Balancing radiant floor heat


Old 02-06-09, 06:35 AM
petrs's Avatar
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Join Date: Dec 2008
Location: MA, US
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Balancing radiant floor heat


I have question about balancing radiant floor heat.

Last summer I installed radiant floor heat in my 2 floor house. Each floor consist of three loops, each loop about 300 ft (+/- 5 ft) using " PEX tubing with oxygen barrier. Each floor uses its own pump that is set to the medium speed (3 speed setting). The tubing is stapled under the subfloor, I used aluminum distribution plates (on the 1st floor almost continuously), then reflective aluminum foil, R19 insulation under 1st floor and R13 under 2nd floor. Under the 1st floor I put one more layer of the aluminum reflective foil simply since I had a lot of left.

Since the 1st floor is over unheated basement and garage I had little trouble reaching the desired temperature and I was thinking to add 2 extra 300' loops under the 1st floor. My question is how it will be with the balance of my system. I would have 3 loops (300' each) in the 2nd floor and 5 loops (300' each) under 1st floor + maybe a little baseboard radiator in the basement. Currently I had 3x300' under each floor so when both zones were open the flow was distributed evenly into each floor.
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Old 02-06-09, 04:46 PM
Join Date: Mar 2006
Location: Wet side of Washington state.
Posts: 18,399
I personally feel that 300 feet of 1/2 inch tubing is way too long for a loop, I would prefer to see no more than about 100 feet in 1/2 inch and maybe 150 feet of 3/4 inch as the maximums.

Be that as it may. All the loops of a particular zone should be made up to a manifold and they should all have the flowmeter (actually rotameter) fittings to allow precise flow adjustment on each individual loop.

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