25
Install field-supplied manual gas shutoff valve with a
1
/
8
-in.
NPT pressure tap for test gage connection at unit. The pressure
tap is located on the gas manifold, adjacent to the gas valve.
Field gas piping must include sediment trap and union. See
Fig. 10. Install a field-supplied gas regulator. Refer to Table 6
for gas manifold sizes and pressures.
Table 6 — Gas Heat Connection Sizes and
Pressures
LEGEND
Size gas-supply piping for 0.3-in. wg maximum pressure
drop. Do not use supply pipe smaller than unit gas connection.
GAS HEAT SAFETY CONTROLS — Safety systems are re-
quired for proper performance of the gas heater. The gas heat-
er shall not be permitted to operate with any safety system dis-
abled. If a fault is found in any of the safety systems, then the
system shall be repaired only by a contractor qualified in the
installation and service of gas-fired heating equipment.
• Combustion Airflow Switch: An airflow switch is pro-
vided as part of the control system to verify airflow
through an induced draft fan by monitoring the differ-
ence in pressure between the fan and the atmosphere. If
sufficient negative pressure is not present, indicating
lack of proper air movement through heat exchange, the
switch opens, shutting off gas supply through the igni-
tion control module. The air pressure switch has fixed
settings and is not adjustable.
• Rollout Switch (Manual Reset): The heater is equipped
with manual reset rollout switch(es) in the event of
burner flame rollout. The switch will open on tempera-
ture rise and shut off gas supply through the ignition
control module. Flame rollout can be caused by insuffi-
cient airflow for the burner firing rate (high gas pres-
sure), blockage of the vent system, or in the heat
exchanger. The heater should not be placed back in oper-
ation until the cause of the rollout condition is identified.
The rollout switch can be reset by pressing the button on
top of the switch.
• Primary High Limit Switch: To prevent the heater from
operating under low airflow conditions, the unit is
equipped with a fixed temperature high limit switch,
mounted on the vestibule panel. This switch will shut off
gas to the heater through the ignition control module
before the air temperature reaches 250.0°F (121.1°C).
Reduced airflow may be caused by restrictions upstream
or downstream of the circulating air blower, such as
dirty or blocked filters or restriction of the air inlet or
outlet to the unit. The high limit switch will shut off the
gas when the temperature reaches its setpoint and then
resets when the temperature drops 30.0°F (16.7°C)
below the setpoint, initiating a heater ignition. The
heater will continue to cycle on limit until the cause of
the reduced air flow is corrected.
• Ignition Control Module: Ignition control modules are
available with a number of different operating functions.
Refer to the Sequence of Operation and Control Diag-
nostic data sheets, provided in the instructions package,
for a detailed description of the control features, oper-
tion, and troubleshooting for the model control installed.
Step 7 — Install Hot Water (Hot Water Units
Only) —
Coils should be piped according to any relevant lo-
cal codes. All external piping must be supported independently
from the coil. See Tables 1-4 for coil connection size and type.
See Table 7 for hot water coil connection sizes. Control valves
for hot water coils are to be field provided and installed.
Table 7 — Hot Water Coil Connections
Step 8 — Make Electrical Connections —
Pow-
er wiring should be connected to the main power terminal
block located within the unit main control section. Power
IMPORTANT: Natural gas pressure at unit gas connection
must not be less than 5.0 in. wg or greater than 13.0 in. wg
for all heat sizes.
INDIV. GAS
HEATER
INPUT
(MBH)
GAS NPT
CONNECTION
(IN.)
MIN. INLET GAS PRESSURE
NG
IN. W.C.
(MBAR)
LPG
IN. W.C.
(MBAR)
75
0.75
5.0 (12.5)
11.0 (27.4)
100
0.75
5.0 (12.5)
11.0 (27.4)
150
0.75
5.0 (12.5)
11.0 (27.4)
200
0.75
5.0 (12.5)
11.0 (27.4)
250
0.75
5.0 (12.5)
11.0 (27.4)
300
0.75
5.0 (12.5)
11.0 (27.4)
350
0.75
5.0 (12.5)
11.0 (27.4)
400
1.00
6.0 (14.9)
12.0 (29.9)
500
1.00
6.0 (14.9)
12.0 (29.9)
600
1.00
6.0 (14.9)
12.0 (29.9)
LPG
—
Liquid Propane Gas
NG
—
Natural Gas
Fig. 10 — Gas Heat Section (Gas Heat Units Only)
A62-7
8
9
INLET HOOD
TEE
90° ELBOW
GROUND JOINT
UNION
MANUAL MAIN
SHUTOFF GAS
VALVE
NIPPLE
CAP
FLUE HOOD
CABINET
ERV
TONNAGE
HOW WATER COIL
CONNECTION (IN.)
A
No
03-05
7
/
8
06-08
1
1
/
8
Yes
03-05
1
3
/
8
B / B XL
No
03-05
7
/
8
06-08
1
1
/
8
10-15
1
3
/
8
18-20
1
3
/
8
Yes
03-06
1
3
/
8
07-08
1
3
/
8
10-12
1
3
/
8
C / C XL
No
10-15
1
3
/
8
18
1
3
/
8
20-25
1
3
/
8
30-35
2
1
/
8
Yes
07-08
1
3
/
8
10-12
1
3
/
8
15-25
2
1
/
8
D / D XL
No
20
1
3
/
8
25
1
3
/
8
30-35
2
1
/
8
Yes
20
2
1
/
8
25-35
2
1
/
8
