SYMPTOM - H/W but no CH

[samparker]

if you don't get heating, test the white wire, then the orange wire with HTG only on. if orange fails.... motor/actuator is faulty!

 

[D_Hailsham]

Turn the power off to the system completely (just setting the timer to CH OFF and HW OFF is not sufficient) so the mid position valve resets to the HW port open position.

Set HW and CH timers to OFF ( DONE)
Turn HW and CH stats to minimum (DONE)
Turn electricity on (DONE)
Turn HW ON at timer and HW stat to MAX - the boiler should light. (YES)

OK so far!

Check voltages on valve white and grey wires - should both be zero. (NO....GREY ZERO BUT WHITE LIVE, VALVE IN W POSITION)

The white gets its power from the CH room thermostat. Could this be faulty? You need to disconnect the white wire and measure the voltage on the loose white wire. If it is zero, then the wall stat is faulty. If 230v, then the white is being fed through the valve - which shouldn't happen - faulty valve.

Turn CH on at timer and set CH stat to max - boiler should continue to run and rads get hot. (NO....VALVE STILL IN W POSITION - NO FLOW TO RADS)
Check voltage on White (should be 240v) and Grey (should be 0v). (NO....WHITE LIVE, GREY ZERO)

Why NO? The voltages are correct, but the valve is not moving. This suggest a faulty motor or jammed valve.

Turn HW stat to MIN - boiler should continue to run. (NO...STOPPED)
Check voltage on White (240v) and Grey (240v) (NO... WHITE ZERO, GREY LIVE)

So why is the white showing zero volts? It should be 230 as it is fed from the CH roomstat. Another indication that the stat may be faulty. Check the voltages at the stat terminals.

Turn HW OFF at timer - boiler should continue to run. (NO....STOPPED)
Check voltage on White (240v) and Grey (240v). (YES BOTH LIVE).

Voltages OK but boiler not working. This says that the orange wire is dead. Disconnect the orange and check voltage on loose end. If zero, the valve is faulty.

In each case I am measuring the voltage between the BLUE (Neutral) and the wire in question at the LWC1 wiring centre.

Have you checked that the correct links are in place on the LWC1?

You need to check the wall stat is working properly. One terminal should measure 230v when the CH is turned on. The other terminal should be 0v with the terminal at MIN and change to 230 when the stat is turned up and clicks on. You will have to disconnect the stat from the white valve wire to do this check, in case the stat is being back-fed through the valve.

 

[matt1e]

if ou remove all of the wires from the wiring centre, then when you do the test you wrote, the reading won't show up!!

hi sam I dont know that was directed at my post but if you read the bottom line

please note readings on colours above refer to where they connect not the actual colours themselves

The I test wrote WILL check that the systems wiring is all correct Quick to do with multimeter and will lead to quick diagnosis of valve as disconnection removes the possibility of stuck microswitches causing strange readings (which I suspect is happening here)

matt

 

[D_Hailsham]

Honeywell Wiring Guide is a very good reference and has fault finding advice.

 

[deagle]

Many thanks for all the replies and advice. I am sure that any one of you could have diagnosed my issue had you the opportunity to physically access the system.

From reading the Honeywell guide, I now understand that the Orange wire is switched live as an output of the midpoint valve to tell the boiler and pump to fire.

In CH only mode, I have power to both white and grey but no Orange has been switched so I agree that the valve is therefore suspect. No sure if the motor or the microswitches.

That leaves the question of why the white is live in H/W only mode (faulty thermostat or perhaps faulty valve) seem to be the consensus. On the basis that it is unlikely that there have been two faults occuring at the same time - then I think the valve - probably microswitches - may be the sole culprit.

Also, I have previously ruled out the room stat by removing it and shorting the live to the output - thus giving 240v ...and the heating does not fire up.


All that said, I'm not going to risk losing the partially functioning system that I have got over Christmas and Boxing day - I would be in the doghouse if I made that mistake... So I will report back in a few days.

In the meantime - happy X-mas to all and thanks again for your help !

 

[jobloggs]

Deagle

I fixed my fault which appeared to be the same as yours (see my previous reply) by replacing the synchronous motor.

 

[deagle]

Deagle

I fixed my fault which appeared to be the same as yours (see my previous reply) by replacing the synchronous motor.

....very interesting - thanks.

 

[deagle]

Now fixed.

For the record, it was the synchron motor.

I did the test suggested by matt1e - prior to fitting and can confirm that a faulty synchron can affect which of the wires goes live - hence making it seem as if the programmer or thermostat was faulty.

JoBloggs - thanks for the post confirming that your problem was also fixed by the synchron motor... I guess that is why B&Q, Wickes, Screwfix etc all stock them !

Thanks all.

 

[seco services]

faulty motor not powering over valve to heating heating/hw.


---------------ORANGE GREY WHITE
ALL OFF -------> NO YES NO - ok
H/W ONLY-----> YES NO YES - wrong
CH ONLY -----> NO YES YES - should be live on orange
BOTH -------> YES NO YES - yes, orange will only be live cause it
in the same terminal as the hw stat live

which you was mentioned on the 22nd that was the fault.