Hi, the standard tariffs in the UK are the same price day or night. There are Economy 7 off-peak tariffs that are cheaper for 7 hours at night, requiring a different meter, and also new tariffs for people charging electric cars overnight. People have to calculate whether an off-peak tariff would be cheaper for them. Heating a house warmer at night to take advantage of an off-peak tariff would normally only make sense if the house was extremely well insulated (which most UK houses are not, as we were used to mild winters and cheap power in the past), so the heat would be stored for the next day. Also the lower temperatures at night means the heat pump is working at a lower efficiency, i.e. less free heat. Mitsubishi used to recommend a small night setback on Weather Compensation, and I personally am quite comfortable with a slightly lower morning temperature, rising in the evening as we sit down and put our feet up. I'm not sure about AA yet, but perhaps it does ramp up with higher power than when on WC, so maybe a setback is less effective, or needs to be a smaller setback when using AA - it would be good to hear other's experience.

Looking at your graphs, I'm NOT an expert, but the difference between flow and return temperatures seems to be only about 2C if I am reading it correctly, and I am interested to know what your flow rate (litres per minute) is, and what COP you achieve.

Regards S

@sliderule Now ‘Winter’ seems to be with us, I am now getting to know the amount of energy that is likely to be required on an average winter day. Currently, approx 1 kW/h is required each hour to keep us snug at approx 22 degrees C. (Yes, I know that is quite warm but we both have medical needs for this elevated temperature). Having only recently had a Homely system installed to control our Daikin EDLA08 pump, I am still getting down to the nitty gritty bits of how best to set night time temperatures without having to burden the pump in the morning. We have good insulation and are now on OE Cosy tariff. At the moment, I am trying a 1 degree boost during the two three-hour Cosy ‘dips; (04:00 - 07:00 and 13:00 - 16:00) and lowering the demand by 1 degree between times; at night a 1.5 degree dip is set up. This may or may not work - I don’t know yet as the Homely is a ‘smart’ controller and may have ideas of its’ own which I am discussing with Evergreen Energy

My posting was not complete as a glitch froze my prosaic brilliance (😉). I went on to say that the Homely has pre-sets for some smart tariffs such as Agile but, as yet Cosy is not listed; I am speaking to Evergreen Energy about this addition. For all I know, the ‘smartness’ of the controller may be overiding my attempts to boost and reduce at various times as it ‘knows best’ time and further discussions will tell I think. Meanwhile the 27 kW/h battery is easily topped up in readiness for the longer gap of twelve hours overnight but is coping quite happily as yet. Regards, Toodles.

@derek-m Hi, I am still experimenting with AA. It was great before the cold weather came. Now it's colder, and the HP wants to run at higher power, I have done a lot of balancing of non-living rooms to smooth it out and avoid rapid ramping up, and have made progress. However, when I try to setback at night by only even half a degree (on Melcloud), or 1 degree on the FTC, the heat pump pauses and switches off the main pumps and 2-way valve for UHF, followed by a very long pause of around 3 hours or more with the flow temperature dropping slowly from for example 38C to 23C and maybe lower, before restarting. I don't like that because it will ramp up using more power than it would need to if it restarted sooner. I have set the Flow Temperature Range minimum at 30C, or even 35C, imagining that this would make it restart before it dropped as low, but it doesn't. I have the Thermo Diff Adjust ON, to reduce cycling, with lower limit at -1C (the highest). When it cycles off (less than  once per hour) due to excess power, it doesn't turn off the pumps and valve, and resumes heating quickly. You could say of course it won't heat if the Target Room Temperature is below the Actual Room Temperature, but I would have thought the AA would have some heat anticipation built-in. Do other users experience this, and will AA learn to smooth it out in time, or is there something I can do to smooth it out?

@derek-m Hi, I am still experimenting with AA. It was great before the cold weather came. Now it's colder, and the HP wants to run at higher power, I have done a lot of balancing of non-living rooms to smooth it out and avoid rapid ramping up, and have made progress. However, when I try to setback at night by only even half a degree (on Melcloud), or 1 degree on the FTC, the heat pump pauses and switches off the main pumps and 2-way valve for UHF, followed by a very long pause of around 3 hours or more with the flow temperature dropping slowly from for example 38C to 23C and maybe lower, before restarting. I don't like that because it will ramp up using more power than it would need to if it restarted sooner. I have set the Flow Temperature Range minimum at 30C, or even 35C, imagining that this would make it restart before it dropped as low, but it doesn't. I have the Thermo Diff Adjust ON, to reduce cycling, with lower limit at -1C (the highest). When it cycles off (less than  once per hour) due to excess power, it doesn't turn off the pumps and valve, and resumes heating quickly. You could say of course it won't heat if the Target Room Temperature is below the Actual Room Temperature, but I would have thought the AA would have some heat anticipation built-in. Do other users experience this, and will AA learn to smooth it out in time, or is there something I can do to smooth it out?

