Changing a 3 wire roomstat to a digital 2 wire

[Kugaman]

Hi,

Hoping someone can help, I would like to replace my old 3 wire dial room stat with a new 2 wire digital one, the problem I have is on my old stat the wiring is as follows,
the terminals from left to right are marked - 4, 5, 1, 3, 2 and wired 4 = Blue, 5 = empty, 1 = Brown, 3 = empty & 2 = black.
On the new stat I have terminals L & SL which I assume to mean 'live' and 'switched live' could anyone advise on which of my wires need to go where on the new stat or is it not possible.
Many Thanks.

 

[Nozzle]

Does the old stat have a wiring diagram on it, or give us a clue as the name of the thing to find a diagram.

Nozzle

 

[Taylortwocities]

Like most (common) queries, the answer is on the wonderful WIKI

//www.diynot.com/wiki/Electrics:How-to-replace-a-room-stat

 

[winston1]

At a guess the brown is line, blue neutral, and black switched live. But one should not rely on guesses. The neutral is so an excellerator can operate to give more precise control. It seems your new digital one does not have this feature so is inferior but I suppose it looks "cool"!

 

[Taylortwocities]

The neutral is so an excellerator

The correct term is Accelerator. You must use the correct words or people will not know what is meant!

On what basis do you feel that a digital thermostat is in some way "inferior" to the older (bimetallic strips and gas-filled bellows) types?

 

[Kugaman]

Hi,

Thanks for all replies, in answer to what make it is a Danfoss, no wiring diagram I'm afraid, I've attached pictures hope this helps.

 

[deadshort]

At a guess the brown is line, blue neutral, and black switched live. But one should not rely on guesses. The neutral is so an excellerator can operate to give more precise control. It seems your new digital one does not have this feature so is inferior but I suppose it looks "cool"!

………. should that not be 'hot' ?

DS

 

[Kugaman]

Sorry, I've found a diagram inside the cover of the Danfoss, please see picture.

 

[Taylortwocities]

As above. Brown=live, Black=switched live and blue is neutral - not used on your digital 'stat. Put the blue in an insulated terminal block as detailed in the WIKI

 

[deadshort]

Hi,

Brown =L
Black =SL
Blue = not used make safe in connector block.

DS

 

[Kugaman]

Got it, thanks for all your help

 

[winston1]

The correct term is Accelerator. You must use the correct words or people will not know what is meant!

On what basis do you feel that a digital thermostat is in some way "inferior" to the older (bimetallic strips and gas-filled bellows) types?

Thanks for the spelling typo.

Inferior as no accelerator, so no so precise control as already explained.

 

[JohnW2]

Inferior as no accelerator, so no so precise control as already explained.

Similar functionality to that of a thermal accelerator can surely be achieved by the electronics in a digital one, can't it?

Kind Regards, John

 

[winston1]

Similar functionality to that of a thermal accelerator can surely be achieved by the electronics in a digital one, can't it?

Kind Regards, John

Maybe. Seems additional complication (i.e. things to go wrong) for no gain however.

 

[Nozzle]

luddite1 - solid state electronics, in ambient temperatures, without dirt or vibration very, very, rarely, if ever, go wrong. EVER. Your coveted accelerator "function" is a kludge to make an otherwise slow-to-respond bimetallic strip actually respond without having huge hysteresis. An electronic version on the other hand doesn't need such as function as the thermistor has thermal inertia tens if not hundreds of times smaller that said strip.

Nozzle