Room stat puzzle with pics

[levelhead]

Hi, hoping I can get some advice on a room stat replacement.

I have a Siemens TLX 2356 which no longer functions, I wanted to replace it with a digital one so I bought a 'UPONOR' DS1-EL

I realise I may have to add another multi core cable but needed some help with the final connection.

My old unit only has two, the live and neutral although i realise the neutral may not be used as such in the setup.

The new unit has a live, neutral and a 'down arrow' symbol? and a symbol for a clock.

There are no zone valves on my system which is gravity fed, there are no other ports etc, it's a very basic system.

Just need to know which wires to connect in the new thermostat based on my current setup.

I have attached pictures of the setup in the junction box, my old stat and the diagram from new stat.

Thanks for looking

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[gavgas]

Your existing thermostat just turns the pump on and off when the timer requires it, it's therefore just a switch on the live conductors. The new thermostat requires a live and neutral as it's electronic so a new or additional cable is needed. If you run a neutral to it from the box, be aware that the temperature will only be displayed when the heating timer is on, the lives are wired the same way as before.

Hope that helps

Gavin

 

[JohnD]

My old unit only has two, the live and neutral although i realise the neutral may not be used as such in the setup.

No, it had a live and a switched live.

 

[levelhead]

Thanks John, I thought that probably would be the case re the switched live using the neutral cable.

Hi gavgas, thanks for the quick reply.

Just so I have this right the live and the 'down arrow' symbol would be more or less the old setup like for like with the exception that the new stat would have a genuine dedicated neutral making three connections.

It is the 'down arrow' symbol on the new unit that is confusing me, just want to make sure i have it correct.

The RT+ and RT_ are for a floor sensor so not req'd and the clock symbol is also not req'd as far as I can tell. I take it the new digital stat does not have an earth? or am i still getting it wrong.

 

[hazetimesfive]

two switched lives tbh

 

[gavgas]

yep, that's it, down arrow is switched live (the one that goes to pump live) although why they couldn't use SL or whatever is beyond me.

 

[Agile]

If its directly switching the pump then that is inductive and could cause arcing when the stat switches it off.

It may not be rated for that kind of load and using it could shorten its life.

If I had to use it then I would connect a snubber network across the pump terminals.

Tony

 

[gavgas]

would the start and run cap not take care of any transients and spikes or am I barking up the wrong tree?

 

[hazetimesfive]

whats a snubber network? don't remember that being mentioned at school

 

[levelhead]

Many thanks for all who replied, really appreciate all your help.

Great forum

 

[stem]

Room stat puzzle with pics

The puzzle for me is why no one has commented on the state of the wiring.

The wiring is dangerous and needs some urgent attention. Everything about it is wrong. It appears to be hanging loose and unsupported. It should be clipped in place, or enclosed in trunking.

The sleeving on the earths is missing and there are no cable grips at the junction box.

Neutral conductors are used as live wires and not identified as such with appropriate sleeves. Which explains your earlier confusion.

In addition you have a metal flush mounting pattress for the FCU which is totally unsuitable for surface mounting, and I'd like to bet it's not fitted with rubber grommets either..............no, thought not.

The connections to the thermostat are also poor, the wires are stripped back way too much and the conductors are not fully under the terminal screws. There should be little or no copper showing.