Getting a system designed (electric & wood probably)

[benf]

Hi folks.

I'm looking for advice on renewing a heating system in an old detached 4/5 bedroom house in Scotland which will be used as a holiday let.

Currently, it has an old oil boiler and the oil tank is looking in bad shape.

My thinking is to move away from oil for obvious reasons. Gas isn't an option. The information I have on wind speed for the locality doesn't suggest that wind power can be an option. The roof ridge runs north-south.

There's one existing open fire which can be used.

I've done some researches and I think that the best sources of energy would be Economy-7 electricity and wood burning. And the best way to use that energy would be a large buffer tank (heat store) and wet central heating (to make use of the lovely ancient radiators).

The particular problems of this house are that:
1. It will be to accommodate up to 11 people so usage of hot water could be very erratic.
2. The house will be empty for long periods in the winter.
3. The people in the house will stay for an average of 1 week and learning about how to use and control the heating system will not be their first priority.

Based on my calculations which may well be wrong, a 1000 litre heat store could provide full central heating for 2-4 hours depending on conditions. A big log burner (21kW total including 14kW back boiler) could provide most of the central heating when burning flat-out. The problem with this kind of setup is that the occupants may not bother feeding the log burner in the morning, and have the central heating ON, taking all the heat from the store. They come back in the evening and want showers and baths and a warm house but are disappointed.

So, my cunning plan doesn't quite work.
There is a big utility room, so going over 1000 litres of heat store is possible. However, I don't think it really solves the problem. I just wonder how clever the controls of a heating system can get (at reasonable cost of course) so that the occupants can't take all the heat out of the heat store first thing in the morning.

Any ideas, or even ideas as to who to ask to design a system?

 

[RF Lighting]

Is a ground source heat pump an option?

 

[dcawkwell]

Holiday let = high reliability needed Idiot proof.

Oil is the answer. Forget anything else.

If I am renting a holiday let I aren't going to be lighting fires!!!

 

[benf]

Is a ground source heat pump an option?

I did think so at first, but then I read somewhere that they get the water up to 50 to 55 degrees only, so when used with existing radiators will not provide the heat that the previous system did.

Then I thought about having 2 heat stores, one for the water heated by heat pump and the second taking the warm water from there and heating it more using conventional electric immersion in the second heat store. At that point I realised that it's becoming a big spend and still only provides 2-4 hours of heating per day unless the heat pump is running on peak electricity.

And thanks, dcawkwell, but I do think it's crazy to put in a new oil boiler plus new oil tank both of which could last 30 years, when I think that oil for burning will probably only be available for about 10 years - you might argue with that, but we all know that as supplies dwindle, the price will escalate.

Yes, I agree it has to be idiot-proof. But it can't be rocket science to have simple controls for a complex system... or is it?