My current setup in the house is 3 zones, one for each level of a 1800sq/ft split level house. Each zone is approximately the same size and length of pipe. Each zone is on it's own valve and the entire system is powered with a Grundfos 15-42f pump.
I just finished a kitchen remodel and swapped out one of the baseboards for heated floors using ultra-fins. I removed around 20ft of 3/4in copper pipe and added approximately 150ft of 1/2in pex. Now the 15-42f is struggling to move the water/heat through that loop!! even with the other 2 zones off, I'm not getting any heat through that loop and it sounds like the pump is struggling to pump (if I open another loop you can hear the pump stop struggling).
So my question is, should I find a way/place to add an additional pump on that loop to help the 15-42 move the water or should I upgrade the 15-42 for a bigger pump?