Carrier 48N User Manual Page 86

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86
22) Lead-lag function shall distribute starts
between the two refrigeration circuits in
an effort to equalize the running time on
the two circuits.
23) Condenser-fan cycling control shall
maintain correct head pressure down to
32 F.
24) Refrigeration system pressures shall be
monitored via pressure transducers.
Alarms for low pressure, high pressure
will be permitted.
25) Timed Discrete Output function shall
control an external function or device
via user-configured activity schedule.
This schedule shall be separate and dif-
ferent from the unit's occupied/unoccu-
pied time schedule.
26) Hydronic heating coil control shall mod-
ulate a control valve in a steam or
hydronic heat system to maintain space
temperature at user-configured set
points. Control valve actuator shall com-
municate via LEN (Local Equipment
Network) protocol.
27) Humidifier control shall provide control
for either LEN communicating control
valve or discrete-type output, to main-
tain space humidity conditions at user-
configured set points.
28) Two-step demand limit control (when
used in conjunction with CEM [controls
expansion module]).
29) Display in Metric units: Display may be
configured to display data in Metric or
English (Imperial) units of measure.
2. Safeties:
Unit components shall be equipped with the fol-
lowing protections:
a. Compressors:
1) Overcurrent using calibrated circuit
breakers (shuts down individual com-
pressor).
2) Crankcase heaters.
3) High-pressure switch (shuts down indi-
vidual circuit, automatic reset type).
4) Low-pressure monitoring (shuts down
individual circuit, automatic reset type).
b. Check filter switch.
c. Belt-Drive Fan Motors:
Overcurrent protection manual reset circuit
breakers.
d. [Electric Heating Section]:
1) Automatic reset high-temperature limit
switches.
2) Manual reset high temperature limit
switch.
3) Primary and backup contactors.
4) Branch circuit protection.
5) Airflow proving switch.
3. Diagnostics:
a. The display shall be capable of indicating a
safety lockout condition (alarm).
b. The display shall also be capable of indicat-
ing an alert condition which does not lock
out the unit, but informs the system monitor
of a condition which could be detrimental to
either the unit or the comfort of the occu-
pants if allowed to continue.
c. Test mode must also be capable of display-
ing outputs of microprocessor-controller and
to verify operation of every thermistor, actu-
ator motor, fan, and compressor before unit
is started.
4. Navigator™ Display Interface:
The Navigator display module shall be a porta-
ble hand-held display module with a minimum
of 4 lines and 20 characters per line, of clear
English language. Display menus shall provide
clear language descriptions of all menu items,
operating modes, configuration points and
alarm diagnostics. Reference to factory codes
shall not be accepted. An industrial grade coiled
extension cord shall allow the display module to
be moved around the chiller. Magnets shall hold
the display module to any sheet metal panel to
allow hands-free operation. Display module
shall have NEMA 4x housing suitable for use in
outdoor environments. Display shall have back
light and contrast adjustment for easy viewing
in bright sunlight or night conditions. The dis-
play module shall have raised surface buttons
with positive tactile response.
N. Operating Characteristics:
1. Unit shall be capable of starting and running at
115 F (125 F for high-efficiency models) ambi-
ent outdoor temperature per maximum load cri-
teria of AHRI Standard 340/360, latest
edition.
2. Unit shall be capable of mechanical cooling
operation down to 32 F ambient outdoor tem-
perature (–20 F with low ambient accessory).
3. Provides multi-stage cooling capability.
4. [Provides 2 stages of electric heating capability.]
O. Motors:
1. Compressor motors shall be cooled by suction
gas passing over motor windings.
2. Condenser-fan motors shall be 3-phase, totally
enclosed type with permanently lubricated ball
bearings and internal over-temperature protec-
tion.
3. Supply and exhaust fan motors shall be of the
3-phase, NEMA rated, open drip-proof (ODP),
ball bearing type, with efficiencies per EISA of
2007 (U.S.A.) requirements.
Guide specifications — 50N units (cont)
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