UPDATED: Air Source Heat Pumps/Air Con - Full Info & Guide, is it cheaper to run than mains gas?

[Deleted User]

nande2000 wrote: »

Hi, when is your heat pump programmed to be on and off to get those figures ?

Wood pellet boilers are far too expensive (if you want one to last longer than 10 years); the only other serious contender i can think of at the moment is a solid fuel / condensing oil boiler / immersun link up.

Will reply shortly as got to get DD from school

Cheers

John_Pierpoint

jeepjunkie wrote: »

The Ecodan is a stunning piece of kit and probably the best out there. The wife loves it more than me :mad:

The only pellet boilers I've seen are in big country houses, where they come into there own.

Had I gone down the rad route i would be looking at those triple rads.

Presumably the Ecodan incorporates a fully variable speed (inverter) compressor and takes its hot water feed off the hot part of a scroll compressor? But I agree there would be no point in turning it on in the summer just for hot water, especially if (solar) PV is available.

I have seen examples for the ordinary domestic house in Austria, but
Austria has a lot more trees and perhaps more room for the prefabricated single garage needed for a winter's supply of wood pellets and their delivery mechanism.

Big country houses, probably have difficulties getting anywhere near reducing the air changes to meet "eco" values, even if they could retrofit the insulation, not to mention the problems of possibly being "listed".

[Deleted User]

nande2000 wrote: »

Hi, when is your heat pump programmed to be on and off to get those figures ?

Wood pellet boilers are far too expensive (if you want one to last longer than 10 years); the only other serious contender i can think of at the moment is a solid fuel / condensing oil boiler / immersun link up.

Our one is always set to on but diferent temps throught the day.

Weekdays 20c 5:30 to 9:00 then 17:00 to 22:00. Out with those times 17c not that the house ever drops that low.

Weekends 20c 5:30 to 22:00.

Obviously if the house is warmer than 20c then it does not come on etc

Currently, two DHW heating cycles per day though with the immersun this should be none in summer with perhaps one DHW heating cycle spring, autum and winter. Hopefully less.

John_Pierpoint

jeepjunkie wrote: »

Just for interest Our 14kw Ecodan consumes roughly 6500 units per year for heating and hot water in a large 100 odd year old house. That is approx £600 at our leccy rate. Hopefully our pending Immersun install will knock off another £150ish. Considering the Ecodan is never really off as has weather compensation etc I really doubt oil could get anywhere near this figure...


Our Ecodan is always set to on but different temps through the day.

Weekdays 20c 5:30 to 9:00 then 17:00 to 22:00. Out with those times 17c not that the house ever drops that low.

Weekends 20c 5:30 to 22:00.

Obviously if the house is warmer than 20c then it does not come on etc

Currently, two DHW heating cycles per day though with the immersun this should be none in summer with perhaps one DHW heating cycle spring, autum and winter. Hopefully less.

Presumably your floor slab is able to buffer and delay the response of the heat pump - is there anything to be gained by making more use of the (12:00 - 07:00 GMT) Economy 7 electricity price band?
Does the Ecodan "heuristics" have any ability to be instructed to learn from the external temperature AND the price of electricity or would you have to do this manually?
Presumably automatically anticipating the next day's thermal gain, is still science fiction?

nande2000

jeepjunkie wrote: »

Our one is always set to on but diferent temps throught the day.

Weekdays 20c 5:30 to 9:00 then 17:00 to 22:00. Out with those times 17c not that the house ever drops that low.

Weekends 20c 5:30 to 22:00.

Obviously if the house is warmer than 20c then it does not come on etc

Currently, two DHW heating cycles per day though with the immersun this should be none in summer with perhaps one DHW heating cycle spring, autum and winter. Hopefully less.

Thats a good point. Inside my house is 19 degrees right now (9 or 10 outside) and I havent had the heating on yet since the spring...maybe we are pretty well insulated and suitable for a heat pump. Totally agree about the immersun, its a must have if you have PV.

I forgot to add I do have access to free wood; probably not enough for 100% of our heating needs, 30% at most. Hence i was thinking a W85/Wood burner back boiler hybrid.

John_Pierpoint

From 2010

• Stovax spent three years trying to sell pellet boilers, but the interest was minimal. They have now abandoned the technology (for the time being) and are concentrating on wood-fueled boilers,

nennyrainbow

Hello
We are thinking of installing an ashp in our 1930's detached house in East Anglia and would really like some impartial advice.

We have just got planning permission for an extension which will require relocation of both our oil tank and boiler (we are off the gas grid). Since the boiler is 12 years old, we would probably be looking at replacing it anyway in the next few years and the oil tank would need to be replaced with a modern bunded one; total cost around 6k. So with the RHI hopefully being introduced next year, we thought it would make sense to go for a non fossil fuel replacement. We have considered two options - pellet boiler and ashp but due to space required for pellet storage, have more or less ruled out the pellet boiler.

