How to size etc. CH expansion vessel

[muggles]

I just use the Flamco calculator

FlexCalc

apps.flamcogroup.com

 

[Johntheo5]

Would you mind using it to calculate the EV size required using the above with the following conditions.
System volume 150 litres.
Flow temperature 70C
Return temperature 60C
Mean temperature 65C.
precharge pressure 1.0 bar
Filling pressure 1.5 bar.
Diaphragm Type inserted bladder

 

[desktop987456]

Fill in these details and I can calculate it for you.

 

[Notch7]

Yes, I mean an 18 litre Expansion Vessel not 18kw. Even I realise EVs are measured thus ... my mistake.

That’s certainly bigger than system boilers, my ideal vogue has a 10 litre tank

I believe the Baxi 600 / 800 system boilers, which are cabinet fit have an even smaller EV.

 

[Johntheo5]

View attachment 334247
Fill in these details and I can calculate it for you.

Thanks but my own basic calculation has worked fine for me for years, when I used the Flamco calc it came up with something like a 30L EV, My calcs above, show that a 14L will result in a final pressure of 2.31 bar.

 

[Johntheo5]

That’s certainly bigger than system boilers, my ideal vogue has a 10 litre tank

I believe the Baxi 600 / 800 system boilers, which are cabinet fit have an even smaller EV.

A 8L EV with pre & filling pressures of 1.0/1.5bar will have a final hot pressure of 2.5bar with a system volume of 83L. If the pre & filling pressures are both 1.0 bar the final hot pressure will still be 2.5bar with almost double a system volume of 157L.
Some do specify both pre pressure and filling pressure, others don't and you can see why.