Heating not working after replacing room stat...

[shorn]

I have bought a new room thermostat to replace our old one.

The old one is a dial type (i think it was a Drayton one), and when i removed this there was three wires. red, blue, yellow, and yellow/green.

The red was in the Live point, the blue was in the Neutral point and the yellow was in a point marked "3" (there is four numbered points in total.)

and the yellow/green, was obviously earthed.

The new thermostat i have is a Honeywell DT200, and this has three connection points

here is the installation guide http://content.honeywell.com/uk/homes/Technical/DT200/DT200Inst.pdf

now im not sure what to connect where????

any help appreciated, (i have checked other topics but cannot find anything that relates closely!)

thanks

 

[bernardgreen]

Red to A ( Live to Common )

Yellow to B ( Switched live to heating required )

Switch in the thermostat connects A to B when heating is needed.


Blue to nothing, termininate it with a terminal block.

Neutral is not needed in the new thermostat.

 

[GaryMo]

It looks like a neutral isn't needed so connect permanent live (red) to terminal A and switched live (yellow) to terminal B.
Make sure the unused neutral (blue) terminated into a single insulated terminal block.

[EDIT] Too slow!!

 

[shorn]

OK I have just done this, connected live to a and switched live to b, turnt all back on and turnt the temp up on the new thermostat. This now shows a flame symbol to indicate that the heating needs to be running to raise the temp, however the boiler in the kitchen is not firing up. (it was with thehh old thermostat)

The upstairs programmer is set to constant CH aswell.

 

[shorn]

is it possible that the yellow (switched live) should be connected to terminal c?

 

[bernardgreen]

Did you at any time connect the neutral to the new thermostat ?

A lot of people do and this wrecks the relay contacts inside the thermostat.

Have you tried turning the thermostat up and down so the flame sign goes on and off. There should be a click sound ( the relay operating ) as the flame sign changes On Off On.....

 

[shorn]

It does make a click when i set the temperature below the current room temp and it clicks when the flame comes on.

 

[shorn]

i did initally connect the N aswell, does the clicking mean it is stil working though??

 

[GaryMo]

i did initally connect the N aswell, does the clicking mean it is stil working though??

Best bet is to (assuming you have one) disconnect all cables and put a multimeter on low ohms setting between A and B then monitor the change in state of the stat by turning the temperature up and down.
This will verify the stat is OK.

If all is well then temporarily connect both red and yellow together to see if your boiler fires (timeclock calling for heat).

 

[shorn]

unfortunatley i do not have a multimeter

 

[GaryMo]

unfortunatley i do not have a multimeter

I suggest you purchase one for times like this.
They really are invaluable and don't need to cost the earth.

 

[RF Lighting]

//www.diynot.com/wiki/electrics:how-to-replace-a-room-stat

 

[bernardgreen]

i did initally connect the N aswell, does the clicking mean it is stil working though??

Ouch.... The stat may be OK. If you put the neutral into terminal C then the relay would have shorted live and neutral across the contacts which are not needed for your heating system. If they are damaged ( without damaging anything else in the thermostat ) it may be the stat will work.

There is fuse in the boiler and another in the FCU ( or 13 amp plug ) that feed the boiler. One or both of these may have blown and need replacing. If as some one has suggested you link red and yellow with a terminal block and the boiler still doesn't fire up then a blown fuse is very likely.

 

[shorn]

Hi all,

right I left this for a few weeks (as its not been too cold) but autumns definatey setting in and its getting colder!

So today Ive had another look at it.
I switched mains off and connected the red and yellow wires at the room stat. (stat removed) switched back on. Made sure that the CH was set to on on the main programmer, and checked the boiler. It did not fire up. removed the front of the boiler and went through the process of trying to relight the pilot, but nothing??

Any ideas?

 

[bernardgreen]

Check the fuses