CEMP-E
TI 810-11
30 November 1998
Figure 4-11d. Control panel interior door layout for central plant high-temperature hot water dual-
temperature hydronic system.
Figure 4-11e. Control panel back panel layout for central plant high-temperature hot water dual-
temperature hydronic system.
Figure 4-11f. Control panel terminal block layout for central plant high-temperature hot water dual-
temperature hydronic system.
Figure 4-11g. DDC control system schematic for central plant high-temperature hot water dual-
temperature hydronic system.
Figure 4-11h. DDC control system ladder diagram for central plant high-temperature hot water dual-
temperature hydronic system.
Figure 4-11i. DDC control system equipment for central plant high-temperature hot water dual-
temperature hydronic system.
Figure 4-11j. DDC control system I/O table and data terminal strip layout for central plant high-
temperature hot water 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, as selected by a panel-mounted
HEATING/COOLING switch, the pumping system and the high-temperature hot water converter operate
continuously whenever the outside air temperature is low enough for the building to require heating. This
temperature is to be selected by the designer. When this condition is met, an outside air temperature
controller starts the system pump, and the converter is under control. As the outside air temperature
rises and falls, the outside air temperature controller resets the hot water supply temperature setpoint in
accordance with a schedule established by the designer.
(3) The hot water supply temperature controller maintains the scheduled hot water supply
temperature setpoint by modulating the high temperature hot water converter valve.
(4) When the system heating/cooling switch is indexed to cooling, the converter valve closes.
The pump continues to run for cooldown of the system water. When the return water temperature falls to
29 degrees C (85 degrees F), the changeover valves divert the water flow from the converter to the
central plant chilled water system.
(5) As long as the switch HS-XX-02 is indexed to cooling, the pump will be energized during the
occupied mode and de-energized during the unoccupied mode.
c. Detailed sequence of operation.
(1) Manual HEATING/COOLING switch HS-XX-02 allows for indexing of the system between the
heating and the cooling modes.
4-18
Previous Page
