Home heating automation

My first observation is that there are only two zone valves, for CH presumably, so I'll assume HW is gravity connected, meaning it heats when ANY of the three controller zones call for heat, CH1, CH2 and/or HW. With such a system, if the controller has a gravity mode, the CH switched lives (SL) only open the Zone valves, the HW live is configured to go live for any of the three zone events, and this is used to fire the boiler.

Alternatively, if the zone valve relays are used to generate a separate Sl when each CH zone activates, the controller can be set in Pumped mode, HW SL goes live only for a HW event, and all three SLs can be combined to fire the boiler.

The significance of this is that Drayton wiser Kit3 does not have a Gravity mode, so CH lives have to be in place from the Zone valve relays, and may need to be wired in if not currently so.

The same is true for the tado wired and wireless set of 3 zone SLs, it can't be set to gravity mode, so CH SLs must come from the zone valve relays. For a single CH and HW Tado install, the new type ext kit controller can be wired to mimic gravity mode, as can the Nest heatlink receiver which also has volt free relay contacts for CH and HW.

Although he may not want to use a thermostat, he can't avoid it if he puts in TRVs, as they all have stats. In the case of tado, the zone for any TRV is opened and fired by its respective stat, but if all rads in that zone have TRVs, the wall stat is effectively only a relay switch. With a full TRV setup, you could revert to a single CH zone setup, both zone valves operated by the single stat receiver relay, or just latched open, or reconfigured as a one for CH and one for HW, assuming I'm correct that HW is gravity or open to boiler pump connection. A combi boiler would simplify things further, reducing your hardware to TRVs and a single stat/receiver relay.

I'm not convinced of the need to have wireless remote app control of HW cylinder stat temperature, and the expense and potential for failure of all these extra powered bits of hardware.The wired mechanical stat is sufficient. Who needs to vary the temperature of their hot tap supply? Set and forget.

55% off Tado 2x rad starter kit (amazon.de)

not sure if this is a mistake or not, but there's a 55% voucher on this bundle - not available on any other bundles

I already have the bridge for 1 thermostat and have 2 more thermostats to install - the bridge in this would be surplus wouldn't it but at that price the offer is still too good to pass up isn't it?

thanks for that - amazon search results show another version at £72.99 and this one at £49 was only listed as a "newer version" on that product page - didn't show in my search results before i posted.

I think what they are saying is that they don't do a thermostat for HW, but they do facilitate Tado app timing of the HW zone. I'm assuming your EPH controller is a three zone device, and you may or may not have a mechanical HW cylinder thermostat.

Your simplest option is to replace the wired CH thermostats with Tado wired. This is a DIY job. You retain the EPH controller with the 2 CH zones set to Always On, as the Tados will now control temperature and timing. The timing of HW continues to be set by the EPH.

Alternatively, you can add the Tado extension kit in place of the EPH controller. This will have no function regarding the wired Tado stats, other than to supply an always on Live to them. It will also provide the timed live for the HW circuit, which will be available on the app. HW will continue to be set by the existing cylinder stat (if present). Theres the extra cost, and wiring of this is a little more involved for very little function other than app control of boost and timing.

One more final assumption I'm making is that you have three independent zones, with three zone valve, and not a gravity system where HW heats when the HW timer or either CH zone is on.

Install two wired thermostats for CH and you will immediately have a huge level of zonal time and temperature control. Very low cost, and a simple DIY Install. Later add a few TRVs , a DIY job if your rads already have manual TRV heads. Leave the timed HW to the existing EPH, if your cylinder doesn't have a HW stat, fit a simple mechanical one.

The wall thermostat is the device which is physically connected to the boiler to fire it when a TRV opens and looks for heat. Without the wall stat the TadoTRVs will just act like ordinary TRVs, closing when the room reaches set temperature and opening when room is below set, but the boiler won't fire unless they are using a wired stat as a wireless relay.

It depends on how it was wired up. Its possible that a loop was created in which the relay in the 'HW only valve' (which I assume is really a CH flow valve), is strapped to the ext kit live out, thereby locking the valve on and creating a permanent live into the boiler Switched Live (SL) for heat. Is there just a single valve? And is this meant to close off CH flow, but allow the boiler to fire when you want HW only? Are you using both HW and CH controls on the Tado app?

With only a single valve, you want the boiler to fire for either a HW or CH timed event, but the valve will only open for a CH event. With two channel timers this is normally achieved by having the timer in gravity mode. It this instance, the HW live out fires the boiler for either a HW or CH event, while the CH live out only opens the CH valve. As the older version of the ext kit does not have a Gravity mode switch, and the newer version requires a little tricky wiring loop to set up the two relays to simulate gravity mode, your problem may lie here.

