Need help wiring a new digital thermostat

[marc1977]

Hi,

I am removing an old Honeywell thermostat and trying to install a new Drayton Digstat +3. However i cannot understand what wire needs to go where.

The old honeywell wires were as follows:

Brown wire in position 1 which is listed as live on the thermostat diagram
Blue wire in position 2 which is apparantly neutral
Yellow/green wire in posiion which is also apparantly neutral.

On the new thermostat I have 3 connections:

C = I believe the brown live goes here??
ON = I believe the blue neutral goes here??
OFF = I put the yellow / green here ?

Any ideas what this should be? when I try the above the fuse blows on the plug that powers the whole central heating electrics.

Thanks

Marc

 

[Billy Bob Bob]

you have a wire missing you should have red,yellow,blue ,yellow and green if your connecting yellow/green to live this will cause a problem as its a earth wire,what system do you have?

 

[marc1977]

Definitely only those 3 wires. It is a standard open vented system.

 

[Billy Bob Bob]

think you need a plumber or sparks the neutral has to be re utilised for a switched live by altering in your wiring centre do you know if its a fully pumped system?

 

[Blake]

red/brown wire to common

yellow wire to call for heat (switched live) to normally on

Stat may not require neutral

 

[Billy Bob Bob]

red/brown wire to common
Blue is neutral
yellow wire to call for heat

yes but the op is connecting a green/yellow cable this is a earth or someone has wrongly used it as a control wire

 

[gasmarc]

sounds good to me blue wire is for the antisapater sorry cannot spell

 

[clydey]

yellow green signifies earth
try c brown on blue
nothing connected to off ie - if the digistat has a square within a square symbol it does not require an earth and so if there is no earth connector then tape up the green and yellow wire so that it cannot touch anything
if all works out then the blue wire requires a brown piece of tape at the connection point to signify that it is a switched live and NOT a neutral
not really familiar with digistat but schematic looks simple enough
hope this helps cheers
also the power is separate on this model and comes through the switch fused spur or plug/socket arrangement including a 3 amp fuse and goes to the 2 separate pins
ie 3 pins for thermostat - use 2 and live/ neutral from mains supply

 

[marc1977]

Just tried C = Brown , ON = Blue. the thermostat seems to work but the boiler does not come on at all?

Happy new year everyone by the way!

 

[Billy Bob Bob]

your better off getting some one in TBH you could damage something or yourself

 

[Blake]

So blue can not be the switched live then, try the earth in the on as that may be the switched live. Or before you do that, remove the batteries from the unit and put them back in again as this will reset it as they can be a bit tempramental.

 

[clydey]

this means that the blue is a switched live the thermostat closes and powers the boiler
q is thermostat programed and calling for heat
ie is there 230 volts across switched blue and neutral
no then the thermostat is not calling for heat
yes then thermostat wired ok but boiler not wired properly
also see if green/yellow has any voltage between it and neutral
hope you are electrically knowledgeable to work safely

 

[Billy Bob Bob]

this means that the blue is a switched live the thermostat closes and powers the boiler
q is thermostat programed and calling for heat
ie is there 230 volts across switched blue and neutral
no then the thermostat is not calling for heat
yes then thermostat wired ok but boiler not wired properly
hope you are electrically knowledgeable to work safely

fuses blowing form your own conclusions

 

[marc1977]

OK tried C = Brown, Yellow/Green = ON. still no luck as the boiler does not come on. I took the batteried out the thermostat. I can hear the relat switching on as it drops below the set temperature so it seems to be working ok. Shall i just try every combination

 

[Billy Bob Bob]

by the sound of it your earth cable has been used as a control wire,which is very wrong that means theres no earth protection,for the cable in the event of a fault or for you if you get it wrong if you get a shock out of this the only thing that can track the electricity to earth is you so i would stop trying and get some one in

 

[clydey]

got a multimeter yes/no
and is it a basic boiler or a combi or a boiler operating through a zone valve
also gasman is right that if it is not a true earth then the cable needs to be changed to a three core and earth

 

[Billy Bob Bob]

i give up

 

[marc1977]

According to the instructions the new thermostat is double earthed and does not require an earth connection. Ive tried tracing all 3 wires to see where they are connected into but they all go into a honeywell circuit box that is just a mass of wires so i cant work out what does what right now. However i would have thought it must have been Brown = C and either blue or yellow/green = ON but noether work?

 

[Billy Bob Bob]

the stat does not need a earth but the cable does

 

[marc1977]

Yes i have a multi meter and it is a standard open vented boiler with no zone valve. can you help me identify which wires should have a current?

 

[Puddle]

Nothing must be anything,boiler probably not coming on now as you may well have blown a pcb or solenoid,if you have not,you have been very lucky,stop trying to blow the system up or set light to the house and get someone in who knows what they are doing,

If you are carrying out tests correctly no circuits will have current in them when you are testing them

try to make it to the new new year !!

imho

 

[Billy Bob Bob]

sense at last,i have dented the wall banging my head against it LOL

 

[Blake]

Why are you trying to wire a new thermostat at this time of night anyway??? Get down the pub and celebrate the new year in.....that's where I'm off. Happy new year all

 

[marc1977]

boiler is still working fine, i reconnect the old thermostart after each attempt to check that. I cannot afford a profesional but if you cannot help then that is fine, i understand.

 

[Billy Bob Bob]

Why are you trying to wire a new thermostat at this time of night anyway??? Get down the pub and celebrate the new year in.....that's where I'm off. Happy new year all

you to mate,have a good one

 

[clydey]

its just been flagged up that it is possible that the earth (green/yellow) has been used as a switched live
if this is so then there is no earth on the cable and it is dangerous.
without being there and with your limited knowledge you could be in a dangerous situation
as not everyone would wire the honeywell conventionally
ie connector 1 live con 2 neutral con 3 earth
when it blew the fuse i assumed you had an earth connected that shorted out the live feed
knowledgeable and skilled people dont just try any combination as its not like baking a cake
you may have started with an unsafe situation that needs to be checked by either a heating engineer or a sparky with central heating wiring experience
its better to get it checked by a pro
sorry best i can do for you
cheers

 

[marc1977]

ok below is a picture of my old setup. I haved a brown wire in position 1, a blue in position 2 and a yellow/green at position 3. Can anyine tell me which relates to C, ON & OFF on the new stat?