Split Aircon to heat a UK detached home?

[MikeT]

My detached home is due for a complete new gas central heating system including rads and boiler.

Downstairs is 1 room 36ftx13ft lounge diner plus kitchen and hall.

I have but am yet to fit a Fuji ASY18UBBJ/AOY18UNBKL split which I am wondering if it will be man enough to heat all the downstairs?
I think its 5.7kw heating/5.4kw cooling.
The kitchen at present has no heating as its always pretty warm in there through cooking. So its Just the lounge/diner area and small hall really.

I also have a Mitsi MSHGA60VB/MUH-GA60VB which I was considering fitting upstairs maybe in one of the 3 bedrooms or on the landing to make use of its 7.2kw heating/6.3kw cooling.

You can see what I am trying to do here cant you, I would be pleased to get some feedback as to if this is even a starter, I bought the splits to use for cooling but with the cheap? heating available from them I start to wonder if I can utilise them and cut back or out the central heating.
I realise ducted would probably be the best way but I do have these units already and would like to be able to put them to more use than just cooling on a few hot summers days/nights.

[The Viking]

It really depends on the layout of your house.

Your Mitsu unit will probably be up to the job of heating and cooling your whole house if fitted above the stairs and there are large open areas for it to work in.

Regarding saving......
Here in UK the gas is too cheap to warrant running heatpumps of the electricity supply, that is, unless you're on LPG or oil.

[Pooh]

Mike
you need to work out the amount of heat you need for the area, this is usually done using a Mears calculator or the like, if you measure the rooms and do a drawing showing number of outside walls room heights and wall type and thickness also if you have concrete or wooden floors your freindly plambers merchant will do the calculations for you if you tell them you are thinking about buying a boiler etc from them.

Viking, maybe not that much saving due to the price of gas but the three grand it will cost for the boiler, radiators etc will go a long way to making it feasible to run the heat pumps.

Ian

[MikeT]

Im down south where the plumbers are rich already so its 4k plus for the central heating job!

So even with the so called free heat from the Mitsi at around 2.5kw max load for 7.2kw output the gas is still a winner?

[The Viking]

The best way to find out is to look at your energy bills.

How much do you pay per kW for the gas and how much for the electricity?

Also, remember that the efficiency of the split heatpump will drop the cooler it gets, so I wouldn't use it instead of a boiler, I would still get a boiler as a supplement.

[Pooh]

For every KW you put in a boiler you get approx 0.8 KW out for every KW you put in a heat pump even air source you will get at least 4 KW out so the gas has got to be at least a quarter of the price of the electric to make it viable.

Ian

[MikeT]

For Gas I pay 3.081p for the first 1027kwh
then 2.451p/kwh for the remainder

Elec is 15.71p for the first 202kwh
then 8.18p/kwh for the remainder

So I guess its marginal.

What I should have asked if your both aircon installers is what do you use to heat/cool your homes as your both uk based.

I would still need some form of heating for hot water as well.

[Pooh]

Mike
I use gas for heating because I have an existing system and electric for AC, however I am looking at fitting a Dimplex or the like air source heat pump for my heating and hot water in the near future, I have concidered ground source but the wife wont let me dig the garden up. At the end of the day its personal preference whether you have a wet or dry system but if you look at the grants available for heat pumps it may make them more feasible.

Ian

[The Viking]

Do I use it at home?

Yes is the short answer but only for cooling in the summer, I can't stand heatwaves. Saying that, summer just gone I think I used it less than a week (suppose that's got something to do with the UK climate).

So, in your specific case,
A modern, condensing, boiler will cost you ~2.7729p per kW/h to run.
A heatpump, assuming a "realistic" COP of 3 (this will vary with the ambient temperature, most manufacturers tend to measure it at +10 degrees C but the cooler it gets the lower the efficiency), will cost you ~5.24p per kW/h to run.
Even if you assume that the COP will be 5, you would pay 3.142p per kW/h delivered.

Looking at the above, it's a no brainer.
BUT and this is a big BUT, how much longer will the gas be this cheap?
The resources of gas is running out and the government is planning for new nuclear reactors to be built, so maybe the balance will shift in the future....

[MikeT]

Ok then guys thanks very much for the replies, looks like I am going to have to make a local plumber even happier and go for the full gas monty.
Of the 2 splits I mentioned above which would you fit downstairs and would the other mounted on the landing do a reasonable job of cooling all the upstairs rooms (3 bed+bathroom) if the doors were left open, the walls are foam filled and loft well insulated and foil backed plasterboard.
As said above if the summers are like this one just gone they wont get used much, I have one old Fuji ALY22 6.3kw through the window box here in my home office and apart from running the fan it only got used in anger for maybe 1 week this year. That uses R22 btw so maybe I should keep the bottle I have for topping that when needed ;-)

[The Viking]

Mike,

As I said in my previous post, is all down to the layout.

For example;
I also live in a 3 bed semi, the stairs are open to the living room. Above the stairs, on the wall facing the bedroom doors, I got a 4.5 kW unit and this is powerful enough to cool the whole house apart from the kitchen (but I don't spend much time in there anyway)