Re: Vaillant Combi Boiler

[Ed Sirett]

> I've just replaced the timing unit for my Vaillant combi boiler as its > never worked properly since I moved in. What I expected to happen is > that when the timer is set to ON, the heating/hot water will come on > (providing its selected on the boiler itself), when the timer is set > to OFF, only the hot water will be available. > Unfortunately, this isn't the case. It looks like the zone valve isn't > working in the boiler. (I've checked and made sure that the timer > works correctly).I do know that when the Vaillant engineer came to > look at it prior to me moving in, he couldn't get the timer working > and therefore "wired it direct" whatever that means. > I assumed that this meant he'd bypassed the timer although now I > suspect he also bypassed this within the boiler. > > Does anyone know how I get round this? Is it safe for me to go delving > around inside the boiler itself? >

1) You don't happen to have a wall mounted thermostat anywhere?

2) All vaillants require a connection between terminals 3 and 4 to run the heating. This applies to Sines, VCWs, & Turbomaxs.

It's mains powered electrical appliance no more dangerous (less actually) to delve into (electrically) than a toaster.

[Ed Sirett]

The 3,4 link should mean the boiler runs the heating all the while (when the summer/winter switch is put to

This is very basic electrics really: if 3 is connected to 4 the boiler runs the heating. You might well find that simply connected the mains to 4 will also do the same, but is best avoided since you might get odd effects. If you want thermostat as well you will take the switched output from the timer and connect to terminal 4 via the thermostat.

The timer should get its power from the L&N direct from the mains and it should conect 3&4 togther to make the heating run.

[Giff]

Thanks for you help. I've wired it all up and the heating is now switched by the timer.

The only strange thing I've found is that when I switch the heating on with the timer, I can hear the boiler fire up and you can see it light. When I switch it off, the heating switches off but the boiler is still making a noise. Sounds like a fan but the fan isn't on. If I switch the heating off using the switch on the boiler then the noise goes likewise if I turn the hot tap on and then switch it off, the noise goes.

I know I didn't add this earlier but is Vaillant is a Turbomax if thats any help.

Anyone out there know what the problem might be?

Andy

[Richard J.]

Our combi (not a Vaillant) does this too, and the noise is from the central heating pump. Even if we switch the CH off, the pump keeps on running. Using a hot tap will always shut off the CH and the pump on our system, and this is why the noise stops if we turn a hot tap on for a second or so. Maybe your system has the same logic.

[Steve Moore]

Known as overrun & takes away residual heat from the core while the burners and body cool down.

Steve [e-mail]

[Ed Sirett]

The length of time this happens for is adjustable. See the installation and servicing guide.

ON Turbomax+ models (leds + digital temp display) its done by changing a setup number in the control computer. On plain Turbomaxs (ladder of Leds) the manual simply says it is automatic (and gives no indication whether it is adjustable or not).