Just a quick question regarding the flow rates. I am installing 1000' of 5/8 pex al pex in slab in 4 -250' What sort of flow rate should I be looking for. I have a manifold in which I can control the flow of each loop

Thanks

Doug

First hurdle is what is the heatloss?

Gordy

I have 1320 ft2 to heat. Loss is calculated at 25000btu. Using a 50 gal/50,000btu water heater(closed loop). The recommnedation from the heatin guy is to run water heater at 90-100F and circulate a little more. Just wondering what flow rates should be

Thanks

Doug

Assuming the slab is going to provide all the heat and that your transfer medium is water, your total flow rate in GPM is 25000/((8.33 * 60 * delta T) = 50/delta T. So at a 10F degree temperature drop, 5 GPM, divided among the four loops, or 1.25 GPM per loop. A 20F drop halves the flow rate.

Assuming all 1000 feet of tubing are in the slab, you have the tubing 16" on center and need 19 BTUH/sq. ft. I don't have my Wirsbo design manual handy, but you will need to look up what temperature water you need for your given slab thickness, insulation, and floor covering R-value to get that output at the given spacing and flow rate.

for what it's worth I'd do the 20 drop, half the flow, and use 1/2" pipe.

5/8" isn't doing much for you here.