Rookie - Trouble with Radiant Floor Heating

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Barley
Posts: 1
Joined: Tue Mar 13, 2012 7:33 pm

Rookie - Trouble with Radiant Floor Heating

Post by Barley »

I'm hoping I can get some assistance. I just bought a house with radiant floor heating and radiator/blowers on each floor. It's a closed system with approximately 1200 ft of copper and pex for the floors. It has Grundfos pumps (UPS15-58 1/25HP). It is also a three story home with a detached boiler shed. From the boiler to the 3rd floor is approximately 40ft in elevation change. The first floor houses the Grundfos pumps. The system pressure at the boiler and the return in the house read 10 psi.

The Problems:
The 3rd Floor Blower: Set to 72 degrees. Only reaches 66.
2nd and 3rd Floor Radiant Heat: Inop - The heat disapates in the first few feet past the zone valve. The pex supply to the 2nd and 3rd floor are cool to the touch.

Suspected Problem:
After some reading is sounds like the psi is a little low. Recommended psi ranges from 12-15. I've also been told by a plumber that psi has no effect, but from all my reading and what seems logical it does play a big role. I tried using the "pressure loss" calculator but the pressure required that I came up with seemed much to high.

I would very much like to learn about the role system pressure plays vs. the pressure output of the pump and thoughts on how to get the system working properly.
admin
Site Admin
Posts: 375
Joined: Mon Feb 08, 2010 7:47 pm

Re: Rookie - Trouble with Radiant Floor Heating

Post by admin »

As water flows in closed circle, height difference is not important, but longest pipe loop is critical and should be checked with pressure drop calculator.
So, you must know the longest loop, loop length and inside pipe diameter, with specification of all tees, elbows valves on the way to calculate resistance factor.
Anyway, 12-15 psi seems very low for me, but it can be checked.
Pipe flow calculations - since 2000
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