Mars I still cannot get my head  round the statement you made that it doesn't make any  difference whether you are heating all or some of the property....

What temp do you have your water? Heat flow temp?

Just checked Symbio.  Offering 12.3 kw which is much better than my present provider.  So thank you

Michael

I also cannot see how it makes no difference heating the whole building, I would think the return flow will be cooler if it has to travel further therefore making the heat pump work harder. 

Welcome Michael. 

Hi Everyone,

Whilst it will require more heat energy to heat a whole house rather than a number of rooms in that house, the difference will not be easy to calculate. Internal walls are not normally insulated to the same degree as external walls, so the heat loss in a room that is being heated will actually increase if an adjacent room or rooms are not being heated, because of the temperature difference. The unheated rooms will be cooler, but not as cold as they would be if there was no heating at all in the house.

As far as heat loss in pipework is concerned it is very much dependent upon the temperature of the water and the level of insulation, also the length and diameter of the pipework and its location.

I thought Mars was saying that you could have one zone (the whole house) but use TRVs to control the room temps, rather than have multiple zones, each with a thermostat, and that it wouldn't make much difference to the ASHP as long as you were aiming for the same outcome.  I've no idea if that's right though...

From our experience, whether we heat half the house or the full house, there is no drop off in the ASHP’s electricity consumption.

The reason for this is, I think, is that we have 100 litre buffer store for our central heating. When the heating comes on, the buffer store has to be heated to 45C (or whatever your heating is set to). That water then circulates through the system. During winter the ASHP runs 24/7 during which time the buffer is always at 45C. So if we circulate through the whole house or just sections, the difference must be nominal because we see zero difference in consumption. 

I would assume that the same will apply to most systems with a buffer store. 

I think Mars has remote TRVs that allow him to create zones. @kev-m. A different solution for different folks. I’ve gone for baseball c TRVs on all radiators and a Nest to control the Daikin ASHP. Simples. But perhaps a more complex but complete control system is better?

My control system theory taught me keep it simple. 

@julianc, many well insulated new builds run on one zone, with no TRVs (all open, all the time) with a Nest or other central thermostat controlling the target temperature. This supports the notion that there’s little difference between heating select rooms over the entire property. 

Hi Everyone,

Radiators can heat up quite quickly, but then cool down quite slowly, so it is not necessary or desirable for your central heating pump to run all the time. The way that our central heating system operates when the outside temperature is around 8C or 9C, is that the central heating pump switches on for around 3 or 4 minutes to push warm water into all the radiators, and then it takes anything up to 1 hour for the radiators to cool down by a degree or two before the pump and boiler are switched on again. At outside temperatures of -5C the pump switches on for 4 minutes or so and then off for approximately 6 minutes. This is because the radiators are heated to about 42.5C, and hence cool down quicker, and also because the heat loss of the home is also greater.

If you are using a thermostat, then the pump on period will probably be much longer and the pump off period will also probably be longer. It is all dependent upon the size and heat output of the radiator, compared to the size and heat loss of the room, along with the temperature difference between inside and outside.

TRV's are designed to regulate the flow of water into individual radiators by opening and closing the valve, so that as the temperature within the room approaches the desired setting the valve will be closed or almost closed. They will only function correctly if the central heating pump is being controlled by another device, normally a thermostat, since I don't know of any TRV's that can switch the pump on and off. If the pump is not switched on with sufficient frequency, then there could be large temperature variations within particular rooms. It is therefore important to locate the controlling thermostat in the area which requires heating most frequently.

Thermostats can be used to switch the central heating pump on and off, but of course only regulate the temperature around where they are located.

To accommodate Julian's desire for a 'simple' system, there should be one thermostat controlling the CH pump, located in the room requiring the most frequent heating, but there should be no TRV's in this room. The remaining rooms should all have TRV's to achieve the desired temperature control.

Mars,

I would suggest that you spend a little time observing how often your CH pump stops and starts in relation to how frequent your ASHP compressor is stopping and starting. It sounds like your system is not adequately balanced.

RE:We are in the process of building a 240sq m Passivhaus and the energy consultants have suggested we install a Heliotherm Comfort compact monobloc ASHP. I cant find any reviews or comments for these from someone who has installed one. We havent yet had a price but suspect they are expensive and wondered whether anyone could suggest a cheaper - but efficient and quiet - alternative? Or has anyone installed a Heliotherm?

Sounds interesting but not heard of heliotherm. Why have they chosen that one? I would also ask them about Sunamp heat batteries (and look them up yourself).  

1. Thanks for inviting me My Home Farm. I'm interested in discussing renewable energy and energy conservation, along with its cost and benifits.Currently running 3 Dailkin heat pumps and a Intergas RF 36 ECO gas condensing boiler.
   

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Posted by: @baz-cambs

1. Thanks for inviting me My Home Farm. I'm interested in discussing renewable energy and energy conservation, along with its cost and benifits.Currently running 3 Dailkin heat pumps and a Intergas RF 36 ECO gas condensing boiler.
   

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Hi and welcome to the forum.  That sounds like quite a system you have there and I'm sure others here would be interested in hearing more. You could start a new thread if you want.

Kev