AC International 8200 Series Useful Formulas, Single Phase Motor Three Phase Motor

APPENDIX “C” FIELD TEST REPORT

USEFUL FORMULAS
1) Head (ft.) =	Pressure (psig.) x 2.31	S.G. = specific gravity;	S.G. of water = 1.0 at 70°F
	S.G.

2)TDH (ft.) = Total Dynamic Head (ft.) = (Disch. pressure gauge reading - Suct. pressure gauge reading) + (Discharge velocity head - Suction velocity head) +

(Elevation correction to disch. gauge - Elevation correction to suct. gauge)

3)PUMP INPUT HP (BHP) - calculated:

Single Phase Motor			Three Phase Motor
BHP =	Amps x Volts x nm x p.f.	BHP =	Avg. Amps x Volts x 1.732 x nm x p.f.
	746		746

where nm = motor efficiency, p.f. = motor power factor, Avg. Amps = leg1+ leg 2 + leg 3 3

4) Pump Efficiency (np):

np = GPM x TDH 3960 x BHP

5) Affinity Laws for correcting GPM, TDH, and BHP for speed (RPM):

GPM1		RPM1			2	RPM1
GPM2	=	RPM2	or	GPM1 = GPM x		RPM2
TDH1 = ( RPM1 )2			or	TDH1	= TDH2 x ( RPM1 )2
TDH2		RPM2				RPM2
BHP1		3			2	3
		RPM1				RPM1
BHP2	=( RPM2 )		or	BHP1	= BHP x ( RPM2 )

6)NPSHA DETERMINATION:

NPSHA = Net Positive Suction Head Available

NPSHA = (Atmospheric pressure - Vapor pressure of liquid + Total suction head)

Total Suction Head = (Suction pressure gauge reading + Suction velocity head + Elevation correction to suction gauge)

NOTE: NPSHA must always be greater than NPSHR (NPSHA ≥ NPSHR) for the pump to operate without concern of cavitation.

NPSHR refers to Net Positive Suction Head Required by pump. This is a published value obtained from the Pump Manufacturer’s curve.

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