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Hi all, I wonder if someone can explain something to me when it comes to expansion vessel sizing.
On the basis of about 4% expansion at 100degrees one would think that for a 200l closed system an 8l expansion vessel would be sufficient, with a bit of a safety factor say 10l.
Worcester installation instructions for Greenstar CDi Classic which has a 7l internal expansion tank says a system larger than 100l needs additional expansion, assuming the above 200l system we're now at 14l
Using the following formula from Advanced Water Company
V= eC / (1- p1/p2)
Where:
V The total volume of the expansion vessel. It is not the acceptance volume.
C The total volume of water in the system (Litres).
p1 The fill pressure in Bars absolute (atmospheric or gauge pressure plus 1 Bar).
p2 The setting of the expansion/pressure relief valve in Bars Absolute (atmospheric or gauge pressure plus 1 Bar).
e The expansion factor that relates to the maximum system requirements.
Assuming I understand what they mean by p1 and p2, gives a volume of just over 201
Asking an experienced and well thought of plumber I know he says 24l......
Upshot of all this, can someone shed any light on how to properly size an expansion vessel for a combi on a larger system? An explanation would be gratefully received as "You're over thinking it, just do this..." doesn't really work with the way my mind works unfortunately.
On the basis of about 4% expansion at 100degrees one would think that for a 200l closed system an 8l expansion vessel would be sufficient, with a bit of a safety factor say 10l.
Worcester installation instructions for Greenstar CDi Classic which has a 7l internal expansion tank says a system larger than 100l needs additional expansion, assuming the above 200l system we're now at 14l
Using the following formula from Advanced Water Company
V= eC / (1- p1/p2)
Where:
V The total volume of the expansion vessel. It is not the acceptance volume.
C The total volume of water in the system (Litres).
p1 The fill pressure in Bars absolute (atmospheric or gauge pressure plus 1 Bar).
p2 The setting of the expansion/pressure relief valve in Bars Absolute (atmospheric or gauge pressure plus 1 Bar).
e The expansion factor that relates to the maximum system requirements.
Assuming I understand what they mean by p1 and p2, gives a volume of just over 201
Asking an experienced and well thought of plumber I know he says 24l......
Upshot of all this, can someone shed any light on how to properly size an expansion vessel for a combi on a larger system? An explanation would be gratefully received as "You're over thinking it, just do this..." doesn't really work with the way my mind works unfortunately.
