Hello and welcome. Your HW COP sounds about right.  Your LWT of 47 degrees is very high unless your house is really poorly insulated and draughty. Mine is more like 35 at 11 degrees ambient.  I have a smaller, similarly insulated house to you and my 14kW ASHP cycles when it gets up to about 9 degrees outside. The COP is 3.5-4 at these temperatures, even when it cycles (in my case it's 2-3 times per hour).    

Having said that, a COP of 1.2 for heating isn't right. How much energy are you using per day for heating at the moment?  It quite difficult to measure COP accurately and the scope for getting it wrong is probably increased by having 2 ASHPs.  Maybe it's delivering more energy that it's saying.

There are other Daikin users who have had good experiences so maybe they can help with settings. 

Difficult to derimine your problem but with the COP figgures you have mentioned, you have some serious problems, and unfortunatly you seam to have a very poorly designed system. Daiken will not generly look at the heating system, just the heat pumps.

What I do find strainge is that you have 2 X 14 Kw units on a 250m2 house, that is 112 w/m2, a heat loss I would expect in a solid stone property with single glazing, drafty and no insulation, I would expect your heat loss, based on the description to be halve that.

The first issue is your flow temperature, it should, at this time of year and external temperaure shouls be no more than 25-30 Deg C. If you have a buffer tank and third party thermostats, that is where most of the efficiency is dissapearing to.

If you can trace a schematic of the system, supply some pictures of the system, we may be able to help improve it.

@kev-m Hi. Over the last 10 days or so we've consumed about 220 kWh of electricity for about 260 kWh out. The settings are as set by the Daikin engineers. I'm wondering if it's too high, hence turning on and getting to temperature too quickly, then switching off, waiting and then turning on from cold again. The system does have two baffle tanks too.

Posted by: @chrislay

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@kev-m Hi. Over the last 10 days or so we've consumed about 220 kWh of electricity for about 260 kWh out. The settings are as set by the Daikin engineers. I'm wondering if it's too high, hence turning on and getting to temperature too quickly, then switching off, waiting and then turning on from cold again. The system does have two baffle tanks too.

220 kWh in 10 days for a house your size running at 47 deg flow at ambients of 10-12 degrees sounds in the right ballpark. I'm suspicious of your energy delivered number though; it seems far too low.  My ASHP has delivered well over 400kWh in the last 10 days and for 4 of these we were away and the ASHP was in holiday mode. My house is 1990 and smaller than yours. COP has been about 4.5. I wonder of there is something wrong with your energy delivered readings. If your flow sensors aren't installed properly it can really mess the readings up. This happened with mine.    

You basically need to have this completely re-plumbed, by Brendon, or someone with his skills.

Throw all the zoning away, fit TRVs into the upstairs bedrooms only, leave the heating on 24/7 with a nighttime setback.

You’re trying to run the ashp like an oil boiler, and that’s a serious mistake.

not you fault though, most ‘engineers’ in this industry are only marginally competent at installing these correctly.

Posted by: @chrislay

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@kev-m Hi. Over the last 10 days or so we've consumed about 220 kWh of electricity for about 260 kWh out. The settings are as set by the Daikin engineers. I'm wondering if it's too high, hence turning on and getting to temperature too quickly, then switching off, waiting and then turning on from cold again. The system does have two baffle tanks too.

As Kev has pointed out there would appear to be a problem with the COP reading for heating. Is the measurement being made by one of the two ASHP's, with the other one showing the DHW COP?

The other concern is the high LWT value, which has been stated should be more in the 30C to 35C range at an ambient temperature of 11C.

I would suggest that you get Daikin to explain why you are only getting a COP value of 1.2 for CH, and also to show the settings of the weather compensation curve, which appears to be in need of adjustment.

Note your energy consumption, COP values, LWT and ambient temperature on a daily basis and post the results.

Do you have the heat loss calculations for your home?

