Home heating automation

Wow thanks for reply very indepth

Just for clarity

There is was a valve removed from downstairs (conveniently installed at the back of a kitchen press ) and the other one upstairs in the hot press.

The valve is orkli mod zv-2v - 3/4"

We have two thermostats one in hallway and one on landing

I don't know does either of those points add or takeaway from the advice given.

This one has the valve relay, and gre and orange wire. Whither they were used or not, you'll have to see.

Dogs Dinner, but you'll find that the SLs from the stats are routed to the valves, and the valves' relays grey and orange are routed back, live connected to usually the orange, with relays' SLs coming back on the greys, which are combined, usually with the SL from the HW timer,( directly or via a HW cylinder stat). Thus all three sources can independently call the boiler, keeping the source SLs from the wall stats isolated from each other.

Spot on. EPH 3, 5 and 7 go to Wiser 2, 1 and 3. It helps to label them with a permanent marker or a bit of tape in case the brown wires get mixed up when you pull off the EPH backplate. Note the order of L and N is reversed on the Wiser, it's N and L from the left, this is important. Knock off power to EPH and Boiler. Earths are all tied in the metal wall base box as far as I can see.

You're saying the boiler will heat the HW when it comes on, even if this is for one of the CH zones? Do you have three motorised valves, one for each zone? Otherwise, HW will heat for any boiler event.

The signal from the receiver opens the motorised valve for downstairs. Once this is opened, a relay in the valve head closes and sends a Switched Live voltage to the the Grant. The SL from all three zone valve relays are combined together into one connection to the boiler, so any zone can fire it.

As you can heat downstairs by manually firing the Grant, or, I suspect, by opening the upstairs zone at the same time, I'd conclude that there is a fault in the motorised valve head unit, which contains the motor and the relay. The actual valve may not be opening sufficiently. it rotates open and the relay contact is closed at the end of this rotation. Try working the manual lever on the downstairs valve, see also how far it moves under power from the motor. This lever moves when the motor operates, but can be manually pushed to the open position and latched open in a little indent.

The heads are replaceable as a unit without any plumbing or pipe work. If the fault is the actual relay contact, these are standard microswitches. though no one is likely to repair these. When the head is off it's easier to manually grip the valve stem and rotate it fully back and forth to see if its sticking.

Then you must have a proper 3 zone system with motorised valve zones. All that's needed is a cheap cylinder stat strapped to the cylinder, or an insert stat if its a more modern cylinder. This stat will break the timer voltage to the HW motorised valve. The motorised Valve doesn't open, it's relay to the boiler doesn't close and the boiler doesn't fire. If the motorised valves are in the same area as the cylinder then it's a simple job.

I don't understand why a plumber would think your system was strange, if it was plumbed and wired correctly as an S plan system, with independent CH and HW. Meantime, if you run your oil boiler at a lower temperature, say 65°, the the cylinder temperature won't exceed this. When the HW calls the boiler it will only fire until the boiler jacket temperature reaches this temperature, then it will stop firing, even though the HW timer is on. The circulation pump will likely be running during this time, but no additional heat above the boiler set temperature will be transferred to the cylinder, unless someone draws down a decent quantity of cold.

This is what a cylinder stat looks like installed into a standard insulation coated cylinder.

This one is set just at 60°, when the water at that point in the cylinder rises to 60, the stat cuts the HW timer voltage.

This is a fancier EPH digital one, which needs a mains power supply to power it, as well as the HW timer in and out through the thermostat relay contacts. Pointless really, but it does have the probe for cylinders which have a probe insert tube.

So it's powering the valve, but the valve motor is not moving. Sometimes the valve head cable is connected to the wiring centre by an inline 6pin plug and socket, which facilitates easy swapping out of the heads, a diy job if you fancied it, otherwise they're hardwired into the wiring centre box which is usually spaghetti junction. The head is held onto the valve by a couple of screws on the baseplate visible when you remove the top cover. https://youtu.be/RlYa19QfYNk?si=L-c7BIwt9pzwRz1l

The OpenTherm connection on a Tado is the + - connection to the right of the base plate. These are connected by an isolated wire pair to the OT connectors on the boiler. Afaik you can only have one souce of OT connection to the boiler. Ideally you would not be using two wired stats, but rather a single one as your TRVs create multiple zones. Your two Zone plus HW system is probably zoned with 3 motorised valves, which require the normal mains switching from the Tado stats and extension kit relays to operate. These valves in turn have relay output which are combined to fire the boiler in on off mode, by connection to the SL1 terminal of the boiler.

