Expansion Vessel - Unvented tank

[Honda5t3v3]

Hi all, this is my first post so please go easy !

My expansion vessel that sits ontop of my Albion Stainless 170 Litre indirect unvented water cylinder has corroded and is dripping water.

The one on is a zilmet 110-Ultra-pro 12 litre, max pressure 10 bar, factory precharge of 3.3 bar.

I have spoken to Albion who have advised that this tank should have a 18 litre one So i have gone and purchased a zilmet 130-calc-pro which is a 18 litre, max working pressure of 4 Bar, precharge of 1.5 bar. Again i confirmed with Albion that a max of 4 bar is fine and i have checked what my tank pressure is and this has never gone above 3 bar.

Question: My system is set at 3 bar, does this mean I need to pump my new vessel up to 3 bar also? or do I leave this at the factory pre charge of 1.5 bar?

Thanks, Steve.

 

[Puddle]

Hi all, this is my first post so please go easy !

My expansion vessel that sits ontop of my Albion Stainless 170 Litre indirect unvented water cylinder has corroded and is dripping water.

The one on is a zilmet 110-Ultra-pro 12 litre, max pressure 10 bar, factory precharge of 3.3 bar.

I have spoken to Albion who have advised that this tank should have a 18 litre one So i have gone and purchased a zilmet 130-calc-pro which is a 18 litre, max working pressure of 4 Bar, precharge of 1.5 bar. Again i confirmed with Albion that a max of 4 bar is fine and i have checked what my tank pressure is and this has never gone above 3 bar.

Question: My system is set at 3 bar, does this mean I need to pump my new vessel up to 3 bar also? or do I leave this at the factory pre charge of 1.5 bar?

Thanks, Steve.

Firstly you say new expansion vessel has working pressure of 4 bar,would like to know max pressure,however if you have checked with Albion and they say ok ,no doubt they will have checked that and usually at least double should be ok

The vessel pressure should be pumped up to just under your 3 bar working pressure ,say 2.8 bar,this will allow for any slight calibration issue and allow maximum use of capacity of your expansion vessel when water heated

 

[Bernie2]

Err! Max working pressure for 18 litre Cal-Pro is 4 bar. The original one has a 10 bar max pressure.

To me 1 bar margin is very low, and basically, it would seem to be the wrong expansion vessel. The Cal- Pro is for sealed heating systems not potable water.

The original Ultra-Pro is for potable water with a max pressure of 10 bar and charge pressure of 1.5 bar.

As a rule you match the charge pressure to the hydrostatic head of the system.

 

[Puddle]

the max working pressure is 4 bar Bernie not max pressure ,I mentioned that in post

 

[Bernie2]

Hi Puddle.

I meant maximum working pressure.

The original expansion vessel was 10 bar max.

The temperature and pressure relief valve is set for 7 bar.

The expansion valve for 6 bar.

What is a maximum working pressure of 4 bar expansion vessel doing on it?

Okay the inlet pressure may be 3 bar as set on the pressure reducing valve. But if the cylinder starts at 3 bar what is the pressure when hot?

Surely 4 bar is to low or if not low very near its max. And it is said you should never set the expansion relief valve blow off pressure higher than the maximum working pressure of the expansion vessel.

So it seems to make sense that the original expansion vessel at 10 bar max working pressure would be about right.