Digital room thermostats...

loveplumbing · 3 Sep 2008

Hi

I am thinking about changing my room stat to a new modern look programmable digi room stat!

is the wiring the same.. ie. 3 wires, common, call and sat?

i have looked at a few sites, drayton, etc to look at what's available.

any recommendations from personal preference?

also one of the spec's i read about room stats (DRAYTON) said "battery powered" : does this mean the lcd digital display is battery powered? i guess it's still powered (via the wiring centre) the same way as normal room stats are, hence the 3 wires also...

seco services · 3 Sep 2008

http://www.plumbworld.co.uk/images/pwiv0012instructions.pdf

example can be battery or mains supply.
live, neutral.
calling for heat, common etc

steved101 · 3 Sep 2008

hi - yes programmable room stats are operated by a battery and usually installed/replaced in the same way as a normal room stat (ie 3 wires, common, call and sat (1, 2 & 3 usually).

twgas · 3 Sep 2008

when you get one make sure you check the instructions re wiring, they often dont use a neutral.

steved101 · 3 Sep 2008

twgas is right-if your old room stat uses a neutral then remove this (also from the junction box end as well as the room stat end). you just need the 3 wires, common, call and sat.

D_Hailsham · 3 Sep 2008

loveplumbing said:
is the wiring the same.. ie. 3 wires, common, call and sat?

Mechanical stats had: Live, Neutral, Switched Live(call) the Sat terminal was rarely used. Digital stats only need a live and switched live as the neutral is no longer required.

any recommendations from personal preference?

Honeywell CM900 series

There are two types of boilers: 1. those which get their 240v supply voltage via the thermostat; 2. Those which have an independent 240v supply and have a pair of "volt free" terminals to which the programmer/thermostat is connected.

Most programmers can handle both types of boiler; just make sure which type you need before you buy.

does this mean the lcd digital display is battery powered?

Many digital programmers use a battery to run the internal electronics and display.

There are several possibilities:

Mains run programmer - switched 240v to boiler: needs 3 wires (+ earth)
Mains run programmer - volt free boiler: needs 4 wires (+ earth)
Battery run programmer - switched 240v to boiler (needs 2 wires)
Battery run programmer - volt free switching to boiler (needs 2 wires)

steved101 · 3 Sep 2008

the DRAYTON room stat (digi) i have has HTG SAT, HTG CALL and COM terminal's (3) in total. The NEUTRAL is not required.

If your old room stat has 3 terminals (probably common, call and sat, then you may need a multimeter to make sure the swap the correct wires!!

twgas · 3 Sep 2008

If your old room stat has 3 terminals (probably common, call and sat,

not many systems use a "sat" on room stat, third wire is more likely a neutral.

loveplumbing · 3 Sep 2008

hi thanks all for your responses

i am slightly confused now! ...

my room stat currently has 3 terminals, i believe them to be common, call and satisfied.

if the new room stat has 3 terminals these obviously just need swapping over (will the new room stat have instructions for this to make it clearer)?

secondly, if my original room stat DOES have 4 terminals as D_Hailsham stated - what do I do with the NEUTRAL terminal that does not need to be used for a digi room stat? do i just ignore it ??

Thanks.

D_Hailsham · 3 Sep 2008

loveplumbing said:
my room stat currently has 3 terminals, i believe them to be common, call and satisfied.

What make/model is you existing stat?
Which terminals have wires connected to them?

if the new room stat has 3 terminals these obviously just need swapping over

Not necessarily correct. If one of the wires is a neutral and the new stat is battery operated, the neutral will not be required and should be disconnected at both ends and cut short. (Don't assume that a blue wire is necessarily a neutral)[/quote]

Easiest solution

Buy a new programmer
Post info about your old stat, your new stat and your boiler.
Someone will tell you what to do

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Digital room thermostats...

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