Im going to replace exhisting gravity fed boiler with worcester greenstar 30 cdi.Im taking out the old boiler and changing some of the exhisting pipework to accomadate the worcester.In manual it says if the system is more than 100 ltrs or has a pressure of more than 2.65 bar an extra expansion tank must be fitted onthe return.Without emptying the system in this weather idont know how to calculate the capacity any ideas. Also what size expansion vessel do i need to fit if its needed.
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