Condense boiler stops working when hot water is turned on

[Johnamlani]

Hello, Can anyone help me, my Vailant Ecotec 428 condensed Boiler works fine for central heating but stops working when hot water is switched on manually or via auto select. And also, while the heating is on the pressure on expansion vessel drops to nearly nothing over the period of 12 hourrs.
i have to top up via main fill.

 

[AWheating]

sounds like you have a fault on your controls, possilbly clock, cylinder stat or zone valve. You also probably have a leak on your system. check all pipework,valves,blow off for drips.

 

[Johnamlani]

Thanks a lot AWheating, I have no doubt cheked the clock, checked divertor valve, cylinder works fine via electric mains.
Is there any short cut to check leaks on Pipework. How about expansion vessel ? Do they go wrong? I had pumped it up to just over 2 bars. But that should not effect hot water or should it???

 

[M.Joshi]

I had pumped it up to just over 2 bars. But that should not effect hot water or should it???

Do you mean you pressurised the system to just over 2 bar (reading on the digital pressure gauge)?

The Vaillant manual for that boiler states the following:

(The actual reading on the digital pressure gauge should ideally be 0.5 bar plus an additional pressure corresponding to the highest point of the system above the base of the boiler 10 m head equals an additional 1 bar reading on the pressure gauge. The minimum pressure should not be less than 1 bar in any installation.)

 

[AWheating]

if your boiler works on heating but not hot water then is more than likely not being told by the controls to run, although i dont know how your systems wired of course. whats the exact design of the system? s plan?

 

[Johnamlani]

Thanks Mr M Joshi, JSK,JAmbe
I meant the pressure in the expansion vessel as pumped via the foot pump from the bottom of the vessel.
The pressure in the system when heating is on stays to just under 1 but gradually drops over the period of 15 hours
My phone no 01279 653173 if you can help

 

[AWheating]

you probably have a faulty expansion vessel or leak, and a faulty control issue. I would call a qualified engineer to get it sorted. Avoid posting your number on the open forum and keep personal details to private messages to avoid spam etc...

 

[Johnamlani]

Thanks,
sorry I have been busy elsewhere
It is Y plan, 3 port divertor was changed only in February. the system was working perfectly till last week.
when hot water is switched on, the liver on the diverter valve shifts to right with a thrush.the boiler power is still on but doesnot fire

 

[Johnamlani]

Thanks for the Tip.
I have asked the proffesional to check.
Just a little help, I would need
If it be Expansion vessel, do I have to change the complete kit like the pressure valve and the Gauge, since the vessel (18L)is only £29.99 at screwfix

 

[AWheating]

it could possibly be a lose wire or faulty relay on the 3 port valve..... hopeful the engineer will suss it out.

if the expansion vessel is faulty then yes you can just get the vessel changed without the control kit, the engineer can advise you further.