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  • FIRST POST
    samtheman1k
    Air Source Heat Pumps
    • #1
    • 24th Jan 08, 10:11 AM
    Air Source Heat Pumps 24th Jan 08 at 10:11 AM
    We recently moved into a house where, due to various issues, we were unable to get gas installed in our house and we also hated our storage heaters, like many others that I have read about on here. Last year, I installed an Air Source Heat Pump based system to provide ourselves with central heating and hot water and have written a description here in the hope that it may be of use to someone!

    The system that I opted for was the Mitsubishi Heat Pump Boiler combined with a Boilermate HP that is sold as a package and are designed to work together as the Boilermate controls the HP and is fully modulating. I went for this system primarily due to ease of installation as the output from the heat pump is hot water that can be fed directly into your central heating, rather than having to deal with seperate inverters and refridgeration engineers! This system can be installed by any competent plumber. The Boilermate is an unvented cylinder that provides mains pressure hot water to the entire house and is heated by the HP (and boosted to 60degC via a 3kW immersion heater if required to meet regulations).

    The first question I often get asked is 'what about the water temperature'?. Well, the temperature from the heat pump comes out at about 50-60deg C during normal use (according to the Boilermate sensors). The Boilermate HP actually has a 3kW inline electric heater to give the water a boost in temperature if required, but I don't think it is using this at the moment, and only will when the temperature drops outside. The boilermate has an external thermoneter to adjust the temperature of the water, but I have found that produces water that is too cold, so I have removed this to ensure that the water temperature stays at the maximum and then regulate the house temperature via a thermostat and TRVs. The following shows the output temperature of the heat pump verses outside temperature:



    So you can see that you'd only really need to use the electric boost if the outside temperatures drop below about -10/-15degC, which is rare for where I live in the South East, if you base your radiator sizes on a water temperature of 50-60degC. In fact, looking at that graph, I think I'm losing too much heat through the pipe between the boilermate and the heat pump, but I haven't finished insulating them yet (make sure you have good stuff (~£5/2m), not the normal stuff and keep the outside pipework as short as possible). ryansairconditioning.com (iirc) is where I got my stuff from.

    I'm not sure exactly how to convert the output temperature to a COP figure, but the HP maximum power consumption is about 2.1kW, so I'm sure someone can work it out! So I am effectively heating my entire 3 bed semi using upto 2.1kW of electric power (or 5kW in the worst case scenerio). I've posted the specs of the HP at the end of this pump for anyone who's interested.

    In terms of radiator sizes, Gledhill recommend that you oversize the radiators by 20%. However, we were a bit cautious in this and actually when for a 50% increase in our living room by swapping a single skin for a double skin one, and went for a 100% increase in the main bedroom as we like to be toasty! We did this by have two single skin radiators (due to the layout of the room). Our kitchen has a plinth heater that is rated at 100% extra IIRC, but it is a fan assisted one so is the same size as a lower rated one. We are installing underfloor heating in the bathroom too with a heated towel rail.

    In terms of cost, it's not cheap upfront. The boilermate and heat pump cost just over £4K to purchase. Then you have to add on the cost of installing the radiators and pipework (which I did myself) and you'll also need 10mm^2 cable running to the boilermate to provide the electric backup and 6mm^2 cable running to the heat pump outside (which of course all needs Part P certifying ) & also the commissioning of the system. We needed to upgrade our consumer unit too as we had a fuse box (with wires) rather than MCDs! Personally, I got a plumber to plumb in the actual boilermate as it is quite complicated! (although remember it just needs a normal plumber, not a specialist).

    I weighed the cost up against the cost of installing gas in our house, and as you have to pay the exact cost of gas installation (at c£2000 per day for the contractors, but less than £1k for a combi boiler), I think that the heat pump worked out cheaper as we'd have a very complicated gas installation due to access issues and the lay out of the land as the trench to the house would have to be dug out by hand!) and of course, there are many who don't even have the option of gas. Oil was another option, but is just as expensive to install and we didn't want a tank in our garden and oil isn't getting any cheaper! We couldn't get LPG as the tank wouldn't be in line of site to the road, so wouldn't meet regs.

