Installation, Start-Up, Adjustment and Maintenance Manual
21
Figure 9
–
WATER PIPING DIAGRAM FOR A SINGLE UNIT
4.2 SIZING A SYSTEM PUMP
When sizing a pump, there are two pieces of information that must be found in order to select the
appropriate pump:
1.
Flow rate (GPM, gallons per minute)
2.
Pressure drop (P.D.)
The OWC-5 has a GPM flow rating of 12 (2.4GPM per Ton) with pressure drop of 13.0 feet of head.
Pressure Drop can be determined by several methods. The equivalent length method is the one
demonstrated in this document. It converts all valves and fittings in to equivalent length of straight
pipe. The pressure drop is determined by the system design (pipe sizes, fittings, equipment). There
are two main units of measure for the pressure, Feet of Head and Pounds per Square Inch (psi).
These two units of measure are related by equation 1:
Equation 1: 1psi=2.31 Feet of Head
To determine the pressure drop using the equivalent length method, follow these steps:
1.
Add up all straight runs of pipe both supply and return.
2.
Count all types of fittings by pipe size and pressure drop.
3.
Find corresponding “Equivalent Length” of fittings on Table
3.
4.
Multiply number of fittings by equivalent length.
5.
Add to
tal length of pipe and equivalent length of fitting together to get “Total Length of Pipe”.
6.
Multiply equivalent length of pipe by friction loss. See Table 4.
1
2
3
4
5
6
OUTLET
INLET
FLEXIBLE CONNECTIONS
PRESSURE / TEMPERATURE
TAPS
WATER FILTER
REGULATION VALVES
WATER PUMP
EXPANSION TANK
1
2
3
4
5
6
7
FILL/DRAIN VALVE
8
AIR BLEED (ON INLET
WATER LINE)
8
7
USE IF THE CHILLER IS THE HIGHEST
POINT IN THE SYSTEM