Completely Custom Heating controller? (UK)

Has anyone thought of creating their own custom Heating control, using existing hardware?

My idea is to use a few multi function sensors in conjunction with a tasmotised Sonoff relay or similar to control my heating.
This would work by reading temperatures from each sensor assigned to its own “Zone” and activating via Webcore each Sonoff to trigger the call for heat.

All temperature adjustment and scheduling could be controlled in app via a custom smart app or hijacking an existing app and modifying it to suit. As I have a wall mounted tablet already as my main hub, overiding and geofencing would be so easy to set with everything being controlled directly by Smartthings.

Here in the UK we have very few options, I have just ordered a Horstman ZW thermostat and receiver but I think this setup is aesthetically quite ugly…

I’m not after using anything that runs it’s own bridge as my router is pretty clogged already with my Solar panel Monitor, Solar battery controller, Smartthings Hub and BT whole home Wi-Fi mesh…

This just seems so easy, just wondered if anyone had done something similar, and if not why not? Is there some regulation I have missed that must be followed which prevents this being done?

I don’t know about the safety regulations in the UK, but I suspect the general issue is that then you would be 100% dependent on the SmartThings cloud being available for running your heating system. And historically it has gone out at least once a month for the last 18 months except, I think, in January 2017. Every time they push out a hub firmware update, for example, your heating system wouldn’t work.

Almost all of the other solutions work fine independently of SmartThings, SmartThings is just giving you additional scheduling options. So when smartthings is out, your heat still works.

If you just mean you intend to do this as a parallel method, people have been doing that since smartthings first existed. The original “keep me cozy“ smartapp was essentially a virtual thermostat operating off of standalone sensors.

Only you can decide what safety issues might impact your own household if the heat randomly came on or went off because of smartthings glitches, Which do happen. :scream:

If your household consists only of able-bodied adults who can get up and Change the temperature controls manually if smartthings is acting up, that’s one thing. Personally, I definitely wouldn’t control any heating zone with SmartThings where a young child or person with disabilities slept.

Family: girl died due to heater malfunction

As I’ve mentioned before, I don’t put anything on SmartThings which wouldn’t be safe to run 24 hours unattended. But that’s just me.

Hi JD, Thanks for the reply…

Firstly I had no idea smartthings was so unreliable in the US… I have had smartthings in the UK for roughly a year and the only outages I have ever had have been when I have taken down the wifi, firmware updates also are pushed here at times when an outrage is not even noticeable…

Secondly, I won’t be running an electric heater, it will be running a water heated system in a fairly small house so any temp issues would be noticed by myself.

As for manual overrides. The good thing about the Sonoff is the facility to add an override button which would work the same way as any standard thermostat, if smartthings ever did go down and I needed to switch on the boiler a simple button press on either zone relay would call for heat to that zone (I only have the 2 zones, upstairs and down stairs).

I don’t believe safety would be an issue on any system which wasn’t running electric heating. Obviously if you are running a high power electric heater I wouldn’t suggest switching it remotely at all…

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Smartthings in the UK has the same level of level of unreliability, it’s just that you may not notice if you aren’t home. Just the scheduled hub updates would have taken your system down at least eight times in the last year. We do normally get a few days notice ahead of time of those, but since you can neither delay nor deny them, it does mean your system is unavailable while the hub is being updated.

In my case, I spend most of my life in one of two rooms (I am quadriparetic), so I am more aware than many people of the glitches that happen. But they do happen.

Still, as long as you are aware of the issue and have a Plan B, which the manual button on the sonoff would be, then that part is up to you. :sunglasses:

So then I guess it’s back to finding out whether there are any safety codes in the UK that would prevent the project. Otherwise, I think it’s one of those try it and see if you like the results kinds of things.

Hi again JD,

yes I suppose that is a fair observation considering your personal circumstances…

To be fair I do monitor my smartthings system quite rigourously, but as you say it could be a case of just not noticing the down time.

I have used a similar Sonoff setup to turn the Smartthings SMH into a smart alarm system, we did have a case of having to set up the Sonoff to return to its last state before going offline as we did in the early days have a few false alarms after wifi problems with the Sonoff set to power on after reconnection…

But for the last 6-7 months it has operated flawlessly we have had to use a variety of different sensors as the Samsung ones seemed to be less than reliable when compared to the Zaipulek door sensors and Xiaomi Aqara motion sensors…

I also use a Sonoff to control both my Garage door opener and the lighting in the garage so I know the Tasmotised Sonoff is a reliable bit of kit…

As you say now it appears to just be a case of seeing if there are indeed an regulations in the UK that could prevent this… I keep looking at the Horstman thermostat and it just seems to get uglier and uglier the more I appraise it, compared to the likes of the nest or Tado thermostats.

