Chilled Water Coil Equipped Units; Evaporative Cooling Equipped Units; Operation; General Information - Trane GRAA Installation Operation & Maintenance

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leakage into unit. The P-trap shall be of sufficient dif-
ferential to overcome negative pressure of the indoor
air blower. A minimum height difference of 2" is
required (See Figure 9). Before unit operation
begins, the P-trap must be primed with either water
(summer) or glycol (winter).
CHILLED WATER CO I L
EQU I PP E D UN ITS (OPTI ONAL)
See Coil Installation/Maintenance
Manual for
General Coil Piping Recommendations. Remove pip-
ing plate located in the near center of the coil cabinet
and cut holes in plate to allow chilled water piping
passage. Provide weatherproof seal around chilled
water pipes at piping plate when installed.
Figure 9 - Drain Pan Connection
DRAIN PAN CONNECTION
UNIT
2 " MIN .
D3Bb7
The Chilled Water Coil has a 600 ft/min (3.048 m/s)
maximum velocity through the coil requirement. This
is due to prevention of condensate blow-off. To cal-
culate the velocity through the coil apply the follow-
ing formula:
Velocity
Cooling Air Flow in CFM (m3/s)
through the coil
Coil Surface Area in ft2 (m2)
Condensate Drain piping must have a P-trap in line
immediately downstream of drain pan connection,
external to the unit, to prevent possible outside air
leakage into unit. The P-trap shall be of sufficient dif-
ferential to overcome negative pressure of the indoor
air blower. A minimum height difference of 2" is
required (See Figure 9). Before unit operation
begins, prime P-trap with either water (summer) or
glycol (winter).
EVAPORATIVE COOLER
EQUIPPED UNITS (OPTIONAL)
Refer to Evaporative Cooler Installation and Service
Manual for water and electrical connections.
IV. OPERATION
GENERAL INFORMATION
Refer to Outdoor Rooftop Gas-Fired Duct Furnace
Installation and Service Manual for specific informa-
tion regarding the heating operation of this unit.
All units are equipped with a intermittent ignition pilot
system. The pilot is lit and extinguished each cycle of
unit heating operation.
Outlet
must be
below u nit
conne ction
The lockout function shuts off the main and pilot gas
valves if the pilot gas fails to ignite within 90 seconds
of the onset of trial for ignition. In order to initiate a re-
ignition trial, the power supply must be interrupted for
30 seconds.
The gas control system operates at 24 VAC and is
supplied by a stepdown transformer found in the
electrical cabinet that will match the unit line voltage
specified. See Figure 6 for unit controls location.
Do not use a thermostatic fan control switch when
either two-stage firing or modulated gas controls are
used.
NOTE : Electronic modulating gas controls are
available on natural gas units only. These con-
trols are not avai lable with propane units .
GAS CONTROL SYSTE M
The standard unit comes equipped for single stage
operation. Unit heating operation is accomplished at
full input.
Each duct furnace is equipped with an individual igni-
tion control system which consists of the following
components: ignition control module, gas valve and
pilot burner.
The ignition control module is the heart of the igni-
tion control system. This control initiates all gas flow,
provides means to light the pilot burner, proves and
monitors the pilot burner operation.
The gas valve consists of two operators which pro-
vide gas to the pilot and main burners. Both opera-
tors are energized and de-energized by the ignition
control module each heating cycle.
On natural gas units, the ignitor will continue to spark
and pilot gas will continue to flow until the pilot flame
The pilot burner includes an ignitor and flame sense
is proven.
probe. The ignitor provides the spark, originating at
the ignition control module, to light the pilot. The igni-
LP (propane) units are equipped with 100% lockout.
tion control module proves and monitors the pilot
flame through the flame sensing probe.
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