'Smart version' of Honeywell ST9400C

The ST9400C is a simple timed relay, there are many relays which can be controlled over the internet, I use one for my lights, I use Nest Gen 3 which is useless, as it does not connect to TRV's. But that is the thermostat not the programmer bit which is useless.

Wiser claim their TRV's have algorithms that work out when they need to switch on to get room to temperature at time programmed, however you like me say you already have internet connected TRV heads, I have two types, 5 x eQ-3 and 4 x Energenie Mihome neither connect to the thermostat/programmer although the Energenie Mihome claimed they would connect to Nest which is one reason I bought Nest, however the app would change them both, but not the wall thermostat, and they worked wrong way around, the TRV should tell the thermostat/hub but Nest has the wall thermostat telling the TRV's what to do, which is useless.

However since you already have the TRV heads, like me you want the wall thermostat if possible to work with them. Interested your using Smartlife, and zigbee, as I also have that, but not for central heating. I did look at Hive, but it has a 22ºC limit, once the wall thermostat hits 22ºC it will not accept any demands for heat, so the wall thermostat needs mounting in a cool place.

Late Mothers house I used the Energenie Mihome TRV's and found I could set the wall thermostat so boiler would auto shut down on warm days, but on cool days the TRV heads did all the work and the Bosch boiler modulated as designed using the return water temperature, the hall where wall thermostat was mounted cooled faster than any other room, so it worked well.

However trying to emulate that in this house did not work, two reason, one hall cools too slowly, and two the boiler does not modulate. And I now realise how much is down to house design, my last house was open plan, heating was easy, one central thermostat, but it was expensive to heat, however living room had a fan assisted radiator 3.5 kW conventional 4 kW and gas fire 4.5 kW so no need for geofencing, it heated up that fast, this house also geofencing does not really work, it turns down the heating when I leave, but I need to remember to turn it up again before I start for home, as the house heats too slowly for the geofencing to reheat it in time for my return.

As to google Nest mini control, I simple don't trust them. Very good playing music, and turning on lights where I can see immediately if it has worked, and also told me how to spell immediately. However with central heating if it gets it wrong, by time you find out it's too late. I had it with high winds last year, EE mast went down, and central heating went into Eco mode as I thought I was not home, but each time I walked past the wall thermostat it returned to comfort mode for a time, so it was nearly 24 hours before I realised what was going on, and house was darn cold.

This house the radiators are big enough to maintain the temperature, but to increase by even just 3ºC takes an age, not the boiler at fault, I can hear that cycling, the radiators are not big enough, I had all big ideas of staggered heating, start at kitchen, the dinning room, then living room etc, so it would reheat faster, and only when required, but the radiators are not big enough. One needs radiators at least 3 times the size of the boiler to use smart heating to heat the home as required.

My problem is once the boiler starts to cycle, the slewing it too high, so water is quite cool before it switches on again.
 
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Thanks everyone for all the comments above.

In recap, I already have a Zigbee setup with electronic TRVs that gives me full App control of their functions anywhere and voice control at home as well. My system is a conventional Worcester Bosch boiler with hot water tank - all pumped (see previous comments) but the current Honeywell ST9400C is the only (manual) way I have of switching the combinations of CH/HW. I only actually need this one additional function operating remotely in order to complete the setup. Therefore some of the more recent considerations above are appreciated but not relevant in this particular case. I should perhaps add that I am a retired IT/Electronics professional so any IT and wiring changes doesn't present any difficulties. It is simply a case of determining the most cost effective way of adding the remote switching capability to the CH/HW control. Whilst appreciating that these are part of most units these days, the sophisticated timing functions available are also not needed in this case. I can already handle this through the open source Smartlife App (Zigbee) and Google Home which also controls my lighting and smart sockets. I am also keen to not become unnecessarily system-dependent on a single manufacturer.

If I am understanding previous comments correctly :-

1. The Honeywell Evo kit is the only equivalent system to the ST9400C (but with remote controls built in) but this looks very pricey for the small additional function that I need ?

2. The minimum Hive system I would require is this (also available at Screwfix) :-

3. Can anyone link me to a specific Drayton Wiser unit that meets my needs ?

Finally, I was amused by McPrinter's comment - "I have Wiser with 5 smart TRVs. Works well. Not sure it is saving me anything TBH." This sounds like something my wife might say - even before the system is tested !!!!

Thanks, once again, for your time !
 
Thanks everyone for all the comments above.

In recap, I already have a Zigbee setup with electronic TRVs that gives me full App control of their functions anywhere and voice control at home as well. My system is a conventional Worcester Bosch boiler with hot water tank - all pumped (see previous comments) but the current Honeywell ST9400C is the only (manual) way I have of switching the combinations of CH/HW. I only actually need this one additional function operating remotely in order to complete the setup. Therefore some of the more recent considerations above are appreciated but not relevant in this particular case. I should perhaps add that I am a retired IT/Electronics professional so any IT and wiring changes doesn't present any difficulties. It is simply a case of determining the most cost effective way of adding the remote switching capability to the CH/HW control. Whilst appreciating that these are part of most units these days, the sophisticated timing functions available are also not needed in this case. I can already handle this through the open source Smartlife App (Zigbee) and Google Home which also controls my lighting and smart sockets. I am also keen to not become unnecessarily system-dependent on a single manufacturer.

