Flow control

BillAllen

Installed a Navien 180 combi. 1 zone fine HW fine but the other zone no flow. T stat calling red light on on TAco SR 502 calling for heat. Circ was on when I left the job heat coming up good. Customer calls no heat. No blown fuses on taco board. I am suspicious about the IFC little plastic flow checks you put inside circs. Just started using them wondering if this is the problem. Could be air although I bled good. Anybody have problems with these types of flow checks? THX