CEMP-E
TI 810-11
30 November 1998
maintain the space temperature setpoint as shown by modulating the secondary hydronic system zone
valve.
(3) When the system is in the unoccupied mode, the space temperature setpoint shall be as
shown.
14. CENTRAL PLANT STEAM DUAL-TEMPERATURE HYDRONIC CONTROL SYSTEM.
a. Description of the hydronic system. This hydronic heating and cooling system consists of hot
water from a steam converter, chilled water from a central plant, and related pumping systems. Figures
4-10a through 4-10f show the system design for this type of heating system using a SLDC control panel.
Figures 4-10g through 4-10j show the system design for this type of heating system using DDC controls.
Figure 4-10a. Control system schematic for central plant steam dual-temperature hydronic system.
Figure 4-10b. Control system ladder diagram for central plant steam dual-temperature hydronic system.
Figure 4-10c. Control system equipment for central plant steam dual-temperature hydronic system.
Figure 4-10d. Control panel interior door layout for central plant steam dual-temperature hydronic
system.
Figure 4-10e. Control panel back panel layout for central plant steam dual-temperature hydronic system.
Figure 4-10f. Control panel terminal block layout for central plant steam dual-temperature hydronic
system.
Figure 4-10g. DDC control system schematic for central plant steam dual-temperature hydronic system.
Figure 4-10h. DDC control system ladder diagram for central plant steam dual-temperature hydronic
system.
Figure 4-10i. DDC control system equipment for central plant steam dual-temperature hydronic system.
Figure 4-10j. DDC control system I/O table and data terminal strip layout for central plant steam dual-
temperature hydronic system.
b. General sequence of operation.
(1) Heating and cooling modes are manually selected.
(2) When the system is in the heating mode, the pumping system and the converter operate
continuously whenever the outside air temperature is low enough for the building to require heating.
When this occurs, an outside air temperature controller starts the system pump, and the converter
control is activated. The outside air temperature controller raises the hot water supply temperature as
the outside air temperature falls.
4-15
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