Features/Benefits (cont)
Safety features provide
protection and increase
reliability
Auto. lead/lag control —
Control
balances operating hours between
refrigerant circuits.
Standby protection —
If a malfunc-
tion or safety cutout occurs, these
2-circuit chillers have the capability for
standby operation. This benefit is
especially desirable in commercial ap-
plications where even brief equip-
ment shutdowns can be extremely
costly.
Electronic expansion valve (EXV)
—
The EXV is controlled to main-
tain approximately 20 F (11 C) refrig-
erant superheat entering the
compressor cylinders. (Ordinary ther-
mostatic expansion valves typically
operate at 45 F [25 C] superheat
entering compressor cylinders.) Pre-
cise superheat control is obtained
through actuation of the 760-step,
long-stroke,
3
⁄
4
-in. (19 mm) valve
positioner to ensure optimized refrig-
erant metering. The accurate refrig-
erant metering provided by the EXV
reduces compressor motor temperature
and extends motor life.
Filter drier —
Refrigerant circuits are
kept free of harmful moisture and
contaminants by a factory-installed
filter drier.
Crankcase heater —
The compres-
sor crankcase heater protects the
compressors against refrigerant migra-
tion and oil dilution.
Moisture-indicating sight glass —
Easy-to-read color indicator immedi-
ately shows moisture content of refrig-
erant system.
Oil pressure safety switch —
Safety switch shuts compressor(s) off if
the oil pressure drops below a safe
operating point.
Protection against single-phasing
—
Manual reset, magnetic trip cir-
cuit breakers protect the compressor
motors against both overload and
single-phasing, and eliminate potential
problems before they become ser-
vice headaches.
Motor overtemperature protec-
tion —
Servicing dollars are saved
because the compressor motors are
thoroughly protected against overheat-
ing by quick-sensing elements.
Other safeties —
Additional safeties
include: Loss of refrigerant charge
protection, low fluid flow protection,
low chilled fluid temperature pro-
tection, low and high superheat pro-
tection, low oil protection for each
compressor circuit, and low con-
trol voltage (to unit) protection.
Thermistors —
Six thermistors are
used for temperature sensing inputs to
microprocessor (a seventh may be
used as a remote temperature sensor
for space or outdoor-air tempera-
ture reset):
• Cooler leaving and entering (return)
chilled fluid temperature control
• Cooler saturation temperatures —
Circuit A and Circuit B
• Return gas temperatures entering
compressor cylinder —Circuit A
and Circuit B
• Remote temperature sensor
(accessory)
Model number nomenclature
NOTE: Refrigerant 134a is not available for these units.
These units are listed with Underwrit-
ers’ Laboratories (UL) and Cana-
dian Standards Association (CSA), and
these pressure vessels have ASME
(American Society of Mechanical
Engineers) certification.
UNDERWRITERS’
LABORATORIES
ASME
‘U’ STAMP
CANADIAN
STANDARDS
ASSOCIATION
4
