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alpha2 max speed

I finally finished my staple up floor heat! It’s 6 loops each loop ~300’ of 1/2” pex-al-pex.
There are a couple (< 3) repair fittings on each loop.
At the design load of ~21K BTU, this gives a total zone flow rate of about:
21000/5000 = 4.2 GPM, which is an average flow rate of .7 GPM per loop,
which implies a head loss around 7 ft.
21000/5000 = 4.2 GPM, which is an average flow rate of .7 GPM per loop,
which implies a head loss around 7 ft.
This is well within the range of an alpha 2 pump, at 4.2 GPM the pump curve is about 14-15ft of head.
If I set the pump to the “high fixed speed” setting, I’m only getting the alpha2 to display 2GPM, and it getting between .25-.5 GPM per loop.
If I set the pump to the “high fixed speed” setting, I’m only getting the alpha2 to display 2GPM, and it getting between .25-.5 GPM per loop.
Shouldn’t I be capable of pushing the water much much faster given this setup?
What am I missing?
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Comments
Don't trust that readout on any of the ECM circulators, it is a calculation not actual measured flow rate, I have seen them off 60% when checked against a lab quality flowmeter.
I have one running on my display right now, shows 0 GPM but the Quicksetter next to it indicates 4 gpm and it is clear plastic tube, so I see the movement and flow speed
Without a reliable flowmeter you really do not know the actual flow rate is.
trainer for Caleffi NA
The magic is in hydronics, and hydronics is in me
that is ~1.5 GPM on the pump.
http://www.taco-hvac.com/uploads/FileLibrary/SelectingCirculators.pdf
k = 0.0394
c = 1.1 (overestimate)
this yields:
H = .0233*L
at 300 feet that’s about 7ft.
If .5-.6 gpm gets the job done, I would not worry about getting exactly .7. Most flowmeters have an accuracy tolerance =or-.
trainer for Caleffi NA
The magic is in hydronics, and hydronics is in me
there are a few fittings on the pipe, then a pump, then a brass nipple into a caleffi 6 port manifold.
each loop is <= 300’ of pipe and each loop may have a few repair couplings.
On what is likely the largest loop, I appear to be getting < .5gpm, reading around .25gpm.
Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England.
Hoffman Equipped System (all original except boiler), Weil-Mclain 580, 2.75 gph Carlin, Vapourstat 0.5 -- 6.0 ounces per square inch
trainer for Caleffi NA
The magic is in hydronics, and hydronics is in me
Could I just measure the Delta-P on the drain cock of the manifold with all but one zone closed?
EDIT: would it work to take a pipe off the drain cocks with a tee and just stick an ordinary pressure gauge on it, sort of like configuration #4 ?
Then, of course, you can put additional taps -- and gauges -- at opposite ends of a loop or whatever you want to measure.
Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England.
Hoffman Equipped System (all original except boiler), Weil-Mclain 580, 2.75 gph Carlin, Vapourstat 0.5 -- 6.0 ounces per square inch