Please can someone help with calculating the size of a low loss header or point me in the direction of a website or guide that has the info. I need to install a single horizontal header to transfer approx 40kw from Plate heat exchanger connected to heat pump in to a single heating circuit. Duty will be 0.93l/sec @30kpa 10degC TD. Pipework going in and out of header will be 42mm copper 
. I would prefer to use a 67mm copper header but cannot work out total length of horizontal header or tapping distances on primary or secondary side???
Any assistance would be most appreciated.
. I would prefer to use a 67mm copper header but cannot work out total length of horizontal header or tapping distances on primary or secondary side???Any assistance would be most appreciated.