    The main drawback is the noise generated by the HP itself. It is 49dB according to the specs, but I would say that it is about the same as a modern washing machine on spin cycle. This may or may not be a problem depending on where you live. The HP needs to be as close to your house as possible to prevent heat losses through your pipes, so you can't hide it at the back of your garden! However, it is hard to hear through a double glazed window, so shouldn't be too much of a problem. However, your neighbours may not be so sympathetic. There are no regs AFAIK on siting a HP as the main problem is the noise and that is already covered by the normal environmental noise regs. If you mounted it on your boundary next to your neighbours windows, then they may well complain. In Ireland, they are suggesting that there should be a 5m distance between any HP and a boundary, so we used that as a guide for England, but our garden is only about 7m wide, so doesn't actually quite meet that but we've done our best to site it in the least annoying place. We haven't had any complaints yet, but only time will tell. As mentioned, if it is a good few meters away, and your neighbours have double glazing, it shouldn't be a problem, although I'm not offering any guarantees! Also note that as it powers your central heating, it won't be running much during summer (bar hot water), so shouldn't be much of a problem when in the garden during the summer. Also, the HP is large. About 90cm by 90cm by 30cm, so you'd need a space to put something that size and is, tbh, rather unsightly! Although this is less than the size of an oil tank I suppose. It also needs a 30cm (iirc) space behind and 50cm infront for the flow of air, so can be mounted on bracket on the wall if you buy big brackets (it weighs about 90kg).

    In terms of running costs, we only installed it about a month ago, and the temerature has been between 0-10degC over the past month, bar a few sub zero days, and it seems to work out about £3 per day if it's on for most of the day, and about £2 per day when we are at work (on in morning/evening only). That is based on 8p/kwH and is the price for all our electric including cooking etc. We have cavity wall insulation, old double glazing (doesn't meet regs) and only 100mm of loft insulation so our house is fairly well insulated, but by no means well insulated.

    The key point I think is that in South east of the UK where I live, it rarely drops below freezing temperature anyway, so should be operating at a reasonable efficiency for most of the time. Obviously if we have an artic winter, then running costs will increase, but during summer, it will provide our hot water for virtually free (well, not quite as cheap as solar, but cheaper than gas anyway!).

    Finally, as the HP is running at greater than 100% efficiency most of time, my CO2 emissions should be less than all you gas boys, giving me a boost when we get a HIP done

    Any questions, then please ask and I'll do my best to answer!


    Info on the boilermate HP is here (under alternative energies);
    http://www.gledhill.net/water-storage/ws-index.htm
    and info on the HP is here:
    http://www.mitsubishi-aircon.co.uk/
    This is the spec sheet of the HP from the manual.
    Last edited by samtheman1k; 24-01-2008 at 11:09 AM.
Page 85
    • lovesgshp
    • By lovesgshp 1st Jul 16, 6:03 PM
    • 1,261 Posts
    • 709 Thanks
    lovesgshp
    Apologies for the late reply as have been rebuilding the computer.

    You should have most of the info you are looking for on the link below. It is in Italian, but should be easy to follow.

    http://www.geotherm.it/wp-content/uploads/2015/06/Pompe-calore-aria-acqua-IVT-AirX-brochure-web.pdf
    As Manuel says in Fawlty Towers: " I Know Nothing"
    • mark11original
    • By mark11original 1st Jul 16, 11:19 PM
    • 2 Posts
    • 0 Thanks
    mark11original
    Thanks for the link. I will have a look through it.
    • Deang
    • By Deang 5th Aug 16, 10:39 AM
    • 1 Posts
    • 1 Thanks
    Deang
    Hi,

    Does anyone have any information on EDG Installations and the daikin air heating system? I've been told I get a government grant to fund a % but the cost comes in at £12000 to be paid over 10 years (finance % included) apparently it will save me no less then 50% on my gas bills and I get £575 a year back from the government for 7 years??? Sounds good but I'm worried it will be a con.
    • Cardew
    • By Cardew 5th Aug 16, 11:09 AM
    • 27,114 Posts
    • 13,228 Thanks
    Cardew
    Hi,

    Does anyone have any information on EDG Installations and the daikin air heating system? I've been told I get a government grant to fund a % but the cost comes in at £12000 to be paid over 10 years (finance % included) apparently it will save me no less then 50% on my gas bills and I get £575 a year back from the government for 7 years??? Sounds good but I'm worried it will be a con.
    Originally posted by Deang
    What do you mean by ' air heating system'? I assume you mean 'Air Source Heat Pump'?(ASHP) i.e. supplying hot water to radiators and/or Underfloor heating.

    It won't save you anything like 50% on your gas bills - in fact it is extremely likely that an ASHP will be more expensive to run than gas CH.

