66 Product Manual PM WSC/WDC
6. A self-metering and adjustable thermal expansion valve shall control refrigerant flow
to the evaporator. Fixed orifice devices or float controls with hot gas bypass are not
acceptable because of inefficient control at low load conditions. The liquid line shall
have a moisture indicating sight glass.
7. The evaporator and condenser shall be separate shells. A single shell containing
both vessel functions is not acceptable because of the possibility of internal leaks.
8. Interstage economizers shall be used between each compressor stage for increased
efficiency.
9. Reseating type spring loaded pressure relief valves according to ASHRAE-15 safety
code shall be furnished. The evaporator shall be provided with single or multiple
valves. The condenser shall be provided with dual relief valves equipped with a
transfer valve so one valve can be removed for testing or replacement without loss
of refrigerant or removal of refrigerant from the vessel. Rupture disks are not
acceptable.
10. The evaporator, suction line, and any other component or part of a component
subject to condensing moisture shall be insulated with UL recognized 3/4 inch
closed cell insulation. All joints and seams shall be carefully sealed to form a vapor
barrier.
11. Provide water pressure differential switches on each vessel to prevent unit operation
with no flow. Furnished, mounted and wired by the contractor.
D. Prime Mover: Squirrel cage induction motor of the hermetic type of sufficient size to
efficiently fulfill compressor horsepower requirements. Motor shall be liquid refrigerant
cooled with internal thermal overload protection devices embedded in the winding of each
phase. Motor shall be compatible with the starting method specified hereinafter. If the
Contractor chooses to provided an open drive motor or compressor, verify in the submittal
that the scheduled chiller room ventilation system will accommodate the additional heat and
maintain the equipment room at design indoor temperature based on 95°F outdoor ambient
ventilation air available.
If additional cooling is required, manufacturer shall be responsible for the installation, wiring
and controls of a cooling system. Chiller selection shall compensate for tonnage and
efficiency loss to make certain the owner is not penalized.
E. Motor Starter:
1. The main motor starter is to be factory mounted and fully wired to the chiller
components and factory tested during the run test of the unit.
-- Or --
The main motor starter is to be furnished by the chiller manufacturer and shipped loose for
floor mounting and field wiring to the chiller package. It shall be free-standing with
NEMA-1 enclosure designed for top entry and bottom exit and with front access.
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