Vaillant Combi condesing boiler losing pressure daily no sign of leak

bambibashercol

Undo the nut (4) on the water pipe on the lower side
of the expansion vessel.
• Remove both screws (1) retaining plate (2) and remove
the retaining plate.
• Pull out the expansion vessel (3) forwards.
• Guide the new expansion vessel back into the appliance.
• Re-connect the new expansion vessel using a new seal.
• Refix the retaining plate.
• Check the pressure of the expansion vessel (minimum
pressure 0.75 bar).
If necessary, adjust the pressure to the static height of
the heating system.
• Fill and vent the boiler.
• After completing the work, check for water leaks and
perform a function check (see section 7.6)!

checking expansion vessel.
Note
It is not necessary to perform this check every
year – a check every three years is sufficient.
• Ensure the boiler CH service valves are closed.
• Release the pressure from the boiler.
• Remove valve cap from expansion vessel charge point.
• Check that the internal charge pressure of the expansion
vessel is between 0.75 and 0.9 bar.
If the pressure is lower than this the vessel should be
repressurised using an air pump.
• Refit the valve cap.
• Repressurise boiler and heating system.
7.5 Recommissioning the boiler
• Carry out electrical safety checks.
• Turn on the electrical supply.
• Open the boiler CH service valves.
• Carry out function checks of boiler operation as previously
detailed.
• Check gas rate as previously detailed.
• Check for water leaks.
• Refit case, ensuring that a good seal is obtained.
7.6 Test operation
Always perform the following checks after completing
any maintenance task:
• Commission the appliance according to the relevant
operating manual.
• Check the appliance for gas and water leaks.
• Check the air/flue gas system for leaks, check its fastening
• Check for ignition and an even flame on the burner.
• Check that the heating system and the water heating
is working (combination boilers only).

bambibashercol

If you have not got the manual i can give you a e mail address where you can see it online

C_Mababejive

Lady_K wrote: »

. I've had 4 plumbers round already that have just said its got to be a leak in the system and until I know where it is they can't do anything. Its also been serviced twice and those times I've told them about the regular topping up and they also didnt say anything other than it must be a leak.

That is poor. Your symptoms clearly describe what the issue is likely to be..i.e expansion vessel problems. these guys were obviously clueless.

Lady_K

Thankyou everyone

I have printed some of the info here off to show the person whos going to look at it for me. I'll let you know how it goes

I actually turned down insurance for the boiler from vaillant when they wrote to me earlier this year because I had no trouble at all with my old one that lasted 18 years and I know they are reliable boilers usually. I am regreting that now

bambibashercol

Don't regret it as its nothing major. post on here tomorrow and if i am about i will pm my phone number and talk your friend through it.

Lady_K

We had a look and couldnt do it we just don't know how to drain the water off or how to.

We tested the vessel valve and nothing came out but a bit of air so my relative checked the pressure with the "-" button not the gauge and it was 0.3 bar z\so he pumped it up checked the pressure with the "-" button again and and did it to 1.5 but as soon as we switched the heating on it went right up to the red bar again. We dont know how to isolate the incoming and outcoming whatever it is and where the drain thing is or how to drain it so this is probably what is wrong. He was worried about not knowing enough and doing something dangerous so I will probably have to get someone to do it unless I can find out what we were doing wrong.

We tried releasing some air from the valve and testing it in stages right down to 1.0 bar but it still rose when heating was on. It is now showing 2.0 bar on the "-" button with heating on but 1.0 bar when heating is off

C_Mababejive

Was the new boiler fitted to an existing older system?

If so,how long ago?

did the installer flush out the system prior to and after fitting the new boiler?

Lady_K

yIt was fited 4 years ago in December and yes they came back and reflushed it as there were various problems since it was installed. It was fitted to existing system but moved from loft down to the kitchen.

Adding to the above post, I have not topped it up with any water today though it started just with pumping the vessel but that obviously is still not quite right as it goes too high when heating is on even when its set at 1.0 bar without heating on

EliteHeat

You cannot pressurise the expansion vessel when there is water in the other side.

If you are really stuck, half empty one of the radiators and then bleed all of the others, bring the pressure up on the boiler and then restart the boiler. The half empty rad will act as a pressure vessel.

This is a temporary, get out of trouble fix.

Lady_K

I wonder why vaillant don't put the cost of thier service warranty on the site, you have to call them to get a quote.

Which is the best one to have they have 3 star or 5 star?