    Loads of information on this forum for you to research.
    • Charlies
    • By Charlies 9th Mar 17, 9:51 AM
    • 2 Posts
    • 0 Thanks
    Charlies
    ASHP Consumption Profile?
    Does anyone have monthly power consumption figures for their Air Source Heat Pump? I know it's difficult to separate from other household consumption but I'm hoping someone might monitor it.

    My goal is to compare that (with electricity rates) to our oil use.

    Thanks.
    • Brittal
    • By Brittal 23rd Jun 17, 4:48 PM
    • 2 Posts
    • 0 Thanks
    Brittal
    Air source heat pump or LPG central heating
    I'm looking for some advice. I moved into a new house in November last year. Currently it's supplied by LPG so have central heating and water tank. Around half of the property is solid wall. I'm considering installing solar panels and know that I need to insulate the solid walls.

    My dilemma is what is the best way of heating my house. I like the thought of ASHP heating air via air con type units partially for the added bonus of cooling in the summer.
    My question is this a realistic economical solution.
    From what I've read ashp are not economical vs mains GAS but as I'm on LPG I guess that means they are at least comparible. I've also read about the 24 hour operation but again if I install solar panels at least during daylight hours that should not be an issue.
    I need to decide before I insulate the solid walls as I would then simply remove the radiators.

    Alternatively I could install a combi boiler but then I think I lose some benefit of solar.

    My other dilemma is on size of the solar system based on current usage I've been recommended a 4 kw system but if I go down the aircon / heat pump solution I assume I'd be better served by a bigger system perhaps 5kw.....does anyone recommend solar batteries my concern is that with the investment in battery technology cheaper better batteries are likely just round the corner.

    For reference my house floor area is about 1700 sq ft

    Sorry for the long post
    • matelodave
    • By matelodave 23rd Jun 17, 5:25 PM
    • 3,191 Posts
    • 1,909 Thanks
    matelodave
    There are two types of air source heat pump - Air to air, which as you say works like an air conditioner and Air to water which heats water to circulate it around a wet heating system, either underfloor, radiators or fan-coil units. Some are reversible and will cool as well as heat.

    Only Air to Water systems are covered by the Renewable Heat Incentive so you wont get any help in the cost of installing an air-air system.

    I've got an Air to water system and can give you some info if you want to PM me. We heat a 1350 squ.ft bungalow out in Fenland very successfully and economically but the system was designed from the bottom up.

    An air to air system might be cheaper to install and run and doesn't need to run all the time like an air to water system. You'd have to take into account that you'd need a blower unit in each room that has to be heated and an appropriate multi-outlet outdoor unit unless you have lots of individual ones. This is a multiroom split-type capable of running five indoor units https://www.orionairsales.co.uk/mitsubishi-electric-air-conditioning-mxz-5d102va-5-x-25-kw-multi-wall-air-conditioning-240v50hz-613-p.asp

    IMO solar power won't help towards heating your home as you'll be heating it in the winter when the days are short, cold and the sun doesn't shine much. Solar batteries wont help either unless you've got a really big one.

    My system uses around 2kw a day in the summer when it's just heating water and up to 40kwh or even 50kwh a day in the winter when its freezing cold and heating the house so you'd need a really big battery bank to provide you with enough capacity to run the system for a week or so, if the sun doesn't shine and an even bigger solar array to try and top it up with only 5-6 hours a day of weak or non existent sunlight.

    You really need to think it through carefully, do a lot of heat calculations and then try and evaluate the cost of installing and running the various systems to get the best solution
    Last edited by matelodave; 24-06-2017 at 9:22 AM.
    Love makes the world go round - beer make it go round even faster
    • matelodave
    • By matelodave 24th Jun 17, 9:14 AM
    • 3,191 Posts
    • 1,909 Thanks
    matelodave
    Does anyone have monthly power consumption figures for their Air Source Heat Pump? I know it's difficult to separate from other household consumption but I'm hoping someone might monitor it.

    My goal is to compare that (with electricity rates) to our oil use.

    Thanks.
    Originally posted by Charlies
    Yes, I've got about 7 years worth of monthly readings and sveral yaers worth of weekly ones
    Love makes the world go round - beer make it go round even faster
    • thozza
    • By thozza 24th Jun 17, 2:37 PM
    • 208 Posts
    • 173 Thanks
    thozza
    I'm looking for some advice. I moved into a new house in November last year. Currently it's supplied by LPG so have central heating and water tank. Around half of the property is solid wall. I'm considering installing solar panels and know that I need to insulate the solid walls.

