Ecodan Coeffeciency of Performance

Yes, the radiator temp should be just warm enough to match the heat loss from the building, so the heat pump is ticking over all the time. 

thank you Julia. Ok so i have it on compensation mode since last night. The house is warm this morning and water at 49. Do i use the internal thermostats just to guide as to the temp in the house and if too high reduce the curve settings until the stats tell me what i want? I would like 20 downstairs and 18 updates and maybe lower during the summer months.

Adjust the curve settings. In weather compensation mode it should be ignoring the thermostats.

OK I will adjust the curve settings until the house is comfortable warm?  If my understanding is correct, this  mode keep the house at the same temp all the time (summer & winter ?) Albeit will have to work much harder in the winter and minimal in summer? I have the curve  set to 40/-3c  and 30/12c, so if after a couple of days its too warm I move lower curve down to something like 40/-3 and 28/12 ? and keep going until i am happy? 

Then at end of month check the COP and see if this is efficient? 

Sorry for all the questions, its all new and so much to learn!  Oil was so much more straight forward🤣, but i am hoping this will be worth it in the end. 😎

Yes, you're correct. The idea of weather compensation is that it keeps the house at a constant temperature whatever the temperature outside.

You can adjust either end of the curve, or both, to get the right temperature all the time.

It's really annoying that the controls are so fiddly because most people won't adjust them for maximum efficiency. I think that's why Mitsubishi introduced auto adapt as it requires less adjustment. I'm considering a controller called Homely which learns how your house gains and loses heat then adjusts the heat pump flow temperature for maximum efficiency. It should be available for Ecodan heat pumps later this year.

Thank you , very helpful. The homely device would be handy and something i would be interested in. So i just completely ignore the thermostatic now.  I did have mine on  auto adjust mode, but i noticed (although the house was warm etc) the pump/fan was off a lot and the COP was 1.48 for March.  This morning the fan was on but not rotating too fast.

I check how the cop is doing on my Daikin by recording the input and output values every day (I may be a bit obsessed). If yours is running slower and more consistently now you should see an improvement in the numbers straight away,

 I might just do this too!  So you’re technically doing a daily COP and what are you hoping for? Anything over 2.8?

It did get to an average of 3.47 in May 2021 but something happened which meant it dropped to 2.25 on average over the winter. My installer is due to check it out soon. The best it’s been recently on a warm day was 2.95 for the heating. I’d hope it could get to 4.0 as that’s not unusual for a heat pump, some reckon to get 5.0 or more.

Wow 3.47 seems excellent. And should the COP remain static through the months or do you see fluctuations?  How do i improve the DHW Cop? I have it on constant Eco mode and its 1.48 COP in March.

It’ll definitely fluctuate throughout the year. Not sure about your dhw 1.48 not very good ☹️

Do you keep adjusting it throughout the year or leave it alone once you found the temp that suits your house? I know i don’t touch the thermostats when on this mode but do i use them as a guide to know what temp the house is at ? I.e i could find at 23c is comfortable and then end up with huge bills getting to that temp!

On the question of dhw cop (sorry one question behind) 45 deg is good and low so no prob there. I heat my hot water two times a day - at 3am and 3pm. The 3pm is generally the warmest part of the day so I don’t miss the heating then (as the system only does dhw or radiators but not both together), when the air is warmest outside the hp is most efficient. At 3am it’s less efficient but suits me as heating not missed then either. If you have a cheap rate electricity tariff then that’s a good reason to heat the water during that time. 
With solar panels of course the time to heat the dhw is when they’re producing lots of free energy, so it doesn’t really matter what the cop figure is.

When you say ‘constant eco mode’ is that reheating throughout the day ? I’d switch it to a schedule eg like mine, I think you have to specify how long it’s doing dhw so that’s prob trial and error depending on what volume it has to heat etc. Mine takes about 50 mins in the afternoon to get to 48 degrees.

The goal is to keep the house at a temperature that you are comfortable with, 21 degrees works ok for us, though I’d love it to be 23 that would be extravagant.

On a sunny day we get lots of solar gain in the mornings and because our system has ‘modulation’ (maybe similar to your auto adapt) it decreases the radiator water temp according to the temperature sensor in the house. Nb this is not the same as a thermostat which is basically an on/off switch triggered by a temperature setting.

Having said that, in the summer the indoor temperature is generally higher than 21 degrees and the heating doesn’t come on at all. I think that’s because the weather dependent graph would set the radiator water temperature to less than the minimum for the system, so it just doesn’t run. I never actually turned the heating off last summer.

 The thing you will be tweaking will be the two ends of the weather graph (it’s a straight line so no idea why it’s called a curve). You should set the room ‘thermostat’ to higher than your target temp so it doesn’t switch off the heating, and just use the graph to set the radiator temperature. All sounds a bit counterintuitive I know…!

