ENGINEERING MANUAL OF AUTOMATIC CONTROL
CHILLER, BOILER, AND DISTRIBUTION SYSTEM CONTROL APPLICATIONS
379
C2588
RELAY
CLOSES
VALVE IF
SAFETY
LIMITS
EXCEEDED
HIGH
TEMPERATURE
WATER VALVE
HTWR HTWS
STORAGE
CONVERTER
STEAM
MAKE UP
WATER
LEVEL
CONTROL
LOW
WATER
CUT OFF
MAKE UP
WATER
CONDENSATE
RETURN
STEAM
GENERATOR
BLOWDOWN
AND DRAIN
FEED
INLET
RELIEF
VALVE
PRESSURE
HIGH LIMITPRESSURE
CONTROL
OPTIONAL
ALARM
HTW STEAM GENERATORS
Using the central HTW boilers for steam production is not
recommended. The HTW system is best used to produce steam
by locating steam generators at the point of need.
The steam generator (Fig. 125) is designed so that the
minimum water level covering the tubes takes up 60 percent or
less of the volume of the shell. The remaining 40 percent for
steam is sufficient to avoid water carry over. A water eliminator
at the steam exit removes most water from the steam.
Flash converters convert HTW to steam by reducing the
pressure. They are not satisfactory steam generators because
water is carried with the steam and control is less stable.
Control of a steam generator is simpler because pressure
changes are sensed immediately and corrections in valve position
are made quickly to maintain the desired steam pressure.
Fig. 124. HTW to HW Multizone Storage Converter.
Fig. 125. Steam Generator Using HTW.
C4627
RELAY CLOSES
VALVE WHEN PUMP STOPS
(NOT REQUIRED TO
PREVENT FLASHING)
HIGH TEMPERATURE
WATER VALVE
HTWR HTWS
STORAGE
CONVERTER
HOT WATER
TEMPERATURE
CONTROL
TO PUMP INTERLOCK
AND/OR OUTDOOR
CONTROLLER
TO HOT WATER
CONVERTER
RESET SIGNAL
FROM OUTDOOR
CONTROLLER
HOT WATER
3-WAY ZONE
VALVE
PUMP
MANUAL
BALANCING
VALVE
TYPICAL ZONE
HWR
HWS
45-95ËšC
ZONE WATER
TEMPERATURE
CONTROLLER
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