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[schoppy]

Wondering if anyone knows what the recommended flow rate should be for each loop of a 10 loop manifold in floor system? It is 1/2" oxygen barrier pex with each loop running 225' to 275' in length. Each loop has a flow gauge and is adjustable.

Thanks, Schoppy

[slimjim]

I don't think it matters as long as they are all flowing about the same!

[willieG]

according to pex universe site, recommended flow for 1/2 is 0.6 gpm (300 foot loop max) should produce between22 and 30 btu per hour per square foot (9 to 12 inch spacing)

each additional 0.6 gpm will increase btu output 5 btu per square foot per hour

[schoppy]

All the loops are nice and even. Last year I was using a much larger pump, B&G NRF36, and the flow rate was way higher than .6 gpm even on low which may have been why my delta T was high. I have installed a Grunfos Alpha now and can still get way over .6 gpm if I want but should be able to back it down and hopefully get a lower delta T.

71 degrees here today so it may be awhile before I get to try it out.

Thanks guys

[willieG]

f your have a header  with 10 loops running off of it and you want .6 gpm to each loop you will require a pump capable of delivering 6 gpm to the header (mixed at your desired temp)  you say you were delivering much higher rates? that should lower your delta. I am no exert on floor loops but the guy who installed  mine said I should look for a difference of no more than 10 degrees (example-110 in 100 out) 

[schoppy]

I was talking about the delta T across my 40 plate heat exchanger not the in to out temp of the 10 loops themselves. When it first starts up there are larger delta T's across both the plate and the floor but I will do more checking having changed the pump for the in floor system now. I think the pump is rated at about 20 gpm and 21 head and it was doing great at about 1/3 the wattage.

[mlappin]

I’m not sure about this, still a little giddy about the cubs winning the WS, but too much flow thru a radiant loop can also be a bad thing if I remember correctly.

[willieG]

yes, moving water too fast through any piping system can cause premature wear on fittings and the pipe itself. I believe the charts I have seen rate 1/2 pex at about 2.3 gpm

[mlappin]

yes, moving water too fast through any piping system can cause premature wear on fittings and the pipe itself. I believe the charts I have seen rate 1/2 pex at about 2.3 gpm

Yah, I was thinking on another forum H and H maybe, that water moving too fast thru a radiant loop won’t produce as much heat as slower moving water.

[schoppy]

If I remember correctly, I am getting about .75 gpm on each loop with the Alpha pump.