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[ralphxj]

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?

[wreckit87]

You've got air in the loop somewhere or a bad circ, maybe both. That circ will push more BTU than your whole house needs

[ralphxj]

Finaly got it. There is a reduction valve between the valve to let in domestic water to fill the system and the main system loop. It wasn't letting in much water and I didn't let it run long enough. Finally get enough water in to fill the loop.

[E Yoder]

I was going to agree with wreckit, sounds like air to me. I did that on my father-in-law's house, added 200' of 1/2" pex on the end of the baseboard loop to heat the entryway and kitchen floor. Teed off to allow most of the flow slide by to avoid choking the baseboard loop, sent just enough into the floor to warm it up. Works great and feels much better than the old baseboard did.