Hot Water Piping Arrangements; General - Honeywell AUTOMATIC CONTROL Engineering Manual

SINGLE
INPUT
CONTROL
HOT WATER
SENSOR
STEAM TO
SUPPLY
HOT WATER
CONVERTER
RETURN
PUMP
Fig. 83. Constant Temperature Hot
Water Converter Control.
STEAM
VALVE
STEAM
SUPPLY
CONTROL
STEAM TO
HOT WATER
CONVERTER
OUTDOOR
AIR
SENSOR
CONTROL
Fig. 84. Hot Water Converter Control with
Constant Temperature and Reset Zones.

HOT WATER PIPING ARRANGEMENTS

General

Hot water piping systems use one- or two-pipes to deliver
the water to the terminal units. The one-pipe system shown in
Figure 85 uses flow diverting fittings to scoop water out of the
single loop into each radiator or baseboard radiation section.
Another fitting returns the water to the main where it is mixed
with the supply water. The next unit will be supplied with
slightly lower temperature water. One-pipe systems are typically
used in small buildings with only one or two zones.
CHILLER, BOILER, AND DISTRIBUTION SYSTEM CONTROL APPLICATIONS
STEAM
SUPPLY
CONDENSATE
RETURN
C2831
SUPPLY
TO OTHER
SYSTEMS
RETURN
3-WAY
MIXING
VALVE SUPPLY
HOT TO SYSTEM
WATER
REQUIRING
SENSOR TEMPERATURE
RESET
RETURN
C2832
LOAD
LOAD
LOAD
EXPANSION TANK
Fig. 85. One-Pipe System.
Figure 86 shows a two-pipe reverse-return system. The length
of supply and return piping to each terminal unit is the same,
making the system self-balancing. The reverse-return is used
in large or small installations.
LOAD
LOAD
LOAD
LOAD
LOAD
Fig. 86. Two-Pipe Reverse-Return System.
Figure 87 shows a two-pipe direct-return system. The direct-
return system is used on small systems. The shorter return piping
reduces installation cost but each load loop must be symmetrical.
361 ENGINEERING MANUAL OF AUTOMATIC CONTROL
LOAD
LOAD
FLOW DIVERTING
FITTINGS
LOAD
BOILER
OR
CHILLER
C2833
EXPANSION TANK
LOAD
LOAD
LOAD
LOAD
BOILER
OR
LOAD
CHILLER
RETURN
SUPPLY
C2834