Dumb TRVs with call for heat

If you just have one or two rooms in mind, how about additional wireless room stats, with the receivers wired in parallel, with the existing stat, to call for heat?

For what you want you will need something to either replace the programmer or is able to connect to it so that the TRV can communicate with the boiler. Most of the smart systems have similar set ups. In our case we have the Hive system this consists of a Thermostat, a receiver and a hub. Putting aside the hub which is there for WiFi . The receiver replaces the programmer in our case because we have a Combi it is a single channel version, the receiver has L & N and a a single zero volt switch. The smart TRVs communicate with the Thermostat which is basically the heart of the system and that in turn communicates with receiver.

Richard

Won't that be out of sync? TRVs have numbers like 1, 2, 3 on them, room stats have numbers of degC on them. Even if you religiously adjust them at the same time you don't know they're aligned.

You could be calling for heat when the TRV is closed, or the TRV open but no heat. If you forget and adjust one but not the other then things will behave more strangely.

If you just have wireless stats (no TRVs) then you'll be heating all the rooms the moment one is cold.

I could see it working for a 1 bed flat, but for anything bigger...

Theo

Modern boilers are "modulating" and my pump is intelligent so the flow is kept constant regardless of how many valves are open or closed. So virtually no drop in effeciancy.

Thats the weak link. If the battery goes flat the room goes cold. There aren't many licence free frequencies so you need more than one but. You also can't set room schedules individually which is how you save money.

Not that I found. Once you have a hub to pair the radio receivers with you need intelligence, so why not add extra functionality?

What most of us want is the ability to set individual schedules on a per room basis. This means an app or at least an intelligent controller.

Well as no one make TRVS like this I am not surprised. However there isn't really any difference between a thermostat and TRV the inputs for a wired version would be the same. All you would need would be a radio receiver, but then how do you pair things? If next door has the same system how do you stop it interfering with yours?

You can still get Radbot TRVs, and they can turn the heating off by sensing room occupancy, but the big disadvantage of these appears to be the lag. My wife wants the bedroom warm at bedtime. With the Radbot it would be cold, and by the time the room was warm it we would be tucked up in bed, when I guess it would go off because we weren't moving, and the room would be cold at getting up time.

I have Wiser and it lets me warm the room before bedtime. Result only slightly grumpy wife, as if she wants to try clothes on in the day she has to ask Alexa to turn the heating on....

Well whilst its not cheap Honeywell Evo home is the nearest thing to what you want in that it does not need an app and it does not need the internet, but it does offer individual room temperatures and schedules so it does more than you want, but the price reflects this...

Dave

I've had a large Evohome system for about 7 years - the ability to control individual rooms is great. I'm happy to (try to) answer any questions about it

But do you need to pay a subscription 'fine' to BG in order to use that extra functionality ?

No. We use the app to set the times and temperatures and use Alexa voice control to make any changes as required. BG offer a heating plus enhancement on a subscription but I am not sure what it does and as the present system suits us as it is we will not be subscribing.

Richard

Drayton Wiser only needs the internet for setup. After that the app connects directly to your hub. There are hacks to connect it to the popular HomeAssistant software, so its possible to have it totally off-line...

Dave

Similar to Hive. Home Assistant can take on the remote access too, but I've not got round to paying for/setting up that side of things.

I've mulled this over in the past.

One thought is to have a bypass loop with a pressure differential bypass valve, set to open only when all the rads are off. Also in this loop, include a flow switch. Any flow detected in the bypass loop can kill the demand for heat signal for, say, 10-15 mins. Obviously, you need the pump to run to detect if all the rads are closed.

If I was implementing this, I would have the pump operate momentarily perhaps every 15 mins and checking the bypass flow switch, just to test if there's a radiator open and it's worth actually demanding heat from the boiler. This will depend how integrated the pump control is with the boiler.

In practice, boilers are not great at driving just one rad at a time, and you really want some logic which says something more like, when there are enough zones calling for heat to absorb a significant proportion of the boiler's lower output power, then demand heat, unless there's a zone sufficiently far below its setpoint which can't really wait for more zones to call for heat before demanding heat from the boiler.

