IM 781-2 Page 11
Figure 9. Lead/Standby Secondary Pumps
Decoupler line temperature
FM
Uni-directional flow meter
(supply to return)
a0102
Using the lead/standby secondary pumps enables the CSM or the user to select what pump is the lead pump and what pump
is the standby pump. If the lead pump fails, the standby starts automatically. The auto-lead feature automatically swaps the
lead and standby pumps based on run time.
Figure 10. Sequenced Secondary Pumps
Note:
If a pressure-controlled loop bypass is used with sequenced
secondary pumps, only one differential pressure transducer is required.
DPT
Differential pressure transducer
Decoupler line temperature
FM
Uni-directional flow meter
(supply to return)
a0103
Using sequenced secondary pumps enables the CSM to turn the pumps on and off to maintain a constant pressure
differential between the secondary supply and return lines.
Note: If a pressure-controlled loop bypass valve (Figure 11) is used in conjunction with sequenced secondary pumps, the
same differential pressure transducer signal can be used to control the pumps and the valve.
Loop Bypass Configuration
The CSM modulates the bypass valve to maintain an adjustable differential pressure. The bypass line and differential
pressure sensor is installed between the chilled water supply and return lines.
Figure 11. Pressure-Controlled Loop Bypass
DPT
Differential pressure transducer
a0104
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