York YK Manual page 102

FORM 160.75-EG1 (519)
Guide Specifications (Cont'd)
The motor drive shaft shall be directly connected to the compressor shaft with a flexible
disc coupling. Coupling shall have all metal construction with no wearing parts to assure
long life, and no lubrication requirements to provide low maintenance. For units utilizing
remote electromechanical starters, a large steel terminal box with gasketed front access
cover shall be provided for field-connected conduit.
Overload/overcurrent transformers shall be furnished with all units. (For units furnished
with factory-packaged Solid-State Starters or Variable Speed Drive, refer to the Option
section.)
EVAPORATOR
Evaporator shall be a shell and tube type, hybrid falling film (evaporator codes A_ to Q_)
or flooded type (evaporator codes R_ to Z_) designed for a minimum of 180 psig (12.4
barg) on H & K compressor models, 235 psig (16.2 barg) on P & Q compressor models;
working pressure on the refrigerant side. Shell shall be fabricated from rolled carbon
steel plates with fusion welded seams, carbon steel tube sheets, drilled and reamed to
accommodate the tubes, and intermediate tube supports spaced no more than four feet
apart. The refrigerant side of each shell is designed, tested and stamped in accordance
with ASME Boiler and Pressure Vessel Code, Section VIII - Division 1, or other pressure
vessel code as appropriate.
Heat exchanger tubes shall be high-efficiency, externally and internally enhanced type.
Tubes shall utilize the "skip-fin" design, providing a smooth internal and external surface
at each intermediate tube support. This provides extra wall thickness and non-work hard-
ened copper at the support location, extending the life of the heat exchangers. If skip-fin
tubes are not used, minimum tube wall thickness shall be 0.035" (~1 mm). Each tube shall
be roller expanded into the tube sheets providing a leak-proof seal, and be individually
replaceable. Water velocity through the tubes shall not exceed 12 ft./sec. (3.7 m/sec.).
A liquid level sight glass shall be provided on the side of the shell to aid in determining
proper refrigerant charge and to check condition of the refrigerant charge. The hybrid fall-
ing film evaporator design has suction baffles around the sides and above the falling film
section to prevent liquid refrigerant carryover into the compressor. Flooded evaporator
designs have a suction baffle on M shells with H9 compressors and an aluminum mesh
eliminator on K - Z shells with K compressors located above the tube bundle to prevent
liquid refrigerant carryover into the compressor. The evaporator shall have a refrigerant
relief device sized to meet the requirements of the ASHRAE 15 Safety Code for Mechani-
cal Refrigeration.
Waterboxes shall be removable to permit tube cleaning and replacement. Stub-out wa-
ter connections having ANSI/AWWA C-606 grooves to ANSI/AWWA C-606 Standard for
Grooved End Shoulder Joints shall be provided. Waterboxes shall be designed for 150
psig (10.3 barg) design working pressure and be tested at 225 psig (15.5 barg). Vent and
drain connections with plugs shall be provided on each waterbox. Low flow protection
shall be provided by a thermal-type water flow sensor, factory mounted in the water nozzle
connection and wired to the chiller control panel.
CONDENSER
Condenser shall be of the shell-and-tube type, designed for a minimum of 235 psig (16.2
barg) working pressure on the refrigerant side. Shell shall be fabricated from rolled carbon
steel plates with fusion-welded seams. Carbon steel tube sheets, drilled and reamed to
accommodate the tubes, are welded to the end of each shell. Intermediate tube supports,
fabricated from carbon steel plates, are drilled and reamed to eliminate sharp edges. The
102 JOHNSON CONTROLS