    My dilemma is what is the best way of heating my house. I like the thought of ASHP heating air via air con type units partially for the added bonus of cooling in the summer.
    My question is this a realistic economical solution.
    From what I've read ashp are not economical vs mains GAS but as I'm on LPG I guess that means they are at least comparible.
    Originally posted by Brittal
    The Notts Energy Partnership has some useful comparison data for different fuel costs:

    http://www.nottenergy.com/energy_cost_comparison/

    Looking at the current figures, Air Source Heat Pumps are slightly more expensive than LPG using their calculated electricity rate (18.57p/kWh), but at a 'best buy' electricity rate should work out cheaper.
    • matelodave
    • By matelodave 24th Jun 17, 3:01 PM
    • 3,191 Posts
    • 1,909 Thanks
    matelodave
    I use a single rate tariff at 11.5p per kwh which gives an effective cost of around 4p/kwh assuming a COP of 3, or 4.6p/kwh with a COP of 2.5.

    The COP of a heatpump is dependent on the input and output temperatures and is usually quoted at 7 degrees outside and 35 degrees for the flow temperature.

    Most ASHP will give a COP of around 4 or even better at 7/35, however as soon as the outside temperature drops or you try to increase the flow temperatures then the COP will drop.

    It's reckoned that increasing the flow temp above 35 degrees will increase your cost by around 2.5% per degree so it pays to make sure that your heating system is optimised for low flow temperatures. Likewise avoid having high hot water temperatures.

    Most heatpumps wont get above 50-55degrees unless you get a specific high-temperature unit. To acheive higher temperatures an additional electric immersion back-up heater is used - COP=1.

    That's why it's never a good idea to bung a heatpump onto an existing heating system, the existing radiators are sized for a 60-70 degree flow and are therefore incapable of heating the place with low flow temperatures. To get effective heating, the ASHP will need to use the back-up heater unless oversized radiators or fan-coil units are installed.
    Last edited by matelodave; 24-06-2017 at 3:04 PM.
    Love makes the world go round - beer make it go round even faster
    • Brittal
    • By Brittal 24th Jun 17, 6:08 PM
    • 2 Posts
    • 0 Thanks
    Brittal
    Thanks for the feedback. My LPG is only 29p a litre so currently I'll be better saving with conventional central heating and I'll avoid the capital outlay. I may switch my attention to energy saving via Heat Genius type smart heating.
    • Martyn1981
    • By Martyn1981 26th Jun 17, 3:16 PM
    • 6,144 Posts
    • 10,280 Thanks
    Martyn1981

    My other dilemma is on size of the solar system based on current usage I've been recommended a 4 kw system but if I go down the aircon / heat pump solution I assume I'd be better served by a bigger system perhaps 5kw.....does anyone recommend solar batteries my concern is that with the investment in battery technology cheaper better batteries are likely just round the corner.

    For reference my house floor area is about 1700 sq ft

    Sorry for the long post
    Originally posted by Brittal
    Hiya, you could do both.

    Keep the LPG system, get PV installed, then install a small ASHP, perhaps 3.5kW (that's what I've done) for about £1k.

    When you don't need a lot of heating, just use the ASHP for the room or two rooms that you use the most, and if there's too much heat you can use doors as a simple way to spread excess around the property.

    During the warmer colder months (Mch/Apr & Sept/Oct/Nov) you may not want the full GCH on, but still have enough PV generation to cover all or most of the ASHP during the day. Or after a morning
    burn of the GCH to warm the house, you use the ASHP to keep the chill off the room or two you use, before an evening GCH burn.

    Obviously, you'd want to go for the biggest PV system you can fit on the property, since the cost goes down (proportionately) as you go bigger, since the panels are relatively cheap now. So if you can fit 5kWp or 6kWp (or even more), worth considering, especially in this scenario.

    You may even find yourself using summer excess to charge an EV in the future.

    Batts will help with a PV system, but for the UK, best to wait for a few years at least, as the market is still young, and expensive, and costs are still falling. A retro fit plug-n-play system will be fine later on if required/economical.
    Mart. Cardiff. 5.58 kWp PV systems (3.58 ESE & 2.0 WNW)

    For general PV advice please see the PV FAQ thread on the Green & Ethical Board.
    • BeeDave
    • By BeeDave 26th Jun 17, 4:45 PM
    • 1 Posts
    • 0 Thanks
    BeeDave
    Air to water heat pump for DHW only
    Hello all,

    I'm an avid reader of forums but this is my first time posting. My partner and I have recently moved into a very old solid wall granite house. It's not on the gas mains and had old storage heaters which we instantly ripped out! We had thought of installing under floor heating but this would have been expensive to retrofit. So we opted for a big wood burner. Last winter this was sufficient for space heating and we were surprised at the insulating properties of the thick walls and as its open plan it heated the living room- kitchen and dining space. We have small electric heaters in the 3 bedrooms and bathroom. We're in the south of Scotland with minus temps for a few weeks each year. My partner works from home so economy 7 electric tariffs aren't beneficial for us.

