Heating Pipe sizing - pressure drops


I have drawn a heating system with design criteria set at max pressure drop of 200 Pa/m, some sections of pipework are coming up much higher than 200 once calculated. For example, a heavy grade steel 15mm pipe @ 80°C and a flow rate 0.062kg/s is showing a pressure drop of 387, would expect it to be much lower than this. 

Please can you advise?