@jeff , 

it's going to be very hard to come up with a number.  This has a bit more info on how it works

What it will give you is more control and a more constant temperature in your house.  

@jeff 

Do you think it will be cheaper to run than just using Weather compensation alone as Mitsubishi say?

Any idea what % difference it might make based on your experience? It might help in the decision process for future changes/installs for some. 

It is quite funny that you have posed those questions, it is something I was just considering whilst making a cup of coffee.

I'm afraid there is no simple answer, it very much depends on your system, your lifestyle, your location and the fabric of the building. As Brendon has pointed out, a system using only weather compensation probably performs better if the building has a high thermal mass. i.e. it takes quite some time to heat up, but then takes quite some time to cool down once the heat source is removed. Variations in indoor temperature due to solar gain and/or human activity would be less pronounced.

In a home that has low thermal mass, the variations in indoor temperature could be more noticeable when only weather compensation is employed, as against Auto Adaptation. Which you choose depends on how accurate you wish to control the indoor temperature, along with how well your system is balanced from the point of individual room temperatures and the location of the sensors.

This brings us to the question of which is the most efficient way to operate your system, from the point of both energy consumption and economics. Would it be more efficient to allow the indoor temperature to rise by a degree or two due to solar gain, which would then reduce the amount of heat energy required later in the day, or would it be more efficient to reduce the temperature increase due to solar gain, by lowering the water flow temperature, but then require more energy later in the day to maintain the desired indoor temperature. Without carrying out very detailed testing, it would be difficult to provide a definitive answer.

The way that we try to reduce our energy consumption is by taking advantage of all available energy sources. We have a South facing conservatory, so on many days in Spring through to Autumn, and occasionally in Winter, we open the door to the lounge and allow the warmer air from the conservatory to act as a heat source. This in turn reduces or removes the need for additional heating, but of course temperature control is achieved by opening and closing the conservatory door.

A further way that we reduce energy consumption, is by using our A2A ASHP to warm up our home when our 4kW solar PV system is generating sufficient energy. In this way by running our ASHP for a couple of hours using totally green energy, our gas boiler can be shutdown for anything up to 12 hours.

The other defining factor with regard to whether Auto Adaptation or weather compensation is more efficient, is the variation in ambient air temperature throughout the day. As I think most people are now aware, the efficiency of an ASHP can be dramatically affected by changes in ambient air temperature, along with variations in the required water flow temperature. If the ambient air temperature remains the same throughout the day, then the reduction in water flow temperature during the day due to solar gain, when auto adaptation is employed, would improve the efficiency of an ASHP. The increase in energy requirement during the night may not be as high as the gain made during the day.

If instead, the ambient air temperature were to fall during the night, the reverse may be the case when auto adaptation is used. As I said previously, there are too many factors to consider to be able to give a direct answer.

Another factor to consider is the changing load factor of an ASHP, particularly during periods of milder weather. An ASHP has a minimum output below which it cannot operate, so if the heat demand is below this level, then the ASHP will begin running for a period of time and then stopping for a period of time. I have not seen any details of how this affects the overall efficiency of the ASHP, though I suspect it will cause a reduction.

I appreciate that the above explanation has not answered your questions definitively, it would be necessary for one to try different scenarios on their particular system and see which produce best results under certain weather conditions. 

Posted by: @kev-m

@jeff , 

it's going to be very hard to come up with a number.  This has a bit more info on how it works

KLIMA-ELEKTRO-SUPE.HR "http://www.klima-elektro-supe.hr/wp-content/uploads/2016/04/ecodan_split_i_package_type.pdf"

What it will give you is more control and a more constant temperature in your house.  

Thanks. 

The difference in flow temperature between auto adaptation and basic weather compensation looks promising. 

Taking their figures at - 10 degrees the difference in flow temperature is 6.6 degrees. They say 1 degree reduction in flow roughly equates to 2% increase in COP. 

So a 13.2% increase in COP at - 10 in their example. 

Not having to fiddle with weather curves to get the internal temperature stable feels like a really good thing for the mass market as well as saving money. 

Is this sort of feature available on many heat pumps? 

Posted by: @derek-m

@jeff 

Do you think it will be cheaper to run than just using Weather compensation alone as Mitsubishi say?

Any idea what % difference it might make based on your experience? It might help in the decision process for future changes/installs for some. 

It is quite funny that you have posed those questions, it is something I was just considering whilst making a cup of coffee.

