Replacement of Salus RT500 Stats

Hi guys I've recently purchased a new house and it's fitted with 4 zonal radiator thermostats. I assume by the model number they are hardwired and not RF.

Then in addition to this I have one controller for the hot water tank.

Question is can anyone recommend a good direct replacement where I can connect them to my local WiFi and control them remotely?

I want the ability to turn heating up before I get home. Any advice welcome.

Quite a few on the market that offer this, Hive, Nest, Tado, Wiser by Drayton to name a few. The Nest can use the existing wiring for their thermostats, and not entirely wireless, but can be controlled by mobile phone.

How is the boiler controlled? On/off or by the ebus for example OpenTherm? As far as I am aware only EPH wall thermostats can be set master/slave and work up to 10 zones, the Drayton Wiser can work three zones there is a OpenTherm module so two central heating and one DHW, I think the rest one zone only, Nest has opentherm but does not connect to any TRV heads, Hive connects to TRV heads but does not have opentherm and EPH does not connect to TRV heads, as to Honeywell EvoHome don't think it works with zone valves, and Tado is completely unknown.

To my mind Energenie works the wrong way around, the wall thermostat tells the TRV heads what to do, every other the TRV heads tell the wall thermostat what to do.

There are some cheap units MoesGo seems to be used a lot, but not really designed for domestic, mobus is a commercial system, but with domestic the big question is cost of installation compared with saving. So if fuel costs £350 per year, and the new system saves 10% and will likely last 10 years then the ceiling for installation cost is £350.

So with programmable TRV heads ranging from £20 to £60 and with say just 10 the cost difference between wifi using geofencing and simple timed is around £400.

So in the main we are looking at a compromise. So my house 5 standard TRV heads, 5 programmable TRV heads (bluetooth) and 4 wifi programmable TRV heads, which I was told would work with Nest, but Nest has withdrawn support, I have one Nest Gen 3 wall thermostat selected as the wires between the flat with boiler and house change colour so don't trust them and I can do everything with just two wires, the flat has a very cheap hard wired thermostat, but flat hardly used, and I have two pumps, two motorised valves and should be two relays but not fitted yet.

But the big question is speed, if you work 50 miles from home, and it takes one hour to get home, the heating has just one hour to heat the home, or at least the first rooms you will use, so the radiators in those first rooms to be used need to be big enough, and the TRV heads need to act fast enough and that is where my Energenie TRV heads failed, the anti hysteresis software was OTT, so had to cheat and set to 22 for one hour then 20 for it to heat the room to 20 in an hour, clearly geofencing can't do that cheat, so the Drayton TRV head is claimed to have algorithms built in that work out time to heat the room, so can heat the room faster without over shoot.

But the big question is, is it worth the installation cost? I got my 5 bluetooth eQ-3 TRV heads for £15 each, although since brexit the price seems to have gone up, but although no wifi they work in some ways better than the Energenie heads, which have got wifi and can be set with IFTTT to geofence.

I use the geofencing on my Nest Gen 3, but it is the TRV heads which let it down, much depends on the lock shield valve setting, if set so TRV can open and close in time to stop over shoot then the rooms are kept to exactly right temperature, but if opened too wide then there is a over shoot problem which can actually improve things when using geofencing speeding up the rewarming of rooms.

And if there are programmable TRV heads why do you need zones? The TRV head makes the zones.

Thanks for your detailed response. I am in agreement that for me it is a toss up between programmable TRV heads and geofence, but I feel the TRV heads will largely give inaccurate results but I should maybe try some to see.

I hear good things about the Honeywell ones and maybe will check Amazon to see which ones have the best review

Did I say Honeywell sorry Drayton has the algorithms, as to accuracy mothers house not this one, i.e. modulating boiler not on/off boiler adjusting the lock shield valves and they were spot on, simple current goes over target close the lock shield a tad, and once set they were spot on. But you have to use a PC, there is a comfort/eco setting but fixed, these far cheaper and you can set your own comfort and eco setting and do it all at the valve, no need for phone or PC. And at home I don't walk around with my mobile, so walking into a room and pressing one button works well.

Hey guys just keeping you updated on my choice. I decided to go go for a Honeywell evohome system which use the trv heads as zone controllers.
In my existing system I have 4 zones each controlled by thermostats, and what I have done is replaced 4 zones with two Evo home controllers which between them control all radiators. In order to achieve the system results I have had to manually remove the Honeywell zone valve in two of the zones and turn the valve to open and set the corresponding thermostat to 5 degrees so they never called for heat. This is not an ideal way to set the system up but until an electrician can come and rewire it then we have no other option.

The problem is is if I manually override the existing valves the boiler will constantly be heating so by removing the the two way valve va and twisting the valve to open regardless of what zone requires heat there are other two zones will always be opened and the trv heads closed.