Replacing Honeywell ST9400C with Tado
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 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?
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All sounds fine. You’ll probably put the Tado box near the tank and valves.
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thanks @Montage. Do you mean placing the Tado extension box near the tank and valves? I thought the extension box would replace the Honeywell programmer ST9400C, and therefore the Tado box would be in the lounge beside the boiler?
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@Tonygrewal1 Hello Tony. We replaced the same setup in 2022, it's straightforward for competent DIYer. The Tado V3+ wireless receiver replaces the Honeywell ST9400C. In the Honeywell wireless receiver, you'll join the wires on A and B (call for heat) with a Wago connector from the starter kit.
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In principle, that’s how it works. If they wired it back to the programmer, it’s a drop in replacement. Perhaps I’m overly cautious in suggesting you might find it differs, especially as you have a receiver/relay by the tank and valves.
I’m not suggesting it’s a barrier. Just go in with the possibility in mind.
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thanks @Montage
@wateroakley - thanks. So am I right to assume that I:
- follow the instructions from the Tado app on how to wire the Tado v3+ wireless receiver using the wiring currently going to the Honeywell ST9400C ?
- from the wire going to the Honeywell wireless receiver, I join the wire going to terminal A with the wire going to terminal B using a Wago connector?
One thing I have read elsewhere is that some people have experienced problems in the Tado wireless thermostat staying connected with the Tado hub (which is connected to a router). Have you experienced any loss of connection between the hub and your Tado wireless thermostat?
Some people have mentioned that the schedules are not kept locally (are kept on the Tado server) so you can wake up sometimes to find the heating hasn't switched on, or hasn't switched off.
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@wateroakley - I received an email today at 7:45pm to say you had left a comment but from this post, I can’t see any comment following my last reply at 5:15pm.
Did you leave a comment around 7:45pm today?0 -
- Hello @Tonygrewal1 Sorry, the post was deleted while I was editing remotely. Reposted …
- 1. When you start the install, Tado support should give you wiring instructions. The Tado wiring guides are also on the main Tado web site. Alternatively, the Tado Professional app has details.
On the ST9400C, IIRC it's a 1-1 wire move. L to L. N to N. CH NO (4) to CH NO. HW NO (3) to HW NO. Add two purple links: L to CH Com to HW Com. Obviously, do this with the power off.
- https://www.free-instruction-manuals.com/pdf/pa_458238.pdf
- 2. Carefully open the Honeywell thermostat receiver. IIRC, it's a clip-on front cover. There should be four wires: L + N to power the receiver; and A + B for the relay. Disconnect the wires on A and B and join them with a Wago connector from the starter kit. Obviously, do this with the power off.
- 3. The V3+ 'internet dongle' and Tado devices talk wirelessly using IEEE 802.15 and 6LowPan standards, not the usual 802.11 home wifi. 802.15 is low power IEEE standard for IOT devices, with a design specification range of circa 10 metres.
Most 3-bed semis are less likely to experience the V3+ range issues that some have seen in larger homes or thick stone construction. Here, a 4-bed 1960s home, we have one rad outside range in the conservatory. We kept the dumb TRV.
There are workarounds for range issues by using e.g. an ethernet cable, wifi dongle, or powerline adapter. Our rellie with a 3-storey 5-bed Edwardian Villa uses a cheap Tp/Link wifi extender with ethernet port.
4. Offline scheduling.
- Hope this helps.
- EDIT: Reposted.
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Many thanks @wateroakley, greatly appreciated.
My main reason for wanting a Tado system (or alternative) is for my rental property. I’m going to spend a few months renovating it so I want to have the ability for controlling the heating & hot water remotely during this period as a minimum.
I also need to get broadband set up along with a WiFi router so that I can plug the Tado internet dongle into it as well as use the WiFi router so that I can connect a WiFi camera to it. I just need to find the cheapest broadband deal available.
Which Tp/Link wifi extender did you get?0 -
Our rellie connects to their Virgin router with one like this:
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thanks @wateroakley. I have ordered the Tado Smart Wireless Thermostat V3+ Starter Kit so just wiating for it to arrive.
I have removed the covers off the Honeywell Programmer ST9400C and the Honeywell receiver just so that I can see how these device are currently wired. I have attached photos of the wiring of these two devices. I have also attached a photo of the Tado extension kit which I found on google.