Having a setpoint range for each zone (which can also be used to implement hysteresis) gives more flexibility. When one zone drops to the lower acceptable setpoint, demand heat for that zone, and when the boiler has got that part of the heating circuit hot, bring in more zones which are below their upper setpoint and coming closest to their lower setpoint, such that the open zones can dissipate the boiler's lowest modulation power. I did hack this up in software controlling my system.

Andrew Gabriel snipped-for-privacy@cucumber.demon.co.uk> wrote in news:vfbibq$288jk$ snipped-for-privacy@dont-email.me:

Nice idea although I feel that with current boiler modulation ranges that the bypass will want to come on sooner than on the smallest radiator calling for heat.

Neat. On my last boiler change (we both used to run Keston Celsius) I went heat only with fully modulating Grundfoss Alpha pump outside, although I don't think it is as clever as they make out.

If you have the room I think the most sensible way of coping with small, and particularly unsynchronised, heat demands is to use a thermal store, heated by a boiler or some other means. I have one zone per room capability here that has not been fully implemented for fears of boiler cycling. I have a 200 litre store waiting to go in so that I can smooth out the bumps and fully implement it.

Yep, neat again but it's not for Joe average.

Sounds a bit complicated to me :-) This is strictly a wiring-only solution, I don't want to touch the wet side.

Thinking is that the smaller rooms (bathroom, utility etc), and also the hall where the thermostat is, will be non-controlled so there will always be some flow. Then the call for heat will be in parallel with the hall thermostat (which can be set low). Call for heat on any TRV will then fire the boiler even if the hall is up to temps.

This boiler is dumb and doesn't modulate, it also doesn't weather compensate

- there's no OpenTherm or anything, the controls are just on/off. I don't know what level of buffering there is in the system (there's no specific buffer component), but how does a dumb boiler cope when most of the rads are turned off? It'll short cycle but is that a problem when it's dumb?

I came across this:

Ordered a Radbot to play with and the new red version (Radbot 1) has a different testpoint pinout from the previous orange version (Radbot 2R, before the company was bought out by Secure Meters), so I'll have to take it apart and see if they've changed any of the hardware and whether that still works, or whether I need to scour ebay for 2Rs.

(Radbot is a lot preferable to systems with schedules IMHO, where you have to programme them according to your routine - which assumes you do actually have a routine, otherwise you have to endlessly fiddle with them, often through complex and/or awful UIs[*])

Theo

Is there a way to use it with a local controller, ie no app and no wifi?

I'm seeing square boxes with displays but they just appear to be room thermostats. Can you control it from one of those (eg turn the hot water on or change programmes)?

You can of course give it a tablet to run the app on, but it's subject to the vagaries of Android/iOS and having good wifi (eg change ISP and the heating can't be controlled because the wifi SSID has changed).

It appears there's some stuff to talk to it locally over IP, but that still needs wifi to be up.

Theo

Is there a way to activate a one-time boost at the TRV? I looked up the HR92UK TRV and it says there's a 'Function button, for binding and configuring', but doesn't mention a boost. Is that button just for setup?

Reason I ask is it's more convenient to have a local boost than going off to find the central controller in another room. You can twiddle the TRV but have to remember to untwiddle it later.

Theo

No needs WiFi , well there are two over-ride buttons on the box that turn on Heating and Water but I have no idea what that does to the radiator settings.

No, these are room stats, so you can override the current settings in that room, but only that room, but you can turn the water on from the interface box.

I always keep the old SSID and Passphrase when I swap ISPs. I have one or two dozen home automation things, such as Tapo cameras, Amazon Echos & Echo Dots, WiFi Switches, Garden Watering System... ... I actually have Draytek Access Points with a separate firewalled WiFi network for the Home Automation stuff .....

Yes, its WiFi only...

Dave

No, only temperature can be adjusted directly at the HR92s (or on the wall stat*), everything else is set on the controller or on the App.

I resent entering a domain where to do anything at all I need an app. I could see that one will end up with hundreds of them, many just to do simple day-to-day tasks like opening the door, turning the heat up. Once you get that many, it will take as long or longer just to find/remember the right one, as to execute the task itself. I also find it absurd that to do this requires that I shell out for a device costing hundreds of pounds, and which itself requires constant coddling - charging, f'rinstance.

There'll be an app for getting out of bed next, or for picking your nose.

I retired mine and went back to a dumb-phone. Only downside is that texting is a bit clumsy, but that helps to discourage doing it.

Another solution looking for a problem.