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GUIDE SPECIFICATIONS — SIZES 155-300 (cont)
d. Capable of introducing up to 100% outdoor air.
e. Equipped with dry-bulb temperature control to
govern economizer changeover.
f. Equipped with a supply sensor that controls the
economizer to a 55° F (30.5° C) control point.
g. Shall fit an outdoor-air opening of 17.75-in. high
and 71.38-in. long (8.8 sq. ft).
h. Shall be capable of differential dry bulb outdoor
air enthalpy and differential enthalpy control.
4. Two-Position Damper:
Two-position damper package shall include single
blade damper and 24-v motor. Admits up to 25% out-
door air, and shall close upon unit shutoff. Damper
shall cover 3.8-in. high by 17.75-in. wide (117.8 sq.
in.) opening in return air upper panel.
5. Accessory Compressor Cycle Delay:
Compressor shall be prevented from restarting for a
minimum of 5 minutes after shutdown.
* 6. Thermostats and Subbases:
To provide staged heating and cooling in addition to
automatic (or manual) changeover and fan control.
* 7. Barometric Relief Damper Package:
a. Package shall include damper, seals, hardware,
and hoods to relieve excess internal pressure.
b. Damper shall close due to gravity upon unit
shutdown.
c. Damper package must be field-installed in return-
air ductwork when used with optional side return
connections.
* 8. Power Exhaust:
Package shall include an exhaust (propeller style)
fan,
1
/
2
Hp 208-230, 460 v (factory-wired for 460 v)
direct drive motor, and damper for vertical flow units
with economizer to control over-pressurization of
building. Power Exhaust package must be field-
installed in return-air ductwork when used with
optional side return connections.
* 9. Head Pressure Control Package:
Consists of an accessory outdoor-air package and a
solid-state control with condenser coil temperature
sensor for controlling condenser-fan motor speed to
maintain condensing temperature between 90 F
(32.2 C) and 100 F (43.3 C) at outdoor ambient tem-
perature down to –20 F (–29.8 C).
10. Low-Ambient Kits:
When used, allows units to operate at lower outdoor
ambient temperatures.
* 11. Electronic Programmable Thermostat:
Capable of using deluxe full-featured electronic
thermostat.
12. Dehumidification Package:
The dehumidification package is a factory-installed
option that provides increased dehumidification by
further subcooling the hot liquid refrigerant leaving
the condenser coil. The package consists of a sub-
cooling coil located on the leaving airside of the
evaporator coil. The location of this coil in the indoor
air stream greatly enhances the latent capacity of the
units.
The package shall be equipped with low pressure
switch(es) and TXVs. Low pressure switch(es) pre-
vents evaporator coil freeze-up and TXVs assure a
positive superheat condition. If the operation of the
subcooling coil is controlled by a field-installed wall-
mounted humidistat, the dehumidification circuit will
then operate only when needed. Optional field con-
nections for the humidistat are made in the low volt-
age compartment of the unit control box.
13. Winter Start Time-Delay Relay:
Used in conjunction with the accessory low-ambient
kit or head pressure control device, permits opera-
tion in cooling at lower outdoor ambient tempera-
tures. See price pages for more information.
14. Hinged Access Panels:
Hinged access panels for the filter, compressors,
evaporator fan, and control box areas. Filter hinged
access panels permit tool-less entry for changing
filters. Evaporator fan hinged access panel shall be
field-convertible to a tool-less entry by removing and
discarding screws. Each external hinged access
panel shall be permanently attached to the rooftop
unit.
15. Convenience outlet:
Shall be factory-installed and internally mounted with
an externally accessible 115-v, 15 amp. GFI, female
receptacle with hinged cover. Voltage required to
operate convenience outlet shall be provided by a
field-installed separate branch circuit.
16. Non-fused disconnect switch:
Shall be factory-installed, internally mounted, NEC
and UL approved non-fuse switch shall provide unit
power shutoff. The control access door shall be inter-
locked with the non-fused disconnect. The discon-
nect switch must be in the OFF position to open the
control box access door. Shall be accessible from
outside the unit and shall provide power off lockout
capability.
17. Electric Heater Package:
a. Fully assembled for installation. The packages
are designed in accordance with UL safety
standards 1995 and listed by ETL. Heater con-
struction approved by UL 5306.
b. Heater element open coil resistance wire, nickel-
chrome alloy, 0.29 inches inside diameter, strung
through ceramic insulators mounted on metal
frame. Coil ends are staked and welded to termi-
nal screw slots.
c. Heater assemblies are provided with integral
fusing for protection of internal heater circuits not
exceeding 48 amps each.
d. Auto reset thermo limit controls, magnetic heater
contactors (24 v coil) and terminal block all
mounted in electric heater control box (minimum
18 ga. Galvanized steel) attached to end of
heater assembly.
e. Certain models (208-230/3/60, 42/56 and 56/
75 kW) require an additional heater control box
that contains a field power terminal block, a field
power wiring fuse block and fuses (125 A, 250 V,
class K5 or RK%); included with the electric
heater assembly package.
f. All power wiring leads are 10 AWG and con-
trol wiring leads are 18 AWG, both rated at
105 deg. C.
551A/558F/559F155-300