Quantech QWC4, Installation Operation & Maintenance, Page: 53 / 156

QUANTECH
53
SECTION 3 - HANDLING, STORAGE, INSTALLATION, AND REASSEMBLY
FORM QWC4-NM1 (221)
ISSUE DATE: 02/28/2021
3
The chiller must not be exposed to flushing velocities
or debris released during flushing. Install a suitably
sized bypass and valve arrangement to allow flushing
of the piping system. The bypass can be used during
maintenance to isolate the heat exchanger without dis-
rupting flow to other units.
Connections
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.
Stop valves may be provided (by others) in the piping
adjacent to the unit to facilitate maintenance.
Any debris left in the water piping between
the strainer and evaporator could cause
serious damage to the tubes in the chiller
and must be avoided. Be sure the piping
is clean before connecting it to the water-
boxes. Keep nozzles and chilled liquid
piping capped before installation to make
sure construction debris is not allowed to
enter.
Make sure that the water quality in circu-
lation is adequate, without any dissolved
gases, which can cause oxidation of steel
or copper parts within the chiller.
Condenser Water Circuit
To properly operate the unit, condenser refrigerant
pressure must be maintained above evaporator pres-
sure. If operating conditions will fulfill this require-
ment, do not attempt to control condenser water tem-
perature by means of automatic valves, cycling of the
cooling tower fan, or other means. QWC4 chillers are
designed to function efficiently when condenser water
is allowed to seek its own temperature level at reduced
loads, and at off-peak seasons of the year. QWC4 chill-
ers can be operated with entering condensing water
temperature that is less than design conditions.
Operating the chiller below its minimum
ECW could result in low oil differential
shutdowns. Different methods are used
to maintain minimum ECW; however, the
most effective method is to install a three-
part bypass valve in the leaving condenser
water line.
Operating below the minimum entering
condensing water will not provide energy
savings, and will result in oil manage-
ment problems. However, if the enter-
ing water temperature can go below the
required minimum, the condenser water
temperature must be maintained equal
to, or slightly higher than the required
minimum.
Checking Piping Circuits and Venting Air
After the water piping is completed, but before any wa-
terbox insulation is applied, tighten and torque the nuts
on the liquid head flanges (to maintain between 30 ft-lb
to 60 ft-lb (41 N•m to 81 N•m)). Gasket shrinkage and
handling during transit may cause nuts to loosen. If wa-
ter pressure is applied before this is done, the gaskets
may be damaged and must be replaced. Fill the chilled
and condenser water circuits, operate the pumps manu-
ally and carefully check the evaporator and condenser
water heads and piping for leaks. Repair leaks as nec-
essary.
WATER TREATMENT
The unit performance provided in the design guide
is based on a fouling factor that is AHRI-specified.
Dirt, scale, grease and certain types of water treatment
will adversely affect the heat exchanger surfaces, and
therefore the unit's performance.
Foreign matter in the water systems can increase the
heat exchanger pressure drop, which can reduce the
flow rate and can cause potential damage to the heat
exchanger tubes.
Do not use aerated, brackish, or saltwater in the water
systems. Consult a water treatment specialist to deter-
mine if the proposed water composition will adversely
affect the evaporator materials of carbon steel and cop-
per. The pH value of the water flowing through the
evaporator must be kept between 7 and 8.5.