Evaporator Pressure Drop - York YVAA Installation Operation & Maintenance

SECTION 4 - INSTALLATION
Drain and air vent connections should be provided at
all low and high points in the piping to permit drainage
of the system and to vent any air in the pipes. Liquid
system lines at risk of freezing, due to low ambient tem-
peratures must be protected using insulation and heater
tape and/or a suitable glycol solution. The liquid pumps
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 as-
sist in evaporator freeze protection. If there is a poten-
tial for power loss, Johnson Controls requires 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 before
installation to ensure construction debris
is not allowed to enter.
All chiller piping connecting the customer
system to the packaged chiller is the re-
sponsibility of others. It is not considered
part of the chiller package.
32
The installer or 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. For normal water chilling duty, evapora-
tor and condenser flow rates are permitted at water ve-
locity levels in the heat exchanger tubes of between 3
fps (0.91 m/s) [3.3 fps (1.0 m/s) for condensers] and 12
fps (3.66 m/s). Two-pass units are limited to 73 ft H2O
(291 kPa) water pressure drop. The three-pass limit is
88 ft H2O (351 kPa). Follow Chiller FOF for more
information on water side pressure drop for specific
chiller configurations. Debris in the water may also
cause additional pressure drop.
Excessive flow above the maximum GPM
may damage the evaporator.
See Table 6 on page 70 for standard
two-pass to determine evaporator and
frame size and to find the evaporator line
to use.
Form 201.47-ICOM1
Issue date: 17/11/2022
JOHNSON CONTROLS