Two Stage Heating; Heat Anticipator; Start-Up & Adjustments; Pre-Start Check List - Oxbox J951X U Series Installation Instructions Manual

SINGLE STAGE HEATING (WITH TWINNING)
AC
UNIT
THERMOSTAT
Y R G C
W1
R
Y G W C
FURNACE
BOARD
6-Pin Wiring
Harness
BLOWER
CONTROL
BOARD
TWIN TERMINAL
PRIMARY FURNACE
TWO STAGE HEATING (WITH TWINNING)
AC
UNIT
THERMOSTAT
Y R G C
W1
R G C
Y W
FURNACE
BOARD
6-Pin Wiring
Harness
BLOWER
CONTROL
BOARD
TWIN TERMINAL
PRIMARY FURNACE
Figure 27. Single & Two Stage Twinning
• Connect C from the primary furnace to the coil side of
the relay (using field supplied wire and 3/16" terminals).
NOTE: Make sure connections are made on opposite
sides of the coil.
• Connect R from the secondary furnace control board to
the COM side of the relay (use included red wire).
• Connect W from the secondary furnace control board to
NO side of the relay (use included white wire).

Two stage heating

• Connect the thermostat wires to the furnace control
board (except W2). Mount the relay on the bracket on the
secondary furnace.
• Connect W1 from the thermostat control to W of the
primary furnace.
• Connect W2 from the thermostat to the coil side of the
relay (using field supplied wire and 3/16" terminals)
• Connect C from the primary furnace to the coil side of the
relay (using field supplied wire and 3/16" terminals).
NOTE: Make sure connections are made on opposite
sides of the coil
• Connect R from the secondary furnace control board to
the COM side of the relay (use included red wire).
• Connect W from the secondary furnace control board to
NO side of the relay (use included white wire).

Heat Anticipator

Set the heat anticipator according to the instructions supplied
by the thermostat manufacturer. To determine the heat
anticipator setting:
1. Add the current draw of the system components; or
2. Measure the current flow on the thermostat R-W circuit
after the circulating blower motor has started.
RELAY
W2
NO
COM
WHITE
R C Y G W
FURNACE
BOARD
6-Pin Wiring
Harness
BLOWER
CONTROL
BOARD
TWIN TERMINAL
SECONDARY FURNACE
RELAY
W2
NO
COM
WHITE
R C G
Y W
FURNACE
BOARD
6-Pin Wiring
Harness
BLOWER
CONTROL
BOARD
TWIN TERMINAL
SECONDARY FURNACE
START-UP & ADJUSTMENTS

Pre-Start Check List

√ Verify the polarity of the connections are correct, the line
voltage power leads are securely connected and the
furnace is properly grounded.
√ Verify the thermostat wires (R, W, Y, & G) are securely
connected to the correct leads on the terminal strip of the
circuit board.
√ Verify the jumper setting (for fan speed) on the control
board. To select fan speed, see
jumper on the control board.
√ Verify the gas line service pressure does not exceed 10.0
inches of W.C., and is not less than 4.5 inches W.C. for
natural gas. For LP gas the line service pressure must
not exceed 14 in. W.C., and must not be less than 11.0
in. W.C.
√ Verify the roll-out and manual reset switch is closed. If
necessary, press the red button to reset a switch. DO
NOT install a jumper wire across a switch to defeat its
function. If a switch reopens on startup, DO NOT reset
the switch without identifying and correcting the fault
condition.
√ Verify the blower door is in place, closing the door switch
in the line voltage circuit.
√ Verify the gas line has been purged and all connections
are leak free.

Start-up Procedures

Do not perform these steps until all of the checks in the
previous steps have been completed:
1. Set the thermostat to the lowest setting.
2. Turn off all electrical power to the furnace.
3. Follow the Operating Instructions on the label attached to
the furnace.
4. Set the thermostat above room temperature and verify the
Operating Sequence (
page 27
5. After 5 minutes of operation, set the thermostat below
room temperature and verify steps 9 - 10 of the Operating
Sequence.
Verifying & Adjusting Input Rate
The input rate must be verified for each installation to prevent
over-firing of the furnace. NOTE: The input rate must not
exceed the rate shown on the furnace rating plate. At altitudes
above 2,000 feet, it must not exceed that on the rating plate
less 4% for each 1,000 feet. To determine the exact input
rate, perform the following procedures:
1. Shut off all other gas fired appliances.
2. Start the furnace and run it for at least 3 minutes.
3. Measure the time (in seconds) required for the gas meter
to complete one revolution.
4. Convert the time per revolution to cubic feet of gas per
hour using
Table 6 (page 32)
5. Multiply the gas flow rate in cubic ft per hr by the heating
value of the gas in Btu per cubic ft to obtain the input rate
in Btuh. See example.
EXAMPLE:
• Time for 1 revolution of a gas meter with a 1 cubic ft
dial = 40 seconds.
• From Table 6 read 90 cubic ft gas per hr.
• Local heating value of the gas (obtained from gas
supplier) = 1,040 Btu per cubic ft.
• Input rate = 1,040 x 90 = 93,600 Btuh.
and set the
Figure 26
).
.
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