I haven't read of a Tado system using OT where zone valves were in use. I did read where the mains relay in the wired stat is disabled when the stat is configured to OT, so operating a valve us not possible. Also, the HW feature of OT is only implemented in direct HW supply from a combi boiler. The OT HW feature is limited direct HW temperature setting, and selection of pre heat, which stores a small amount of HW constantly in the boiler HW heat exchanger.

If you treated your system as a single zone, with the CH valves always open, the TRVs effectively 'zone' as and when. All TRVs can be assigned to one wired Tado, which will be the interface to the boiler OT connection. I can't say for certain if the OT implementation in Tado can work when the Tado is calling for heat on behalf of a TRV, or if the flow temperature modulation of the boiler will be controlled by reference to the Tado stat measured temperature, or the temperature of a TRV. What happens when multiple TRVs are open? How does OT trim the flow temperature to maintain a steady state temperature when there are multiple temperature measuring devices making demands on the flow.

It was always my understanding that the OT implementation in Tado catered for a single zone CH only system, where there is one source of feed back to the boiler of the set room temperature status, from the single main stat. This facilitates the boiler to run in a modulated manner to effectively reduce flow temperature to the lowest required to maintain set stat temperature, thus maximising the condenser performance of the boiler. Gas boilers can't vary the heat transfer and subsequent flow temperature by reducing the burn rate, that's constant, so its only on/off modulation achieves this. How responsive and smart the boiler is in maintaining this is a function of its design, and not the OT connection. If the boiler is using sufficient and accurate temperature sensors on its input and output flow, it should be able using predictive calculations to maintain a steady flow temperature. Your experience suggests a more crude control when cycling near the 57° setting, giving temperature overshoot and undershoot when the drain from the CH flow is low because only a single TRV is active.

The OT spec does allow for simple on/off calling of the boiler, by just closing the OT input terminal with a short. For a HW call, the isolated volt free connections from the HW motorised valve relay are simply joined across the OT terminals. This will switch the boiler on with no feedback from the stat OT, until such time as the HW timer or cylinder stat closes the HW motorised valve. If CH is active during this period temperatures will continue to be controlled by the TRVs. I don't think they contribute to the OT feedback loop anyway, only the main stat has this function.

In summary, you could possibly have some element of OT feedback to vary your boiler flow temperature, but how well are TRVs integrated in this is a question Tado support can answer. Your HW will need to continue to operate the boiler in onoff mode, as its not a combi boiler with direct HW. This is possible according to the general OT spec by closing the OT data connection with a volt free relay. You'd have to establish if the boiler implemented this, but my guess is it should. The real risk IMHO is the possibility of accidently placing SL mains boiler calls from the zone relays onto the OT low voltage connections, which would fry your Tado and the boiler data OT data input. It's not surprising that a plumber, let alone an electrician, might be reticent about getting involved in rewiring to OT, especially as you have on off control still required for HW, and you still have two CH zone stats and valves, when the OT connection is limited to one.

Multiple source OT is defined in the OT standards. I've only read of one thermostat manufacturer who has an OT hub receiver which can accommodate more than one stat. It's an Irish manufacturer also, but I haven't read anything since the initial publicity some years ago, and I forget their name. I posted about this here, so I might be able to search that out for the reference.

Meantime, I understand your issue with the cycling temperature during low demand. Boiler output is always going to be much higher than the demand of a single rad, so return temperature will be high and the boiler chamber will heat very quickly. There are probably more advanced boilers out there that might cope better. In general operation, with most zones running, the Tado stats do quite a good job if establishing a steady learned state, and maintaining it by its own modulation pattern. It should in theory even anticipate demand from scheduled TRV zones, as it can see the temperature raise expected by an upcoming scheduled event, so would fire the boiler accordingly. Nothing's perfect I suppose.

@deezell I really appreciate the in depth reply. 

