Combi boiler pressure vessel

[AndySmith]

Hi all. I am wondering if someone could tell me what are the consequences of putting too much pressure into a combi boilers pressure vessel? My understanding is the pressure vessel should be charged with 1 bar of air.

What problems would potentially materialise if it is filled it to 2bar or more?

Thanks in advance.

Andy

 

[St0rmer66]

Not a lot other than it will fail to do it's job correctly. 2bar plus the water pressure on the other side of the diaphragm should still be within the safe working limit for it not to do any permanent damage. 1bar is a common figure but it depends on the size of the vessel among other things, not all are the same.

 

[londoner1]

You would release some pressure by bleeding your rad, that will bring it down to 1.0 to 1.5 bar.

The only other problem could be that if you keep it at 2bar and you operate the boiler, when it reaches 3 bar the prv will kick in and dump water via the copper pipe outside, this will mean a possible prv replacement and repressure of the vessal.

 

[AndySmith]

Just to be clear, I am not referring to putting water into the system. I am talking about how much to charge the pressure vessel with air.

Vaillant Ecotec Plus Expansion Vessel Part No. 181051 is the item in question.

Thanks for the replies.

 

[St0rmer66]

Yes, I realised you were talking about air... my advice was for that.

Ecotec is 0.75bar +/- 0.2bar (that was from memory!).

 

[Madrab]

I think that was in reply to Londoner Storm

Andy, 2 bar of air pressure means that it will take > 2 bar of pressure on the wet side for the EV to start doing it's job, which is to absorb the expansion of the hot water and keep it below the safety release pressure. It should be a simple process to bleed some air pressure from the EV through the valve until it sits at at least 0.75bar. Just get a tire pressure gauge to set it.

 

[Agile]

How do they access the EV without removing the room sealed case?

 

[Madrab]

lol... Yup fair enuf, get the GSR that overcharged the internal EV back to set it up correctly or the above if the vessel is external to the boiler.

 

[AndySmith]

Thanks for the replies, please forgive my ignorance but what do you mean by room sealed case?

There is one big screw at the bottom of the boiler, once undone the cover comes off. Then you have access to the expansion vessel on the top right.

What I was wondering is, could the EV not be ruptured if too much air is pumped inside or create excess pressure elsewhere in the system?

Again thank you all.

 

[Agile]

The air pressure in the EV should always be recharged with the system depressurised.

Then however much pressure you put in it, it is always contained by the outer metal case.

When the system pressure is higher the water just pushes the diaphragm back so there is never any stress in it as the pressure is balanced and the same on both sides.

Tony

 

[Madrab]

Room sealed case Andy - Only a GSR is qualified to remove the case and enter that type of boiler, to do the work needed on the EV. Opening the case is considered to be entering the combustion area.

 

[TCCHeating]

Thanks for the replies, please forgive my ignorance but what do you mean by room sealed case?

There is one big screw at the bottom of the boiler, once undone the cover comes off. Then you have access to the expansion vessel on the top right.

What do we mean by room sealed case?

Probably the one with the big screw at the bottom that when removed gives you access to the expansion vessel

 

[Agile]

Not only is there a nut/screw, but there should be two stainless steel clips at either side too!

Only RGIs should remove the case on this type of boiler as the case seals form the room sealing of the boiler so combustion gases have no way to enter the room.

Tony

 

[AndySmith]

Thank you all for the useful information. Much appreciated.

 

[simond]

With an ecoTEC exp vessel, they only last about 4 yrs anyhow (Zilmet). Over pressurizing it can only make it even shorter.