viessman vitodens 100 expansion vessel problem

[cdel2005]

hi guys,

I have a pressure problem with a viessman vitodens 100 where the pressure rapidly reaches 3 bar once heating is turned on and PRV discharges

I have checked the charge in the expansion vessel and it is at 1 bar
when i press the Schrader valve water comes out

would this indicate the expansion vessel needs replacing?

thanks

 

[nortonj]

Yes needs replacing, or an external one fitting if you have the space.

 

[ScottishGasMan]

No, it does not automatically mean that at all. While the vessel may be faulty. Check a few things first.

1. Have you taken the water pressure off the system down to Zero Bar and left the drain open before checking the pressure in the vessel? If not your reading on the vessel is meaning less.

2. Its quite normal to have a reasonable amount of water in the air side of a vessel due to condensation, yet thousands are replace every year with out a thought.

Open Drain to bring pressure off of heating system (with boiler turned off) recheck with an accurate gauge the pressure in the vessel, set to (for talking sake) 1bar air pressure and leave for say 10 min, check pressure again and if its still at 1bar its doubtfull the vessel is at fault. Now you have a bar of airpressure in the vessel, close the drain and refill/vent system to say 1.2bar, then run heating as normal and see how it goes.

Theres more to vessels than this but start with that.

 

[holty]

could check the braided hose for blockage, seen plenty of vessels changed were the ev was ok but the braided hose was choked . grant oil boilers being a main one. guessing this is an older wb1a with red expansion vessel. or wb1b with grey?

 

[JohnD]

No, it does not automatically mean that at all.

how could water come out of the schraeder valve if the vessel was not faulty?

 

[Tibbot]

It can. SGM has already explained how.