Replacing Honeywell ST9400C with Tado or alternative

[windsor-tg]

In my 3-bedroom semi-detached house, I currently have a conventional central heating system comprising of:

• a MAIN HE Condensing boiler (located in lounge)
• a Honeywell programmer ST9400C (located in lounge beside boiler)
• a Honeywell HCW80 (Y6630D1007) Battery Powered Wireless Room Thermostat (located in hallway)
• a Honeywell relay/receiver HC60NG/R6660D (located in a bedroom cupboard beside the hot water tank, zone valves, and pump)
• a wiring box (located in the same bedroom cupboard where the hot water tank is)
• I believe I have a S-Plan setup with 2 x 2-port motorised valves controlled by the room thermostat and hot water cylinder thermostat (photo attached)

I am looking to replace this with the Tado Wireless Smart Thermostat Starter Kit V3+ with Hot Water Control, or an alternative smart system so that I can control the central heating and hot water remotely.

Assuming the Tado Wireless Thermostat Starter Kit V3+ is compatible, is it fairly straight forward to remove the Honeywell set-up and replace it with the Tado system? I would like to do it myself but there are a fair amount of wires.

[marshian]

What’s the driver for wanting go change the control system?

 

how old is the boiler?

 

The boiler has a fairly hefty min output of 11.9 kWh - I think it would have to be a very poorly insulated 3 bed semi to need that level of min output?

 

 

[windsor-tg]

@marshian - the driver to change is to have the ability to control the heating & scheduling remotely. 

 

The boiler was installed in 2019. I'm not planning on changing this until such time the boiler packs up

[marshian]

2 minutes ago, windsor-tg said:

@marshian - the driver to change is to have the ability to control the heating & scheduling remotely. 

 

The boiler was installed in 2019. I'm not planning on changing this until such time the boiler packs up

OK that’s absolutely fine - I just wanted to ensure that you weren’t equating “smart” with “energy saving” 

If your honeywell controller was installed at same time and  is hopefully on a universal back plate and if TADO units use the same it should be plug and play

[windsor-tg]

@marshian, thanks. The honeywell kit replaced a previous controller if I recall. 

 

One thing I'm not sure on is what to do with the wiring going to the Honeywell relay/receiver HC60NG/R6660D as I'm assuming this receiver will become redundant once the Tado has been installed? 

[Bramco]

13 minutes ago, marshian said:

If your honeywell controller was installed at same time and  is hopefully on a universal back plate and if TADO units use the same it should be plug and play

I'd be surprised if the TADO units fitted onto the Honeywell backplates but I guess someone out there will know.

Be careful with updating the old Honeywell kit with newer 'smart' kit.  The Tado thermostats for example use rf comms back to a hub that needs an ethernet connection to a router or a switch. One of our Tado thermostats is further away from the 'hub' - not a long way and the doors are normally open between them - but occasionally the connection is lost.  Minly not a problem, except that the schedules are not kept locally, they are on the Tado server, so you can wake up to find the heating hasn't switched on, or hasn't switched off.  We're seriously thinking of swapping out our Tado thermostats for something simpler with locally held schedules. 

 

Sadly that will be the second set of 'smart' thermostats we've ditched. The others had a 'smart' feature to turn the heating on at some random time before the start time to get the room up to heat. You couldn't turn this off, so for us we had to get rid, as we only run the ASHP on the 7p Octopus Go Intelligent rate to batch charge the insulated slab.

 

[windsor-tg]

thanks @Bramco. My router is located in the landing on the 1st floor and the Tado wireless thermostat is planned to be located in the hallway on the ground floor. Is there a high possibility the Tado thermostat will lose connectivity with the hub?

[Bramco]

I've no idea - rf comms is supposed to be better than wifi but if it has to go through lots of solid walls, it might be a bit flaky.

 

Sadly, there's probably no other way than to try it to see if it works.  They are designed for 'normal' houses though, so should work.  Hard wired kit hasn't got this problem.

[marshian]

4 hours ago, Bramco said:

I'd be surprised if the TADO units fitted onto the Honeywell backplates but I guess someone out there will know.

 

If manufacturers don't use universal back plates I wouldn't use them out of principle you shouldn't need to be an electrician to change a controller.

 

My old Danfoss programmer from the mid 90's was on a universal back plate and I remember well the headache I can converting to that from an old clockwork timer (if anyone remembers them)

 

But when it died and I changed to a Wiser system all I had to do was

 

1. power down.

2. Loosen two screws under the Danfoss unit to remove it from the backplate

3. Replace with the Wiser Hub

4. Do up two screws

5. Power Up

6. Connect the hub to the Wifi

7. Pair the "Smart" TRV's

8. Pair the "Roomstat"

9. Set up the schedule for one room and copy to all the other rooms

 

Absolute doddle to do.

[marshian]

Found the pictures I wanted

 

When we bought the house this was the HW and CH timer

 

 

It was fine for years until someone used the toaster that lived under it without bothering to move it forward - the resulted melted mess necessitated replacement

 

I fitted this Danfoss Unit

It came with an Industry std backplate (often called universal backplate cos that's molded into it too)

 

 

Eventually it died - kept losing display and sometimes the programme

 

So I purchased a Wiser Hub, 13 "smart" TRVs and a "smart" Roomstat there is nothing "smart" about any of it but the fact I could fit the Wiser Hub on the existing backplate with no changes of wiring was a big plus for me