I have had 2 quotes from established local installers but they have both recommended and therefore quoted us for different things. One was for a 16kW Daikin Altherma HT, the other for a 16kW Daikin altherma LT with upsizing of rads. We will have underfloor heating in the extension but the rest of the house including 5 bedrooms and 2 downstairs rooms is on rads. The existing house has cavity wall insulation, double glazing and 270mm loft insulation and the new part will obviously be built to modern building regs. We also have log burners in the downstairs rooms which we use to boost heat every evening during the winter.

I'm leaning towards the HT, partly because the installer has offered a better price and also because the rads in the existing house can be left as they are without upsizing. However, I have a major concern about this model which is that I have read (off internet forums) that it uses 200W all the time even in summer when it's not in use apart from the hot water. I spoke to the proposed installer and he confirmed that it can use up to 4kWh/day just on standby. I am struggling to see how can this be marketed as a green alternative to fossil fuels when it uses so much power doing nothing. Our current oil usage is only about £400 / year and wood another £500, so the way I see it, we'd be spending about £200 just to maintain the heat pump, without it actually doing anything. And that's before we've paid for its annual service. Is this really the case? And is there any way around this?

1) I wondered if installing solar thermal panels could help: could the heat pump then be switched off from say May to Sep inclusive when heating wasn't required? Or does the heat pump still need to be switched on because the hot water cylinder is integral to the design of the Daikin altherma?
2) we already have 2.85kW of solar PV which presents another option; I have heard about the Immersun and it sounds great but would this work with the Daikin HT because it doesn't have an immersion heater?
I'm guessing that if we didn't install any solar thermal or immersun, much of the standby power for the heat pump would be provided by the PV in daytime so it wouldn't be 4kW/h every day, probably 2kW/h per day in summer but it till seems wasteful.

Sorry it's a long post. Thanks in advance for any advice.

TiredGeek

Nande, sounds like you have a good house for an Ecodan. If you have timber floors you can improve the insulation very cheaply and easily by using the foil type laminate floor insulation under carpets, works wonders at killing drafts.

I'd go for the 14kw unit, it can wind itself down as low as 5kw so it only provides as much heat as is actually needed. Weather compensation controls sort out what flow temp is needed.

If you've got the budget, fan coils are the way to go, if not then big radiators are cost effective if UFH isn't an option. Saying that, it's probably worth sitting with catalogues and price lists to work out exactly how many radiators will give out the same heat as X number of fan coils and compare the costs. My house has 39 radiators, assuming I could have halved that number by using fan coils, the costs would probably have not been all that far apart when you start to consider all the extra pipe, valves etc I required. Luckily I did the plumbing myself so labour wasn't a factor for me.
What you're looking for is to run the system as cool as possible while getting the house to your preferred temp. The cooler the water, the cheaper to run, hence why UFH is the best.
A good company will do the calculations and tell you if it's a good choice for you and what radiators you should have in each room to achieve the required temperature.

If you have access to free wood I'd still get the 14kw unit and use the wood to allow you to run the Ecodan a couple of degrees cooler, or simply look nice in the wood burner.
A combination system brings complications of control and plumbing into it and would probably cost more to install than you'd save on running costs. Just use an ordinary wood burner and leave the room doors open to let the heat into the rest of the house....

nande2000

Has anyone on here done a retrofit of an Ecodan (or other ASHP) with just rads ? I've just done my individual room sizings and checked the rad sizes with a calculator that Mitsubishi have given me. Even with me specifying that the rooms are drafty and the house is exposed it tells me all my rads bar 3 are above the minimum size needed.

It seems too easy...comments ?

[Deleted User]

nande2000 wrote: »

Has anyone on here done a retrofit of an Ecodan (or other ASHP) with just rads ? I've just done my individual room sizings and checked the rad sizes with a calculator that Mitsubishi have given me. Even with me specifying that the rooms are drafty and the house is exposed it tells me all my rads bar 3 are above the minimum size needed.

It seems too easy...comments ?

TiredGeek and Edale, off the top of head, have. Do a search for their experiences but here a few posts from earlier.

http://forums.moneysavingexpert.com/showpost.php?p=42144098&postcount=769

http://forums.moneysavingexpert.com/showpost.php?p=42570174&postcount=2

http://forums.moneysavingexpert.com/showpost.php?p=42700794&postcount=817

I only have one tall towel rail rad off mine. It's more there for function i.e. hang towels and look good. UFH does the real heat. One downside I have noticed... the low temp running through this rad never really dries towels properly so can start to pong. Just means new towels every couple of days. Also fancoils are crap for the clothes horse in winter as the blown air barely feels warm yet like last night they lift the temp from 17.5 to 20 in about an hour. So if raining we tend to waste logs in the stove to dry clothes. Might be cheaper to get a tumble drier for when it's sunny...?

Anyway will stop rambling now!

Cheers