If I am understanding previous comments correctly :-

1. The Honeywell Evo kit is the only equivalent system to the ST9400C (but with remote controls built in) but this looks very pricey for the small additional function that I need ?

2. The minimum Hive system I would require is this (also available at Screwfix) :-

3. Can anyone link me to a specific Drayton Wiser unit that meets my needs ?

Finally, I was amused by McPrinter's comment - "I have Wiser with 5 smart TRVs. Works well. Not sure it is saving me anything TBH." This sounds like something my wife might say - even before the system is tested !!!!

Thanks, once again, for your time !
 
Thanks again.

I'm now going to see if either of the Hive or Drayton App controls can be used in reverse via Google Home enabling commands to be passed to the Zigbee hub !? My IT experience says probably not but we'll see !! If it is possible to do this then it would simplify the operation in the sense of having all the heating control in one place without needing to replace the existing TRVs with proprietary ones.
 
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Finally, I was amused by McPrinter's comment - "I have Wiser with 5 smart TRVs. Works well. Not sure it is saving me anything TBH." This sounds like something my wife might say - even before the system is tested !!!!

I have had Wiser for about 6 months
There have been a lot of changes in the house
I finally sorted the loft insulation from collapsed 100mm to 300mm. Insulated the upstairs bay window from zero to some.
Energy provider moved me to a different supplier losing historic data.
Mrs McP now works from home, so do not have any good comparison data.

It works well in that various rooms get to temp at the time I need them to. I can remotely control temps and off/on.

Your smart TRVs are not capable of switching the boiler I presume? Tado, Wiser and Evo are.

You could possibly interrupt the CH and HW switching lives with a smart relay/switch of some description?
 
Thanks McPrinter.

No, the exiting TRVs only receive temperature commands and report existing room temperature at their location (afaik) but will check !?
Your last idea of intercepting the switching circuit is also worth investigation !
 
How are you using the existing TRV's if they don't control the boiler? I dont see the point of them if that is the case as all they can do is open and close like a manual TRV but without boiler control nothing happens if the boiler is off.
 
How are you using the existing TRV's if they don't control the boiler? I dont see the point of them if that is the case as all they can do is open and close like a manual TRV but without boiler control nothing happens if the boiler is off.
Providing the boiler is running, the ability to vary the temp in each room at different times without touching the TRVs.
i.e. only heat Bed, Bath and Kitchen in the morning. And hall of course assuming stat is there.
Before Wiser, I had a standalone programmable TRV for Mrs McP home office. 20 deg Mon-Fri 8 to 4. 15 the rest of the time.
 
Providing the boiler is running, the ability to vary the temp in each room at different times without touching the TRVs.
i.e. only heat Bed, Bath and Kitchen in the morning. And hall of course assuming stat is there.
Before Wiser, I had a standalone programmable TRV for Mrs McP home office. 20 deg Mon-Fri 8 to 4. 15 the rest of the time.
Is that how the OP uses theirs? Why set a temperature outside of the boiler on period when it makes no difference if the boiler doesn't fire up when the temp goes below 15c. Is the OP's boiler constantly on? I think I must be missing something.
 
I appreciate that my use is very simple compared to many and, being retired, we don't have a set regime for heating. I can sit in my chair and say "Google - set the lounge/extension/hall/bedroom TRV to ... degrees". The absolute temperature at the valve is largely irrelevant to me as I can simply balance the heat output from the radiators individually to suit the needs of the persons in the room. This function is duplicated remotely via the Smartlife app without any additional hardware. I no longer have a linked 'room thermostat' - just a standalone one above the fireplace as reference. As I said at the outset, the only thing I can't currently do remotely is to switch the CH/HW combinations. From the help above, I can now select a replacement controller to do this. Thanks to all.
 
I appreciate that my use is very simple compared to many and, being retired, we don't have a set regime for heating. I can sit in my chair and say "Google - set the lounge/extension/hall/bedroom TRV to ... degrees". The absolute temperature at the valve is largely irrelevant to me as I can simply balance the heat output from the radiators individually to suit the needs of the persons in the room. This function is duplicated remotely via the Smartlife app without any additional hardware. I no longer have a linked 'room thermostat' - just a standalone one above the fireplace as reference. As I said at the outset, the only thing I can't currently do remotely is to switch the CH/HW combinations. From the help above, I can now select a replacement controller to do this. Thanks to all.
Do the TRV's turn the boiler on when you request a temperature change?
 

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