Air Source Heat Pumps

matelodave

We've got an over-lay undefloor heating system which is a bit more responsive than a concrete one and each rrom is a zone with it's own programmable thermostat.

The unit is an 11kw Daikin split ASHP and has a 6kw back-up heater which I have switcehd off.

The 200l tank is heated every morning for two hours to 45 degrees by the heatpump and has a 3kwh immersion which kicks in on Saturdays for about 15-20 minutes for the sterilisation function (which usually means the tank doesn't heat on Sundays)

The CH flow temperature is weather compensation and is set 25 degrees flow with an ambient of 20 degrees and 42 degrees with an ambient of -5. This seems to give us an average flow of around 30-35 degrees although the flow temp is increased by 3 degrees between 1800 to 2200 as the house cools when the sun goes down.

Because of the underfloor heating we can get away with a comfort temp of 19 degrees. The set back is 17 degrees.

Each room is programmed to it's use.
Bathroom & main bedroom 19 degrees from 0700-0900 and 2000-2200
Hall - continuous 17 degrees
Study - 19 degrees from 0700 to 1900, then set back
Spare bedroom - 15 degrees unless it's in use
Kitchen 18 degrees 0700-0900, 1200-1300, 1800-1900
Lounge/Dining 19 degrees from 0700 to 2200.

These times seem to keep the house about right and the rooms are comfortable when we use them.

When we first got the system we, like most people, set it on & off like a normal system and the initial costs were high and it took ages to get the rooms to temperature.

We also found that if we shut it down to go away it took about two day to get the house warm again. However, all the stats have a holiday mode so we can shut it down and turn the system on the day before we return which gives around 36 hours of preheating which seem to work ok.

It took all of the first winter to get it about right and we seldom touch it although my wife does tweak the the one in the study up to 20 or 21 when she's in there but as it's programmable it reverts back to it's normal settings.

Our total energy bill (all electric) for the first year was 8500kwh but that's dropped to an average of around 7000kwh. I estimate we use around 3500 for general use (incl hot water) so heating is around 3500kwh a year which isn't bad for a 140 squ.m bungalow.

c13pep

Hi
Just an update on my ASHP system which I am sure will raise a few eye brows. I do run it like a normal heating system with a total shut down from 10.00pm until 05.30am. The system is set to achieve a temperature of 24 degrees in the lounge due to my wife's health problems, there are 20 radiators heating 6 bedrooms etc. most of which were upgraded to doubles on installation (retrospective), the hot water operates at 42 - 52 degrees.
The overnight shut down means that the ASHP does not operate when temperatures are lowest and thus its efficiency is maximised. I have gone to great lengths to ensure that heat is retained in the house and that my solar panels are regularly cleaned and retain effectiveness.
The system works very well as it is, with monthly electric bills at £186 which for this size of house I feel is correct, however I do get back £900 each for the solar panels and the ASHP from the government!! Thus my annual running costs equate to around £450 per year currently.(we are all electric)
The system incorporates our original LPG boiler which should kick in at minus 12 degrees however it never has.(I wish it would, just to use up the 50% of gas we have left in the tank)
The system is Mitsubishi Ecodan 12Kw with refrigerant pipes between the outside unit and the Hydrobox in the loft
In the four years of use we have needed a new pump inside the Hydrobox (warranty) and a replacement remote control unit.
CHRIS

Cardew

c13pep wrote: »

Hi
Just an update on my ASHP system which I am sure will raise a few eye brows. I do run it like a normal heating system with a total shut down from 10.00pm until 05.30am. The system is set to achieve a temperature of 24 degrees in the lounge due to my wife's health problems, there are 20 radiators heating 6 bedrooms etc. most of which were upgraded to doubles on installation (retrospective), the hot water operates at 42 - 52 degrees.
The overnight shut down means that the ASHP does not operate when temperatures are lowest and thus its efficiency is maximised. I have gone to great lengths to ensure that heat is retained in the house and that my solar panels are regularly cleaned and retain effectiveness.
The system works very well as it is, with monthly electric bills at £186 which for this size of house I feel is correct, however I do get back £900 each for the solar panels and the ASHP from the government!! Thus my annual running costs equate to around £450 per year currently.(we are all electric)
The system incorporates our original LPG boiler which should kick in at minus 12 degrees however it never has.(I wish it would, just to use up the 50% of gas we have left in the tank)
The system is Mitsubishi Ecodan 12Kw with refrigerant pipes between the outside unit and the Hydrobox in the loft
In the four years of use we have needed a new pump inside the Hydrobox (warranty) and a replacement remote control unit.
CHRIS

Excellent post! presumably you think the 'raised eyebrows' will be because of the 'non-standard' operating mode.

