Specifications

25
JOHNSON CONTROLS
Form 201.28-NM1.EN.PED/CE (0211)
4
There should be a straight run of piping of at least 5 pipe
diameters on either side. The flow switch should be wired
to Terminals 2 and 13 on the 1TB terminal block. A flow
switch is required to prevent damage to the cooler caused
by the unit operating without adequate liquid flow.
The flow switch used must have gold plated contacts for
low voltage/current operation. Paddle type flow switches
suitable for 10 bar (150 PSIG) working pressure and having
a 1" N.P.T. connection can be obtained from Johnson
Controls as an accessory for the unit. Alternatively, a
differential pressure switch fitted across an orifice plate
may be used, preferably of the high/low limit type.
The chilled liquid pump(s) installed in the piping system(s)
should discharge directly into the unit cooler section of
the system. The pump(s) may be controlled by the chiller
controls or external to the unit. For details, refer to
“Electrical Elementary and Connection Diagrams.”
Pipework and fittings must be separately supported to
prevent any loading on the cooler. Flexible connections
are recommended which will also minimize transmission
of vibrations to the building. Flexible connections must
be used if the unit is mounted on anti-vibration mounts,
as some movement of the unit can be expected in normal
operation.
Piping and fittings immediately next to the cooler should
be readily de-mountable to enable cleaning before
operation, and to facilitate visual inspection of the
exchanger nozzles.
The cooler must be protected by a strainer,
preferably of 40 mesh, fi tted as close as
possible to the liquid inlet connection, and
provided with a means of local isolation.
The cooler must not be exposed to flushing velocities or
debris released during flushing. It is recommended that a
suitably sized bypass and valve arrangement is installed
to allow flushing of the piping system. The bypass can
be used during maintenance to isolate the heat exchanger
without disrupting flow to other units.
Thermometer and pressure gauge connections should
be provided on the inlet and outlet connections of each
cooler. Gauges and thermometers are not provided with
the unit and are to be furnished by others.
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
temperatures should be protected using insulation and
heater tape and/or a suitable glycol solution. 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 cooler
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.
The cooler is protected by heater mats placed under
the insulation, which are powered from the unit control
system power supply. During cold weather when there is
a risk of freezing, chiller power should be left switched
on to provide the freeze protection function unless the
liquid systems have been drained.
Any debris left in the water piping between
the strainer and cooler could cause serious
damage to the tubes in the cooler 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.
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 cooler.
WATER TREATMENT
The unit performance provided in the Design Guide
is based on a fouling factor of 0.018m2/hr °C/kW
(0.0001 ft2hr°F/Btu). Dirt, scale, grease and certain
types of water treatment will adversely affect the heat
exchanger surfaces and therefore the unit performance.
Foreign matter in the water system(s) can increase the
heat exchanger pressure drop, reducing the flow rate and
causing potential damage to the heat exchanger tubes.
Aerated, brackish or salt water is not recommended for
use in the water system(s). Johnson Controls recommends
that a water treatment specialist should be consulted to
determine whether the proposed water composition will
adversely affect the evaporator materials of carbon steel
and copper. The pH value of the water flowing through
the evaporator must be kept in a range between 7 and 8.5.