the quick fill loop generally is connected to c/h flow/return & then to the main. but should only be connected while fillng boiler.remove once filled. because of contamination. put hose on c/h flow/return whichever has connection & just open valve & release pressure ,remember for boiler to be off.take down to nearly !/2 bar to 1 bar that should be adequate enough. it may be going off at high pressure /high limit
due to no movement of flow.
gary
March 2008