As @M.isterW mentioned earlier, not sure how having 2 thermostats affects this ??

Good luck ! Let us know how you get on.

Maurice Kelly Why would you want the ASHP to be running after it has reached the desired temperatures? If the pump ran continuously you would be paying astronomical bills… My Ecodan was fitted at the beginning of May and although I am super pleased with having hot water on demand and heat in my home within about 15 minutes of demanding it, (compared with my old storage heaters and Horstmann water control), the COP isn’t brilliant, about 2:1 at best, 1.5 average. COP is not a critical factor for me (as long as it is ‘t negative….!) - any savings are a huge bonus - but it bothers me that it is supposed to achieve 4:1 in summer conditions and it only achieves 1.5.

It is set to Auto Adapt, and it is not set to timed settings for either heat or water. This is logical for our wintry conditions here from November through to April,, because if it were timed, it would spend ages cranking up the hot water temp before the heating could kick in, and then it would spend ages cranking up the heating from cold. 

I am finding that as I have used the heating occasionally in the past couple of weeks, it has been slightly more efficient in correspondence. Obviously it will consume a certain amount of electricity even for minimal use, and it appears that that baseline amount of electricity is 2.5Kwh a day. That gives me hot water on demand, but no heat, as I don’t require it. If you don’t require it to deliver heat often, as in the past couple of months, then it isn’t going to achieve a COP of 4:1?

I find that if I want heat I just flick up the target temperature on the indoor thermostat by 0.5 or 1 degree (I have it set at 18 at the moment, 17 at night) and the ecodan soon kicks in, brings the temperature up and then stops, kicks in again if the temperature falls below the target temperature. If it kept running after reaching the target temperature, I would be worried…

I have big radiators with thermostats that are all set to open, one zone only, and the water temp is set to 50 with 40 as the trigger temperature for water heating. On this setting the water heats up about once every 12 to 15 hours. I have fathomed out some of the settings, but I was left with zero information by the installers, so it has been a learning curve.

Hi @amanda1 it’s so typical to have zero information from the installers 🤦‍♀️ That’s one big failing of this heat pump industry I think.

When the system is heating your hot water to 50 deg it will always result in a lower COP because it’s got a larger temperature rise to reach than it would with your radiators, which may only need to be at eg 35 or 40 deg. So in the non-heating months the overall COP is less likely to get up to 3 or 4. If the heating’s on a bit over the ‘summer’  the average COP will improve a bit too.

Sounds like you have your hot water on ‘reheat’ so it only runs the pump when the tank temperature drops below 40. You could try scheduling instead, if you heat the hot water in the warmest part of the day (around 3pm) the temp uplift will be the least and the COP will be slightly higher. You could also try lowering the tank temp down a bit, eg 48 deg or lower.

Regarding running the heat pump 24/7 I wouldn’t worry about that till the cooler months when you want the heating on all the time. Basically you are balancing the heat loss from the property with the heat from your radiators. The heat pump will be at its most efficient when it’s running all the time rather than switching on and off. 

@juliamc that tallies with what I thought - re the water, the temperature is taking about fifteen hours to drop to 40, so only heating water twice in a 24 hour cycle, so effectively, it is scheduled. I have changed the legionella settings but that is all I have changed so far. I don’t use huge amounts of hot water. This of course partly accounts for the comparitive inefficiency. I am waiting to see how the system performs with these default settings when the winter comes. It’s a bit Game of Thrones up here in the Cairngorms….The system prioritizes the hot water. At the point in Autumn when the water needs to reheat more often,  50 degrees with a 40 degrees lowest temp will mean less frequent cycles, and therefore less time without heating, or 45 degrees with a 40 degrees temp, meaning more frequent cycles and more time without heating. I am used to living in a cold house with long stretches during the day when there is no heat coming from the storage heaters, and running out of hot water by midday. With ASHPs it all depends on what luxury you have or have not been used to!

Yes they all prioritise hot water over heating. Some people have two heat pump installed, one for each function! In the coldest days down here in SE England (-7deg) we did notice the house cooling when the hot water was being heated, and of course the incoming mains water was very cold too so it had a lot of work to do and I think it took over an hour to run. 
The other time to have the hot water heating is of course when you’re in bed and won’t notice the heating going off, but that’s probably the coldest part of the night and you’ll get an even lower COP. We set the house temp back a degree at 9pm which in effect turns the pump off. Perhaps that would be the best time to heat the hot water 💡🤦‍♀️

@juliamc thanks - I might try setting up some timed settings later in the year. But that shortfall of heating while the water heats up isn’t going to bother me unless it happens often in winter. In winter the water may cool more quickly, given the location of the tank in my particular case. I think the COP will never be very good given our winter temperatures, and I expect to spend a lot of time clearing snow away from the front of the pump.

