Bell & Gossett 193 TECHNOVAR VARIABLE SPEED PUMP CONTROLLER AND INTEGRATED AJUSTABLE FREQUENCY DRIVE - Manual (Page 40)

Operating Instruction
40
Generally a slight pressure drop is allowed on the first pump before the next is started.
This allows for brief systems fluctuations without pump cycling. Once the next pump
starts, however, you will want the system to resume its normal set pressure.
To do this, enter the amount of pressure drop you will
allow before the next pump starts (= value of
parameter ACTUAL VALUE DECREASE). The diagram
shows the pressure drop and increase.
To increase the pressure even more to compensate for
system loss at higher flows, enter the total of the
system drop allowed before next pump starts and the
increased pressure (ACTUAL VALUE INCREASE) desired.
Application example:
1) Pump 1 reaches the speed of ENABLE SEQ: CONTROL or more
2) Pressure falls and reaches the start-value of the 2 nd pump
(= REQUIRED VALUE – ACTUAL VALUE DECREASE)
3) Pump 2 is switched on automatically
4) The required value is calculated new, after the start of the 2 nd pump in the following
way!
New required value = REQUIRED VALUE – ACTUAL VALUE DECREASE + ACTUAL
VALUE INCREASE
Generally:
k ... Number of active pumps
P = P
set
+ (k-1)*[lift value – fall value]
· Lift value = Fall value Þ Pressure constant when pumps switch on
· Lift value > Fall value Þ Pressure rises when lag-pump switches on
· Lift value < Fall value Þ Pressure falls when lag-pump switches on
Enter the required value by pressing the and button ACTU. VALUE INC.
7,1 psi
Press the button to confirm and change to ACTU. VALUE DEC.
2,1 psi
ACTUAL PRESSURE DECREASE (= Fall value):
This value determines amount of pressure drop you will
allow before the next pump starts.