I'm afraid there is no simple answer, it very much depends on your system, your lifestyle, your location and the fabric of the building. As Brendon has pointed out, a system using only weather compensation probably performs better if the building has a high thermal mass. i.e. it takes quite some time to heat up, but then takes quite some time to cool down once the heat source is removed. Variations in indoor temperature due to solar gain and/or human activity would be less pronounced.

In a home that has low thermal mass, the variations in indoor temperature could be more noticeable when only weather compensation is employed, as against Auto Adaptation. Which you choose depends on how accurate you wish to control the indoor temperature, along with how well your system is balanced from the point of individual room temperatures and the location of the sensors.

This brings us to the question of which is the most efficient way to operate your system, from the point of both energy consumption and economics. Would it be more efficient to allow the indoor temperature to rise by a degree or two due to solar gain, which would then reduce the amount of heat energy required later in the day, or would it be more efficient to reduce the temperature increase due to solar gain, by lowering the water flow temperature, but then require more energy later in the day to maintain the desired indoor temperature. Without carrying out very detailed testing, it would be difficult to provide a definitive answer.

The way that we try to reduce our energy consumption is by taking advantage of all available energy sources. We have a South facing conservatory, so on many days in Spring through to Autumn, and occasionally in Winter, we open the door to the lounge and allow the warmer air from the conservatory to act as a heat source. This in turn reduces or removes the need for additional heating, but of course temperature control is achieved by opening and closing the conservatory door.

A further way that we reduce energy consumption, is by using our A2A ASHP to warm up our home when our 4kW solar PV system is generating sufficient energy. In this way by running our ASHP for a couple of hours using totally green energy, our gas boiler can be shutdown for anything up to 12 hours.

The other defining factor with regard to whether Auto Adaptation or weather compensation is more efficient, is the variation in ambient air temperature throughout the day. As I think most people are now aware, the efficiency of an ASHP can be dramatically affected by changes in ambient air temperature, along with variations in the required water flow temperature. If the ambient air temperature remains the same throughout the day, then the reduction in water flow temperature during the day due to solar gain, when auto adaptation is employed, would improve the efficiency of an ASHP. The increase in energy requirement during the night may not be as high as the gain made during the day.

If instead, the ambient air temperature were to fall during the night, the reverse may be the case when auto adaptation is used. As I said previously, there are too many factors to consider to be able to give a direct answer.

Another factor to consider is the changing load factor of an ASHP, particularly during periods of milder weather. An ASHP has a minimum output below which it cannot operate, so if the heat demand is below this level, then the ASHP will begin running for a period of time and then stopping for a period of time. I have not seen any details of how this affects the overall efficiency of the ASHP, though I suspect it will cause a reduction.

I appreciate that the above explanation has not answered your questions definitively, it would be necessary for one to try different scenarios on their particular system and see which produce best results under certain weather conditions. 

Fair comments. It is not an easy question. 

First of all i think you have done a great job supporting people. 

I think personally i am unlikely to be able to do a better job than Mitsubishi across a year so assume their Auto Adaptation feature is probably going to be better than any of my manual tweaks to a weather compensation curve, irrespective of my house fabric or the way i use my house. Of course i may be doing myself a disservice and i don't have an ashp myself. There may be many issues with auto feature for all i know. The thought of potentially having to tweak curves at different outside temperatures isn't something i would relish. 

For me what this has shown is the challenges if the install isn't great from the start (things like poorly positioned sensors, too many TRVs, low flow values, unnecessary 3rd party heating controls and buffer tanks, poor radiator balancing and in some cases poor sizing etc. ). If we just had installers putting in very simple systems well and defaulting to manufactures auto controls i suspect we would have many more content customers.

I worry it is going to be almost impossible for installers to get the weather compensation curves right for every install, they simply can't spend that much time with each customer. It sometimes feels like installers are setting themselves up to potentially fail.

Of course the ability for some customers to be able to tweak systems is useful and many enjoy the challenge. 

@jeff 

Hi Jeff,

Taking their figures at - 10 degrees the difference in flow temperature is 6.6 degrees. They say 1 degree reduction in flow roughly equates to 2% increase in COP. 

Without wishing to appear too critical, the graphs shown in the example are over a short time period and would appear to be quite selective.

If you look at the bottom graph, at the start of the time period the room temperature is 22C, so a normal room temperature control system would automatically be pulling back to lower the temperature to the desired 21C.

With only the weather compensation active, it is indicated in the middle graph that the water flow temperature would have increased from 34.6C to 36.6C, which may have increased the room temperature slightly. Without knowing the thermal mass of the house and the heat loss, it is impossible to say.

The other factor to note in the example is that the property has UFH, which reacts slower to changes than a radiator based system.