Can you rig up any kind of screen or roof over the unit to stop snow drifting around it ? It’s the grille on the back that will freeze regardless of snow. The liquid in the pipes reverses to defrost the unit regularly so you’ll see the ice melt every so often. Did your installer have an opinion about snow ?? 

@juliamc I’m considering building a kind of canopy over the top, because while I can dig the snow away from the front of it, the snow falls off the roof eventually, and will land just in front of the ecodan, or worse still, on top of it. Tons of snow. The installers are based in Edinburgh and Glasgow, and I suspect they don’t actually know what real snow looks like, let alone have any opinions about it. They weren’t big on opinions, just on getting in and out of the North as fast as possible. They are fitting these ASHPs on a massive scale in Moray with council and government grants, and their attitude is “you’re getting it for nothing, so you are on a need to know basis”. What they have done, based on the experience of people up here who have gone through a winter with the ASHP, is set the Freeze Stat function to * (0 - effectively deactivating it), because it is set by default to kick in when the outside temperature reaches 5 degrees, but up here, it is 5 degrees or less most of the time in winter, and so people’s ASHPs were running 24/7. To do this you have to have sufficient glycol in the system. They have checked that the glycol in the system is sufficient. There is a separate anti-freeze function that kicks in anyway. I have been advised that if the coils freeze up it is OK to trickle warm water over them. This seems counter-intuitive, electricity and water and all that, but it worked for my neighbour last winter and she is still alive…..

@amanda1 The way auto adapt is designed to work is that is manages the flow temperature to keep your house at the selected temperature. By adjusting the thermostat up and down you’re interrupting the system’s attempts to run at maximum efficiency which results in a lower COP. The ideal way to run it is to set the main house thermostat to a single temperature (with a reduced temperature overnight, if that suits you) then leave it alone.

In cold weather it wouldn’t be unusual for the heat pump to run most of the time, particularly if you’re using auto adapt. It will run with a low flow temperature and provide just enough heat to keep the house at your chosen temperature. This is the most efficient way for it to run and will use less electricity than having it supplying a higher flow temperature and switching on and off.

Unfortunately installers are very bad at providing the sort of information and education that helps people run their heat pumps in the most efficient way. We’re all used to running heating systems that operate at a fixed efficiency (gas boilers, electric storage heaters etc) and heat pumps require a completely different mindset.

@M.isterW thanks for your clear info - that’s exactly what I try to do - the main house thermostat is set to a single temperature, 18, all the rad thermostats are fully open, and I reduce the set temperature overnight to 17.  Just lately however the room temperature on the main thermostat has been higher than my set temperature, but the house has been chilly - the room thermostat is in the hall and the hall is obviously quicker to heat up. Or maybe it’s just me….we have had a few nights with freezing temperatures lately also. To get the heater to actually come on, I have had to raise the single set temperature by a half a degree or so above the room temperature. This has been about once a day, for about half an hour or so. I don’t like doing this but it fascinates me to have heat on demand….you say, we are all used to running heating systems that operate at a fixed efficiency. But although storage heaters give 1kwh for every kwh consumed, to get them to heat the house sufficiently in winter they need to consume 60kwh a day - therefore despite their fixed efficiency they are expensive and useless. I have had 10 years of them, because we do not have mains gas - bills in excess of £2000 pa for almost all of those ten years, not just for the last year - in return for a cold house with damp walls; and I am still getting used to having a wrap around warmth almost instantaneously. I am not expecting the COP to be high, because I live in a cold area, and the house has been retrofitted with cavity wall insulation, but there is still some heat loss.  I will be interested to see if in winter the ASHP (Hirohito…) consumes 60kwh a day. It’s the kwh consumption per day that I am interested in, the raw cost, rather than the ratio of consumption to delivery.

Do keep us posted on your system. You are in such an extreme location compared to me - our lowest nighttime temp has been about 13 deg recently.
To keep the damp out you’ll need to have some ventilation. Do you have double glazing with trickle vents ? That’s another game - for ‘ventilation’ read ’heat loss’ 🙄

@juliamc I do have double glazing with trickle vents. The damp is due to condensation. So the cavity wall insulation should make a difference. Since the cavity wall insulation was fitted last month, the damp smell has been less noticeable, and I think also that having pipes under the floor carrying heat some of the time has made a difference. But it is summer and we have been enjoying really hot weather in June - although this month has been wet and colder than average so far - so I really can’t tell at the moment how much difference all this new kit will make. These systems have been very common in Scandinavia for a long time, and in North America also, so I am assuming that the Ecodan will cope with the cold. They do sell it as being good in very cold conditions. I found some interesting Norwegian stats on COP  at cold temperatures. See graph