Vailliant Combi Boiler bugging me

[Dougie212]

Hi there.

Does anyone have any idea what may be causing the following problem please.

We have a Vailliant combi boiler (model number coming shortly). It works fine... provides hot water, and heats the house no problem. But the problem I have is that when the heating is on, if if use the hot water the radiators cool down. The boiler still sounds as if its running, and the timer power light suggests the boiler is running but the radiators aren't heated.

Any ideas what could be the cause and a possible fix please. Its not a major problem, but just a bit of a nightmare having to turn the heating off and on again everytime we use the hot water when the central heating is on.

Many Thanks

Dougie

 

[kidgreen61]

There is nothing wrong with your boiler, combis either provide hot water or heating, but not at the same time.

 

[Dougie212]

right.. but when i do use the hot water when the central heating is on, is it right that i have to turn the heating off and on again or should it re-send the heat back to the radiators automatically?

 

[kidgreen61]

You need do nothing, as long as external controls are calling for heat, the boiler will revert to ch mode.

 

[Dougie212]

right.. well.. its not reverting back to ch... thermostat is all set.... so what makes it switch between hot water an ch?

 

[MrV]

What is the model?

 

[Dougie212]

its a vaillant VCW GB221 H.. Thanks MrV

 

[MrV]

How are you having to reset it?
If it is by switching the power off and back on, it could be the anti cycle failing to re-establish.
Try removing the front enamel panel and find a silver screw on the electronic box with a +&- next to it. Remove the screw, and with a small electricians screwdriver, insert into the hole and locate a screw beneath. Gently twist it a few times and leave it fully anti clockwise.
See if that solves your problem.

 

[Dougie212]

yes mr V, to reset it I have to use turn the power off and on.

I have just tried what you suggested and the following has happened.

turned the CH on and let the radiators heat up.

ran the hot water tap, until hot water came through

turned the hot water tap off. the boiler again sounded as if it was still running, but through the spy glass saw only the pilot light on. The burners havent re-ignited for the heating.

any ideas please?

 

[Andygasman2010]

These can stick in time-delay mode which is just like what you describe. The delay period can be adjusted between 1 - 12 minutes but if this is a new problem then it's more likely a faulty thermostat board. There's a check you can do if you're handy with a multimeter??

It could be lots of other things too though. Like... Does the diverter valve move back to the heating position when you turn the tap off?

 

[Dougie212]

its not a new problem, ive posted on here about it a few times before but never had any answers or suggestions... its been happening for as long as I can remember...

Whats the test.....? If you would describe it step by step please... I'm still in xmas mode so need it in simple terms..lol

Thankyou

 

[Andygasman2010]

Get the boiler into it's fault state then make access to the mains terminal strip. Check DC volts between terminal numbers 9 and 7, you SHOULD have 13vdc or greater. If you get less than that it's likely that the thermostat PCB is stuck in time-delay mode.

Make sure the diverter valve is pulling fully inwards after hot water demand.

Make sure that the DHW servo is fully home too, not still in hot water position. Give it a little nudge downwards to make sure.

 

[Dougie212]

ok..... your first point.... no problem...

the next 2.... i dont really know my way round a boiler... so if you could just sort of guide me in and tell me what to do i'd be really grateful..

Thankyou

 

[Dougie212]

and i take it the mains terminal strip is under the metal cover on the right hand side of the boiler.. theres a metal one with 4 flat blade screws and a black plastic cover underneath with 1 flat blade screw in the middle. Which one should i remove?

 

[MrV]

Locate the diverter valve. It is situated on the right hand side near the rear lower part of the boiler. It has two red microswitches attached to it.
When you open the tap, it should move outward with both microswitches disconnected within approx 2 second when you open the tap.
It should return fully in with both microswitch connected when you close the tap.
It should return to a central position with the bottom microswitch only connected when you turn the power off.
Does it do this?