You mentioned 3 motorised valves. I only have 2 one for each floor. I have the Extension kit running off the electrics in the hot-press relating to the zones and the original controller set to CH On with Hot Water on always. You taught me that trick many moons ago :-)

I did wonder myself how it would work with two stats, I thought maybe the code dealt with it, like adding two slow calls to make a medium one :-).

That's the last thing I want is to fry any thing (other than a good Irish one :-) )

I guess one possible half solution is to remove the upstairs heating value and leave it open, disable the upstairs stat and that would leave a simpler configuration, in terms of a single stat and HW to work with.

Out of curiosity, if you know, based on how you explained the above and how I've inferred it, being that SL/1 is firing the boiler, if the open therm is controlling the flow and the stats are wired on MC and COM relating to SL/1, i assume then it's just moving the MC and COM wires and the brains of the operation is the motherboard on the boiler.

Indeed, nothing is perfect.

Eventually found the post from 2018 , page 33 of this thread...in relation to my extension kit install.

Maybe we should call this thread the @deezell thread :-)

@deezell Thanks. You spotted what I spotted in the manual, no reference to OT unless you use the weather compensation module. I did look at the Honeywell at the start, but Tado did what I needed at a better price point, so going to stick with the Germans :-) At the end of the day, system is working perfectly and i have full home and room control. What more really can one ask more, I hear everyone say....other than cheaper energy prices...at which point I wouldn't even be having this conversation :-)

Yes I had noticed the Brits were getting upset about 1. the modulating version being removed from the UK market and 2. struggling to acquire said item into the UK. There was a interview on Heatgeek and the Tado guy basically said they removed it because no one used it. Which is understandable, if your product isn't selling remove it.

I only recently, as I said learned about this whole new world and by all accounts most plumbers would not know about it either.

I assume the Analog/Digital connection in the EU kit below is the OT connection.

Net result would seem as if a third version of the kit would ideally be needed to cater for modern homes so save a whole lot of plumbing changes, and I guess there is no ROI for it.

As an aside would there be any benefit in using the Weather Compensation module on the boiler, i don't believe so, as i think it more designed to keep the entire house at a set temp all the time ideally and works better without TRV and colder/less insulated homes.

Right bar is open, time for a wee drink or two :-)

That would be a partially correct assumption. The TRVs, smart or manual, will regulate the local room temperature to their setting, as long as heat is being supplied by the action of the Hive stat calling the Boiler. When this stat reaches it's local target, the boiler halts. The temperature in a room controlled by a TRV may or may not have reached it's target setting in this time, but if it has, it's room temperature may well be set higher than the temperature set on the Hive, as the Hive can only measure where it is located. Thus the Hive may be set for 20° say, located in the Hall or living room, but another room with a TRV may be set higher, to 22°, an office say, and it might reach this temperature and close before the Hive has reached its lower target.

The difference between using manual TRVs or non Hive smart TRVs is that neither can instruct the boiler to keep firing when the main Hive stat has reached target and has cut off the boiler. A room which hasn't yet reached it's TRV limit is at the mercy of the main Hive stat resuming a call for heat to the boiler. Adjusting the lockshield valve on the other end of radiators, and having sufficiently large radiators depending on room size will ensure that rooms managed by passive TRVs will have the capacity to reach their TRV target before the main Hive stat closes. Hive smart TRVs only are in communication with the main stat receiver, and will continue to call the boiler to achieve their target temperature.

It may be possible for non Hive smart TRVs to do this if you are into writing scripts using third party controls and hubs, such as IFTTT and others, so that a non Hive TRV can issue an instruction to the Hive stat to fire the boiler. I'm sure someone has managed this somewhere.

Your assumptions are spot on. Alternative brand leaders are as follows.

Drayton wiser Kit 2 with 2 wireless stats, and 3 zone controller receiver is the simplest direct replacement for your controller. It has a full array of app control and smart integration. Stats are wireless, can be wall or table mounted. If you have existing old wired wall stats, they can be removed and hardwired on, or left and just turned up full the close the circuit from the Drayton receiver to the valves.