Using £186 a month for electric and taking into account input from PV panels that would mean using around 24,000kWh pa??

A couple of questions if I may.

What kWh allowance for RHI do the government allow?

How much did the system cost to install?

c13pep

Hi
My annual KwH allowance is 11847 giving a quarterly payment of £228 which has recently been revised downwards to £225 due to their original miscalculation, but hey not the end of the world.
The original investment was £12000 for ASHP and £6000 solar panels (the panels are black Canadian Solar) , all are less now, however we have been told by an estate agent that the house will now command a premium because of the ener
gy saving features etc. even after 2021 when the government grants will end.
Considering we were LPG before at a then proposed cost of £250 per month then we are pounds in front.
Do not forget the maintenance costs of the two systems which equate to about £150/annum ASHP (independent engineer) and £40 solar panel cleaning/annum.
I also do actively monitor the electricity deals available currently we are with SSE
CHRIS

matelodave

What's you flow temperature to acheive 24 degrees in the lounge in a short space of time.

Have you tried running it at a lower flow temperature but for longer and only setting back the night-time temperatures by a few degrees. You might find that the increased efficiency of the HP at low flow temps and a more even house temperature could actually save you money.

Th02msn

Thanks to all for the replies

Firstly - what is the ‘flow temp’ and where do i find it?

I dont have radiators - i have underfloor heating. Approx 200 sq meters.

My immersion boost is set to come on for 30 mins every morning from 5am to 5:30am.

So do i leave my HW setting at constant or should i have it on timer? There are only 2 of us in the house but certainly dont want to get up in the morning to a cold shower! Brrrrrrr!

Also Richard C - what do you mean by ‘night set back’ ??

Thanks again everyone for the info. I understand it is a bit of a trial and error practice.

richardc1983

Th02msn wrote: »

Thanks to all for the replies

Firstly - what is the ‘flow temp’ and where do i find it?

I dont have radiators - i have underfloor heating. Approx 200 sq meters.

My immersion boost is set to come on for 30 mins every morning from 5am to 5:30am.

So do i leave my HW setting at constant or should i have it on timer? There are only 2 of us in the house but certainly dont want to get up in the morning to a cold shower! Brrrrrrr!

Also Richard C - what do you mean by ‘night set back’ ??

Thanks again everyone for the info. I understand it is a bit of a trial and error practice.

You leave your heating set to constant when you would normally have a timed on period you set it to a comfortable temperature when your out, in bed or don't want comfort temperature you set back the temp a few degrees lower. Eg 21c for the comfort period and 18 or 19c for the set back temp. This way the house never gets too cold and it's able to recover easier.

The flow temp should be on the settings somewhere usually a heat curve though eg hotter when colder etc.

Th02msn

So.....

When i go out or go to bed - i flick the setting on controller over to ‘timed’ (which is obviously set to the slightly lower temp)?

As for the flow temp - im completely baffled!

My head is sore now 😂

richardc1983

Th02msn wrote: »

So.....

When i go out or go to bed - i flick the setting on controller over to ‘timed’ (which is obviously set to the slightly lower temp)?

As for the flow temp - im completely baffled!

My head is sore now 😂

However your controller does it your heating is on 24 7 but when unoccupied or in bed set to the lower temp.

Flow temp will be in the manual and is the setting of how hot the radiators get. If you post the manual link we may be able to help you change this.

Th02msn

OK give me a minute and il try to send a link. Please bear in mind that there are no rads - underfloor heating (if that makes any odds)
My room stats are not programmable. They are digital but only increase or decrease them temp.

Righty - will be back soon with link.

Thanks so much