Posted by: @sliderule

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@derek-m Hi, I am still experimenting with AA. It was great before the cold weather came. Now it's colder, and the HP wants to run at higher power, I have done a lot of balancing of non-living rooms to smooth it out and avoid rapid ramping up, and have made progress. However, when I try to setback at night by only even half a degree (on Melcloud), or 1 degree on the FTC, the heat pump pauses and switches off the main pumps and 2-way valve for UHF, followed by a very long pause of around 3 hours or more with the flow temperature dropping slowly from for example 38C to 23C and maybe lower, before restarting. I don't like that because it will ramp up using more power than it would need to if it restarted sooner. I have set the Flow Temperature Range minimum at 30C, or even 35C, imagining that this would make it restart before it dropped as low, but it doesn't. I have the Thermo Diff Adjust ON, to reduce cycling, with lower limit at -1C (the highest). When it cycles off (less than  once per hour) due to excess power, it doesn't turn off the pumps and valve, and resumes heating quickly. You could say of course it won't heat if the Target Room Temperature is below the Actual Room Temperature, but I would have thought the AA would have some heat anticipation built-in. Do other users experience this, and will AA learn to smooth it out in time, or is there something I can do to smooth it out?

 

I'm afraid that I don't have details concerning the AA algorithms, but a normal industrial type control system would probably react in the same manner.

As far as I am aware, the control system, in AA mode, is designed to keep the room temperature constant, so by dropping the setpoint by 1C or even just 0.5C, you are basically telling the control system that the room is over temperature. The control system does not have any forced cooling, so its only option is to stop the heat pump to bring down the room temperature.

If you are fortunate to have good insulation, the IAT will reduce slowly, and because the water pump should not be running, the LWT will fall at a faster rate probably down into the 20's or even lower. If the LWT gets too low then the freezeStat function should operate.

If the IAT falls to the new setpoint then the heat pump should restart, but I would  not expect the startup to be too aggressive if the setpoint is still reduced. The heat pump will increase its output when the setpoint is raised to the higher desired value, which will use more electrical energy until the IAT increases.

Unfortunately there does not appear to be a ramp up function within heat pump controllers, so if you wish the heat pump to operate in a more gentle manner, you could try raising the setpoint in 0.5C increments over several hours.

@derek-m Thanks.  Yes, I will setback only 1C, and ramp up as gradually as I can, about 12 hours later.

Hmm. Just got 2 wireless room controllers and I found out that I can't set both zones to AA mode - when I set one zone to AA (based on room temp) the other zone has only WC or FT mode available (so only 2 out of 3). But I can have different WC for each zone (and FTC controls additional pump and mixing valve).

Is there something that I am missing?

@Sliderule

Looking at your graphs, I'm NOT an expert, but the difference between flow and return temperatures seems to be only about 2C if I am reading it correctly, and I am interested to know what your flow rate (litres per minute) is, and what COP you achieve.

I don't know how to answer that because I have additional pumps for each zone. Pump from ecodan is only heating the mixing tank

@damijand I'm sure you will have read this, but the FTC Installation Manual page 16 Option A says " If more than one wireless remote controller is used, the last temperature setting adjustment/demand will be applied to ALL rooms in the same zone." It shows a wired room thermostat for zone 2, not a wireless one, which is connected to IN6. So the system would operate as AA , controlled by the zone 1 wireless thermostat, with the zone 2 thermostat switching off zone 2 when the set temperature is reached. Usually zone 1 is the main living room, which requires the most heat most of the time. 

I can't see how one FTC can operate more than one heating mode, so everything will either be AA, controlled by the (last) wireless thermostat (to input) in zone 1, or everything will be WC, with the room thermostats pausing the heat pump when the set room temperature is reached. But I don't have a mixing tank so I have no experience with that system. I am happy using AA with the wireless controller in my living room/kitchen and programmable thermostats switching on the UHF in the hall in the day and the bedrooms and bathrooms in the night and morning, which provides enough demand to avoid nearly all HP cycling but minimise the power consumption. 

@sliderule thx for reply:

- I am familiar with the more than one wireless remote controller (WRC) in the same zone rule (last temp is used)

- If I use WC I can have different curves for each zone. But they are not completely independent: meaning zone2 can't have higher flow temp than zone1. I mean you can set whatever you want but as zone1 has direct heating circuit (HC) and only HC for zone2 is using mixing valve that means that flow temp in HC2 can be only up to flow temp of HC1.

(but that is ok, because zone2 requires little less in my case)

- AA is in a way just automatic WC with knowledge of room temperature and I don't see any reason why both zones can't use AA at the same time. Essentially that means that only one zone can use WRC: I don't know why it is possible then to assign WRCs to different zones. 🤔 

Anyway if I remember correctly someone here said that he/she contacted Mitsubishi directly. I would really like that contact info to ask them this. Because I am afraid that our local dealer has no detailed info on the matter.

If I can dream I would like the access to the firmware code for few days and I would improve/fix things that are clumsy  😀