at this as I do exactly the same thing, ...
By Grantmethestrength , 13 hours ago
-
@eliuccio there are some very high level arguments in t...
By Judith , 13 hours ago
-
RE: Is my Samsung heat pump working too well?
@pooneil Apparently you can set up a different water la...
By bontwoody , 14 hours ago
-
RE: Solar Power Output – Let’s Compare Generation Figures
That's fine @irmartini and @editorbut let's keep this i...
By Transparent , 14 hours ago
-
RE: Battery sizing - How low can you go!
So just for completeness here is may last update on thi...
By bontwoody , 14 hours ago
-
RE: Mitsubishi Ecodan System Pressure Changes - An Issue or Expected ?
@alsocold123456 I would have thought it would last a bi...
By ASHP-BOBBA , 1 day ago
-
@editor Thank you for the information,do you have any i...
By Potatoman , 1 day ago
-
@cathoderay Years ago (40+) I enquired about moving our...
By Toodles , 1 day ago
-
RE: Share Your Experiences with Heat Pump Manufacturer Support
I didn't realise that Samsung even had customer support...
By JamesPa , 2 days ago
-
RE: New Heat Pump - mixer shower pressure
Just a little update, I eventually decided to put a pre...
By Spanners , 2 days ago
-
RE: Setback savings - fact or fiction?
I'm not a statistician, but I have had to use statistic...
By cathodeRay , 2 days ago
-
RE: Who's your electricity provider and what's your tariff?
@matthew_w It's a complex area and every case is diff...
By JamesPa , 3 days ago
Most Active This Week
# | Name | kWhs |
---|---|---|
1 | Mars | 412 |
2 | bontwoody | 175 |
3 | JamesPa | 169 |
4 | Pooneil | 158 |
5 | Majordennisbloodnok | 120 |
6 | Heatgeek | 111 |
7 | Toodles | 108 |
8 | ASHP-BOBBA | 108 |
9 | Transparent | 105 |
10 | cathodeRay | 94 |