Evaporator Pressure Drop; Figure 5 - Three Pass Water Pressure Drop, English Units - York YVAA Installation, Operation & Maintenance Instructions Manual

SECTION 4 - INSTALLATION
The liquid pump(s) may also be used to ensure liquid
is circulated when the ambient temperature approaches
freezing point.
Insulation should also be installed around the evapora-
tor nozzles. Heater tape of 21 Watts per meter under
the insulation is recommended, supplied independently
and controlled by an ambient temperature thermostat
set to switch ON at approximately 2.2°C (4°F), above
the freezing temperature of the chilled liquid.
Evaporator heater mats are installed under the insula-
tion, and are powered from the chiller's control pan-
el. In sub-freezing conditions, unless the evaporator
has been drained or an appropriate water-to-glycol
concentration is maintained, high voltage power to the
chiller must be kept on to ensure the heater mats assist
in evaporator freeze protection. If there is a potential
for power loss, Johnson Controls recommends that the
evaporator is drained or that water in the chilled water
circuit be replaced with an appropriate water-to-glycol
concentration.
Any debris left in the water piping
between the strainer and evaporator could
cause serious damage to the tubes in the
evaporator and must be avoided. Be sure
the piping is clean before connecting it to
the evaporator. Keep evaporator nozzles
and chilled liquid piping capped prior to
installation to assure construction debris
is not allowed to enter.
50.0
Water Temperature = 50°F
40.0
30.0
20.0
Evaporator Type
A
10.0
B
D
C
E
H, K
F, G
0.0
I, J

FIGURE 5 - THREE PASS WATER PRESSURE DROP, ENGLISH UNITS

40
200 400
600
Flow Rate (GPM)
The installer/user must also ensure that
the quality of the water in circulation is
adequate, without any dissolved gases,
which can cause oxidation of steel or
copper parts within the evaporator.

EVAPORATOR PRESSURE DROP

The evaporator is designed in accordance with
ARI-590-92 which allows for an increase in pressure
drop of up to 15% above the design value shown in the
Pressure Drop tables shown in Figure 5 on Page 40
and Figure 6 on Page 41. Debris in the water may
also cause additional pressure drop.
Excessive flow above the maximum GPM
will damage the evaporator.
To determine evaporator/frame size See
Table 12 on page 109 to find the appli-
cable evaporator line.
800 1000
FORM 201.28-NM1.1
ISSUE DATE: 1/31/2018
1200
LD20287
JOHNSON CONTROLS
LD