Heating Help

loop length, pump choice

Have a zone that has 8 loops each about 330' long.  Used insultarp under slab, loops are spaced 12" apart.  Inlet temp is 110 return is 71 degrees.  Pretty sure the insultarp is the biggest problem.  But curious if a bigger pump would help with a higher return temp.  Trying to keep return water to boiler higher and perhaps make more efficient.

Biggest Problem

Is that if you used 1/2" pex your loop lengths are to long. What pump are you using? What is the heat loss of the space?

Exactly,

what is the problem?  Yes, that's a large delta T, but the low return water temperature will make the boiler condense nicely. 

Is the zone heating up?

Looks like

The only thing to do is use a bigger pump, its too late to replace insultarp with better insulation.

With out knowing what the btu requirement is, I can't figure out the needed pump.

330 ft of pipe gives you 17 ft of head, not including elbows.

so you need a pump that will move 1 gpm for every 10,000 btu @ 17 ft of head.

Also the only way to know true rating of a pump is to use a pump curve.