Quick Thermostat Wiring Question

[EFLImpudence]

If you're talking about the wireless sensor/transmitter, that presumably requires no wires at all (the clue is in the "wireless"!),

True, but there must be a receiver which requires power, and connection to the boiler.
The idea of a battery powered receiver would be pointless because it can be placed near the supply and/or boiler.
The one in your link states " All models in the range are available in hard-wired and wireless versions".

so I'm not sure why they would comment specifically that it was ideal for upgrading a 2-wire stat. I think I must be getting confused!

Because, I think, if not used as wireless it allows different temperature ranges and, because of the battery, can operate with only the two wires present and has a display.

If used as wireless then it is conventional and the receiver may as well be put in the right place.

In either case, it does not seem to have a clock but merely a day/night selector switch.

It, presumably does not have the transmitter if you do not buy the wireless version (that would be a waste but nowadays, who knows?)

The thermostat on its own is £32.
http://www.heatingcontrolsonline.co.uk/danfoss-randall-retb-room-thermostat-p-243.html


There are also better ones than this which are fully programmable (times and temperature) which are battery powered so can use the two wires.
http://www.honeywelluk.com/products...-Digital/CM907-7-Day-Programmable-Thermostat/

 

[JohnW2]

If you're talking about the wireless sensor/transmitter, that presumably requires no wires at all (the clue is in the "wireless"!),

True, but there must be a receiver which requires power, and connection to the boiler.

Certainly a connection to the boiler. As for power, what's all this about 'battery-powered' thermostats, then? If it's wireless, then the transmitter/sensor is presumably always battery-powered (or isn't it?).

The idea of a battery powered receiver would be pointless because it can be placed near the supply and/or boiler.

'Pointless' in general, I suppose - but, as I've been saying would (if it existed, which maybe it doesn't) be 'ideal' for the OP, to enable him to do what he wanted as a 5 minute DIY job!

so I'm not sure why they would comment specifically that it was ideal for upgrading a 2-wire stat. I think I must be getting confused!

Because, I think, if not used as wireless it allows different temperature ranges and, because of the battery, can operate with only the two wires present and has a display.

Yes, although it does not make it clear, I suppose the comment of theirs I've been quoting may not relate to the wireless ones.

Kind Regards, John

 

[ban-all-sheds]

I must be having a bad day, because I don't understand the logic of that. Why would they regard it as 'ideal' if, as you say, the 'more sophisticated replacement' that one wanted to install in the same place could not be powered by the 2 available wires at that place? I must be missing something!

It's battery powered.

That's what makes it ideal for replacing an old 2-wire wired one, because being battery powered means it can go there, because being battery powered means it doesn't need power from any wires. Which is ideal when there isn't any power available from wires.

 

[JohnW2]

I must be having a bad day, because I don't understand the logic of that. Why would they regard it as 'ideal' if, as you say, the 'more sophisticated replacement' that one wanted to install in the same place could not be powered by the 2 available wires at that place? I must be missing something!

It's battery powered. ... That's what makes it ideal for replacing an old 2-wire wired one, because being battery powered means it can go there, because being battery powered means it doesn't need power from any wires. Which is ideal when there isn't any power available from wires.

I'm still confused. The single 'unit' of the non-wireless version is presumably equivalent to the receiver of the wireless version (both those being the things that do the switching of the boiler) - and I thought we had established that the receivers are probably not battery-powered?

Kind Regards, John

 

[EFLImpudence]

The single 'unit' of the non-wireless version is presumably equivalent to the receiver of the wireless version

No, it is the thermostat (transmitter) which in non-wireless version is wired.

(both those being the things that do the switching of the boiler)

But not at the same time.

and I thought we had established that the receivers are probably not battery-powered?

With a receiver being used the transmitter (thermostat) will not be wired.

 

[ban-all-sheds]

I'm still confused. The single 'unit' of the non-wireless version is presumably equivalent to the receiver of the wireless version (both those being the things that do the switching of the boiler) - and I thought we had established that the receivers are probably not battery-powered?

Well OK - the same ideal nature of a battery powered one works there too.

An integrated unit making and breaking the connection between the two wires from the boiler needs power to do it's stuff, as it's not just a mechanical bimetallic strip and a cam. But with only two wires it can't get its power from them, so it has a battery.

It doesn't matter whether the switching is done in the controller, or in a receiver which the controller talks to over a wireless connection, the controller needs power, so if it can't get it from wires it gets it from a battery.

You might also find a battery powered receiver useful, but it would be pretty unlikely to be very useful because it would be pretty unlikely that you'd be unable to supply it with wired power.

