Vaillant eco tec 615 system boiler losing pressure

[Tally101]

Hi All
I have a 10 year old Vaillant eco tec 615 system boiler thats losing pressure, it loses approx 0.1 bar per day so I have to top it up each week. Nothing comes out of the PRV, no loss of water on any rads, no signs of water loss. The heating engineer found on a recent service a valve that was leaking and signs that it was leaking and changed it but the rest of the boiler looked ok.
Question is what do I do next please.
Thanks

 

[Tally101]

pressure doesn't go up when boiler on.

 

[CountryFan]

Could be the main heat exchanger, any loss on a motorised valve?

 

[Tally101]

no loss seen on a motorised valve, both was replaced about a year ago I know that doesn't mean its not faulty but there's no sign of a water leak.
If it's the main heat exchanger is it worth replacing as its 10 years old or changing the boiler ?
Thanks

 

[CountryFan]

If it's the main heat exchanger is it worth replacing as its 10 years old or changing the boiler ?
Thanks

Probably new boiler time given the age, depends if it's served you well. New main heat exchanger approx £700 for the part no labour! You could isolate the boiler from the system to help find the loss.

 

[Tally101]

Last 2 boilers lasting 10 years each was Vaillant. Is it time to change for a another system boiler ?

 

[CountryFan]

Last 2 boilers lasting 10 years each was Vaillant. Is it time to change for a another system boiler ?

Maybe see how this one pans out?

 

[spile]

Last 2 boilers lasting 10 years each was Vaillant. Is it time to change for an another system boiler ?

I’ve concluded that Vaillant went through a bad time 8-12 years ago and their boilers during that window have more faults than the norm.

 

[Tally101]

How do I test if rads are leaking if I can't see any water drips, the boiler engineer changed the part that looked like it was leaking but said all other parts look dry, how can I check if its the boiler thats the problem or the rads ?
Thanks

 

[Harry Bloomfield]

How do I test if rads are leaking if I can't see any water drips, the boiler engineer changed the part that looked like it was leaking but said all other parts look dry, how can I check if its the boiler thats the problem or the rads ?

With boiler cold - Switch the boiler off, so it cannot fire, then turn off both central heating isolators at the boiler. Check and record the pressure, wait, then check it some hours later. If the pressure reduces, your boiler has a leak.

 

[Tally101]

Thanks Harry Bloomfield

 

[Tally101]

Hi . Im ready to do the test but I have just realised I was going to leave it 24 hours to do the test, I have an immersion heater to heat the water but its got a Solar Boost connected as we have Solar panels and excess to to boiler. do I just turn off the Solar Boost when I want to heat up the water as the imersion switch is open all the time now with the Solar Boost or won't the immersion now workman all from mains electricity .
I thought it was an Allen key to shut off the valves underneath but I cant see the valves properly is it Allen keys or another type of key

Thanks

 

[Tally101]

Hi All

its this I need to turn to isolate the boiler Vaillant 0020010296 Service Cock

VAILLANT 0020010296 SERVICE COCK | Direct Heating Spares

Buy the Vaillant 0020010296 Service Cock from Direct Heating Spares. DHS Part Number: 1379470 - Manufacturer Code:20010296. We have over 20,000 items in stock and available Next Day. Free Boiler Manuals also available to download.

www.dhsspares.co.uk

what do I use to turn it on/off
thanks

 

[dilalio]

Allen key to turn off both flow and return valves.

 

[CountryFan]

4mm or 4.5mm Allen key to turn off both flow and return valves.

Edited for clarity