Home heating automation

No. Each nest needs a heatlink to operate. The heatlink has only one CH relay. Nest is what it is, it was developed from the American offering, which had multiple low voltage wired connections on the actual wall device designed to work directly with US HVAC standards, entirely unsuitable for here or Europe. Nest created the European version with the extra heatlink receiver for mains voltage switching for HW and CH.

I installed one in Holland for family when it was first released in the European version, many years ago. They never altered the product since other than to create an eco version with CH only, the Nest E , with a smaller battery operated receiver.

This might be a viable route to a second nest zone stat, but I couldn't say if it can be integrated onto a single app for both stats, they're almost completely different products. The E stat is a plasticity version of the Nest 3rd gen, and uses a rechargeable battery, and can be powered from a charger/adapter. It's also still pretty expensive for what it is.

The E was discontinued in the US, and the future of Nest products and support is uncertain, with the parent Google scrapping a number of Nest devices. There have been no advances since its introduction, no TRV support, and a strange approach to powering the stats themselves has created a product that is probably baffling to the heating trade, indeed, to electricians and engineers. If support at the app level is withdrawn, you'll end up with a product that's just a wireless wall stat with no cloud or Internet support. This is my read on it anyway, I don't see a long future for it.

https://www.currys.ie/products/google-nest-thermostat-e-10186639.html

Probably asked a thousand tunes so apologies. I have an eph 2 zone system and would like the ability to remote turn on the heating. Can I replace the eph timer with something else?

Just want the ability to boost for an hour remotely if I'm away from the house

Hi All.

I've had a hive system installed for the last number of years and love it. It's a 2 zone with hot water on gas. I installed it myself pretty easily with some help from online sources. It really changed how our house is heated. Previously we used to just boost every now and then and this resulted in peaks and troughs. Once I installed hive I was able to keep the house at a consistent enough temperature without any significant increase in gas usage.

So fast forward to Black Friday this year and Amazon ran a good discount on the Hive TRVs, so I decided to jump on them and purchased 9 of them. Here is my review (Spoiler, they are useless).

1. I installed and paired them without any fuss, it was basically seamless apart form 1 radiator that the plumber for some reason installed an old 28mm connection instead of the 30mm everywhere else and none of the adapter supplied with hive worked (not hives fault obviously).
2. I had read that it takes a long time to calibrate so I did the immediate calibration which took around 4 hours with the heat boosted during this time. All the valves calibrated fine and were ready for use.
3. I enabled Heat on Demand, which essentially means as each room drops below a target temperature the individual valves will call to boos the heat until it reaches the target temperature. For the most part this operation seems to work fine.
4. Where everything falls apart is when more than 1 valve calls for HOD during the same window none of them will close off heat until the last one is finished. So in essence the only part of HOD that works is the boosting. The valves remain open constantly and overshoot significantly.
5. The limitation of how the valves measure temperature is clear as day. Unless you have the ideal conditions (no radiators under windows, radiators completely free for air flow etc), the temperature readings are way off. By as much as a few degrees. This causes a perpetual boost stop boost cycle where the valve falls below target temperature, call for heat, reaches target temperature, stop calling for heat, quickly drops temperature again, calls for etc, and round we go.

Regarding point 4 above, I was reading online that the reason that can happen (valve not closing off), is due to the valve not being fitted correctly. I ruled this out by running a simple test. I turn the valve completely off from the app and boost the heat. In this situation the valve clearly works and the radiator in question doesn't heat up. So that proves that it is installed correctly and the fault of the valve not closing off when on a schedule is down to software. This same behaviour is repeated with all the valves not just one of them so it's a systemic issue. So wit all this in mind rather than the valves adding to the efficiency of the overall system it causes more gas to be used than without them. I tested over 2 days with identical outdoor temperatures. One with the valves enabled on a schedule controlling the heat and another with the valves just set to open and reverting back to using the main thermostat.

So TLDR, these valves are not fit for purpose. Whatever algorithm they use to control the opening and closing of the valves simple doesn't work (or has way too much latency in them). Once they call for HOD it seems they don't close for hours regardless of whether they reach target temperature of not. I keep reading people online saying they work great for them, but I guarantee that they haven't actually tested them correctly and are just under the illusion that because they see individual TRVs calling for heat that they are working fully.

