Air Source Heating - Tips, tricks and best way to use!

nkingy2003

Hi All!

In July of this year I had a 14kw Daikin Altherma split system installed with radiators throughout. I have a 170sqm chalet bungalow and I’m currently going through the process of upgrading insulation throughout. It’s not simple as there are rooms in the roof and dormer windows, etc.

I started using the heating about a week ago. I have individual meters fitted to the Heat Pump, Hydro unit and Tank/Immersion. I’ve been monitoring all of these and they all seem to be going well, no excessive use, although it hasn’t been particularly cold yet.

I just have a few questions about fine tuning the system…

We (me and the wife) both work full time so we are only at the house in the morning, evening and weekends. I know that these systems need to be kept at a reasonable temperature even when no one is home otherwise it costs a lot to heat back up. Our installer fitted a wireless non-programmable thermostat, we have been leaving this at 19 degrees day and night and then turning up to 20/21 when we get home for the evening and at weekends. I would like to start being a bit smarter with this and perhaps turning down to 17 degrees overnight and during the day and heating back up to 20/21 in the evening/weekends, perhaps taking advantage of economy 7 overnight rate. For this I will need a programmable thermostat and I would like to go for a Nest thermostat as this allow me to monitor usage even better. I’m just wondering if anyone else has a Nest thermostat and how you programme your heating at various times throughout the day?

My system has the option for weather dependency, but the installer has disabled this as they often find users play with this and don’t understand it. I feel that I am sufficiently familiar with the system and how it operates for this to be turned on. Would you advise on having weather dependency turned on or would you just stick with a constant flow temp (mine is currently set to 45)?

Also, I have my hot water set to 44 degrees and to reheat constantly (I believe it reheats when the hot water drops by 2 degrees). I know other people have theirs set to, say 45 degrees, but to only reheat once per day (perhaps taking advantage of economy 7 overnight rate). What do you do with yours?

Thanks!

matelodave

Mines an 11kw Daikin Altherma split, but feeding an overlay underfloor system. I spent the first winter (the very cold one in 2000) working out how it all worked and put some effort into tweaking the set-up.

Because we've got u/f we can control each room individually and each room has it's own programmable thermostat. Each stat is set to a background of 17 degrees and then uplifts the room temperature to suit our requirements. Lounge is set to 19 during the day an 20 in the evening, Study is 20 from 0800 to 1700. Bathroom and bedroom 19 between 0700 and 0900 and 2000 to 2200.

We find that the system is very slow to respond so it can take a long time to recover if you let the place get too cold. Our first winter we went away for a couple of weeks and I turned it down too far and it took nearly 48 hours to get back up to temperature. I now set the stats to turn the system on at least 24 hours before we return home.

I've got weather compensation set and it does reduce the flow temperatures but you've got to try and balance it against the time it takes to reheat the place - our system runs between 30 degrees and 42 degrees between outside temps of 15 degrees down to -5 degrees. I've got the back-up heater shut off so it cannot come on unless I physically switch it on.

The lower the flow temperature the more efficient the unit becomes so you could try reducing your 45 degree flow to 40 to see how it affects your comfort and reheat times (it's reckoned that for every degree above about 35 degrees will increase the running cost by around 2,5% so beware turning it up high). If you crank it up above about 50 degrees the 6kw back-up heater will kick in an cost you a lot to run so keep the flow temps down

We heat our 200l hot water tank to 45 degrees once a day (the unit is timed for 0500-0700) and that gives us sufficient hot water for all our needs (we don't have a bath, just showers) with a sterilising boost to 60 degrees on Saturdays (using the tank immersion heater). We use less than 2kwh a day heating the hotwater (I've got an energy monitor which records the energy consumption)

As the unit does most of it's work during the day (we are at home all day) there's no point in us having E7 so I go for the cheapest single tariff deal I can get (presently 15/p s/c and 12.5p/kwh). You really need to check your heating times to see if E7 would be of any benefit - although you get cheaper off-peak leccy overnight your main heating time is probably during peak times when it's more expensive than a single rate tariff.

Personally I'd change the stat for a programmable one which should give you as much control as you need. If we do feel we need it a bit warmer then it's easy to override a programmable stat and it will revert back to it's programme at the next switching sequence so it's impossible to forget. I really can't see a lot of point in having a Nest because of the slow response time of the system so there's no advantage in short term tweaks

nkingy2003

Hi Dave,

Thank you for your detailed reply. You sent me your heating system write up back in March before I had mine installed, it was very informative!