To correctly wire the Tado extension kit, am I right in the following:
- move N (blue wire on ST9400C) to N on Tado
- move L (red wire on ST9400C) to L on Tado
- move black wire on location 3 on ST9400C to HW NO on Tado
- move yellow wire on location 4 on ST9400C to CH NO on Tado
- move green/yellow (with a bit of white paint on tip of wire) from first location on ST9400C to the Tado ground point (between HW NO and Parking P1)
- The Tado extension kit photo already shows two purple link cables between L and CH COM, and between CH COM and HW COM - I assume I will need to make sure these links are in place when the extension kit arrives?
On the Honeywell receiver, the photo shows the 4 wires. Do I:
- disconnect the brown wire in A and the blue wire in B, and join them together with a Wago connector?
- do I leave the L and N wires as they are in the Honeywell receiver?
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@Tonygrewal1 Hello. In principle, all of your proposed wiring appears correct.
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@wateroakley - I got everything all wired up and it all seems to be working apart from when I turn on the heating. It appears that the hot water also comes on too. Do you know what may be causing this?0
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Stick up a photo of the wiring please.
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thanks @Montage. It's been installed in another house and I will not be there until later this week so I will take some photos when I am next there and will post
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also, when I was following the instructions on the Tado app, these attached responses appeared
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I have been in touch with Tado and they say that since my system is a gravity-fed system, for the heating to work, the hot water must also be activated.
This would explain why the hot water symbol on the extension kit is LIT when I only turn ON the heating (as shown in the attached photo). Tado said this is how gravity fed systems work, and it cannot be changed.
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Is it actually a gravity fed system?
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@Montage, yes, as far as I am aware. There is a tank in the loft as well as a hot water tank in the airing cupboard.
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None of those are differentiating features. Does it not have a pump? Often found in the airing cupboard.
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@Montage - yes, it does have a pump and two motorised valves (see images)
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So it’s not gravity fed.
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@Montage - is that because it has a pump and two motorised valves? I'm not that familiar with heating systems ☹️.
I'll get some photos of the wiring posted soon
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Just tell Tado it’s not a gravity fed system. That’ll sort it.
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@Montage - aah ok. Since I have two motorised valves and a pump, would that mean I have a Y/S plan system? At the moment, I have configured the extension kit to be a gravity fed system (blue LED light) so I assume I would need to change this to the Y/S setting (green LED light) ?
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As per your first post, you have S Plan. A Y Plan just has the one motorised valve. Change it from gravity (which it isn’t) to S Plan.
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@Montage, @wateroakley - so last night, I changed the configuration on the extension kit to a 'S/Y plan' such that the green LED light was lit up. I checked this again by pressing both the 'heating' and 'water' buttons together for 5 secs and the power LED light turned 'green' before becoming a solid White light.
To test, I pressed the 'heating' button on the extension kit and the boiler fired - the 'water' button on the extension kit was UNLIT when I pressed the heating button to fire the boiler. After a couple of minutes, I turned off the boiler by pressing the heating button on the extension kit.
So I thought everything was sorted. I don't think I tested the hot water scenario by pressing the water button to see if the boiler would fire but I'm 99% certain, the boiler would have fired.
However, with the boiler off, when I went on the Tado app and turned up the heating temperature, nothing happened. The boiler would not fire which I would have expected to. Only when I pressed the heating button on the extension kit would the boiler file.
I then changed the configuration on the extension kit back to a to a gravity fed system (blue LED light). When I pressed the heating button, the boiler would fire BUT the hot water LED light on the extension kit would also be lit. Upon pressing the heating button again, the boiler would turn off and the heating & water LED lights on the extension kit would also turn off.
Using the Tapo app again and turning up the heating temperature, the boiler would fire and the heating & water LED lights would both be lit (I think!).
So in summary, when the extension kit is configured as:
- a S/Y plan, the boiler will only fire when the buttons on the extension kit are pressed BUT any adjustments on the Tado app get ignored
- gravity-fed, the boiler happily fires via both, pressing buttons on the extension kit AND making adjustments on the Tado app
I have attached photos showing the 'BEFORE' wiring on the Honeywell Programmer ST9400C and the Honywell Receiver.
I have also attached photos showing the 'AFTER' wiring on the Honeywell Receiver and the Tado extension kit (2 photos).
Any thoughts will be greatly appreciated.
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