I think I will be returning mine for a refund and would not advise that anyone purchase them for their setup unless all they want is a limit on the lowest point for temperature because that part works but it will overshoot your target temperature and continue to heat up as long as the boiler is on.

Point 4 sounds very wrong. I can only venture a guess as to why they might remain open after scheduled period is up. It seems they are acting as if no other source is calling the boiler, so they just instruct the relay to stop the boiler, but not close the valve. They may not be closing the valve either when they are the only TRV in operation, but they stop heating as the boiler is no longer under call from any TRV. It seems to point to mechanical calibration, the TRVs are not pressing the pins fully home to close the valves.

Well that shows that all the valves which were 'off' hadn't pressed the trv valve pin down to the bottom. This is what I suggested, that the valves are not closing the valves fully. There may be some algorithm whereby a valve will close partially but assume the boiler zone will be off, so no circulation. I haven't read on any forum of this before, though recall a Tado TRV owner having valve closing problems. You got the TRV valves fitted specifically for Hive TRVs, you didn't already have TRVs with mechanical heads. Is it possible the TRV valves are mechanically unsuitable for the Hive. There might be some 30mm heads with the right 1.5 thread, but perhaps the pins are a bit short and need extenders to ensure the hive closes them.

Thats what's puzzling. If you can have other radiators in the zone heating, and one definitely closed to the heating flow, stone cold when off in the app, but once turned on, remains on if you manually or in the app set its temperature well below its current measure. What was the brand of manual TRVs, if you've kept any of the heads.

No problem. When you boost the heat with the zone stat, of course the boiler runs and the zone valve opens, so, as the TRV can close the valves fully on OFF, it would seem then that when they're part of a zone, they only soft close as if to reduce the flow sufficiently to allow the radiator cool to its next lower temperature in the schedule. Can you insert an OFF in the schedule, or just a virtual off as in a very low temperature. This is all you can do in the Tado, set a time slot to 5°, or manually hit the off button.

It does look like a software quirk, perhaps an attempt to reduce battery consumption by not hard closing the valves at the higher torque required to seal them.

The Myson petite anyway are standard M30 1.5, no thread adapters or pin adapters required according to the Tado chart, which I'd expect applies to all standard size trvs. We probably haven't heard the end of this.

One CH and one HW

I wonder if it's trying to maintain a bypass flow in that zone in the absence of a specific bypass radiator. I know that heating-therory-101 says that you're supposed to have a bypass rad with no TRV on it, but few I would think do this in practice. The net effect of fully closing off a zone (with no others open) is that the water pressure backs-up in the heat-exchanger and the boiler can go into a thermal trip.

Should also have asked, does your heating have a wall stat, and do you wish to remote control of HW also

Nope, no remote sensor and no offset.

The only remote sensor is the main thermostat for each zone but not per valve.

Thanks for the reply. I have a number of smart sockets already and the smartthings app, also controlled by Google homes. I could possibly wire in a smart plug somewhere alright

I looked at this boilers installation manual, its very much and advanced boiler, with myriads if add on options and bus controls. It does, however, still have a basic switched live boiler call link between live and terminal 1 of connecter 96.

Bridging this with an external timer relay will fire the boiler, assuming the internal timer is set to on. Your Danfoss rx2c wireless receiver would control the zone valves for HW and CH, these valves in turn would jointly supply a switched live to terminal 1 connecter 69 of the viessmann, which will then fire provided it's timer is set. The Danfoss has no timing function, and can easily be replaced by a smart controller to supply timed lives to the zone valves. You would set the Viessmans internal timer to always on, or configure it out of the system, I'm guessing the former would be easier, the latter will require quite a bit of understanding of the Viessman configuration. I'll link the manual.

Because the cylinder thermostat is presumably also wireless to the Danfoss receiver, (check this), you could retain the Danfoss for this function, wiring its HW live out via the HW relay of your new smart controller, or vice versa, the HW out of the new controller into the Com terminal of the Danfoss HW channel. The Danfoss CH channel live out is diverted to the CH out of your new controller, and your new smart wireless stat installed.