Either ext. kit can operate the gravity mode logic if the relay built in to the valve is utilised, and wired as the only source of SL for CH to the boiler. You must not connect the CH live from the ext. kit directly to the boiler, as this will create a locked loop.

As the master bedroom thermostat controls the call for heat for all upstairs rooms, the switched voltage to draw heat flow from the pump to the upstairs zone is located in this stat. If you were to install smart TRVs on the upstairs rooms, with a wireless receiver for these mounted next to and wired to the master room stat, any room with a smart TRVs could call the heat pump even if the master stat is up to temp. Ideally, you could replace this stat also with the TRV receiver, (which could be a Tado wired stat for example), and put a TRV in the master bedroom. This will allow rooms with a TRV to cut the heat flow when up to temp while other TRVs are calling for heat.

A simpler non smart solution is simply to balance the rads by restricting flow to the master bed, and front facing upstairs rooms by using the lockshield valves on the radiators. This will slow the rate of heat delivery to the front/master bedroom, allowing a longer period of heating to the other rooms. Its not a perfect solution, as you're trying to overheat the cold back room before the main stat is up to temp, so that this room, which cools quicker, will still have a reasonable temperature before the master bed stat kicks in again

Thanks deezell,

With regards to the either the wireless receiver or replacing the current thermostat with a stat for the smart TRV's I will likely need an electrician to ensure everything thing is down correctly?

Am I correct in saying that the heatmiser thermostat would be considered the 'dumbest' type of smart home heating automation!?

Your suggestion of limiting the flow to the other rooms while a logical work around, I think I would prefer to go the smart route.

I assume the smart TRV's have the individual thermostats built in to monitor the temperature per room and then use either suggest option to call for heat specifically to each room if needed?

Finally I assume replacing the heatmiser with the stat which is also a receiver for the TRV's would be the better option all told?

Thanks again deezell, seriously detailed response which is really appreciated. From what you have said the Tado seems the easiest and best solution. Just in relation to knowing if the upstairs rads have manual TRV's how would I check that!?

It also sounds like replacing the heatmiser for the underfloor heating with the Tados would be a good idea as it would give much more control over the UFH and allow for increasing the temperature when returning from being away and having the house up to a comfortable temp by the time we would get home, unless I have totally misunderstood what you have said?

Hi deezell or anybody else who can help. I just about managed to get my Hofmann 37xl removed. I'm installing a wiser based on your assistance a few months back, only getting to it now. I had expected per the Hoffman 37xl wiring diagram you shared that there'd be off signals also but I just seemed to use channels 1,3,5 and there are two wires going to the live and neutral. I'm thinking it would be quite easy now as no extra wires. 1,3,5 go onto 1,3,2 on the wiser and I'll put the earth on 4 to keep out of the way. One issue is that I think I'll have to install it upside down.

As the fuse is in the way and moving that seems like hassle!

Just wanted your vote of confidence in my wiring plan or anything to watch out for. I'll do it at weekend :-)

Thanks in advance, apologies for sideways photos, didn't know how to change

Correct in all respects. As the master bed has no TRV valve, it will continue to heat past its set temperature when other rooms with TRV's call for heat through the Tado. This effect can be minimised by turning down the manual valve (or the lockshield one at the other end if the rad), to reduce the flow to the master when other TRVS are open with less flow resistance. It would also be a minor task for a plumber to swap the manual for a TRV valve body, to enable full individual control of timing and temperature of each room.

The Tado stats don't just click on and off either side of set temperature like simple stats, which have a heating graph of over, under, over by as much as 2-3°. The Tado will note the progression of temperature rise or fall, and will modulate the on-off cycles to approach and maintain a steady temperature. This is particularly effective on slow response systems like UFH, where it will learn the rate of change, and also factor in outside temperature by reference to online weather data. Super smart. Any nerdos like myself out there who are amused by the theory of this type of control, here's a very easy essay on the subject of proportional, derivative, etc. temperature control. https://newton.ex.ac.uk/teaching/CDHW/Feedback/ControlTypes.html

Great, I thought something was odd with my wiring when no off connections. Good to get reassurance. Yeah I've got a phase tester and confirmed the isolation when I removed the h37xl yesterday. I think getting that box off the wall might turn out to be the hardest part of the work!

Thanks, it does look simple enough, which was a pleasant surprise. I'll keep you informed of my success!