Home heating automation

Track down the location of the existing zone valves which split the flow to living , bed and HW. If they're all together in the upstairs hot press, then you should be able to branch off a flow and return to the attic room.

Failing that you should be able to link it to the existing bedroom loops if the plumber can comfortably branch from an existing radiator flow and return. The new radiator could be fitted with a smart TRV head, which would allow it call the Bed zone, regulate that rooms temperature, and close it off from the Bed zone when its not needed. A Tado wireless kit would take care of the living room cintrol and HW timing, plus a Tado wired stat in place of the mechanical Bed zone one. A Tado TRV on the attic rad as discussed would give it some independence from the Bed Zone wired stat, it would use this as a relay to fire the boiler. A shortcoming of this is that all beds will heat when the attic TRV activates, as it's part of the same zone. A fully independent 3rd CH zone with its own wired stat or wireless if Hive or Drayton), is only possible with break out zone plumbing with its own zone valve operated by its stat.

Never heard of that, Drayton are made by Schneider, so hardly Farage influenced, 'stats for pratts'.

Vintage stuff alright. The Legrand is a thermostat, it should respond to temperature increases. When you rotate it right so that it clicks on, if you then set it back just enough that it doesn't click back off, a few degrees of room temperature increase should be enough to click it off. Having said that, its ancient and probably worn out mechanically, so it's now just acting as a crude switch, with its internal mechanical temperature sensitive gubbins probably knackered.

Because it does act as a CH switch, provided the obscure Danfoss Randall timer (only 2 event in 24 hours) is on, a simple solution for you is a Tado wired thermostat kit, which will replace the Legrand. The Randall timer is then switched to always on, and the Tado provides both a timing schedule and temperature control via the two wire connection into the Legrand. Very simple and DIYable.

It won't provide seperate HW only heating. This is sometimes inherent in old systems with just a mechanical timer and a wall thermostat, in that the wall stat only switches power to the circulation pump, or to a CH zone valve, and HW only is then heated when the timer is on but the wall stat is turned down. This doesn't appear to to be the case in your setup.

You will need plumbing modifications to seperate out HW cylinder heating from radiator heating,but again, in old installations this is often not possible to easily achieve as the HW flow and return connection to the boiler is mid circuit on the same pipes as CH radiators. A plumber will quickly tell you if this a big job or not. Even if the HW flow is tapped straight after the boiler, having a zone valve fitted and wired to close CH and enable HW only heating will cost a fair few quid in plumbing materials and labour.

A better future solution might be to install smart TRV's on the radiators to enable closure of these individually, but thats possibly an even bigger job if the existing rads don't have existing mechanical TRVs, with the required TRV valve body.

Of course, the legacy solution was simple, just turn off the boiler in the fine weather, and heat HW from the immersion. That's become almost prohibitively expensive wirh current electricity costs, and if you have an old poorly insulated HW cylinder, ots even more costly.

One final tip, you can buy the wireless Tado kit ( or orher brands like Hive or Drayton wiser) which have a receiver with a HW relay. You'd install this receiver in place of the Randall timer, turn the old Legrand stat permanently on, and just locate the wireless thermostat in a suitable living space to get a read of room temperature. This will work exactly the same as the wired stat option, a little more competence required for the wiring, but it will provide a relay for seperate HW timing should your plumbing be upgraded to support two zones. That just about covers all the angles. I've not dealt with putting electric immersion switches under smart thermostat control, thats a seperate discussion.

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Thats the right approach to take.

Fwiw, All mechanical thermostats click when theyre set past the current room temperature, thats the point that the stat set temperature is increased beyond the actual temperature, causing the bimettalic strip actuator to overcome the spring resistance and flip the switch on. Equally, as the room heats further, the strip bends and overcomes the opposite spring pressure flipping the switch to 'off'.

The knob is not an analogue adjustment like a volume control. There's a measure of lag or 'hysteresis' to use the technical term, wherby once its 'on', or off, it takes up to ± 2° heating or cooling to flip the switch. So if set to 20° say, it should click off at 22°, and as the room cools, it will click back on at say 18°. This cycling air temperature is averaged in terms of radiant heat, so you experience 20°.