None of this requires any tinkering with the wiring of the Viessman, as it is still fired by the zone valves. previously under the control of the Danfoss (which is still used to relay the HW cylinder stat control). As timing for HW and CH has now been moved before the valves, rather than inside the boiler, it is only a case of setting the boiler timer to always on. It will only fire when the independent HW and CH timers of the new receiver are on, and their stats are closed. I'd recommend the Tado wireless starter kit as a replacement, or the Hive mini CH plus HW kit.

Something like this, put it in a single wall socket box beside the eph.

https://amzn.eu/d/j5cakW1

One that works remotely by WiFi, and not just locally.

That's the wiring centre

Does any one have a system with an outdoor sensor with open therm that is rock solid and recommended?

Thanks a ton for the detailed info. I have an Ideal Independent 15 boiler on S plan with two heating zones and the water, and solar thermal. If I understand you correctly, the gas wont work with open therm but maybe the immersion? Immersion counts as direct? I don't use the immersion but it would be nice to have it set up online a as a back up. I was looking into getting a module to connect the solar thermal to the web via Germany. I notice on the Vbus website they have outdoor sensors depicted https://www.vbus.net/#/

I am not into extreme home automation, at least not right now but I would love reduce my bills as much as possible and maybe have a sensor here and there for alerting me to post delivery or water leaks.

That is highly informative. Maybe I am speaking without wisdom but it really seems the tech is not mature by the sounds of it.

I have a Climote. Basic system but it suits me fine mostly. I presumed Climote can't modulate but I don't even know this. I have an upstairs and downstairs adjustable EPH thermostat, I presume wired. I am planning to do some serious alterations in in 1-2 years so I may be able to lay more wires if it helps.

Yes, but if you just use any decent smart system as named earlier to run your three zones, you'll get close to the same results as using an OT boiler control. Tado in particular mimics boiler boiler modulation, by responding to heat calls with three different levels of firing intensity, a type of pulse modulation, so as a room approaches temperature it modulates the boiler firing, slowing the rate if delivery of heat, which has the effect of maintaining the desired temperature with a lower flow temperature.

Tado also uses local weather conditions and outside temperatures as supplied online by Accuweather, to adjust the delivery rate of heat, so its effectively like having an outside sensor fitted. The only thing it can't do is adjust or limit the max flow temperature of your boiler, but you can set this yourself, to limit excessive flow temperatures and lack of condenser heat recovery, while at the same time having enough headroom in your system to maintain set temperature during cold external temperatures.

I've read somewhere that development of Evo is stalled, there's been no innovation or upgrades of the hardware or software for some time. There had been a few posters here hoing back who were heavily invested in it, but its been a while since I've seen it mentioned.

You can install a Tado wired stat to each UFH zone valve for €100 a go from Screwfix currenty, with a master wireless stat receiver and internet bridge, a bargain at only €111, call to the heatpump for any UFH zone. Trivial cost in terms of what you're probably paying for the geothermal heatpump and UFH install.

Tado assert that their stats can operate with UFH. In terms of smarts, the away mode is useful for saving, as is open window detection, infinitely variable zone schedules, very fine control of specified temperature, and outside temperature compensation. Also, a separate HW timer is available on the wireless starter kit if your heatpump has a HW specific calling mode (higher flow temp required) and you have a HW cylinder.

You'll need to know how many individual wall thermostatically controlled zones you have, and cost each one in comparison to the model the UFH installers might use. Unless they use a really cheap mechanical stat or a basic digital electronic stat, they'll still be spending in the region of €80 to 100 for decent units, which may only be manually and locally programmable, if even that. Tado state that their stats can learn the response profiles of the heating system they control, and thus adjust 'firing' times and intensity to get optimum heating with minimal lag or overshoot.

The only significant difference that I can think of is that none of the smarter stats can accommodate an underfloor temperature sensor in addition to the wall air temperature sensor. The Heatmiser range do have this facility, if your UFH installers are believers in its usefulness. I'm inclined to think its use is limited to preventing overheating of the floor surface. You can ask your installers what they think.

@deezell Just wanted to thank you for all the advice. We finally got our Drayton Kit3 set up today & it’s working really well. So handy to be able to control everything from the app!

Thanks so much, you’ve made it all so easy for us 😊