the flows are always the one that gets hot first so turn it on and hold the pipes
floyche
December 2009
with the system cold, turn on the boiler,now place back of your hands on the 22mm or 28mm pipes coming out of the boiler.within a couple of minutes (more if a old unpumped system ) you should detect HEAT this will be the FLOW the other the RETURN, quickly go to each rad in the system and see if the HOT supply is on the lock shield side(the one with the x head) if not simply swop the caps over .
wirecutterman
November 2009
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