boiler does not fire when timer comes on - unless HW also on

[Fireblade01]

Hi. We have a gas boiler on an unvented central heating system.
Recently the CH stopped coming on when on the timer, unless the HW was set to come on at the same time. If the CH is set to come on it does not, but does once the HW timer comes on 2 hours later and then all is OK.
Once running all seems to work OK even when the hot water has gone off and the CH responds to the thermostat in the normal way.
We have a Honeywell motorised valve (2 port) on the CH and a Orkli 2 port on the HW.
I have replaced the head on the CH valve ( I already had one in the loft) as I thought it was perhaps not turning the micro switch on properly and also checked the movement on the valve base and this is fine. Unfortunately this has made no difference. I do not really want to purchase a replacement valve for the HW if this is not the problem.
Any ideas?

 

[jackthom]

Do you have a multimeter to check a couple of voltages on the Honeywell valve wiring?

 

[picasso]

Anyway the timer has been set to gravity system by mistake ?

 

[Fireblade01]

No I do not have a multimeter. We had not changed anything when the system stopped working

 

[picasso]

Your a bit stuffed without a MM, I would hazard a guess at a faulty timer but its just a guess without further checking.

 

[jackthom]

With the DHW turned off, have you tried latching the Honeywell valve open manually using the side lever to see if the boiler fires?

 

[Fireblade01]

OK I will try that. Seems as if the CH may be on all the time since I replaced the valve head this morning!
Think I will let it cool down and start testing again this evening including the above suggestion.
Will let you know how I get on.

 

[Fireblade01]

Forget my last post, problem is as originally stated.
With the HW off and the CH on I have latched the Honeywell valve open manually and the boiler does not fire.
However, if I then move the HW valve open the boiler fires immediately, even though the HW is off. If the HW valve is then released and returns to the auto position the boiler turns off.
Does this help?

 

[Fluffster]

Have you bought a Multi meter yet, they are only £10.00 a lot cheaper than changing motorised valves. Is the room stat sending a signal to your wiring centre?

Pete

 

[Fireblade01]

Just going to get a multimeter now but will not have much time to check stuff today as I have got my twins birthday parry to attend.
Never used a MM before so should be a good learning curve.
Thanks

 

[jackthom]

Maybe there is no mains voltage going to the Grey wire of the Honeywell valve (to the microswitch)

or

the 230V on the Grey is there but the microswitch is not switching this through to the pump and boiler (Orange lead from the valve).


You really need a multimeter to see what's going wrong.

 

[Fireblade01]

Sorry It has been some time since last post - busy week!
To recap the system had been working fine for 2 years without any problems. Since the issue I have replaced the head on the Honeywell Valve (CH) with a brand new one and this has not changed the issue so it would seem doubtful that the Honeywell Valve is the problem.

I have now got a multimeter and have been testing.

The permanent live feed shows a current of 248 which is the first terminal on the electrical connector block. From this terminal there are 2 grey wires, one to each of the motorised valves and a brown wire up into the timer.

I have found that when the CH comes on (without the HW) none of the other terminals become live, I assume this is why nothing happens!

However, if the CH and HW come on together then terminals 2,4, 5 and 6 become live and everything is OK and boiler fires.

I can let you know which wires go where from these other terminals but my logic would seem to suggest the problem lies with the timer - it is not sending a signal to anything when just the CH comes on.

Does this seem a reasonable assumption or should I do further testing before buying and replacing the timer?

The timer is only 2 years old and is Dreyton Lifestyle LP522.

 

[jackthom]

Yes it looks like the programmer or the wiring to it is at fault.

Can you visually locate where the the CH ON wire (from the programmer) connects in the wiring centre and check it's physically secured at both ends of it's run?

With power OFF and the programmer removed from the wall a continuity check on this wire would be useful.

 

[Fireblade01]

Thank you.
I have already checked all of the connections in the timer, thermostat and all the electrical connections and all are tight.
Not too sure how to do a continuity check - will look at the multimeter instructions and let you know.

 

[Fireblade01]

Just run the continuity test and the instructions say there is an audible warning if below 50 ohms.
The warning goes of and the reading is 003. Unfortunately I cannot interpret what this means. Is it just the wire that has broken and would it be worth replacing this before I replace the timer?
Thanks