    Getting to the point- I recently bought a second hand Worcester bosch air source heat pump for only £100. I liked the idea of being eco friendly and having an outdoor boiler room to free up space in the house. The air source unit is 9.5kw. Primarily I want it to heat all of our domestic hot water- bath, two showers and washing the dishes etc. As a secondary, if it runs well and is working we could plumb in some over sized radiators to the bedrooms and bathroom. It has a 200l tank with it. We'll have to plumb in pipes from the boiler room to the house (about 4 meters).

    Some people have taken one look and said that with a unit that size it'll be less expensive to just have an immersion heater for hot water. What do you all think? Any advice much appreciated!
    • Cardew
    • By Cardew 26th Jun 17, 6:15 PM
    • 27,114 Posts
    • 13,228 Thanks
    Cardew
    Getting to the point- I recently bought a second hand Worcester bosch air source heat pump for only £100.
    Originally posted by BeeDave
    Welcome to the forum.

    Why was it being sold?

    From your post it is an Air to Water heat pump. Without pouring cold water! on your project, it is difficult enough to get such a system installed when purpose designed.
    • matelodave
    • By matelodave 26th Jun 17, 6:19 PM
    • 3,191 Posts
    • 1,909 Thanks
    matelodave
    It dpends how much hot water you get through.

    We've got a 200l tank connected to our 11kw Daikin ASHP. at this time of the year. It's on for two hours a day and it uses around 1.8-2kwh to heat our tank to 45 degrees. That gives us all the hot water we need for a couple of showers, hand washing & washing up - we can get four showers because we dont stand in there for ages - around 4 minutes each and we've got an eco shower head.

    The unit heats the whole of our 135m2 bungalow in the winter using an overlay u/f heating system. As said, you need to keep the flow temperature low, which means oversized rads and running it for longer periods than a conventional heating system but if you got it cheap and the plumbing is realatively easy then I'd certainly go for it.
    Love makes the world go round - beer make it go round even faster
    • bazer
    • By bazer 10th Jul 17, 10:33 AM
    • 3 Posts
    • 0 Thanks
    bazer
    Comparissons
    That would be great, I am in Somerset and getting very conflicting prices, quotes, sizing of units, and makes! Mitsubishi Eco Dan 11.2KW vs Daikin 16Kw LT Split! Any suggestions. Thanks Bazzer
    • lovesgshp
    • By lovesgshp 10th Jul 17, 7:03 PM
    • 1,261 Posts
    • 709 Thanks
    lovesgshp
    Hello all,

    I'm an avid reader of forums but this is my first time posting. My partner and I have recently moved into a very old solid wall granite house. It's not on the gas mains and had old storage heaters which we instantly ripped out! We had thought of installing under floor heating but this would have been expensive to retrofit. So we opted for a big wood burner. Last winter this was sufficient for space heating and we were surprised at the insulating properties of the thick walls and as its open plan it heated the living room- kitchen and dining space. We have small electric heaters in the 3 bedrooms and bathroom. We're in the south of Scotland with minus temps for a few weeks each year. My partner works from home so economy 7 electric tariffs aren't beneficial for us.

    Getting to the point- I recently bought a second hand Worcester bosch air source heat pump for only £100. I liked the idea of being eco friendly and having an outdoor boiler room to free up space in the house. The air source unit is 9.5kw. Primarily I want it to heat all of our domestic hot water- bath, two showers and washing the dishes etc. As a secondary, if it runs well and is working we could plumb in some over sized radiators to the bedrooms and bathroom. It has a 200l tank with it. We'll have to plumb in pipes from the boiler room to the house (about 4 meters).

    Some people have taken one look and said that with a unit that size it'll be less expensive to just have an immersion heater for hot water. What do you all think? Any advice much appreciated!
    Originally posted by BeeDave
    If you are just looking at DHW at the moment. then possibly try the Ariston Nuos heat pump, as that could fit your needs.
    As Manuel says in Fawlty Towers: " I Know Nothing"
    • Th02msn
    • By Th02msn 5th Oct 17, 9:08 PM
    • 1 Posts
    • 0 Thanks
    Th02msn
    Hi everyone. Im a newby but i have a question (or 2)......

