Pressure gauge problems

[westniner]

I have an ecoTEC Plus 624 boiler which ran perfectly until I bled 2 rads up on the top floor (one I had to do twice), both of which had been cold for about 2 years. I increased the pressure after the 1st bleed as the pressure seemed very low, then increased it again a bit after the 2nd. rad. I then noticed a couple of days later, quite by chance, that the gauge was in the red area. Now the gauge is fine when I have the water on but as soon as I put the heating on, the gauge starts climbing and after about 20 minutes it is very near the red area so I chicken out and turn the heating off again. The gauge then returns to normal.
When I spoke to Vaillant before the New Year break they suggested that there might be air in the system and a rad might need bleeding. I have checked and all the rads seem fine. Of course they are now closed (despite the charge of 60p a minute on their technical line!)
Does anyone have any bright ideas as to what the problem might be and what I can do about it? I'm upset with my husband and daughter being so cold and would really like to have a 'eureka' moment.
Can anyone help? Many thanks.

 

[bengasman]

Expansion vessel dead of flat.

 

[xr4x4]

what is the pressure cold?

 

[westniner]

Do I have an expansion tank with this type of boiler? If I do then I'm in more trouble than I think I am as I don't know where it is! I've searched all the obvious places and the not so obvious places and can't find one. If it is in the small loft space then I can't access it as there is no loft hatch! Is there a pipe trail I can follow to locate it?
Thanks for your help.

 

[bengasman]

Look in the manual

 

[westniner]

xr4x4
When cold the pressure is where it should be, in the middle of the grey area, 1.2 whatevertheyares, and rises only slightly when I am heating the water. But as soon as I start up the heating the gauge starts climbing and i panic after about 20 mins at 2.6 whatsits and turn it off. It then goes back down to 1.2 things relatively quickly.

 

[westniner]

bengasman
the maual is less than helpful, as is the website. Very few trouble shooting answers and those that there are are very basic, like, have you remembered to put your thermostat up if the boiler won't fire up!

 

[xr4x4]

1.2 maybe a little high, depending on the system. but unlikey to be causing your problem.

0.5 to 1 bar is normal.

i dont know alot about this boiler but its poss the expension vessel is inside the boiler.

this may need recharging or is blown. if air comes out the valve, its most likey blown.

 

[bengasman]

Manual should have an "exploded view" or something similar that shows you where the major parts are.

Vaillant are without a doubt the worst company in the UK when it comes to aftersales/ customer support, which is the main reason why I will never install another one of their products.

Your best bet is to get a good, reliable local independent to service the boiler, as it is probably due for one anyway.