calculating gpm through chiller barrell

[hvac17011]

I have pressure gauges on supply and return of evap chiller barrel. how do I calculate gpm through chiller barrel to make sure it meets charts.

[jrbertalot]

Use pressure differential and the manufacture's chart. This pressure drop will correspond to a specific water flow for that manufacture.

[txhvac]

Like stated above, use manufacturers flow chart. If you don't have one, you can use this equation : ^T(delta) x gpm / 24 = Tons. You've got tons & delta, ^T / 24 x tons = gpm. There is one which involves square root for ACTUAL gpm....can't remember it though. Your gauges are there to determine not just pressure, but ft. of head. (1 psig = .433 ft) this will help show if the pump is putting out properly. The equation above is more rule of thumb, but it is helpful. Hope this can help.

[wonder_boy]

1 psig=2.31 ft head /you need the chiller spec sheet to find out design gpm and pressure drop thru barrel then you take the actual pressure drop thru barrel and plug it into formula: design gpm multiplied by square root of actual pressure drop divided by design pressure drop

[airdata870]

1 psig=2.31 ft head /you need the chiller spec sheet to find out design gpm and pressure drop thru barrel then you take the actual pressure drop thru barrel and plug it into formula: design gpm multiplied by square root of actual pressure drop divided by design pressure drop

i agree with wonderboy,very well put and 1psi=2.31 ft hd and 1 ft hd = .433 psi. good luck

[drivewizard]

only use one guage to take supply and return pressure readings.
If possible manifold supply and return to one guage using valves to isolate, or use petes plugs to take readings.
Never use two separate guages, not if you want accurate readings.

[bertoh]

dont forget to subtract or add for difference in elevation of two points of measurement

[jayguy]

you can also get the pressure differential through the pump and check the pump curve.

good luck.