CEMP-E
TI 810-11
30 November 1998
switches and should be wired as a return fan, as shown in figure 4-6g. The right side of the figure shows
the pump starter wiring. A safety shutdown circuit is not required. A jumper is shown installed between
terminals 205 and 206. Each pump will have an "ENABLE-OFF" switch.
j. Figure 4-6i shows the HVAC control panel power wiring for ac and dc sources.
11. CENTRAL PLANT STEAM HYDRONIC HEATING CONTROL SYSTEM.
a. Description of hydronic heating system. This hydronic heating system consists of a steam to hot
water converter that provides hot water to a primary pumping system. The primary pumping system
supplies hot water to secondary pumping systems that provide hot water to separate zones of space
temperature control. Figures 4-7a through 4-7f show the system design for this type of heating system
using a SLDC control panel. Figures 4-7g through 4-7j show the system design for this type of heating
system using DDC controls.
Figure 4-7a. Control system schematic for central plant steam hydronic system.
Figure 4-7b. Control system ladder diagram for central plant steam hydronic system.
Figure 4-7c. Control system equipment for central plant steam hydronic system.
Figure 4-7d. Control panel interior door layout for central plant steam hydronic system.
Figure 4-7e. Control panel back panel layout for central plant steam hydronic system.
Figure 4-7f. Control panel terminal block layout for central plant steam hydronic system.
Figure 4-7g. DDC control system schematic for central plant steam hydronic system.
Figure 4-7h. DDC control system ladder diagram for central plant steam hydronic system.
Figure 4-7i. DDC control system equipment for central plant steam hydronic system.
Figure 4-7j. DDC control system I/O table and data terminal strip layout for central plant steam hydronic
system.
b. General sequence of operation.
(1) The primary pumping system and the steam/hot water 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 primary pump, enables the converter control
4-7
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