Vaillant 620E

[Henpecked1]

I have a Vaillant 620E which keeps faulting to F28. The pressure drops quickly because the system is spewing water out of the overflow.

Reading about a different Vaillant boiler on the forum, the advice was to empty the boiler via the PRV under the boiler; pressurise it to 0.5 bar through the schrader valve at the top, back of the boiler; then close the PRV, refill the boiler and see if it's sorted.

Is this right? If so, where is the schrader valve on a 620E please, or is it obvious when the boiler casing is taken off?

Any other thoughts/suggestions please?

Regards
henpecked1

 

[Dan Robinson]

Don't use the prv.

 

[Henpecked1]

Ok - is it right that the boiler's expansion vessel needs to be repressurised and can I do that easily?

 

[ianmcd]

yes that is correct but as already advised dont use the PRV to de-pressurise, easiest way is to slacken a bleed point on a radiator wait till the water stops flowing, recharge the expansion vessel with the bleed point still open and water will start coming out again so leave a container there to catch it, once the vessel is at the desired pressure close bleed valve and re-pressurise system if water is still coming out of the prv but system pressure is not going up to around 3 Bar, you most likely need to replace the PRV

 

[Henpecked1]

Thanks for that. The house has underfloor heating though, so there isnt a bleed valve available. Can I use the inlet valve to depressurise the boiler [or is that the same as using the prv which is the wrong thing to do]?

Can you tell me where the schrader valve is please?