No hot water if the heating is running, but otherwise okay.

[kevinhpainter]

I have a strange fault with a Vaillant EcoTec combi-boiler.

It's 100% reliable whenever the heating is called for, ie. by the room-stats.
It's also 100% reliable when hot water is called for, ie. hot tap or shower, as long as the heating isn't running at the time. But if the heating is already running when hot water is called for, the bolier fails to re-light after the diverter valve has operated. The flame light is flicking on, suggesting it's sparking, but presumably the gas valve isn't opening because it doesn't re-light and after several attempts locks out.

We're limping along by turning down the room stats before we run the hot water. So far we've changed the spark electrode, the HT lead and now the main PCB but made no difference... now stumped, any ideas?

 

[Deleted member 120897]

Don’t know why you’ve guessed and changed parts. What error code do you get on lockout? Which model/year of Ecotec?

 

[kevinhpainter]

Don’t know why you’ve guessed and changed parts. What error code do you get on lockout? Which model/year of Ecotec?

Hi Chris, thanks for replying. It's a 2010 EcoTec pro 28. F28 error but it's too general as of course I know it fails to light because I watch it trying to light and failing.
For me the key point is that this only happens if the heating is running when we turn on the hot water. I can see the flame extinguish. I can hear the diverter valve operate. I can see the flame light flashing, but it doesn't ignite and after several attempts it locks out... and of course after a while the hot water runs cold. Contrast that with when the heating is not running. I open the hot tap, I hear the diverter value operate, I see the flame light staying on... and of course, after a while the water runs hot.

 

[Deleted member 120897]

Components need testing and check the condensate pipe is clear

 

[kevinhpainter]

Components need testing and check the condensate pipe is clear

 

[kevinhpainter]

Thanks Chris, which components specifically?

 

[Deleted member 120897]

Thanks Chris, which components specifically?

Sorry, that’s as much as I can give, the rest would be gas related advice which isn’t permitted on an open forum.

 

[ShaunCorbs]

Closed time to get a gas safe engineer out