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

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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 I TS (
OP TI
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
mu s t be
b
e low u ni t
co nne c t ion
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
ava
i
lable
with propane
units .
GAS
CONTROL
SYST E 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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