Trane GRAA - Gas Input Adjustment; Pilot Adjustment; Primary Air Shutter Adjustment; Controls

3.
Set
thermostat to highest level. This
will initiate
the
sequence of operation
detailed in the
Gas
Control
System section.
Check main burners for
operation.
4. Set thermostat
to lowest
level.
This will Interrupt
power to the ignition control
and shut off gas.
Confirm pilot
and main burners have
been
extin-
guished.
5. Set
the
thermostat
to the desired setting.
For complete
unit shutdown, proceed
as
follows:
1.
Turn off the
gas
valve(s)
main manual valve.
2. Set
thermostat to
lowest
setting.
3 . Shut off all electr
i
c
power
.
GAS INPUT
ADJUSTMENT
When
shipped from
the
factory,
all
equipped for the
average heat
content
which
is stamped
on the unit rating plate.
units are
of the
, gas
CAUTION
: Since the
heat ' cont
e
nt
of gas varies
by locality , the
input must
be checked after instal -
l ati
on of t he
un
i
t . If th e un i t i
s
ov
e rfired i t wi l l
shorten
the
life of the heat exchanger
. Never
exceed the input
on the rating plat
e.
For.
an accurate input rate
measurement the
follow-
ing meter
method should
be used to determine unit
input rate.
If
the
meter
method is not possible,
a
manifold pressure
check should
be made.
Meter Method
of Checking
Input Rate
1. Obtain
the heating
value
of the gas from the
local utility
or gas dealer.
This should be in units
of
Btu/ft3
(MJ/m3).
2. Determine
the
gas
flow
rate as shown in the
fol-
lowing
example.
EXAM PL
E :
Assume
this unit
has
a input rate of 250,000
B tu/hr (73.2 kW)
and
the heating
value
of the gas is 1 000 Btu/ft3 (37.3
MJ/m3).
Gas
250,000 Btu/hr (73.2
kW)
Flow
=
1000
Rate
Btu/ft3
(37.3 MJ/m3)
x 60
min/hr
= 4.17
ft3/min (1.974
Us)
Before determining
the
gas flow rate to
the unit,
all
other gas
appliances
connected to the same
meter
must be turned
off.
Fire
unit according
to instructions.
After
approximately
15 minutes of unit
operation,
determine
volume of gas
used in five minutes
of
3 .
4 .
5 .
unit operation.
For the Example above the unit
should use 4.17 ft3/min x
5
minor 20.8 ft3
(1.97
Us x 5 min x 60 s/min = 591 L) of gas. Minor
input adjustments can be made by removing
pressure
regulator cap and turning
regulator
clockwise
to increase input or counter clockwise
to
decrease input. Any appreciable adjustment in
input rate should
be made by
reorificing.
Method
to Check Manifold Pressure
1. Close the manual valve
of
unit gas valve.
2.
Install
a'1/8" pipe connection
in
the tapped
hole
provided
in the gas valve body near outlet of the
valve.
3.
Attach
manometer to'1/8" pipe connection by
means of
a
rubber hose.
4.
Fire unit according to instructions and observe
the
pressure and confirm it matches the unit
manifold pressure
from
the unit rating plate.
5.
Small variations
in the
manifold pressure
can be
made
by
means
of the gas
valve pressure regu-
lator.
Remove pressure regulator cap and turn
regulator clockwise to increase pressure or
counter-clockwise to decrease pressure.
P I LOT ADJUSTMENT
1. Disconnect wire from terminal marked MV at
gas
valve.
2. Provide call for heat.
3.
Pilot
adjustment
is found on
the
gas
valve.
Remove
pilot adjustment
cap.
4. Adjust the pilot
screw to provide
properly sized
flame.
5.
A
proper pilot burner flame is a soft
steady
flame that
envelopes
3/8 to 1/2
inch (9.5
to
12.7
mm) of the flame sense
probe
tip.
6. Replace the pilot
adjustment
cap.
PR I MARY
AIR SHUTTER ADJUSTMENT
After the unit
has been in operation for at least 15
minutes,
adjust
the
primary air flow to
the
burners.
Turn
the friction-locked manually rotated air shutters
clockwise to
close, counter clockwise to open. For
correct
air
adjustment, close the air
shutter until yel-
low tips
in the flame appear.
Then open
the air
shut-
ter
to the point just
beyond
the position
where yellow
tipping disappears.
CONTROLS
Primary
L
i mit
Control : The primary limit control
is
a
factory installed
component surface
mounted
in the
14-