Vaillant Ecotec Plus 418 problem - will not start up

[tagb61]

Hi, my heating which uses a Vaillant ecotec plus 418 boiler installed on an open vented central heating system using S plan has stopped working. The problem is the boiler is not firing up. The boiler status shows S30, which means there is no external demand for heat.
I checked the SL to the boiler on Terminal No 4 is live when I call for hot water, or heating via the programmer, and the cylinder and room thermostats are not satisfied. The heating and hot water two port valves open if there is a demand for hot water or heating, and then the pump starts up and terminal 4 of the boiler (SL) becomes live indicating the 2 port valves are working correctly. However the boiler does not start, and always indicates S30, no demand for heat. I have reset the boiler and powered the system off and on but with no effect. I checked the pump is powered and motor is spinning when there is a demand for heat/hot water.
I'm baffled, any ideas anyone ?

 

[Johntheo5]

Probably not much help but check D.30 as well which will probably be 0 anyway if S.30 is true.

 

[Agile]

If the boiler is showing S30 which remains at S30 even when terminal 4, the SL connection, becomes live then it would seem to indicate a PCB error.

But it all depends on the history of the boiler and it is always possible that an engineer's setting has been reset to a value that does not allow the boiler to operate.

 

[tagb61]

Probably not much help but check D.30 as well which will probably be 0 anyway if S.30 is true.

View attachment 340855



View attachment 340854

I'll check later today just to be sure.
Thanks

 

[tagb61]

If the boiler is showing S30 which remains at S30 even when terminal 4, the SL connection, becomes live then it would seem to indicate a PCB error.

But it all depends on the history of the boiler and it is always possible that an engineer's setting has been reset to a value that does not allow the boiler to operate.

The boiler was working fine Saturday, but wasn't working on Sunday. No changes have been made to any settings for several years.
My own suspicion is the PCB too, although the various menus, and status displays all behave fine which means the processor and sw are running ok.
Thanks

 

[Johntheo5]

I think terminals 3&4 are linked out and should read 230V to N with switched live

 

[Agile]

You say that the pump starts up!

That indicates that the pump is not supplied from the boiler as is intended. ( that was the way of doing things in the days of cast iron heat exchangers before low water content boilers became the norm. )

This is so that the boiler can supply pump over run and run it as part of a frost protection procedure.

I have had a look at the MI for the boiler and have to admit that although the diagrams show the pump cnnected to the boiler it fails to say in the wording of the need for the boiler to supply the power to the pump.

 

[Agile]

I think terminals 3&4 are linked out and should read 230V to N with switched live

The link should have been removed on installation when a remote switched live connection was provided.

3 is just a mains connection to enable a room stat to be connected between 3 and 4 if very simple controls are being used. Or just linked if no external connections are to be used. But that is not very sensible as it prevents the boiler from providing a pump over run or frost protection.

 

[tagb61]

The link should have been removed on installation when a remote switched live connection was provided.

3 is just a mains connection to enable a room stat to be connected between 3 and 4 if very simple controls are being. Or just linked if no external connections are to be used. But that is not very sensible as it prevents the boiler from providing a pump over run or frost protection.

Link 3-4 is not fitted. As your reply installation instructions say it is removed when using external controls.
As you noted, the pump is not connected to the provided pump connector on the boiler, but is connected to the same circuit as boiler SL. I'm not sure why that was done by whoever installed it. I suspect it was left over from the previous boiler installation.
But it doesn't explain the current issue as it's always been that way on this system AFAIK .
Regards

 

[Johntheo5]

Its connected this way?.

 

[tagb61]

Yes it is.
The installer didn't use a wiring centre but it has the same connections to the components.

 

[Agile]

Well you really should get the pump connected back to the boiler.

And the boiler needs to be connected to a permanent live.

Your system have no pump over run at all and that will cause thermal shock to the heat exchanger immediately the boiler turns off. And it will prevent the frost protection from operating and also the daily one minute pump exercise run.

And it probably would invalidate the warranty if any warranty repair engineer noticed it. Manufacturers often try to find reasons not to do warranty repairs when there is a serious installation error.

 

[tagb61]

The boiler does have a permanent live feed as it should, as well as the SL.The boiler is far too old for a warranty repair but if this current problem can be sorted, I may look at correcting this afterwards.
Thanks

 

[The831Bunny]

If the boiler is showing S.30 with 240VAC on T4, odds on its a new PCB. Double check at D.8, 0 is no signal recognised from external controls, 1 signal recognised from external controls. Expect 0 in your case. Double check the wire to T4 is tight and test to the Neutral terminal or T5 on the PCB. A board replacement is not out of the way at 10+ years. They are susceptible to power supply rail issues the older they get with capacitors failing, so don’t feel too hard done by. Setting up and combustion checks with a FGA need to be carried out by a GasSafe engineer when fitting a new PCB.

 

[DP]

If the boiler is showing S.30 with 240VAC on T4, odds on its a new PCB. Double check at D.8, 0 is no signal recognised from external controls, 1 signal recognised from external controls. Expect 0 in your case. Double check the wire to T4 is tight and test to the Neutral terminal or T5 on the PCB. A board replacement is not out of the way at 10+ years. They are susceptible to power supply rail issues the older they get with capacitors failing, so don’t feel too hard done by. Setting up and combustion checks with a FGA need to be carried out by a GasSafe engineer when fitting a new PCB.

Welcome back stranger.