To be fully convinced of their claims, I would need to see much more data, over a longer time period, and under differing climatic conditions.

@jeff I think we'll end up with a system based on weather curves from heat loss calcs. I dont see why its not possible given we know the size of heat emitters and the building losses. It should be straightforward to devise a weather compensation estimate.

For example I know my heat loss is about 8.7kw or 34w/m2 of floor space when its -1 outside. This is how they determined which heat pump I needed. I don't see why they couldn't just use this to work out the appropriate curve settings. Just playing with the calcs at 13 degrees my heat loss is 3.7kW - I am sure you can correspond this to a flow temperature.

@jeff 

 The thought of potentially having to tweak curves at different outside temperatures isn't something i would relish. 

Hi Jeff,

Sorry for the delay in replying, I'm afraid that I had to obey 'she who must be obeyed' when she had a task requiring my attention in the garden.

As I feel certain that Kev, Justin, Mark and Batalto will confirm, once the weather compensation curve has been optimised, it should not require any further adjustment as the ambient air temperature varies. It is just a matter of establishing the slope for your particular property. Over several years of observations and tests, I have found that for our home, a 1C fall in ambient air temperature, requires approximately a 1C increase in water flow temperature. By applying some initial settings in the controller and monitoring the resultant effect, it should be possible to calculate the slope and hence establish the required settings. It should not be necessary to keep making adjustments over a lengthy period of time.

The reason it would appear that many installers are not prepared to follow this route, is as you suggest because of the time element, or the fact that they don't fully understand weather compensation and how it works.

As I gain more knowledge about ASHP's and how they operate and are controlled, I can see no reason why installers, as you suggest, cannot install an ASHP system with approximate weather compensation settings and auto adaptation. Provided that the rest of the system is well designed for the type of property, then it should work well from day 1, without the need for return visits to make adjustments. The problem is that the majority of installers take the easy route and install thermostats, with which they are probably much more familiar.

With regard to the glossy brochure you supplied, you are probably like me, and take the details of any claimed fantastic results with a pinch of salt. I prefer to place much more faith in the manufacturers data within the specifications, which has to be obtained under specified testing conditions. I think the brochure in question was actually produced by a company called Deltron, who are probably a Mitsubishi supplier and installer.

@batalto thanks - weather comp not on yet - will start to look at this when home in a weeks time. 

@derek-m Hi Derek

Not got to grips with controller yet, I work away so not much time but keeping close eye on melcloud data. Saw @justinsb talking about cop's of 5.1 and was intrigued.

Main controller located in loft. It's a bungalow 224m* underfloor throughout uponor thermostats in each room.

Definitely feel twitchy about messing with the settings but also understand it's what everyone says you have to do. Initial set up is flow temp of 40*, hot water tank set to 50*, installer said to just leave alone and let the room thermostats call as they need it. Averaging about 30kwh per day at moment. We replaced LPG system.

Thanks for responding.

@kev-m Hi Kev been following your comments as knew you had same ecodan. Thanks for responding. 

We have ufh not radiators. We replaced a boiler based LPG system that wasn't working well at all.

Has your weather comp changes meant an increase in cop and therefore a decrease in cost according to melcloud?  

At the minute our operation mode reports state that in last seven days pump is 38% stopped, 57% on for heating, 4% for hot water and then a touch for legionella.

I'm home in a week or so. Will take a deep breath and start playing with settings - need a bit of time with the manual. If you have any tips re settings for weather comp then gratefully received. 

@rv3 this seems to be over double my Watts/m2 (30000/224 = 133w/m2) of power to heat your home. So first stop is weather comp to lower your temps. I'm in a slightly larger house and our minimum is 25@17  degrees

Posted by: @rv3

@kev-m Hi Kev been following your comments as knew you had same ecodan. Thanks for responding. 

We have ufh not radiators. We replaced a boiler based LPG system that wasn't working well at all.

Has your weather comp changes meant an increase in cop and therefore a decrease in cost according to melcloud?  

 

At the minute our operation mode reports state that in last seven days pump is 38% stopped, 57% on for heating, 4% for hot water and then a touch for legionella.

 

I'm home in a week or so. Will take a deep breath and start playing with settings - need a bit of time with the manual. If you have any tips re settings for weather comp then gratefully received. 

 

Hi RV3,

As Batalto has stated, your energy consumption is much higher than others are now achieving. When you are back home, I feel certain that Kev, Justin or Mark will be able to guide you through the simple process of setting your system for weather compensation, and also how to adjust the slope of the curve.