What is most efficient way to run heating for my Mitsubishi Ecodan Air Source Heat Pump?

You’re in the right place, @Brennie66. Let me ping a few of the most helpful heat pump forum members and we’ll get you some advice @nealmurphy @jason.lewis @James_N 

From previous consensus, running the thing low and slow seems to be popular...

Hi @Brennie66 and thanks @Tim_OVO for the mention.

I haven’t got an Ecodan myself, though others on this forum have so may be able to personalise the advice.

It sounds like there may be an opportunity to turn down your flow temperature if you feel your flat is getting too warm if you need to override the thermostat.

Do you use a ‘weather compensation’ setting that adjusts the water flow temperature based on the outside temperature? You may be able to reduce the settings so that the pump is only having to heat the water to a lower temperature. This may mean the flat takes slightly longer to warm but should be more efficient. I try to stop my heat pump having to cycle on and off by doing this. The aim being so that it only just manages to reach my desired room temperature  - the room thermostat being used as an override to stop it getting too hot.

It may be useful if you can tell us more about the heating system. Is it standard radiators? Do you have thermostatic radiator valves? I assume you are on a single rate electricity tariff?

Hi, The heating system is a Mitsubishi electric Ecodan System. My radiators are standard so, I have them on 4. With this system the radiators do not get hot to touch but still warm in flat. Do you think I should only have the hot water on for once a day for an hour or so ? Also they have fitted a ventilation system in flat with a large disc in hall way when windy outside it is very cold as it comes from loft, they said it would cost £40 per year to run 

@Brennie66 you may want to look on YouTube at the range of consumer focussed vids by Heat Geek. They will teach you how to refine your system to be most efficient and comfortable - I have done this and it has made a difference.

As others have said, low and slow using weather compensation is the way forward with heat pumps.

Please feel free to ask further questions once you have looked at Heat Geeks

A few more questions @Brennie66 .

What control have you used to set 19 degC ? Is it a thermostat and where is it in your flat?
Do you know what make the ventilation system is ?

Also what temperature is your hot water set to ? It doesn’t need to be more that about 45degC (but needs a 60degC heat up once a week to avoid legionella).

Hi there @Brennie66 ,

I have an ecodan and would agree with the above posters’ comments. I have found that about ¼ of my electricity is for hot water, and ¾ for heating. So getting the heating right will save you the most money.

For hot water I changed 2 settings: the temperature that the system heats my water to is set to 49C, also i turned off the automatic heating so it just heats the tank up very early morning and evening.

For heating you probably want the thermostat set to the temperature you find comfortable (eg 20C) and leave it at that (or maybe switch down just a bit overnight eg to 18C). It takes a long time for heatpumps to change the temperature in your home, so its actually better to keep it at the same temp all the time. You want the heat pump set to weather compensation mode. This means that your radiators will get warmer when its very cold outside, and just slightly warm when it is mild outside. 

Changing these settings on the ecodan control panel isn’t very obvious so best to google it and watch a video of someone doing it

water should be straightforward once you see how. Let us know if you have problems

We had the Ecodan Airflow system fitted 21st November and the bills are running away with us. 

Our Thermostat never reaches the target temp which is located in a hallway where our front door and downstairs bathroom is, we can get a comfortable 20c in our living room and upstairs is warm but the system just keeps running, we have tried the timed settings but we're told by the engineer the system heating needs to run all the time which is just not affordable as it never goes off.

It is possible the thermostat is located in the wrong room? It took 5.5hrs for it to go up 1c in the hallway from 15c but the rest of the house was fine. 

I haven't heard of an Ecodan Airflow. What is it? Do you have pictures?

Sorry I meant its the mitzibishi Ecodan airflow heating system

Still no wiser 🤣

Is it an Ecodan air source heat pump? If it is, how are you controlling it?

Are you using a fixed flow temperature or weather compensation?

What controls do you have inside the house?

Do you have radiators or underfloor heating?

If radiators, do they have TRVs?

Sorry its very new to us and driving me crazy.

We have an airflow unit attached about 10ft up on the side of the house, all the radiators except the hallway have TRVs, and all the radiators were upgraded to bigger ones. We have no underfloor heating. 

We have a digital thermostat in the hallway it's currently set on a timer morning and late afternoon but has the option to leave on all day or use the weather compensation control which I still cannot get my head around.

We have tried leaving on all day with no joy other than expensive bills as it won't go off due to temperature in the hallway where the thermostat it. 

I believe the flow temperature was set at 55, was 45, we don't have control of this as its password protected by the housing association. 

Do you have a controller somewhere that looks like this?

It sounds like you have a fixed flow temperature, which is the worst way to run a heat pump and 55 degrees is far too high. Your efficiency will be really low, which will cost you £££

If you can change the settings to weather compensation then do this. My kid's birthday party is about to start so I can't explain how to do it at the moment. I'll be back later, unless someone else wants to help before then.

Yes we have the same digital panel just no idea how to set it correctly to get it to run more efficiently 

I’m back…

So, what’s weather compensation? Let’s start from the basics, as it’s useful to understand why something works (apologies if you already know this).