Electronic or smart stats will trigger on 0.1 of a degree, and will also 'anticipate' the heating or cooling rate using learning, thus preventing overshoot when the stat has switched off the boiler but the temperature continues to rise as the rad is full of very hot water. Smart and electronic stats at the minimum use PID, proportional integral differential control algorithms, mathematical formula that wrecked my head in control systems lectures in college in the 70's, (and I love maths), so I'll forgive anyone who gets weak at the thoughts of it. Don't fret, its how all feedback control works, from audio filters to car shock absorbers.

The actual temperature scale is completely worn off that old stat, so you don't even know what setting it's at.

A steal.

He is correct. Bosch don't support OpenTherm which third party controllers like Tado extension kit would use, instead they have their own proprietary closed system.

You can go back to relay mode which is the easiest install but you will need additional TadoX hardware, the wired thermostat. It won't modulate like OpenTherm but still works fine.

Reinstall EPH controller, set heating to always on & then program the TRVs with the wired thermostat as the zone controller.

Edit: Does your existing system have a thermostat? Or did you just set it to come for 30 mins, 1 hour & that's it.

Who said @MojoMaker requested he connect the TadoX receiver via OpenTherm? It has a relay. He was replacing the EPH, also relay connected, so I'd imagine it was a simple wiring replacement, SL from the EPH NO or CH On terminal transferred to the NO (normally open) terminal of the TadoX receiver. That he suggested he himself had connected to NC does not inspire confidence. A simple press of the Tado X boost would have allowed him to check with a phase tester screwdriver that the mains was going out on NO. Then he arrives back and can't solve it. Did he, er, put a link from the Live L into the Com Terminal of the TadoX receiver? Unlike some controllers, Live is not prewired to the relay Com Terminal. You must do this if the the boiler expects a SL on a single wire to fire it.

The relay being supplied volt free is to allow compatibility with volt free and low voltage control input boilers. Pop the cover on the receiver and see if the link is there, or post an image. The OpenTherm theory is a red herring. Bosch boilers and others will always have a simple SL or relay mode of firing the boiler. That's how the EPH fired it, so no OT used.

At most there may have been a two wire connection from the boiker, carrying the live in and the SL back to the boiler. These two wires would have been connected to Com and No of the EPH if it had a volt free wiring scheme. Its also possible that L, N and SL wires came from the boiler to power the EPH, rather than having it on its own plug, which is not safe should the boiler be unplugged and the EPH left plugged in. It should have been a simple swap, and a simple test of the app/boost to confirm the relay was closing. Ill take a look at the greenstar wiring terminals to confirm it takes SL

Another possibility is if the electrician mixed up the L and N into the Tado X, it will still operate normally, but if he did put a link from L to Com, it won't send live to the boiler SL. because Live in is connected to N, and Neutral in is connected to L. The boiler wont fire in this case as you're connecting N to it's SL cable.

A quick look at the installers manual shows that the boiler is supplied with live and neutral on terminals L and N of connector ST10, and this Live and Neutral is available to go out to a controller/timer/receiver, along with the SL back from the receiver, from terminals Ls, Ns, and Lr (Live return or Swithed Live). These three wires would already have been externally available on the EPH, no need to go inside the boiler cabinet, and incur the wrath of Jedward or a registered gas installer.

Note the digital interface EMS bus is listed as connector ST19, but its not shown, and EMS only mentioned once more in this manual as 'not used'. There is no chance that the sparks tried to make an EMS connection, let alone an OpenTherm one, not at the boiler end anyway. Who knows how he wired this up.

If you've a phase tester screwdriver €2) to ttip terminals and check for live, go for it. Post a picture of the cables into the tadoX receiver. You will need the Tadox thermostat powered to send wireless instructions to the tadox receiver to close its relay. I'm assuming this is done.

At the minimum you must add the wall thermostat and the receiver to the app as devices. You will also need the bridge powered up and connected to the router. The wall stat, TRVs, Bridge and receiver communicate with each other wirelessly (but not by WiFi). The bridge provides the link to the Internet, and from there to the App.

If you go to settings/rooms and devices, you'll see the rooms you've created. With a wireless starter kit, its a list of just one, say 'Sitting Room'. This will show the wireless temperature sensor in it's list of devices. If you click on the > to the left off 'Sitting Room', you will see the sensor serial no. listed as the measuring device, and the receiver serial no. as the Zone controller, as in this image

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The above image is from V3 Tado, but afaik the interface for Tadox is identical, it's the same app. The boost button on the receiver has a 30min default time. In the app, the manual time setting of the associated measuring device, the Wireless stat, can be set to a custom time, or to finish with the next scheduled change, or until you manually cancel.

