I recently started up my radiant system and I am having some flow problems. I have a geothermal 3 ton heat pump feeding 3 zones(Taco 571-2 zone valves). First is the basement and walk- out sunroom. It is a 7 loop manifold, each loop is approx. 300’. the basement is suspended with the staple up plates and the sunroom is a concrete pad. The second zone is my garage floor. It is a 3 loop manifold with 300’ loops. The third zone is a small unit heater in the garage for make-up air. All my supply lines are ¾” pex approx. 150’ total and the loops are all ½” pex. The pump is in the basement roughly the same height as the basement floor. The garage floor is 10’ above the pump and the unit heater is roughly 20’ above the pump (not sure if the height has anything to do with it). The pump is a grundfos UPS 26-99FC specs are here: http://www.grundfos.ca/web/homeca.nsf/Webopslag/PAVA-53CT8Y

When I run the system I am not getting any flow on my flow meters on the two manifolds. The manifolds are the same as this one:

http://cgi.ebay.com/4-Branch-Brass-Deluxe-PEX-Manifold-Radiant-Heating-/270714906361?pt=LH_DefaultDomain_0&hash=item3f07dda6f9

The basement floor can run on its own or with the garage floor, but when I try to run the garage floor on its own my furnace trips out on an over pressure. The garage slab and sunroom slab are cold as it is winter here I would put them at about 0 to 5 deg C. I am also running 50/50 glycol and water. So I don’t know if the glycol is too cold or if my pump is too small. What do you all think?

Thanks,