JOHNSON CONTROLS
26
SECTION 6 – UNIT WATER PIPING AND HOOK-UP
FORM 155.17-N1
ISSUE DATE: 4/1/2013
THREE-WAY MIXING VALVE
The temperature of the tow er water to the absorber
shell of the unit must be main tained at all times be-
tween 68°F, (20°C) and the design tem per a ture of the
unit [typically 85°F, (29.4°C)]. How ev er, at unit start-
up, the tower water may be as low as 59°F, (15°C)
providing the water temperature reaches 68°F, (20°C)
in a 30 minute period. The tower water must not
change in temperature more than 0.5°F (0.28°C)
per minute.
A three-way mixing valve (or tower bypass valve)
with ac com pa ny ing temperature controller, as in di cat-
ed in the Unit Water Piping and Hook-Up section of
this doc u ment, is recommended to con trol tow er wa ter
tem per a ture. This valve could be installed at either the
inlet side (di vert ing flow) or outlet side (mixing flow)
of the cool ing tower. The sizing of this valve is crit i cal
and should be left up to the build ing pip ing en gi neer to
prop er ly size the valve so that de sign chill er flow can
be maintained under all op er at ing con di tions. Detail of
a 3-way mixing valve is shown in Figure 10 on page
26.
DETAIL A
CONDENSER
ABSORBER
D
10' MAX.
COOLING TOWER
B
C
D
10' MAX.
Before
commissioning the ParaFlowTM Chiller/Heater,
all unit system water piping must be leak checked and flushed.
All water strainers must be cleaned after flushing and trapped air vented.
PIPING USING
A TOWER
BYPASS
VALVE
SQUARE HEAD
PLUG COCK
3-WAY
CONTROL
VALVE
FIGURE 10 - PIPING FOR TOWER WATER - THREE-WAY MIXING VALVE
ld05846
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