combi flow and return

[foz]

Chaps,
are combi boilers flow biased,ie, does it matter which pipes i plumb the heating circuit into,
should I trace the direction from the original pump?

[johnb]

hi foz yes you must connect flow to the existing flow find the flow from the old installation as the pump may not have been on the flow if pump is flowing from rads this is the return if flowing too rads it is the flow, also y our boiler manufacturer may require you to fit an automatic bypass valve between flow return. check all the best john

[wingleburtbenglebink]

Your thermostatic rad valves may cause water hammer unless they are bi-directional. If you can connect as existing it might save you some agro.