Yes you can, but what's the point? You could just as easily wire up a light switch. You should get all the parts connected and added to the app, test it on the kitchen table, just use a phase tester to see if NO lights up with mains for all the possible inputs, turning up the stat manually, via the app, via the boost. Then transfer It to the EPH wiring.

if @MojoMaker is an AI as you think and just wants to switch something on and off, he already could do that with the EPH. I dunno, he hasn't posted an image of the receiver wiring. Maybe hes on a slow charger.

Straight out of the box the receiver might/should respond to its boost buttons, these also double as pconfiguration buttons, though I'm only familiar with V3. It's not a manual switch though, the boost settings have default time once its all up and running, 30 mins iirc. I've never operated any Tado devices without first adding them to the system, and assigning measuring device and zone controller. A wireless kit on a new app install will default to the two devices anyway, as thats the minimum, and of course they must be paired to the bridge first in order for the app to see them. A wired stat is the simplest, it sets itself as measuring and controller from the beginning.

It gets trickier when you start adding additional wired stats for say an S plan system and adding a wireless stat later can cause problems if the receiver grabs the first wired device as its measuring device. You will have to go into installer mode on the stat display to move it to its own zone, by assigning it as relay 2. It can get messed up, but ultimately, you can see what any 'room' is using as its measuring device, and to which relay, (wired stat or extension kit receiver), it's using as a zone controller.

Let's see what @MojoMaker, or his AI alter ego has to say!

None taken by me, though you might get a visit from a disgruntled 🤖. I pose technical questions directly to Google all the time, in relation to various devices configuration, av, phone, car obd and coding, routers and internet ,smart home, garden tractirs and power tool repair, and of course heating.

Aside from the AI semi correct answers, I'm hoping to get hits from real human sources, reddit, specific product forums, discussion groups, technical manuals and youtube explainers. (not facebook though). These are the real goldmine, only the other day I found the full dealer procedure for troubleshooting and calibration of my cars rear camera system. This is not available to the public, so no surprise it had a url with a . ru domain. 'Oh! those Russians', as Boney M would sing. Fittingly, the song is Ras-Putin.

Keep up the AI detection. I prefer to use my own flawed and trusty Longmans grammar which was painlessly fed into our heads in primary school, no beatings,unlike the Irish language psychos.

Just follow the steps in the wireless starter kit instructions, starting with installing the App and getting the bridge, stat and receiver added, WIFi connected to the bridge, and stat and receiver paired to the Bridge

Have them all powered and working. With the app controlling the receiver, or the manual controls on the thermostat doing the same. Only then connect the boiler firing SL wire to the NO contact. You can bench test all these before mounting.

That might be the relay in the motorised valve, or the valve itself sticking. In this design, knows as S plan, the switched live voltage for CH from the Tado receiver, the RF switch you mentioned , goes to motorised valve, nowhere else. This valve must actuate and fully open at which point the rotating mechanical valve motor mechanism operates a microswitch which then sends live to the boiler SL input, instructing it to fire. There would be a second valve doing a similar operation, sending hot water flow to the HW cylinder, firing the boiler also. Many homes will have three motorised valves, upstairs CH and downstairs CH and HW.

You can check the mechanical action of these valves while looking at them. Turn the the CH up high, the valve should whirr and an indicator lamp if fitted will light. There is also a mechanical lever to manually open the valve mechanism, this can be moved to indicate the resistance of the actual flow valve. It should move with a firm press. If there is no indication lamp, you would need a meter or a phase tester to check that the SL voltage of the valve is being sent to the boiler. This SL voltage comes out of the valves usually on the Orange wire from the valve body, and can be tested at the wiring centre box where all the zone valve cables terminate.

If the zone valve is sticking, or it's motor has failed, you can get your heating going in an emergency mode by just opening the CH valve's mechanical lever and lock it in position on the notch. You can then fire the boiler using the other zone, HW, and when the boiler fires for this, hot flow will go to the rads as well as the cylinder.