Trane GRAA - Optional Gas Controls; Air Handling Requirements and Adjustments

All
units follow
the
same basic
sequence of operation
and is
as follows:
1. Thermostat
calls for heat.
Power vented
units
only : D raftor
relay ener-
gizes
draftor
with call
for heat.
2.
Ignition
control
module energizes
pilot operator
of
gas valve
and initiates
spark at ignitor
of the pilot
burner.
3. Pilot
burner ignition
is
proven to the ignition
con-
trol
by the flame
sense
probe and
sparking of the
ignitor
is discontinued.
4. Once pilot
burner
operation is
proven, the ignition
control
module
energizes the
main
burner opera-
tor
of the
gas valve, allowing
gas
flow to the main
burners.
Po we
r v e nt
e d un i ts only
:
In
addition,
draftor
operation
must
be proven
by draftor
end switch
before ignition
control
module
energizes
main
burner operator
of gas valve.
5. Approximately
60
seconds after the
main burners
light the
fan time
delay
initiates fan
operation.
6. Thermostat
is satisfied
and call for
heat
is
removed.
Pow er v
e nted
units only :
Draftor
relay
de-ener-
gizes
draftor
with
removal of
call for heat.
7. Ignition
control
module
de-energizes
pilot
and
main
burner
operators
of
the
gas valve,
ceasing all
gas flow.
8. Approximately
two
minutes after
satisfying
the
thermostat,
fan
operation
ceases.
OPTIONAL
GAS
CONTROLS
These
units are
available
with optional
gas controls
which will
give
either
multi-stage
or modulating
oper-
ation.
The
sequence
of
operation
of those units
equipped
with these
optional gas
controls
differs only
at what
rate
each
duct furnace's
main
burners ignite
and
operate
at or the
order of duct
furnace firing
for
those
units
equipped
with two
or three
duct furnaces.
Two Stage
Units
: Two
stages of heating;
first stage
is 40%
of full
rate,
second
stage is 100%
of full rate.
Main burner
ignition
is at
first stage
only.
Th ree
St a g
e Units
: Triple duct
furnace
models
only.
Each
duct
furnace
is equipped
with
single stage
heating
but fired
independently,
giving
three stages.
Each
stage
is
33%
of the unit's
full input
rate. Duct
furnace
one will
always light
first and
disengage
last.
Four St
a ge
Un i ts
: Dual
duct furnace
models
only.
Each
duct
furnace
is
equipped with
two stage
heat-
ing
but fired
independently, giving
four stages. Each
stage is
25% of the units
full input rate. Duct
furnace
one will always
light first
and disengage last.
Six Stage
Un i ts
: Triple duct furnace
models only.
Each
duct furnace
is equipped with
two stage heat-
ing
but fired
independently giving
six stages. E
ach
stage
is 16.5%
of the units
full input rate. Duct
fur-
nace
one will always light
first and
disengage last.
Mechanical
Modulation Units
: These units
are
equipped
with
a
hydraulic
modulating control
which
provides
unit firing
capabilities
of
40 to
100% of the
units full
input rate.
This control is found in
the gas
train
downstream
of the gas valve and allows
main
burner ignition
only at the minimum
rate. A tempera-
ture sensing
bulb, located
in the discharge
airstream,
controls
the
level
of
modulation. These units
are
available with
a
modulation
bypass
which
will give
single stage
or full
input operation.
Electronic
Modulation
Units :
(Not available
with
propane units)
These units
are equipped with
a elec-
tronic
modulating
control which provides
unit firing
capabilities
of 40
to 100% of the units
full input rate.
This
control is
found in the
gas train downstream
of
the gas
valve and allows
main burner ignition
only at
the
maximum
rate. A thermostat
with remote
setpoint
adjustment
modulates the
gas
input.
Multi - Stage
w / Electronic
Modulation
Units :( N ot
available with
propane units)
T hese
dual and triple
duct furnace
models are
equipped with an electronic
modulating control
on duct f urnace
one and single
or
two stage
heating
on each successive
duct
furnace.
Furnace
one
(modulated) will
fire first and disengage
last.
Additional
stages
of
heat
will engage
after fur-
nace one
has fired at
maximum modulation
capabili-
ty
for the
duration
of the delay
setting. The amount
of modulation
and
each stage size
depends upon
unit size
and the
number of stages.
See following
chart.
Modulation
Stage
Number
Capabilities
Size
of Stages
(% of full
Input)
(% of full
Input)
2
25
- 50
50
3
16.5 -
33
33
4
25
-50 25
6
16 .
5 - 33 16.5
AIR HANDLING
REQUIREMENTS
AND
ADJUSTMENTS
CAUTION
: Remove
wooden shipping
support
from beneath
blower
housing
of Blower
Section
to prevent possible
unit
damage or
improper unit
operation
(if applicable)
.
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