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Plumbing / pump undersized?

« on: October 03, 2013, 08:18:36 PM »

Thinking my pump is greatly undersized but can't get my head wrapped around the calcs so need your expertise.
My main loop is 300' one way of 1" pex with crimp style fittings so effectively 3/4" and more or less level grade to house.
 In the total loop I have 12 90 degree fittings and a 30 plate dhw. Off the main loop in close t feeds and returns with 007
pumps I have a 20 x 20 hx in my furnace,a 4 loop radiant in floor manifold, and a 6 loop infloor manifold in my 36 x 48 shop.
The main loop pump is a 3 spd 15-58 grundfos mounted in my shop on the return side 50' before the boiler. My return temps
 fluctuate of course depending on demand but can be as much as 60 on a cold morning. Not totally concerned with the lower
return temps as my feed returns to center of boiler amidst secondary heat exchangers but thinking I could improve return temps
 and not have the thoughts in the back of my mind of cold shock possibilities.
Appreciate any thoughts or recommendations on brands and sizing.
Tony