We recently moved into a new (to me, not new build) home and are already missing the Honeywell 7 day wireless thermostat we used to have. The ability to move the stat around the house was very useful.

New house has a traditional mechanical stat with 4 wires, I think I should be able to replace it with the Heatmiser unit for more effective heating control.

Do let us know how it goes.

And as you say, you can use WiFi to talk to the system too, as an addon goodie. This does make a lot of sense, in that via your firewall you can serve the controls so you can remotely switch your heating from your smartphone.

Using RF as the primary control channel to your boiler does sound like it would make it less reliable. A client of mine had a Buderus wireless controller: he took it out and replaced it with a wired one. He couldn’t use a standard one because this German boiler is so “clever”.

But good luck.

I suppose the issue with implementing something clever over the mains wiring is that there are doubtless regulatory issues and a lot of work in coming up with a new protocol, not to mention the fact that in an increasing number of homes, there may be other technologies signalling over the mains, like HomePlug, and you’d have to ensure you didn’t interfere with that too.

Embedding HomePlug in the thermostat, and in a slave receiver would probably put the cost up quite a bit, and complicate things more; meanwhile, there are lots of modules easily available to perform things like switching functions via RF in the unlicensed bands

And, I agree, running neutral via the earth conductor is really naughty/stupid. There is no requirement for E & N to be at the same potential; usually are close. It is also very bad practice because there is then no earth conductor the unit, and if the house wiring isn’t 17th edition you have no leakage protection at all.

@everybody:
Most boilers just need to know if it is ok to be on or not: timer+temperature. This is traditionally achieved by having two switches in series: when time and temp are closed then current flows.

It is annoying that you need WiFi to do the control, because the bandwidth you require is so tiny. There are low bandwidth protocols, such as ANT+, but only works over 3m. That will work off a single CR2032 for several years.

In a real house the enduser control panel is fixed, and is usually in the same place as the old mechanical thermostat, so I don’t see this as a problem. Kinda silly that your clever controller just uses the wire to get juice and then uses wireless to get the signal, when the original copper pair can do the job nicely.

No standards on the horizon for clever over-wire protocols and hardware? Then you can have a slave unit by the boiler and the panel elsewhere. Some panels/slaves communicate over wire, and others via some wireless.

For as long as I’ve had any interest, and more, most mechanical room thermostats have had a compensating heater which means they need a neutral connection. Without it they tend to have possibly several degrees of hysteresis between switch off and switch on temperatures which causes the room to heat up and cool down in an uncomfortable manner.
It could be that the person who wired it up used the earth for this. It’s wrong, but I’ve seen worse.

If you really want to go overboard, you can get systems that will control every room individually, and connect to your network for setup and monitoring. Do be sitting down before you look at the prices though.