A heat pump works by moving heat from outside to inside. The electricity it uses isn’t being converted into heat, it’s being used to move the heat. The way it moves the heat affects your efficiency. As an example, you could drive your car 100 miles at 50 mph or 100 miles and 100mph. You would go the same distance but would use more petrol driving at 100mph.

You make your heat pump as efficient as possible by running it at the lowest flow temperature (you get the most heat moved for the least amount of electricity). The problem is, when it’s colder outside you need more heat so you need the heat pump to run hotter. But you don’t want it to run that hot when it’s warmer outside. That’s where weather compensation comes in. It allow you to tell the heat pump what flow temperature to use depending on the outside temperature. Hotter when it’s cold outside and cooler when it’s warm outside.

This is a link to a youtube video that explains how to set the weather compensation curve - https://youtu.be/-983aLzVZ_I

The next question is, how do you know what to set your weather compensation curve to?

When your heat pump was installed the company should have done a heat loss assessment. This is a series of calculations that works how how much heat each room of your house loses if it is a set temperature inside (normally about 22 degrees) and a set outside temperature (normally a really cold temp). This tells the system designer how much heat each room needs to stay warm and how big a radiator each room needs. If they’ve done this correctly every room should have a radiator that is exactly the right size to keep the room at your required temperature with a given flow temperature (or fairly close to the right size). This means that if set your flow temperature exactly right it will keep the house at the right temperature without any need for any other controls. You can get rid of the TRVS and room thermostats… well, not get rid of them but open the TRVs fully and turn the thermostat up high.

By adjusting the weather compensation curve you are searching for that sweet spot where the flow temperature is exactly right to keep your house at the right temperature. It might take some playing around to get it there but most people suggest making a small change then allowing at least 24 hours to see if it’s right before making another change. You might have to adjust the temperatures at the end of the ranges at different times of year, when the weather is coldest and in the spring or autumn.

Lots of people like their house to be a bit colder at night so I think you can set the system to drop the compensation curve down a couple of degrees overnight. I don’t know how to do this so I’m hoping someone else on here can help. If you want your house cooler during the day and only warm in the evening you could do the same thing.

You might notice that the heat pump runs more if you use weather compensation mode. But it’s running more efficiently so should be using less electricity overall.

Here are a few more videos that might be useful:

A guide to the heating modes - https://youtu.be/RX31v4NoQf4

A guide to using the controller - https://youtube.com/shorts/MI_OHZwenBE?feature=share

As I mentioned, your aim should be to make the heat pump as efficient as possible but you can only do that if you know how it’s performing. To work out how efficient your system is you need to calculate the Coefficient of Performance (COP). This is how much heat you’re getting for each unit (kWh) of electricity. The controller will show you how much electricity your heat pump has used and how much heat it has generated.

Press the right hand rectangular button to get a screen with these figures on the right hand side. It shows the figures for the month. Divide the heat by the electricity to get the COP.

If you press the right hand button again I think you get to a screen that shows more energy monitoring figures.

Thank you, I will give it ago but will moree than likely end up ringing mitzibishi tomorrow as its just so complex, frustrating as I am tech savvy but this is a whole other ball game to me.

We had a pressure test done in the house just in one room and all doors/windows had to be closed, afterr that a guy with a clipboard saying how big radiators were going to be.

I'll keep trying to make sense of the video and pray I can get it more efficient ass it's costing £300pm for a 3bed semi. 

Hello! Im new to this group and would like advice if anybody knows/can help. Bought a house with ecodan ashp and am trying to sort it out…. Have set flow temp to 49 after reading blog after blog and have set the weathet compensation curve as per a chap on a you tube video … my question is.. do you have this running on ‘play’  constantly or do you set the timer? I want 6am-10pm 20 degrees but 18 at night… do i set this as normal?

Hi @Jenp 

Some Ecodan users will likely be along at some point.

Can you tell us if you have a smart room thermostat or smart radiator valves to control room temperatures? Actually is it radiators or underfloor heating that you have?

If you have a thermostat with timer I would set it slightly higher than your desired temperature as an overshoot cut off and then try and use the weather compensation controls on the heat pump to try and just reach the required temperature so it's not working too hard.

If the chap on YouTube is Heat Geek then look at the videos on zoning.

The first thing to do is check your COP (coefficient of performance). This is how much heat you're getting for every kWh of electricity that's used. When you know this you can decide if it's efficient enough and you have something to measure changes against. There are some instructions up there ^ that tell you how to find the information.

Ok cop is 3.5.. rads only..normal trv’s.. fc9 normal wall control…wasnt heat geek but an Irish chap. Pump set at 5 flow is 16 litre which is low, think should be above 20 so asking for secondary pump from installer, flow temp was 55.. which apparently is default so reduced it… i just dont know if i can run this on curve..well i can. But should it be on play/constant.. or timed?! Oh no zones… 17 rads…just like normal system really but bigger double rads…

A COP of 3.5 is quite good. If the house is warm when you want and you have enough hot water I probably wouldn't change anything.

If you want to learn more about weather compensation curves and that sort of thing, Heat Geek on YouTube is a good place to go.

Thank you! Heat geek gets a cop of 5.9 in a badly insulated office of his!