Assuming your system has two wired wall stats, another very cost effective option is Tado wired smart stats in their place. You can retain the old controller for HW timing, set the two CH zones to always on and the Tado wired will take over time and temperature schedules of the CH via the app. Replacing the old wired stats with the Tado wired is a competent DIY job. If you require Tado control of HW, one of the CH stats can be purchased with a wireless CH + HW receiver, to replace the old controller, while the other CH zone with a hardwired Tado wall stat the Live on the Tado receiver sent to the wired Tado wall stat location

Similar to the nest but at less cost would be the Hive system. Two wireless stats and two receivers, one with CH + HW , one CH only. The wiring challenge the same as the two Nest install.

All the above brands have smart integrated TRV radiator valves available for future individual room control. Nest does not market a TRV option.

Do you have a 3 zone controller and wall stats similar to these

If so, Your simplest solution is two tado wired thermostats, one in a starter kit with an Internet bridge, the other as an add on stat. These are a DIY replacement for the two mechanical stats, just 2 wires, a few minutes work for a sparks. You then set the zone timer on full for the CH zones as the smart stat takes over time and temperature schedules. You can continue using the HW timer on the zone controller.

Alternatively you can replace the zone controller with a tado ext kit, part of the Tado wireless starter kit. You will then replace one wall stat with a wireless Tado stat, and the second one with a wired Tado stat. The extension kit will take over HW timing, all through the Tado app. Wiring is a little more involved, but no plumber required, just a sparks or competent DIYer.

Ok, I'm fairly certain that those EPH wall stats are wireless to the controller, EPH Controls Curve TRFi Wireless Room Thermostat (UP12). If these are the original zoneed system installed, then it's unlikly that there is a wire pair from the controller to the back of the stats. You can check if they're unwired by popping down the front panels by loosening the front bottom screw. I assume they are battery operated, but there are a confusion of similar looking EPF stats in the past, some wired, some mains ,some battery. If you have to change batteries occasionally, then you propably open the case occasionally. If they were installed as an upgrade to previous mechanical stats, there may be unused or blanked off wires beneath, but i'd expect these stats were installed where there was previously no wall stat, or perhaps just one. Running wires to wall stats in no easy task. as a consequence, The Tado wired stats probaly will not be suitable, and replacing the EPH stats with wireless tado stats is problematic, as the Tado wired receiver has only ony wireless CH Zone, so you would need to be able to wire at least one Tado stat bak to the receiver.

An alternative and virtually drop in replacemt smart stat system is the Drayton wiser Kit 3. This has a three channel receiver which is a direct replacement for the EPH, and two wireless stats. There is only one caveat, in that you may also have a wiireless EPH thermostat fitted to your HW cylinder. I see a little antenna icon in the top left corner of each zone. There is only a temerature reading display on the controller for Zone 2, it's not clear if this can also report the temperature of Zone1/CH1, or HW if it has a wirelles EPH thermostat ( it may just have a manual one). Unfortunately EPH are one of the few stat and controller manufacturers who use a wireless to controller thermostat option for their HW zone. the other players who make smart systems tent to just proovide HW timing from their receivers/controllers, and let the user fit a standard mevchanical thermostat on the cylineder into the HW circuit to interrupt timed heating when the cylinder reaches set tempearture.

Check if you have an EPH device attacked to your HW cylinder, or any stat. take a pic. Lift one of the wall stat covers to see if they have and cables visible. I assume you have two of those stats pictured, one upstairs and one down. If the EPH controller is timing the hotwater and also has a wireless cylinder stat to provide temperature feedback, it might be preferable to leave HWcontrol to the EPH device, and replace just the two EPH stats with Smart wireless stats, connecting their receivers beside the EPH controller and moving the CH zone cables only across to the new receiver(s). The Drayton Kit 3 would still be viable, you could also install Hive smart stats with their individual receivers.

As with Tado, these brands can be further extended with smart radiator contols, or TRVs as they are known. You say you already have mechanical TRVs on the radiators, so with Wireless smart TRVs you have the option of creating room by room programmable zones. No plubing required, just change the TRV heads. With Tado, this is often the route taken during upgrade. You set your home back to one general heating zone with a single Smart wall stat, wired or wireless, then implement smart TRVs on as many radiator as you wish, to create numerous individual or grouped room zones. A pic of one of the radiator vales also with a brand name visible just to check comaptiblity with Tado and other smart TRV valve heads woould be useful.