Vaillant turbomax not reigniting for a while after use

[Plaasboy]

Hi All,

I'm trying to figure out whether this is a thermostat or diverter valve problem. My combi boiler is working just fine from cold, however, after a decent use (like a shower), it takes a good 10 or 15 minutes before it will fire again which is not a good thing in the time critical period before heading off to work. The system is fine for the duration of a single use - no temperature fluctuations, no pressure loss etc - but once the hot tap is turned off, the boiler won't fire again for 10-odd minutes and in that time, the water through the hot tap is cold. Any help would be appreciated.

Cheers

 

[gaspro1981]

could be a duff ntc sensor or the diapragm in the dv need some more info really

 

[Plaasboy]

What does NTC stand for and where is that located, I'm more inclined towards the temperature control (which I'm assuming is the TC in NTC) being the fault as I replaced the diverter valve a couple of months ago and it works perfectly from cold. Having said that though, the system is not working properly from warm/hot so it could br an issue with the pressure not being sufficient to open the thermostat.
I can keep the hot water running from tap to tap. For instance, If I leave the shower running then turn on the hot tap in the basin before turning the shower off, then the water from the hot tap in the basin will stay hot. The problem comes when I turn the tap off. If I then turn another one on I get whatever warm water was left in the pipes followed by cold water with no activity from the boiler. The boiler is a Vaillant Turbomax 242E.

 

[ColJack]

NTC = Negative Temperature Coeficient. A sensor that tells the PCB how hot the water in the pipes is.
there are 3 on a turbomax..

one on the CH return ( top right ) View media item 13607one on the CH flow ( top left ) View media item 13608and one on the CH return connection to the heat exchanger.. View media item 13609
are there any status or fault codes shown on the lcd display when it happens?