Change 4 zone heating system to smart thermostatic radiator valves instead?

[kieran]

I've just moved into a house for the first time where I don't just have a single heating zone. This house has a central timer unit and 4 room thermostats that control 4 Honeywell V4043H1056 valves beside an currently unidentified Johnson Starley combi boiler (although there is also a hot water tank). The problem with this is that the zones are a bit strange and don't really match how we use the house.

So I was wondering if it would make sense to remove all the old room thermostats and replace them with something like the Honeywell Evohome TRVs to give me per room control and scheduling? I've got 20 radiators with 14 of these currently having TRVs and the rest not.

My other alternative I was considering was just replacing the fixed room thermostats with digital ones so that at least I can time and control the zones a bit better than the fixed temp ones I've got right now and the global scheduling I've got via the single timer unit. This is going to cost a lot less I guess, but given the poor layout of the zones, it's not going to give me as much control.

Any thoughts or alternative ideas I could consider to give me more efficient usage of the system?

Thanks,
Kieran

 

[Brambles]

Evohome - or similar - for a 20 radiator system divided into 12 zones will cost around £1600 ( if you include new valves) - for 20 zones you would need a second controller - circa £230.

I think that they are very effective systems for large properties where all the zones/rooms are not used on regular basis. Others will no doubt have differing opinions.

On a pay back basis, it is not particularly cost effective - around 3 to 4 years assuming you are on gas - but it gives you excellent control of the system.

 

[kieran]

Thanks brambles. Good to hear I'm not crazy for thinking that could be a solution, although an expensive one.

Should have mentioned the current radiators are across the house as follows. It'd be nice to not need an additional controller if possible. I think I could rationalise this down to 12 zones.

Kitchen: 1 x thermostatic
Cloakroom: 1 x thermo
Toilet: 1 x thermo
Hall: 2 x non thermo
Lounge: 2 x thermo
Basement: 2 x thermo
Landing: 1 x thermo
Bathroom: 1 x thermo, 1 x non thermo
Office 1: 2 x non thermo
Bedroom 1: 2 x thermo
Bedroom 2: 1 x thermo
Bedroom 3: 1 x thermo
Office 2: 1 x thermo
Shower room: 1 x non thermo

 

[Brambles]

I am not promoting Evotherm - there are are a number of similar systems, Evohome has its faults, but it is proven - and in my experience as an installer very reliable.

There is currently a scheme running to try it for a month on a sale or return basis

 

[EvilDrPorkChop]

Evohome is a great system, fitted many and don't even consider any alternatives as it's that good.

The only issue you might find, if it's a large property then you might struggle with signal strength. That's where two controllers may come in handy.

 

[kieran]

Evohome is a great system, fitted many and don't even consider any alternatives as it's that good.

The only issue you might find, if it's a large property then you might struggle with signal strength. That's where two controllers may come in handy.

So do they do their own wireless network rather than piggyback on an existing home wireless network then?

 

[Murdoch]

So do they do their own wireless network rather than piggyback on an existing home wireless network then?

you need to engage an evohome specialist ...

 

[Brambles]

Yes - around 868MHz. Home wifi starts at 900MHz.

The control unit(s) connect with home wifi for external control through a phone / pc/ Mac et al

 

[Chuck]

Any thoughts or alternative ideas I could consider to give me more efficient usage of the system?

If the house is already zoned the benefits of switching to what is essentially a finer-grained zone scheme will be marginal.

For saving money, zoning works best when the house is large and poorly insulated. A better ROI is usually achieved by improving the insulation, which increases the pay back time for zoning as a side-effect.

Treat claims of the savings possible with complicated controls with skepticism. They tend to use very primitive systems as the baseline for comparison. The law of diminishing returns applies strongly.

 

[kieran]

If the house is already zoned the benefits of switching to what is essentially a finer-grained zone scheme will be marginal.

For saving money, zoning works best when the house is large and poorly insulated. A better ROI is usually achieved by improving the insulation, which increases the pay back time for zoning as a side-effect.

Treat claims of the savings possible with complicated controls with skepticism. They tend to use very primitive systems as the baseline for comparison. The law of diminishing returns applies strongly.

Fair points there Chuck, thank you. I'm not yet 100% set on this at all and will definitely be looking at other energy saving measures. Even if it doesn't end up being massively energy saving, I'm hoping at least just to get a lot more control so that I can for instance have just my office warm late at night and nothing else on at all.

 

[Chuck]

I'm hoping at least just to get a lot more control so that I can for instance have just my office warm late at night and nothing else on at all.

For this scenario, you need to know that most boilers have a minimum output in the range 5kW–8kW. This means they won't drive a typical single radiator directly without short-cycling. I'm aware of only two really satisfactory solutions. The nicer one, fit a buffer store, is relatively expensive in terms of money and space. The other one, use an electric panel heater, is much cheaper to install but leccy is significantly more expensive per kWh than gas so you need to think about the total cost of ownership over however long you will be living in the house and using your office late at night in the winter.

My advice would be to try the £100 panel radiator first and if you don't like it, spend the ca £2k needed for a more sophisticated solution. IMO, it's good to own a couple of electric panel heaters in case the gas boiler breaks down and can't be repaired immediately.

 

[Jerry]

tado or evohome

or replace the controls with digital programmable room stats and save your money for more effective money saving schemes. like a new boiler