seancmalloy
New Member
I recently installed a Rinnai i120cn with short 1" copper ch loop split by 7 port 1/2 pex-al-pex manifold that connects cast iron radiators. The system has grundfos ups15 internal pump and grundfos UPS15-55SFC external pump after return side of manifold but does not seem to be enough to push water through loop effectively. If I close all ports but a couple it does seem ok. I am at the end of my troubleshooting "expertise" and need professional advise. What can I do to get this system to supply more hot water for central heating?