Hi Chris, there's some fantastically experienced and knowledgeable ASHP people here, you've come to a good place for help. As others have said, based on current outdoor ambient, 47degC CH water supply temperature is very high, mine is sitting at 36 right now for 10degC outdoor air temperature. If you are needing 47degC water to heat a 1970s house in the current mild weather, something is wrong somewhere. Either your radiators are very under-sized, and/or the house insulation is nowhere near as good as what has been assumed in the system sizing calculations. What is your SAP rating for the property? (SAP calculations are not to be relied on for ASHP system sizing, but give a general indication of your home efficiency)

I've converted from a 25yr old oil boiler quite recently, in a 140m2 property with 20 wet rads. 12 were up-sized for a system design temperature of max 50degC. Your CoP should be sitting between 3.5-4:1 right now, with some better control and efficiency checks that could be improved on (I'm still tweaking things on my system).

If you used to burn oil to heat your house and hot water, you'll know how much heat energy you were consuming per year. Kerosene 28sec is 10.35kWh per litre, so if your boiler was 80% efficient, 80% of the calorific value of oil you burned was heating your house and hot water. How does that value compare to now? Per annum, an ASHP should consume considerably less kWh than a direct fired boiler, about 1/3 to 1/2 depending on CoP and how warm you heat the house to now compared to how you used to.

The essential key, and the thing installers get wrong and don't tell you, is not to try to run an ASHP like a fired boiler. But if you've only ever had a fired boiler, this is counter-intuitive. I set my system back to 15degC at night, which means it tends to switch off in the evening. As we move towards winter it will run over night in set-back. When it kicks in, the first hour or so is spent purely pre-heating the system volume in the primary and secondary sides, which is very inefficient and power hungry. If you do that twice a day, morning end evening, you're consuming a lot of electricity.

I have smart TRVs so that, first thing, only certain rooms call for heat, the ones we circulate in first thing, which means the pre-heat time is reasonably short. Once the CH system is pre-heated, the HW cylinder will charge for 30 mins (250litres), then the ASHP system runs all day. The main controlling thermostat set high so the ASHP runs continuously, programmable zone valves and TRVs control it from there, warning up rooms to suit our daily pattern, but background heating is always provided into some areas of the house at a minimum 18degC during the day. My 10kW ASHP will modulate down to provide 3-4kW output consuming less than 1kW after a couple of hours running. In the current mild weather it's averaging 1kWh during the day until the evening HW charge of 30mins (if the Solar iBoost has not already done that)

You can do your own approximate ASHP heat output calculation, if you know the system flow rate and the supply and return temperatures: Q(kW) = flow (l/s) x (flow & return temp difference degC) x 4.2kJ/kg/degC. This formula holds true for water systems without additives such as glycol anti-freeze. Additives reduce the thermal conductivity of fluid.

Grant fitted me a low loss header, which costs some efficiency, and is questionable requirement for a single zone simple primary and secondary side wet rad CH and mains pressure HW design. The header has a 3kW immersion included which can be configured variously, either to boost system pre-heat in winter, boost overall system output if necessary, or help with defrost. It's only something to use if necessary, as it has a CoP of 1 of course. I originally considered a 13kW ASHP, but my calcs suggested 10kW would be fine, and we have secondary heating via a wood burner (we get lots of power cuts so I would never be without it). The smaller 10kW unit has good inverter modulation and means less on/off cycling of the compressor than a larger unit might need on partial load. The 3kW back-up immersion is an insurance policy (of sorts) in case I need a bit more heat than the ASHP can deliver in extreme winter weather. Grant and the installers didn't do a very good job of balancing primary and secondary sides of the low loss header, primary side flow rate was far too high, and they forgot to enable weather compensation. It was obvious within a few days something wasn't right as the ASHP was continually trying to deliver 50degC CH water with the compressor kicking in and out and not modulating down on inverter control, that's hugely inefficient. This is a common story - poor commissioning by the installers and almost no proper customer handover.

Good evening,

This sounds like the perfect forum for some help. We have just had an airsource installed and I was wondering if someone could help with the settings? We had a terrible sales driven company sell it to us, installer was great but lacking settings and it seems to be costing. 

Posted by: @will_b

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Good evening,

This sounds like the perfect forum for some help. We have just had an airsource installed and I was wondering if someone could help with the settings? We had a terrible sales driven company sell it to us, installer was great but lacking settings and it seems to be costing. 

Hi Will and welcome.  If you start a new thread in the ASHP section and include some details about your house and ASHP someone will be able to help.