Central Heating Failure

[PayneP]

I hope someone can help.

My Central Heating has stopped working. The boiler is working and I have hot water in the cylinder. My controller (Drayton Tempus Three) does not seem to be working. The display is all intact and I can read all the numbers etc... on the screen. I have set the Timers for Water and Heating at Continuous. When I press the Select or Override buttons I do not hear the usual clicking noises on the Controller.

When I manually set the 2 zone valves (Drayton ZVA22) to "Open", the heating works but there is no thermostatic control. When I rotate the Thermostat (Drayton), I hear the click indicating the temperature in the room.

Does this indicate one or more components that are the problem? Please help me move forward with potential solutions.

Thanks

 

[Armo74]

Could be that the motor has failed which is why you get heating by manual override of the valve.

 

[PayneP]

Armo74

Thanks for your reply. Please ignore me if I suggest something that is hopelessly wrong but if the pump was not working, I would assume the water in the rads would then go cold eventually. Is my rationale wrong?

I can hear noise from the pump (although this does not mean it is pumping). BUT, if the pump is not working, would this affect the timer/ controller? As mentioned, the controller is not clicking on when pressing, for example, the override button.

Many Thanks

 

[Hugh Jaleak]

Think Armo meant the motor in the (Drayton) valve. Are you confident to use a multimeter on mains voltages?

 

[Armo74]

The valve relys on the motor to put the valve in its open position when heating is called for. When the valve is in its fully open position it activates a micro switch inside the actuator which in turn fires the pump and the boiler. If you can open the valve manually it obviously isnt stuck which would lead me to think it was a motor problem. The clever guys on here will tell you how to test for it

 

[PayneP]

Thanks guys

I am taking on board everything you are saying. Can you explain the lack of "click" when I press the "override" button on the timer/ controller. Would this not be the beginning of the process, that triggers everything else.

Again, many thanks.

 

[sandybeach]

If the timer is calling for heat then there should be voltage at the room stat.If there isn't 240 volts at the room stat then the fault could be at the timer.
You need a set of test lamps or a multi meter to check each component for voltage.
If you can hear a click when pressing the HW selector but nothing when pressing the heating selector then it is most probably the programmer.

 

[Hugh Jaleak]

Good flowchart of the electrical 'paths' through the wiring here: http://octaveblue.co.uk/central_heating.html

 

[PayneP]

Again. many thanks.

Sandybeach, when I press the "Override" buttons on the controller for Hot Water or Heating, there are no clicks. Also. when I press the "Select" buttons for Once, Twice, Off or Cont for Hot water or Heating on the controller there are no clicks. What should this be telling me?

Hugh, thanks for the diagrams, I do have the capability to measure voltages if necessary.

 

[sandybeach]

The first thing to check is there is power going to the sychronic motor in the heating valve.This is the most common and likely source to the fault.
If there is power,and the valve isn't opening,then the motor needs replaced.
No power at the motor would suggest a fault on either the programmer or the room stat.

 

[PayneP]

Thanks, again.

Due to the controller not "clicking" on for either Water or Heater, does this mean both valves need checking or am I barking up the wrong tree?

Thanks

 

[PayneP]

Guys, thanks for your help so far.

I've got the multimeter out as you suggested and measured the voltages on the following.

Drayton Tempus Three (removed cover plate)

Terminals N and L. 230 volts
Terminals N and 3. 0 volts
Terminals N and 4. O volts

Earth Terminal no wires
N Terminal. 2 neutral wires
L Terminal. 2 live wires
1Terminal. No wires
2Terminal No wires
3Terminal. 1 Live wire
4Terminal. 1 Live wire

Drayton thermostat. 0 volts. (removed cover plate)

Apologies if this is a dumb question but where should I go now. I assume Terminals 3 and 4 are the outgoing water and heating "live" wires. Do I still need to measure the V on the motor(s) in one or both of the valves(I took the covers off and could not see a direct way to measure it anyway).

Cheers guys

 

[sandybeach]

Did you check for voltage at the room stat with the programmer mounted on the backplate and switched on?

 

[PayneP]

Yes, I measured the room stat with programmer on backplate and after selecting Override on Water and Heating. As mentioned previously, there is no clicking noise when selecting program's on the programmer.

Please advise what to do next.