    Recently built a new house in Scotland Aberdeenshire. Installed a 16kw Grant air source heat pump.
    I have noticed that the unit is using a vast amount of electricity. Up to 90 units per day!! Thats everything mind you - household appliances etc....

    My question is, what settings does everyone use for the hot water and central heating with the heat pump?? I was using mine on a timed program. Central heating coming on for 2 hours in morning & 2 hours evening. Hot water 1 hour in morning and 1 hour at night ( also boosted by the 3kw immersion daily for 1 hr). Should i have the central heating set to ‘ON’ constant?? We have digital room stats that would maintain the temperature. My thinking now is that the heat pump is having to draw considerable power in order to get the rooms up to the temperature set on the stats (21 degrees)
    If i leave it on constant - it will draw far less power as it will be just ‘ticking over’ to maintain a steady temperature.

    Any help appreciated folks.

    Also - should the hot water be set to ‘ON’ as well or left on timed?

    Thanks all
    • richardc1983
    • By richardc1983 5th Oct 17, 9:50 PM
    • 1,889 Posts
    • 1,006 Thanks
    richardc1983
    Hi everyone. Im a newby but i have a question (or 2)......

    Recently built a new house in Scotland Aberdeenshire. Installed a 16kw Grant air source heat pump.
    I have noticed that the unit is using a vast amount of electricity. Up to 90 units per day!! Thats everything mind you - household appliances etc....

    My question is, what settings does everyone use for the hot water and central heating with the heat pump?? I was using mine on a timed program. Central heating coming on for 2 hours in morning & 2 hours evening. Hot water 1 hour in morning and 1 hour at night ( also boosted by the 3kw immersion daily for 1 hr). Should i have the central heating set to ‘ON’ constant?? We have digital room stats that would maintain the temperature. My thinking now is that the heat pump is having to draw considerable power in order to get the rooms up to the temperature set on the stats (21 degrees)
    If i leave it on constant - it will draw far less power as it will be just ‘ticking over’ to maintain a steady temperature.

    Any help appreciated folks.

    Also - should the hot water be set to ‘ON’ as well or left on timed?

    Thanks all
    Originally posted by Th02msn
    You leave it on constant with set back temps. Your thinking is right. To have it work extra hard to get it upto 21c it will struggle. Also your flow temp should be as low as possible to heat the house. Night set back should be say 18/19c no lower. Then comfort temp of 21c. If you turn it off fully it has to work extra hard to get house back upto temp also the house will feel colder even when is it at that temp as the fabric still has to warm up. Also when you installed it did you oversize radiators for the lower flow temps?

    What’s your flow temp at? Having the hot water on timed is not a problem really as the tank will be so well insulated it will lose hardly any heat.
    If you found my post helpful, please remember to press the THANKS button! --->
    • matelodave
    • By matelodave 5th Oct 17, 10:33 PM
    • 3,191 Posts
    • 1,909 Thanks
    matelodave
    As Richard says you cannot use a heat pump like a boiler. They should run for a lot longer but at much lower flow temperatures.

    Most boilers run at around 70 degrees whereas a heat pump should ideally be no more than 40, less if possible. That means they take a long time to get the house up to temperature. Instead of turning it on and off as with a conventional boiler you reduce the temperature by around 3 degrees. It takes a bit of trial and error to get it right.

    Likewise the hot water, we keep ours at 45 degrees with a boost once a week to 60 degrees to protect against legionella. We've got a 200l tank which heats for about two hours every morning before we get up and there's plenty for us to both shower and for all our hot water needs throughout the day and a bit left over for the next day. It uses laround 2kwh of leccy.

    Most heatpumps wont go much above 50-55 degrees so by having the water hotter than than causes the backup or immersion heater to kick in which has a COP of one.

    Looking at the Grant ASHP info it has a COP (Coefficient of Performance) juts over 4 when the outside temp is 7 degrees and the flow temp is 35 degrees. however this drops to around 2.6 when the flow temperature is 55 degrees. Costing 60% more to run it.

    You need to learn how it works and to tweak it to optimise it's performance
    Last edited by matelodave; 05-10-2017 at 10:47 PM.
    Love makes the world go round - beer make it go round even faster
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