Forget all the wireless stuff for a moment - if you wanted to replace a dumb mechanical bimetallic strip thermostat with one which you could program, and possibly do all sorts of things with (like have it learn), but all you had coming out of the wall were the two conductors from the boiler going to the volt-free contacts in the old thermostat, would you think it would be jolly useful to have your new intelligent programmer work off batteries?

 

[JohnW2]

The single 'unit' of the non-wireless version is presumably equivalent to the receiver of the wireless version

No, it is the thermostat (transmitter) which in non-wireless version is wired.

I'm coming to think that we are maybe into terminology issues yet again! With a single-unit non-wireless version, there is obviously no such thing (or concept) as a 'transmitter'. In such a case, the 'thermostat' (by which I assume you mean temperature sensor) has to be connected, via any intervening electronics (which need power), to the boiler it is controlling. It therefore has to be 'wired', regardless of how the electronics get their power.

Kind Regards, John

 

[JohnW2]

You might also find a battery powered receiver useful, but it would be pretty unlikely to be very useful because it would be pretty unlikely that you'd be unable to supply it with wired power.

That's really the point I've been making. I've agreed that such an animal would not generally be very useful - since, for the reason you give, it would not often be 'necessary'. However, in the context of this thread, the OP's specific (and unusual) position is perhaps the exception that proves that rule - for him, the availability of a battery-powered receiver would have turned his task into a very easy DIY job (simply just replacing his current 2-wire thermostat with a 2-wire battery-powered receiver).

Kind Regards, John

 

[EFLImpudence]

The single 'unit' of the non-wireless version is presumably equivalent to the receiver of the wireless version

No, it is the thermostat (transmitter) which in non-wireless version is wired.

I'm coming to think that we are maybe into terminology issues yet again! With a single-unit non-wireless version, there is obviously no such thing (or concept) as a 'transmitter'.

Well, not in the RF sense but it transmits the result of temperature measurement to the boiler.

In such a case, the 'thermostat' (by which I assume you mean temperature sensor) has to be connected, via any intervening electronics (which need power), to the boiler it is controlling. It therefore has to be 'wired', regardless of how the electronics get their power.

There are no intervening electronics.
The electronics in this case are merely to operate the display, measure the temperature and make a switch.

 

[EFLImpudence]

However, in the context of this thread, the OP's specific (and unusual) position is perhaps the exception that proves that rule - for him, the availability of a battery-powered receiver would have turned his task into a very easy DIY job (simply just replacing his current 2-wire thermostat with a 2-wire battery-powered receiver).

It would.

Would it then be advertised thus:
"This makes it an ideal solution for system
upgrades when replacing conventional electromechanical
two-wire thermostats which have foolishly been fitted on the landing?".

 

[JohnW2]

I'm coming to think that we are maybe into terminology issues yet again! With a single-unit non-wireless version, there is obviously no such thing (or concept) as a 'transmitter'.

Well, not in the RF sense but it transmits the result of temperature measurement to the boiler.

Indeed. As I said, I think there may have been some terminology-based confusions here!

In such a case, the 'thermostat' (by which I assume you mean temperature sensor) has to be connected, via any intervening electronics (which need power), to the boiler it is controlling. It therefore has to be 'wired', regardless of how the electronics get their power.

There are no intervening electronics. The electronics in this case are merely to operate the display, measure the temperature and make a switch.

I think this may be getting ultra-confusing! In what sense are you now using 'thermostat'? We were talking about non-wireless ones and, in that case, if they are 'clever' (programmable or whatever) there must be some electronics (and, presumably, a relay) 'intervening' between the temperature sensor (which I thought is what you were calling the 'thermostat') and the switch wires to the boiler, mustn't there?

Kind Regards, John

 

[JohnW2]

However, in the context of this thread, the OP's specific (and unusual) position is perhaps the exception that proves that rule - for him, the availability of a battery-powered receiver would have turned his task into a very easy DIY job (simply just replacing his current 2-wire thermostat with a 2-wire battery-powered receiver).

It would.

That's really the point (and the only point) I've been trying to make all along. However, it seems that it's probably flawed by the fact that the devices I have been postulating probably don't exist!

Would it then be advertised thus: "This makes it an ideal solution for system upgrades when replacing conventional electromechanical two-wire thermostats which have foolishly been fitted on the landing?".

Maybe However, I think you may be underestimating the potential market. Whilst there probably are not too many 2-wire thermostats which have been 'foolishly fitted on the landing', there probably are a good few which 'semi-foolishly have been fitted in non-ideal locations'.

Kind Regards, John