Form I-XE/CRGB/RPB, Page 16
Disconnect
Alternate
Location
Blower
Section
Service
Panel
Furnace
Service
Panel
Optional
Downturn
Plenum
Cabinet
Disconnect
Alternate
Location
Test Gauge
Connection
Gas
Supply
Maintain clearance for
burner rack removal.
Electric
Supply
Weatherproof
Disconnect,
Wiring and
Connector
FIGURE 18 - Disconnect Switch Locations (Keep electric
and gas supply components clear of service panels.)
12. Electrical Supply and Connections
11. Gas Pressures (cont'd)
Manifold or Orifice Pressure Settings (cont'd)
A disconnect switch is a required part of this installation. Switches
are available, as options or parts, or may be purchased locally. When
ordered as an optional component, the disconnect switch is shipped
separately.
The disconnect switch may be fusible or non-fusible. When provid-
ing or replacing fuses in a fusible disconnect switch, use dual element
time delay fuses and size according to 1.25 times the maximum total
input amps.
When installing, be careful that the conduit and switch housing are
clear of furnace panels and inspection plates. Allow at least four feet
(1.2M) of service room between the switch and removable panels.
See
FIGURE 18
for suggested locations.
Field-Supplied Wiring Size from Disconnect to Electrical
Box for Connection to Motor Contactor or Starter
Voltage/Phase
Motor HP
Wire Gauge
BX Cable
120/1
1/4 - 1/2
14
3/8"
1
12
3/8"
208-230/1
1 - 1.5
14
3/8"
208-230/3
1/4 - 3
14
3/8"
5
12
3/8"
460/3
1/4 - 5
14
3/8"
575/3
1/2 - 5
14
3/8"
For Natural Gas:
When the heater leaves the factory, the combination
valve is set so that the outlet gas pressure of a single-stage valve or high
fire of a two-stage valve is regulated to 3.5" w.c. Low fire on a two-stage
valve is set to 1.8" w.c. Inlet supply pressure to the valve must be a
minimum of 5" w.c. or
as noted on the rating plate
and a maximum of
14" w.c.
NOTE:
Always check the rating plate for minimum gas
supply pressure.
Minimum supply pressure requirements vary based
on size of burner and the gas control option. Most units require a mini-
mum of 5" w.c. of natural gas as stated above, but Sizes 350 and 400 with
electronic modulation require a minimum of 6" w.c. natural gas supply
pressure. Sizes 300 and 350 with mechanical modulation require 7" w.c.
For Propane Gas:
When the heater leaves the factory, the combination
valve is set so that the outlet gas pressure of a single-stage valve or high
fire of a two-stage valve is 10" w.c. Low fire on a two-stage valve is set to
5" w.c. Inlet pressure to the valve must be a minimum of 11" w.c. and a
maximum of 14" w.c.
Before attempting to measure or adjust manifold gas pressure, the inlet
(supply) pressure must be within the specified range for the gas being
All electrical wiring and connections, including electrical grounding MUST be made in accordance with the National Electric Code ANSI/NFPA No.
70 (latest edition) or, in Canada, the Canadian Electrical Code, Part I-C.S.A. Standard C22.1. In addition, the installer should be aware of any local
ordinances or gas company requirements that might apply.
Check the rating plate on the heater for the supply voltage and current requirements. A separate line voltage supply with fused disconnect switch
should be run directly from the main electrical panel to the furnace, making connection to leads in the junction box. All external wiring must be within
approved conduit and have a minimum temperature rise of 60°C. Conduit from the disconnect switch must be run so as not to interfere with the
service panels of the furnace.
CAUTION: If any of the original wire as supplied with the appliance must be replaced, it must be replaced
with wiring material having a temperature rating of at least 105°C, except for blocked vent, energy cutoff,
and sensor lead wires which must be 150°C. See Hazard Levels, page 2.
If the heater has field-installed options that require electrical connections, consult the instruction sheet and wiring diagram supplied in the option
package. Specific wiring diagrams that include standard and factory-installed options are included with the heater.
Typical wiring diagrams are on
pages 18-23.
WARNING: If you turn off the power supply, turn off the gas. See Hazard Levels, page 2.
Disconnect Switch
Convenience Outlet Option
When a convenience outlet (Option BC) is included, a separate power
supply must be provided to the receptacle. This circuit MUST BE on a
ground fault breaker to meet requirements. All wiring to the convenience
outlet must meet National Electrical Code ANSI/NFPA No. 70 (latest edi-
tion) and any local or utility codes that apply.
used both when the heater is in operation and on standby. Incorrect
inlet pressure could cause excessive manifold gas pressure immedi-
ately or at some future time.
Instructions to Check Valve Outlet (Manifold)
Pressure:
1)
With the manual valve (on the combination valve) positioned to
prevent flow to the main burners, connect a manometer to the 1/8"
pipe outlet pressure tap in the valve. NOTE: A manometer (fluid-filled
gauge) is recommended rather than a spring type gauge due to the
difficulty of maintaining calibration of a spring type gauge.
2)
Open the valve and operate the heater. Measure the gas pressure to
the manifold. To measure the low stage pressure on units equipped
with a two-stage valve, disconnect the wire from the "HI" terminal on
the valve. (Be sure to reconnect the wire.)
Normally adjustments should not be necessary to the factory preset
regulator. If adjustment is necessary, set pressure to correct settings by
turning the regulator screw IN (clockwise) to increase pressure. Turn
regulator screw OUT (counterclockwise) to decrease pressure. Con-
sult the valve manufacturer's literature provided with the furnace for
more detailed information.
