Electrical - Lennox Merit Series Installation Instructions Manual

IMPORTANT
!
When testing pressure of gas lines, gas valve
must be disconnected and isolated. See Figure 13.
Gas valves can be damaged if subjected to more
than 1/2 psig (3.48 kPa).
Figure 13
MANUAL MAIN
SHUT-OFF VALVE
WILL NOT HOLD
NORMAL TEST
PRESSURE
CAP

ELECTRICAL

ELECTROSTATIC DISCHARGE (ESD)
Precautions and Procedures
CAUTION
!
Electrostatic discharge can affect electronic
components. Take precautions during
furnace installation and service to protect the
furnace's electronic controls. Precautions will
help to avoid control exposure to electrostatic
discharge by putting the furnace, the control
and the technician at the same electrostatic
potential. Neutralise electrostatic charge by
touching hand and all tools on an unpainted
unit surface, such as the gas valve or
blower deck, before performing any service
procedure.
These units operate on 240 volt, single phase, 50Hz
electrical power. Refer to figure 14 for field wiring and
Figure 16 for schematic wiring diagram and troubleshooting.
1. Select circuit protection and wire size according to
requirements listed on unit rating plate.
2. Snap-hole plugs are provided on both sides of cabinet to
facilitate wiring.
3. Install room thermostat according to instructions provided
with thermostat.
18
GAS VALVE
FURNACE
4. Install a separate disconnect switch (protected by either
fuse or circuit breaker) near the unit so power can be
turned off for servicing.
5. Before connecting thermostat or power wiring, check
to make sure wires will be long enough to facilitate
servicing at a later date. Remove blower access panel
and swing panel to check wire length for access.
6. Complete wiring connections to equipment using wiring
diagrams provided with unit and in field wiring diagrams
shown in figures 5. Use 18 gauge wire or larger for
thermostat connections.
7. Electrically ground unit in accordance with local codes.
8. Three 240 volt accessory terminals are provided on the
control board. Two are energised with the indoor blower
and one is energised with the combustion air blower. Any
accessory rated up to one amp can be connected to the
accessory terminals with the neutral leg of the circuit
connected to the 240 volt neutral wires.
9. This unit is equipped with an integrated control board
that controls blower operation, fan off timings (EGC Board
0nly) and ignition. The board includes a terminal strip for
thermostat connections and two diagnostic LEDs. See
figure 6 for control board configuration. Diagnostic codes
are given in a chart at the back of this manual.
The red diagnostic button can be used to view the last
failure code. (EGC Ignition Board Only)
10.Refer to blower speed chart on wiring diagrams for
factory set cooling, heating and continuous fan speeds.
Systems using a cooling thermostat sub-base may
operate the blower continuously (factory set at low speed)
through the thermostat "FAN ON" switch. Systems, which
do not include a cooling sub-base require a toggle switch
which must be wired between terminals "R" and "G" on
the thermostat connection terminal strip. The blower
motor will operate at the designated speed during cooling
or heating demand; however, when demand is satisfied,
blower speed will revert to selected continuous speed.