Wiring of gas central heating

The color code for thermostat wiring is as follows.
The "R" terminal is power into the stat from the boiler control transformer. Normally 24 volts. The "Y" terminal is for cooling. Normally left blank for a boiler. The "W" terminal is for heat. This one used to start the heating cycle.The "G" terminal is for fan operation. Probably not used for a boiler. Check the boiler terminal board for these functions and write down the wire color on each one. Match the boiler colors to the right function on the stat. If you need more than this, let me know.

Control systems operate on a much lower voltage than the boiler. You should be able to put any kind of thermostat in for it. Just be sure of the wiring when doing it. If its a line voltage stat, I'll need more information to advise correctly.

All wireless wall thermostats are Millivolt controlled. rather than having an 18 or 24 volt (transformer) wired wall thermostat. Before purchasing any wireless wall thermostat, you need to determine what your oil fired boiler requires for activation. My experience tells me, that it's going to require either 18 or 24 volts. In which case a wireless thermostat won't work.

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You didn't mention if you had electric heat or gas heat. If you have electric heat you must move a wire on the thermostat to make the fan come on. Most all wall stats come ready for gas heat. No need to make a wire change for gas. Anyway I have a diagram of a typical central unit HERE

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HI right first i would look at a worcester greenstar combl
best you can get and you have full back up from worcester leave all rads with stats as they are i think you will have to remove one , the that would be the bath room also the greenstar comes with a clock bulit in these are on the worcester bosch web site i have been a gas fitter fot 30 years and this what i would go with a really good combi, you can also get awire less room thermostat for this hope this helps

You definetly have a control issue. However trying to diagnose the exact problems that you have would be very difficult without actually seeing the wiring. You defintely have a wiring/control issue but I cannot tell you exactly what it is without more info. Sorry, I would love to help you more...

Hi do you have the make and model of central heating boiler

back boiler run from a gas fire? check the instructions to operate the gas heat to the back boiler not just the fire
I presume that this a fully pumped system - air lock doubtful There maybe on/off valves on the pipes to and from the back boiler [situate close to cylinder] make sure they are on - anticlockwise turn
or there could be a blockage in the outlet from header tank usually in the loft. or If there is no water in it maybe the mains cold feed it is off.
Note if no water in it DO NOT USE the back boiler

the stat works using a bi metalic strip so that click you here is making a contact and telling the boiler to call for heating so if you getting no click you need a new room stat. Replace with same model and note the wiring most stats only use 2/3 wires depending on system

most likly or a shorted wire unhook the wire from the boiler see if it stops then if it's still is on it's in the boiler if off try unhooking it at the t-stat on the heater this should narrow it down for you dan