I will try reducing the flow rate as you say, I'm sure this time of year the lower flow rate would still heat the house fine. But, would you suggest I try weather dependency? At least this it would adjust the flow rate automatically for me?

I'm currently running at about 3kw per day for hot water, set at 44 degrees on constant reheat. I will give it a go as you suggest, reheating once per day. I'll do it overnight to make use of E7 rate.

Can I ask what electricity supplier you are with? 12.5p/kwh is very good!

My thinking behind the Nest was that it will also help me monitor usage. I have individual meters so I can monitor kwh usage but it would be interesting to know the usages in time too. I'm not sure if Nest could also programme the Hot Water?!

matelodave

I'm now with Symbio for my leccy, I was with Eversmart which was only 11.5p/kw but their daily s/c was about 7/p a day more expensive.

I dont know how your Daikin controller works (mines now 9 years old so probably a lot different) but mine controls the hotwater temp and on/off times so I dont think that a Nest could control it.

I would have though that by now the Daiking controller would have had an option for remote monitoring/logging - I've just got an Efergy Engage monitor clamped around the power cable feeding the unit which tells me how much is being used and when - I can view it in real time on my phone, tablet or mobile phone and download a data log and view it in Excel should I so desire. This is what I've got, however I got it cheap £25) from Maplins before their demise https://uk.efergy.com/engage/

Jonesya

For your hot water temperature of 45 degrees C you need to consider Legionella

http://www.hse.gov.uk/legionnaires/hot-and-cold.htm

Andy_WSM

I've got an 8kW cool energy heat pump running to a hot water tank and radiators in a 2 bed detached bungalow. I have the flow temp at 44C for both hot water and radiators which is plenty and means the heat pump isn't ever working particularly hard. The hot water gets heated with excess solar PV every day too and more often than not will reach 65C so the heat pump realistically isn't doing much domestic water heating.

I leave the room thermostat at 20C day and night 24/7/365 and just let it do it's thing. In a particularly cold spell of weather I will light the wood stove on an evening which means the heat pump won't come on in the coldest of weathers when it is most inefficient.

Electricity cost wise I still come in at well under £800 a year in an all electric property and turn an overall profit after FITs from the Solar.

matelodave

Jonesya wrote: »

For your hot water temperature of 45 degrees C you need to consider Legionella

http://www.hse.gov.uk/legionnaires/hot-and-cold.htm

The Daikin unit sterilises the tank once a week, so legionella shouldn't be a problem.

I cant see how it would be anyway with a mains pressure water system. It's fed from the mains with chlorinated water and not open to the atmosphere.

mrmmhf

I’m just wondering if anyone else has a Nest thermostat and how you programme your heating at various times throughout the day?

We fully automated our heating using a variety of devices - we replaced our oil boiler with an ASHP and wanted to make sure it ran as efficiently as possible.

For our underfloor heating, we installed wireless thermostats from Heatmiser (three of them) and we've programmed them to heat rooms at different times to set temperatures.

We've also changed all our TRVs to smart TRVs (Eve by Elgato - 11 off them) and that's allowed us to set a heating schedule for every room in the house. It's been hugely effective.

We found the Nest set up to be a tad pricey, so opted for a more cost-effective solution and our heating is running very efficiently now and not costing us anywhere neat as much as the oil boiler.

mrmmhf

On that note, our air source heat pump has been in operation for five months, over spring and summer, so it is a good time to review the performance and efficiency of our Caernarfon 18kW Eco Air Source Heat Pump (ASHP) from Global Energy Systems.

Most ASHP owners in the UK use Mitsubishi, Hitachi or Daiken ASHPs, so it should be interesting to see how a British manufactured ASHP, made for the British climate, will perform and compare. Would be very interested to hear how our pump stacks up to yours.

As part of this video, I’ve addressed our coefficient of performance (COP), performance and efficiency, the control panel and settings for the ASHP, noise rating and some general thoughts. I've also dropped our hot water temperature.

I will do a follow up video in autumn and winter to provide a full performance and efficiency comparison.

YouTube: https://youtu.be/P8cBKBTTLBw

Additional information and data sheets: http://myhomefarm.co.uk/air-source-heat-pump-efficiency-and-performance-review

I've also just looked at the performance of the ASHP when the temperatures have started to drop in October, which has been very interesting and I'm looking forward to seeing how this will change over the course of the December, January and February: https://myhomefarm.co.uk/air-source-heat-pump-when-temperatures-start-to-drop