Air Source Heat Pumps

Andy_WSM

Question also for Albyota:

Is the flow temp of 55C necessary for the underfloor heating? Could you lower the temp without hitting heating performance too much, thus gaining a better COP?

I know it's a different kettle of fish, but I have electric underfloor heating in my conservatory (which I'd gone for wet, but that's a different story) and it is set at just 22C floor temp to achieve a 20C room temp and worked very well through all but the coldest of weather.

albyota

paceinternet wrote: »

Great info, many thanks albyota.

Flow temp dropped from 55 to 26. So what happened next?
I guess your underfloor mass didn't drop to 26, but how long did it take to recover the flow temp, and was the heat pump on max power during the recovery?

UFH does not change as all circuits go through blending valves anyway....absolutely no loss in heating......the recovery time is very short.....remember I normally run the heat pump at around 36 degrees anyway....I actually forced the system to defrost, so with experiment over, I reduced flow back to 36 degrees..... when I first installed it in Oct 08, I had been running it at 50 degrees and recovery after defrost cycle of 2 minute was a further 3 minutes but always increasing from around 26 to 50...yes for those 5 minutes it is at max power......pulling 23 Amps.
the heat pump has a running current of 10.3 Amps.

albyota

Andy_WSM wrote: »

Question also for Albyota:

Is the flow temp of 55C necessary for the underfloor heating? Could you lower the temp without hitting heating performance too much, thus gaining a better COP?

I know it's a different kettle of fish, but I have electric underfloor heating in my conservatory (which I'd gone for wet, but that's a different story) and it is set at just 22C floor temp to achieve a 20C room temp and worked very well through all but the coldest of weather.

As previous post I run my UFH at 36....yes 36 degrees........house is toastie. At this time of year I have COP's of around 3.0 Air 2/Water 35 with ambient 2 degrees....with ambient at 7 degrees I should see COP of 4.18 but overall the better efficiencies are from heating my hot water in the summer, I will try and capture some more data....if we get a summer.

albyota

littletiger82 wrote: »

I have the HW coming on for an hour from 4-5 every morning as that seems to give me enough hot for the day. CH is now programmed to be on from 5-11 in the morning and 5-11 in the evening as I work shifts and could be coming in or going out at pretty much any time so its difficult to set tight timescales.

I've turned the thermostat on the HW tank down to 55C - is that right?

littletiger82, The timing of the CH can be whatever suits you / comfort, however like any system, the more you use it the more it will cost to run....but when it is cold.....health and comfort is more important!
As for the hot water in the cylinder, yes 55C is fine....you don't need it any hotter for washing, showers or baths.......the Ecodan only heats at 60C anyway....but check with a thermostat the actual water temperature at the tap...and adjust T'stat accordingly. If your system has been installed and set up correctly....you will find that once per week the electric Immersion heater should be set to switch on directly after the heat pump has finished its cycle of heating (say Sunday morning) for one hour, this is for thermal disinfection.... (legionella prevention) however to raise the cylinder from 55C to 65C.....only takes a matter of minutes which will cost between 5p and 15p.

richardc1983

albyota wrote: »

As previous post I run my UFH at 36....yes 36 degrees........house is toastie. At this time of year I have COP's of around 3.0 Air 2/Water 35 with ambient 2 degrees....with ambient at 7 degrees I should see COP of 4.18 but overall the better efficiencies are from heating my hot water in the summer, I will try and capture some more data....if we get a summer.

what temperatures do you achieve when you say toastie. Some ppl are toastie at 18c! Lol

Andy_WSM

albyota wrote: »

As previous post I run my UFH at 36....yes 36 degrees........house is toastie. At this time of year I have COP's of around 3.0 Air 2/Water 35 with ambient 2 degrees....with ambient at 7 degrees I should see COP of 4.18 but overall the better efficiencies are from heating my hot water in the summer, I will try and capture some more data....if we get a summer.

Thanks for the info

Summer? - LOL!

richardc1983

lomb wrote: »

After reading your post your system is loosing nearly 2 kw at -5 degrees compared to 6 or 7 degrees. Lets say we round up the manufactuers figures. Bottom line is better too big than too small especially if they can ramp down.

yeh so my system at -5c is running at bang on the heat loads for the rooms. 2kw per room! Hence the oversize to ensure at very low temps the system still could provide the required output to heat my rooms. I haven't had to use fan heaters either apart from one day when the system had been off all weekend when I returned from being away for the weekend. The house was at 11c! So used a halogen heater to sit in front of whilst the system was catching up for a couple of hours.

littletiger82

albyota wrote: »

littletiger82, The timing of the CH can be whatever suits you / comfort, however like any system, the more you use it the more it will cost to run....but when it is cold.....health and comfort is more important!
As for the hot water in the cylinder, yes 55C is fine....you don't need it any hotter for washing, showers or baths.......the Ecodan only heats at 60C anyway....but check with a thermostat the actual water temperature at the tap...and adjust T'stat accordingly. If your system has been installed and set up correctly....you will find that once per week the electric Immersion heater should be set to switch on directly after the heat pump has finished its cycle of heating (say Sunday morning) for one hour, this is for thermal disinfection.... (legionella prevention) however to raise the cylinder from 55C to 65C.....only takes a matter of minutes which will cost between 5p and 15p.

Thank you so much for all your help albyota, one last question...how do I know if the immersion is coming on? and if not, how do i set it??

albyota

littletiger82, does it look like this?

DIGITAL IMMERSION & GENERAL PURPOSE TIMESWITCH IHT-DIGI 20






instructions here......

http://www.tfc-group.co.uk/assets/graphics/static/IHT%20Digi20%20Plus.pdf

albyota

richardc1983 wrote: »

what temperatures do you achieve when you say toastie. Some ppl are toastie at 18c! Lol

pretty normal I suppose.....
ground floor rooms have digital night setback stats.... these are set to drop back 2 (or 3) degrees from set temp at 10pm and during the night until 7am back to set temps.
At these settings the house is always comfortable.... the thing is left on even when were at work etc... as with UFH...due to lag it can take a couple of hours to get it back.

Living room is at 23
Kitchen...where I am is 23
Hall, stairs & landing probably at about 18 or 19
Utility room and downstairs WC circuits are at 18
bedroom 1 set at 19
Bedroom 2 set at 20 (daughter on PC)
bedroom 3 not in use ATM but about 17/18
bedroom 4 set at 20 (daughter)
Bathroom and en suite at 23 UFH & T' Rad

all set temps are always achieved.
The house is left to look after itself with all the room stats and the weather compensation on the Ecodan....this looks at ambient temp and adjusts flow temp according to what it thinks the house needs....quite clever really.