expansion tank sizing

[xalid]

Please help me to find out the simplest way to estimate water volume in a central air conditioning system in order to calculate (Diaphragm Expansion tank size) thanks

[The Viking]

Length of pipe in meters X volume of pipe per meter + additional extras like buffer vessels and chillers.

But generally a good estimate is all that is needed and then go up one size on the expansion vessel compared with what your estimated volume demanded.

Alternatively, if you got AAVs everywhere where they are needed, you could drain the system and refill it via a water meter...

[Brian_UK]

If you don't know the water content use 12 litres per kW of cooling.