I will need to see if I can maybe get a good looking LCD thermostat to somehow integrate with the sonoff for an even better all round solution…

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ZThere are many great commercial offerings for the UK and I don’t feel you should be concerned about your router / WiFi bandwidth. It would cope admirably.
As far as regulations aside from the accepted GasSafe plumbing issues and standard electrical wiring regs I think from a ‘control’ aspect you’re pretty free to do as you wish. However there some obvious safety issues to do with flow temperatures, boiler bypass arrangements and especially heating of any pressurised hot water tanks.
My approach to HA has been to implement islands of functionality (heating,lighting,security,AV etc) that work independently of my HA system and the Internet. This way should there be an automation outage things still work and the family stays onside. Yes you might lose some smarts of the system during outages but everything is still useable.
On the heating side your main choices would be how you setup the zones (rooms) and measure temperature within them, you can use zone valves, TRV’s that are wired or wireless with associated choice of ZWave, ZigBee WiFi etc. You may have concerns with motor noise from TRVs too.
The commercial offerings have great experience in minimising temperature overshoots usually through modulation of the flow and proportional flow control through radiators to create a room balance rather than just continual on/off and also to reduce boiler cycling.
There’s a lot of posts on the various HA forums about DIY systems

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Here’s one similar heating project you might find interesting… It’s based around OpenHAB but some ideas could be useful to you

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Hi xAPPO, I think you may have misunderstood what I was after, nothing so complicated as controlling flow valves or even messing with any plumbing.

I am basically attempting to use a smartthings multi sensor as a thermostat, this will then by a decent custom Webcore piston trigger the Sonoff relay to call for heat to each old thermostat position where the Relay will be housed, without changing any wiring or plumbing this setup will essentially replace just the thermostats of which I currently have 2, but what this achieves is remote functionality, and obviously with Smartthings controlling the Relay also a whole host of options open, up including geofence heating say to turn on the heating once I leave work… With Webcore it will be very easy to get to certain temp and then cut the heat via the Sonoff relay once more… A similar setup will sort my hot water aswell and this means I can remotely override either if needed…

Looking at my current setup I have 2 honeywell thermostats Cm707’s which are basically just temperature triggered relays with an override button and scheduling built into the stat, Smartthings would be a very easy and intuitive replacement… I could also look into trv’s of which there are a few which work directly with Smartthings but this will be at a later date once I iron out how the Sonoff setup works…

Hi again Kevin, that link is pretty much what I am going for, although my house already has 2 zones so my setup would be even easier to accomplish…

Thank you very much for the info

Actually reading through his whole post… it seems a bit over complicated… Why not just add Samsung multi purpose or like I have motion sensors in each room to monitor the temp and just switch the Sonoff relays that control the valves via webcore… the Samsung motion sensors are pretty reliable from my experience and if you use them as I do as part of my Alarm system they have a double or of even triple purpose if you use them as lighting triggers aswell…

Although technically you could probably do that.
I can’t see your insurance being valid though as the Sonoffs CE marks are only self cerficated.
Also don’t forget to check the wiring some of these boards use 12v/24v connections instead of 240v
And to be honest I don’t find the temp readings from my SmartThings devices to be very accurate they often report less/more than what the temp is.

Thanks Steve, yes I am very familiar with Sonoffs and I would never have just a Sonoff carrying the switching common… There will be heavy duty 16amp CE marked relay which will actually be doing the call for heat, the Sonoff essentially will just be switching that relay, sorry that wasn’t clear… Insurance shouldn’t be an issue but even if I were using the Sonoff as the call for heat what issues with insurance would I have?

I may be wrong here you would need to check but if you did tell the insurance they may ask you to seek building regulations approval, which I think would be denied.

Thanks Steve, will trawl over the link and any info I can dredge up…

So on Checking Steve there are a few things that must be complied with for the building regulations which come under Part L for heating controls.

  1. Must have a room thermostat.
  2. Must have functionality to adjust time and temperature settings.
  3. Must be able to turn on and off boiler at set point temps for optimum start and boiler interlock.

All of this is achievable from the smartthings app, I may need to as you say get a more reliable temp sensor and there a few available for use with Smartthings…

Also with regards to CE marking, All CE marking is a certificate to say that an item comply with EU regulations the CE mark for the Sonoff is valid…

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That’s an interesting one. Is that really meaning ‘optimum start’ which I believe is calculating and varying the start time such that the room just reaches it’s temperature setpoint at the correct time? Only quite fancy thermostats/timer do this and it will take some programming to achieve. Although it says ‘at setpoint temps’ so not sure

Kevin attached a copy of the page within the document…

Could you post a link to that whole document ?

Interestingly at the end it does say…

“It must be capable of starting the boiler at the optimum time to achieve the set-point temperature at the start of the occupancy period (i.e. optimum start). Implicit in this is some form of learning within the device.”

… so yes a significant requirement but I am not sure that this is a requirement for part P … most thermostats don’t offer this. Maybe it’s only for those that want to call themselves ‘smart’ and instead you can use dumb thermostats .

Hi Kevin,

It is part L not P, here is the link…