Room thermostat wiring conundrum

[Dave Plowman (News]

Do you really need the ability to control your thermostat from a mobile phone, etc? Making it more expensive and less reliable? Purely to be in fashion?

[Roger Mills]

Not necessarily - although it almost certainly is.

The traditional bi-metallic stat didn't need electricity to drive it. The only reason for the neutral was to provide a return for the accelerator heater - but the stat would still work if you didn't connect it.

[Roger Mills]

There needs to be a *bit* of hysteresis to avoid rapid cycling - but mechanical stats have this naturally, with a margin between the on and off points. *However* if the room stat only switches the heating off when the set point is reached, the rads are still hot and the room temperature will go on rising. Not only does this waste heat, but the room then takes a long time to cool and the occupants start to feel cold before the heating comes on again.

The accelerator heater fools the stat into thinking that the set point has been reached a bit before it is actually reached. This greatly reduces the overshoot.

[JohnP]

"Dave Plowman (News)" [e-mail]> wrote in news: [e-mail]:

Yes - people call in a Plumber to fix a boiler! People expect an electrician to be able to fix a washing machine.

What some tradesmen lack is an understanding of "Control Logic".

Time Served Qualified Plumber - what does this mean - can bend and fit pipes?

I recall at a place where I worked we employed "Instalation Electricians! and "Maintenance Electricians" Different aptitudes.

[Pancho]

You sound convincing. I would need to think long and hard to get it straight in my head. It was six years ago and I may have confused things then or in my memory now.

A provisional apology to TNP.

[Pancho]

Yebbut, I am a software developer, so the technology is slightly more accessible to me.

Whist I appreciate this technology might not be there yet, it is useful and the actual cpu chip part of the controller should only cost pennies. Longterm/theoretically it could become very reliable.

[ARW]

Not on a heating room stat.

[Fredxx]

If the cylinder stat is remote from all the other wiring it might make sense to swap cylinder stat and room stat over, and swap the ports on a diverter accordingly.

Just to play devil's advocate :-)

[Peter Johnson]

It was 5A, which I suspect was my doing, when I installed the previous timer, but I've been to B&Q and got a pack of 3A, so I am now compliant, and have spares. Thanks.

[Roger Hayter]

I've got a traditional one in my shower room, on a SELV circuit which wouldn't work the heater anyway.

[Roger Mills]

Most people probably don't. But the Hive system at my holiday flat has been very useful during the Covid crisis - enabling me to see what is happening temperature-wise when I'm unable to visit.

[Dave Plowman (News]

I can see the point of a wireless stat if a new installation. But not when the cables are already there.

And having a boiler which can be programmed by Wi-Fi etc. But not a stat.

[alan_m]

I've seen many room stats placed in positions where they were easy to wire rather than in a room that you may want the most control. A wireless room stat enables the receiver to remain in the previous position and the transmitter to be moved to an alternative position in the house.

My thermostat used to be upstairs in the stair well but now better positioned in the "living room" where most TV is watched and most play on the laptop occurs.

[Dave Plowman (News]

I'd say if the theremostat has simply been put in the most convenient position for the installer, it won't be the only bodge in your system. ;-)

[Andrew]

No-one seems to have used the magical phrase 'volt-free' which I come across in other documentation. Presumably the replacement is 'volt-free' (even though it has a battery) ?.

[bert]

Oh come on. You know the rule. If a fuse blows - fit a bigger one and tune for maximum smoke.

[bert]

Having had one of these wired without the neutral by the installer I can assure you it is there to reduce the hysteresis. The old style had enough without any assistance.

[bert]

My very old (40 yrs+) mechanical stat worked very well without a neutral. When the system was replaced about 10+ yrs ago the installer didn't bother with neutral as none was present. So I used the earth wire as neutral and performance was improved. ISTR I was advised in here that that was a bit naughty so I have since replaced it with a Honeywell battery operated electronic one which doesn't require neutral.

[John J]

I spent some time training service leavers to become electricians. The company I worked for also ran training courses for plumbers and they came to me for basic electrics as part of their course. The intent was to educate them sufficient to safely install (in compliance with building and wiring regulations) power supplies, bonding and controls for central heating, showers etc. On completion of their course they had a portfolio folder with all the stuff they had covered and been assessed as doing correctly at least once. They could of course forget it all when they went out of the gate .......

[Mike Clarke]

It might have been common once for the same person to deal with both plumbing and electrical work. Back in the 1950s I remember seeing tradesmen advertising themselves as "plumber and electrician".