A little while ago I wrotesome notes describing my “ideal” central heating control system, which I was planning to build myself.  Time is short so it looks like this system won’t be built for a while so I need something which I can buy off-the-shelf which will satisfy as many of my requirements as possible and also leave the door open to DIY tinkering in the future.  This blog post is a collection of notes about off-the-shelf central heating control systems.


  1. Programmable room thermostat in each room (which senses the temperature in the room, compares that to a temperature schedule for that room and turns on the TRV valves on the room’s radiator if necessary).  This could be integrated into the TRV. 
  2. All communication should be wireless. (I have run a few cables around the house but not for every room).
  3. Room thermostats must be able to signal to the boiler to request more heat.  Having a single boiler schedule and thermostat to control the boiler is so utterly dumb it’s frightening.
  4. The system needs to be able to work with our underfloor heating
  5. It would be awesome if the system could be controlled from a laptop / iPad / Android phone / iPhone, both within the house and outside the house

Current Plan

I need to explore the ELV MAX! system.  Very good prices.  Has radiator TRVs, room thermostats and a LAN gateway.  Hekkers has done lots of work with with ELV MAX! system (including talking to them)

Look into the AlertMe smart heating kit available though British Gas.

I should also check for new products on http://www.automatedhome.co.uk/category/hvac

…and figure out what this very affordable wireless Conrad TRV does.

…and look into http://www.salus-tech.com (they do programmable TRVs and a bunch of other stuff) (thanks Derek for the link!)

… and look into Owl’s heating controls!…

The LightwaveRF system looks like a good bet.  There are some questions I need to answer before going for it though (see below).  LightwaveRF do have some TRV valves on the market today but these are one-directional (and hence can’t call for heat from the boiler).  “Complete zonal bi-directional heating control system (early spring 2012)”. The last forum post on the topic suggests that LightwaveRF’s heating kit might be available Q3/Q4 2012.  The LightwaveRF Android software gets rather bad reviews.

If LightwaveRF doesn’t work out then the idea I’m thinking of is something like this: use Conrad Wireless TRVs, Room Thermostats and Boiler Control for basic heating control (still need to figure out exactly how the FS20 system will control the UFH). Then use a Nanode+JeeLabsWireless to add an open-source “Internet gateway” to the FS20 system to allow for remote control and monitoring of the heating system. One of the nice properties of this system is that, when we move house (which may be in only a few year’s time), I can remove the DIY components from the system (i.e. the Nanode) and the core FS20 system will continue to work.

I still need to look into the Homematic system.

And I also need to consider if I really want central programming.  The easiest solution would be just to add programmable TRV heads to each radiator (can be bought for £15-35 each) and forget about controlling the system from the network.  I could add a simple Nanode system to turn the boiler on/off from the web.



  • hackable / open API? (some discussion of protocol here and here)
  • how to control boiler?
  • how to control UFH? (the TRV replacement heads won’t fit on my UFH manifold) guessing I’ll have to use a switchable mains socket or something
  • I’ve heard the heating system can only do 3 zones, is this correct?

FS20 System

Controlling our living room UFH system

Current plan: will probably have to give up on the living room’s UFH being connected to the boiler and/or the other controls.

Option 1

Buy the HomeMatic 4-zone Under Floor Heating system For 630 euros. This is way over my budget and I only have two UFH zones. So this option is far from optimal but it does demonstrate that it is possible to control UFH with FS20

Option 2

Buy the FLV wireless thermostat plus wireless mains switch for 55.95 euros. Use the mains switch in series with a wired floor probe thermostat to control a wired actuator (i.e. heat will only be sent to the floor IF the FS20 thermostat calls for heat AND IF the floor temperature is below 28 degrees C). Big question: will this system work with the FHT8W Boiler Control? (I’d guess it does) (update 21/9/10 - no, the STR thermostat wont work with either the FHT 8W or the FHZ1xxx PC controllers)

Option 3

Buy a Conrad FHT 80B Room Thermostat, a FS20 AS1 switch and the FHT8W Boiler Control and hope that the 80B can be configured to talk to the AS1 switch. This wont work if the 80B cannot communicate with the AS1 switch. (update 21/9/10 - the 80B cannot work with the AS1 switch)

Option 4

Buy an FS20 room thermostat plus wireless actuator plus window sensor. Hack the window sensor so that it is connected to a wired floor temperature probe. This will almost certainly work. The components could be bought from Conrad-UK or from HouseTechSolutions. (update 21/9/10

  • won’t work: the FS20 wireless actuators are too bulky to fit onto UFH manifolds!)

