Drayton LP522 not firing central heating

[BowerHinton]

I have a Drayton LP522 programmer controlling a non-condensing Baxi gas boiler (i.e. with a hot water tank) in a high pressure system (no cold water tank).

When heating is selected the boiler doesn't fire up although the room thermostat clicks OK and it has worked fine in the past. Hot water works fine. I've had the boiler serviced recently and the man said it was working fine. Is there any way I can find out where the problem is? (e.g. room thermostat, LP522 programmer, boiler or mid-position three way valve connected to the hot water tank)

And a related question, should I call a plumber or an electrician?

Many thanks for any help.

 

[learnplum]

Do you possess a voltage measurement device?:tounge_smile:

 

[BowerHinton]

Yes, I have a digital multimeter and can measure voltages if I knew where.

 

[AWheating]

if the boiler runs on hot water its not the boiler, its going to be either the clock, room stat or the most likey the motorised valve.

 

[Aquazone]

First check I would do, turn off HW on the clock, turn on HTG and turn up room stat. Look at valve to see if lever is floppy, and also take valve head off and check its not a seized spindle stopping it moving all the way over.

If that offers no solution, and you are confident live testing then you can look for voltages in wiring centre. Or call a plumber.

 

[Leo21]

Iff your competent with electrical testing, you need to check you've got power through your room stat. If you get stuck, call a heating engineer. Electricians are uber useless normally on heating electrics.

 

[learnplum]

Turn clock to heating only and put stat to max setting.
There should be an electrical join by the cylinder.
Look for the white cable on the valve, and see if there 230volts on it.
If there is check to see if there is now 230v on the orange cable of the valve.
If 230v on white and zero volts on orange, then internal switch in valve knackered.:tounge_smile:

 

[Leo21]

Turn clock to heating only and put stat to max setting.
There should be an electrical join by the cylinder.
Look for the white cable on the valve, and see if there 230volts on it.
If there is check to see if there is now 230v on the orange cable of the valve.
If 230v on white and zero volts on orange, then internal switch in valve knackered.:tounge_smile:

Or you could check power to the sycron motor.

 

[learnplum]

Another check you could do, to make sure its wired correctly in the first place, is when you put the clock in heating only, and stat on full, check the grey cable on the valve is at 230v.
So you want 230v on the grey and white, so then the orange will recieve 230v and fire the boiler up.:tounge_smile:

 

[Leo21]

Another check you could do, to make sure its wired correctly in the first place, is when you put the clock in heating only, and stat on full, check the grey cable on the valve is at 230v.
So you want 230v on the grey and white, so then the orange will recieve 230v and fire the boiler up.:tounge_smile:

Unless it's never worked, it's going to be wired right.

 

[learnplum]

I beg to differ.:tounge_smile:

 

[Leo21]

Beg away my good man.

 

[learnplum]

Hi leo most Y plans are wired wrong, but customers live with it?:tounge_smile:

 

[Leo21]

I beg to differ.

 

[learnplum]

Hi leo, the domestic hot water off, facility was never used on old systems?:tounge_smile:

 

[Leo21]

They usually were, just wired into Randal 103,s. So it went of on the cylinder stat. But no option on the clock .

 

[BowerHinton]

Many thanks for all the advice and especially to learnplum who suggested where to measure. With heating on and room stat at max the white wire is about 240 volts and the orange wire about 38 volts. There are two sets of gray wires, one set measures about 240 volts as long as power is on.

So it looks like I need to get a plumber to replace the valve, right?

 

[learnplum]

Yipppppeeeeeee, I may of gave a little bit of advice, instead of asking for it.:tounge_smile:
Ok not sure why you have two greys, at the join, unless you have a new coloured coded cable, from the clock to the join.
(new colours, brown/black/grey).
But if you identify, the grey of the valve, and this has 230volts on it, and at the same time, the white of the valve, has 230volts on it, then you should have 230volts, on the orange of the valve.
The valve uses the grey to signal to the orange, to fire the boiler up.
Power on the white only, holds it in mid-position.
So central heating and hot water in that position.
By gettin 230v on white, you have proved the clock and stat are ok.:tounge_smile:

 

[BowerHinton]

Well oddly enough the CH started working all of a sudden last night. My wife thinks I've fixed it and I don't like to tell her I only measured a few things! I guess there is something sticky in the valve causing intermittent failures but at least I know what to replace to fix it permanently.