Changing a thermostat


Postby flower power » Tue Oct 28, 2008 9:13 pm

hi,

Just wanted to know your thoughts on changing a thermostat. We have inherited an old satchwell thermostat in our new home and it is not very sensitive to temperature change, so is therefore not really doing it's job! How easy is it to change a thermostat? I am a keen DIYer.
Can you suggest a good digital one and where to buy?

Many thanks :wink:
flower power
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Joined: Tue Oct 28, 2008 9:00 pm

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Postby ericmark » Wed Oct 29, 2008 1:14 pm

I changed mine for a Horstmann DRT2 from screwfix which unlike the original also has a clock built in so instead of using original time clock I use the one in thermostat which instead of switching off and on it changes the temperature setting at different times of day. It was not expensive and works very well 4 time zones Mon - Fri and 2 each Sat and Sun so in all 8 time periods. So impressed also fitted one for my daughter.
Works very well in my house and easy to fit. Only problem have to change batteries about every 2 years but only AAA cells.

However in my daughters house she has thermostat radiator valves and not quite so good as a result as although it keeps kitchen to correct temperature when it cools down at night and comes on as below 16 degs set kitchen has least radiator area of house so rest of house heats up to full 20 degs before kitchen has warmed up the 1 deg temp span which is factory set.

It does show the room temperature and time which the old mechanical type did not. And if my daughter set the night temp lower it would work OK as time clock and thermostat in the summer with thermostat radiator valves you still need a thermostat to stop cycling of boiler and it does that OK.

Eric
ericmark


Postby flower power » Wed Oct 29, 2008 4:54 pm

Thanks for your thoughts Eric,

I went out today and bought a Salus Digital Electronic Thermostat, it looks quite easy to install, but when I took the back off the old Satchwell thermostat it has 4 wires not three,

They are coloured red, white, blue and red, so I presume
red = L
blue = neutral
white = close
yellow = open

If anyone can help me to attach the new thermostat, which only wants a L and a Switched Live I'd appreciate the help
flower power
Posts: 5
Joined: Tue Oct 28, 2008 9:00 pm


Postby ericmark » Wed Oct 29, 2008 7:40 pm

Sorry three wires plus earth I would expect but no idea why four. It is normal for old thermostats to have a neutral connection which is required for temperature compensation to reduce the difference between switch on and off temperatures this is not required on the new type. I would have thought the old thermostat would have been marked as to what each terminal did and with exception of neutral will be like for like. Some boilers do require no volt contacts but not very common sorry.
Eric
ericmark


Postby flower power » Wed Oct 29, 2008 10:24 pm

Hi Eric, thanks once again for your comments, on further investigation it looks like the yellow is the earth.

The new thermostat only wants Live and Switch Live wired in. So I am thinking Red for Live and white for Live Switch, if I wire it up this way can I damage the unit if it is not correct?

thanks
flower power
Posts: 5
Joined: Tue Oct 28, 2008 9:00 pm


Postby ericmark » Thu Oct 30, 2008 8:21 am

If you connect an earth or neutral to line vir the switch it is likely to blow something.
But what you account does seem to make sense and is likely correct.
Eric
ericmark


Postby flower power » Thu Oct 30, 2008 10:58 am

Thanks for your help, might get someone in then, in case I blow the circuit!
flower power
Posts: 5
Joined: Tue Oct 28, 2008 9:00 pm


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