Honeywell Total Connect

  • http://www.mytotalconnect.com/comfort/yourhome.php
  • No details at all.  Cost?  Tech specs?  Detailed feature list?!  Nope; just patronising stock photos of “happy families”.
  • Prestige 2.0 thermostat costs £279 each!  Rediculous!  But, wait - it comes with a “high definition” display; oh joy</snark>.  Seriously guys; stop taking the piss.

Bridging the FS20 wireless network to a TCP/IP network or a computer

The FHZ1300 Radio Home Centre PCbridges from the FS20 wireless network to a PC via USB.  Apparently the software supplied with the FHZ1300 is all in German). PC can then either run the Homeputer Web Server{.external .text} for £44 or the GPL’d Fhem{.external .text} software. There is a FHEM iPhone app{.external .text} in development too (or was it just a proof of concept?). The software is well maintained and the web stuff is optimised for Android browser. There are more software apps listed here: http://fhz4linux.info/tiki-index.php

Simple programmable TRV heads

If you simply want programmable thermostats & actuators built into a TRV head then such things can be bought for as little as £15.  But none seem to be network-connected.  (e.g. search the Conrad website for Honeywell HR20). Honeywell make an HR80UK (£80) which wirelessly connects to either the CM Zone or Evotouch Control Panel.

Wired actuators

Thermal actuator TS 230 V

Thermal actuator TS+


Multi-Fit Thermal Actuator 24v (Low Voltage)

Multi-Fit Thermal Actuator 230v

Programmable room thermostats


Networked programmable room thermostats


  • Do a wide range of room thermostats including wired, wireless and WiFi. Expensive though.  WiFi thermostats start at £149 each.
  • Their “Internet Remote Control” costs £383!

John Guest

  • The John Guest Programmable Room Thermostats can definitely be controlled from the web although it’s not clear if this control has to be done via several hundred quid’s worth of boxes or if the thermostats have an Ethernet port. I’ve emailed to ask

1-wire interface to Lux thermostats


Hacking the Honeywell HR20





“KNX is a standardised (EN 50090, ISO/IEC 14543), OSI-based network communications protocol for intelligent buildings. KNX is the successor to, and convergence of, three previous standards: the European Home Systems Protocol (EHS), BatiBUS, and the European Installation Bus (EIB or Instabus). The KNX standard is administered by the Konnex Association.”

http://en.wikipedia.org/wiki/KNX_(standard){.external .free}

KNX has definitely been used to connect room stats. E.g. KNX BRINGS 21st CENTURY CONTROL TO HEATING AND OTHER SERVICES IN FARMHOUSE RENOVATION{.external .text}

A Google Shopping search for “KNX room thermostat” suggests they start at £125.

There’s a KNX touch panel with integrated web server for access from the web / iPhone http://www.iddero.com/en/products.php

And there’s a KNX Siemens IP viewer gateway thingy for about £500 http://www.knxstore.com/knxstore/product/8/siemens-knx-ip-viewer-n-151/lang/en

There’s a KNX valve actuator for £50 http://www.knxstore.com/knxstore/product/48/siemens-knx-230v-ac-valve-drive-electro-therm-ap-560r



An interesting forum topic on OpenTherm boilers and room stats: http://www.diynot.com/forums/viewtopic.php?t=222182&postdays=0&postorder=asc&start=0

Tech notes

  • The connector for TRVs is “swivel nut (M 30x1.5)”

Quick rant

Having been through the pain of searching for decent home heating systems, I can’t help thinking that this market is long overdue a fundamental shake up.  Most “modern” products are obscenely over priced, come with a miserable feature set and are pro-install only.  If someone can come up with a decent-priced, DIY-installed, wireless heating control system, with a TCP/IP bridge and an open API (to allow 3rd party developers to build iOS / Android apps) then I’ll be first in the queue.  The market for thermostats seems to be stuck in the mid-1990s.  Honeywell, for example, lists “high-definition full-color display” as the most important feature of its top-spec thermostats, FFS; yet a 2.5” colour TFT touch screen is only £10 from Farnell.

update 13/3/2012: Ars Technica has an article entitled “The five technologies that will transform homes of the future.”  Guess what number 2 is?  Smart heating and power systems!  (they don’t mention disaggregation though)

update 7/12/2015http://www.wifithing.com - “internet of things made simple” have some home heating controls.