Technical data

4.10 Glycol Solutions
For unit operation with chilled liquid temperatures
leaving the evaporator at below 4°C, glycol solutions
should be used to help prevent freezing. Section 9 gives
recommended solution strength with water, as a
percentage by weight, for the most common types of
glycol. It is important to check glycol concentration
regularly to ensure adequate concentration and avoid
possible freeze-up in the evaporator.
When using glycol solutions, pressure drops
are higher than with water. Special care must
be taken not to exceed the maximum pressure
drop allowed.
4.11 Condenser Water Circuit
For proper operation of the unit, condenser refrigerant
pressure must be maintained above evaporator
pressure. If operating conditions will fulfill this
requirement, no attempt should be made to control
condenser water temperature by means of automatic
valves, cycling of the cooling tower fan or other means,
since chillers are designed to function satisfactorily and
efficiently when condenser water is allowed to seek its
own temperature level at reduced loads and off-peak
seasons of the year. However, if entering condenser
water temperature can go below the required minimum,
condenser water temperature must be maintained equal
to or slightly higher than the required minimum. Refer to
Figure 4.3 for a typical water piping schematic.
4.12 Stop Valves
Stop valves may be provided (by others) in the
evaporator and condenser water piping adjacent to the
unit to facilitate maintenance. Thermometer wells and
pressure taps should be provided (by others) in the
piping as close to the unit as possible to facilitate
operating check.
4.13 Flow Switches (Field Installed)
A flow switch or pressure differential control in the chilled
water line(s) adjacent to the unit is an accessory
furnished for connection to the control panel. If a flow
switch is used, it must be directly in series with the chiller
and sensing only water flow through the chiller. The
differential switch must sense pressure drop across the
unit.
4.14 Drain and Vent Valves
Drain and vent valves (by others) should be installed in
the connections provided in the evaporator and
condenser liquid heads. These connections may be
piped to drain if desired.
4.15 Checking Piping Circuits and Venting Air
After the water piping is completed, but before any water
box insulation is applied. Tighten and torque (to maintain
between 41 and 82 Nm) the nuts on the liquid head
flanges. Gasket shrinkage and handling during transit
may cause the nuts to loosen. If water pressure is
applied before tightening is done, the gaskets may be
damaged and have to be replaced.
Fill the chilled and condenser water circuits, operate the
pumps manually and carefully check the evaporator and
condenser water heads and piping for leaks. Repair
leaks as necessary.
Before initial operation of the unit both water circuits
should be thoroughly vented of all air at the high points.
4.16 Refrigerant Relief Piping
Each unit is equipped with pressure relief valves located
on the condenser and evaporator for relieving excess
pressure of the refrigerant charge to the atmosphere as
a safety precaution in case of an emergency, such as
fire.
Refrigerant relief vent piping (by others), from the relief
valves to the outside of the building, is required by code
in most areas and should be installed on all chillers. The
vent line should be sized in accordance with the
ANSI/ASHRAE-15, or local code. The vent line must
include a dirt trap in the vertical leg to intercept and
permit clean out and to trap any vent stack
condensation. The piping MUST be arranged to avoid
strain on the relief valves, using a flexible connection, if
necessary.
4-4 160.81-ICOM-GB0 (01/02)
Figure 4.4 Typical Refrigerant Vent Piping from
Relief Valves