Help with heating controls

[LaChab]

So that I can get the wiring installed, I'd really appreciate some guidance with sorting out the controls for my future heating system.

 

It's a fairly well insulated and airtight new build, and the spreadsheet shows I need < 2kw.

 

I'm planning to fit a heat pump, with 1 or 2 kick space heaters (fan coils) in the lounge / kitchen and a towel radiator in each of the bathrooms upstairs.

I was thinking I could have 2 zones, one with a (portable) room stat for the kick space, and the other with smart TRVs that can switch the heat pump.

 

I've spent ages on the Tado website, but still not sure that it could do what I want.

 

There must be others.............

 

Thanks for looking,

[JohnMo]

56 minutes ago, LaChab said:

with 1 or 2 kick space heaters (fan coils) in the lounge / kitchen and a towel radiator in each of the bathrooms upstairs

 

Are you planning on just 1/2 small fan coils and towel rads? Or do you have UFH/radiators as well?

 

The kick space coils, I would look at the spec, as they will most likely have a flow temperature permissive to run the fan, this could be based on a boiler flow temperature and not suitable for a heat pump.

 

Are you doing cooling also, that will make a different answer.

 

 

[LaChab]

@JohnMo Thanks for the thoughts.

 

No UFH (sorry!) or radiators.

I'm hoping that over time the house will mostly be at the same temperature.

Not planning cooling with the heat pump.

I thought this KS might be ok. Says it goes down to 30c. And I can always disable the flow temperate relay!

https://kitchenheaters.co.uk/product/thermix-kph-1-5-smart-wifi-heat-pump/

[JohnMo]

Heat output is pretty poor on low flow temperatures, you don't really want to be flowing 50+ on the cold day. I would be doing 3 or 4 not 1 or 2. Or better still a proper fan coil that is wall mounted. Design them to provide enough heat at 30 to 35 degs and then run fixed flow temp.

 

Suspect towel radiator output at low temperature will be almost zero, they have almost no surface area.

 

My opinion is if you want to run high flow temperature in a low heat loss house, don't bother with the heat pump, save on capital spend, just go direct electric or storage heater. Use the money saved on heat pump and buy a battery, use octopus storage heater tariff at around 10p per kWh from April.

 

We did UFH, you don't know it's there.

[marshian]

Just to echo @JohnMo's comments on towel rails as heat emitters when running on low flow temps (Sub 35 Deg C) they really don't cope very well - the design of most towel rails allows short circuit at low flow temps so even if the heat requirements (in a well built house) are really low they almost have same flow temp as return and the heat doesn't rise up the rails it would in a higher flow temp situation.

 

I moved my bathroom towel rails to a downstairs toilet and a utility room and replaced with both with vertical rads (same size but much larger surface area) and fitted with diverters to ensure the flow was spread around the whole rad - heat loss in both bathrooms at -2.5 Deg OAT is ~200 W and at that temp 35 Deg is my target flow temp and the bathrooms comfortably maintain 21 Deg C

 

At T50 the current rads are rated at 900 W at T15 they are 220 W