ENGINEERING MANUAL OF AUTOMATIC CONTROL
CHILLER, BOILER, AND DISTRIBUTION SYSTEM CONTROL APPLICATIONS
387
The primary side includes shut off valves, differential
pressure, and flow control equipment provide safety functions
and a required differential pressure or flow. Heat metering is
also included. The water flow here is divided into two parts.
The HEX transfers the heat from the primary system to the
DHW loop. A valve placed in series with the HEX controls the
flow. The other part of the primary flow enters the secondary
Fig. 135. Hybrid Heat Transfer Substation.
CONTROL APPLICATIONS
DDC CONTROL OF HIGH PERFORMANCE SUBSTATION
Table 10. Description of Figure 136 Reference Points.
PRIMARY SUPPLY
PRESSURE
CONTROL
∆P=CONSTANT
PRIMARY RETURN
HEAT
EXCHANGER
(DHW)
DHW SUPPLY
DHW RECIRCULATED/
COLD WATER
HEATING SUPPLY
HEATING RETURN
M11433
circuit and transfers the heat to the consumer directly. The
supply flow temperature is controlled by one three-way valve,
two two-way valves, or one jet pump making an additional
circulation pump redundant.
In cases without a jet pump, circulation pumps provide the
needed differential pressure.
Reference Description Reference Description
LIC 56 Water level supervision & control TI 31 PRF temperature (HEX 12)
LIC 63 Water level supervision & control TI 47 SRF temperature
PDIC 14 Primary differential pressure TIC 28 SSF temperature (HEX 1)
PDIC 45 Secondary differential pressure TIC 38 SSF temperature (HEX 12)
PI 13 PSF pressure TIC 44 SSF temperature
PI 16 PRF pressure (internal) TSA+ 22 High temperature limit Primary Return Flow
Heat exchanger 1 (PRF HEX 1)
PI 46 SRF pressure TSA+ 32 High temperature limit (PRF HEX 12)
PI 110 PRF pressure (outdoor) TSA+ 25 High temperature limit (SSF HEX 1)
PIC 57 SSF pressure TSA+ 35 High temperature limit (SSF HEX 12)
PLC S9000 Supervisory Control TZA+ 26 Safety temperature limit (SSF HEX 1, locked)
PSA+ 52 Safety pressure limit (refill pipe) TZA+36 High temperature limit (SSF HEX 12, locked)
PSA+ 58 Safety pressure limit (SSF) TZA+ 41 Safety temperature limit (SSF total, high)
PZA+ 24 Safety pressure limit (high) Y 11 Actuator valve Primary Supply Flow (PSF)
PZA+ 34 Safety pressure limit (high) Y 17, Y 18 Actuator control valve (PDPC)
PZA+ 43 Safety pressure limit (SSF high) Y 19 Safety close off valve
PZA-27 Safety pressure limit (low) Y 23 Actuator control valve
PZA-37 Safety pressure limit (low) Y 29 Damper (secondary flow, HEX 1)
PZA–42 Safety pressure limit (SSF total low) Y 33 Actuator control valve
QIR 53 Metering refill quantity Y 39 Damper (secondary flow, HEX 12)
QIR 62 Cold water metering Y 48, Y 49 Secondary flow circulating pumps
QIR 111 Heat metering Y 51 Actuator valve (water refill from PRF)
TI 01 Outdoor air temperature Y 54 Vent valve
TI 12 PSF temperature Y 55 Compressor
TI 15 PRF temperature (total flow) Y 61 Actuator valve (cold water refill)
TI 21 PRF temperature (HEX 1) Y 64 Feed water pump
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