Bard WG242DA, Installation Instructions Manual, Page: 37 / 81

Manual 2100-376L
Page 37 of 81
30. SEQUENCE OF OPERATION –
HEATING
On a call for heat from the thermostat, the induced draft
blower is energized. Once sufficient draft is
established, the pressure switch contacts close and the
ignition system is energized. The direct spark ignitor
will be energized allowing gas to flow. At the same
time the main valve is energized, a 30-second blower
delay timer is activated.
After this delay, the heating speed blower relay
energizes. The blower will begin operating and remain
in operation until the set delay time after the call for
heat has been satisfied. (See Tables 10-15 for selectable
blower off time delays.) This timing sequence
guarantees blower on, blower off operation.
This unit is equipped with a flame rollout switch which
is wired in series with the control circuit. This is a
manual reset switch and is used for the purpose of
preventing possible fire hazard in the event of a system
malfunction. If this switch has opened the control
circuit, there could be a possible system malfunction.
Some of the conditions that might cause a rollout to
occur are blockage or sooting of primary heat
exchanger, overfiring of furnace due to improper main
burner orifices or incorrect manifold pressure,
insufficient combustion air, or installation deficiencies
with respect to return air duct design or sizing.
Once the problem has been resolved, reset the switch by
pressing down on the reset button on top of the switch.
See Figure 17 for additional information.
31. SEQUENCE OF OPERATION –
COOLING
On a call for cooling from the room thermostat, the high
speed blower relay will be energized as well as the
compressor contactor. Following termination of the
cooling cycle, the blower motor will continue to run for
one minute.
See Figure 17 for additional information.
The unit may be equipped with a low ambient control
for lower outdoor temperature operation in the cooling
mode. If equipped with this optional control the
condenser fan will not operate immediately upon
compressor start up, and will cycle on and off until the
condensing pressure remains above 280 PSIG.
DEHUMIDIFICATION
–
Dehumidification is
controlled through a humidistat and is independent of
the thermostat. On a call for dehumidification mode of
operation the compressor and three way valve of the
unit are energized through circuit R-F to provide
dehumidification. Dehumidification will continue until
the humidistat is satisfied.
If there is a cooling call issued through circuit R-Y, it
will cancel dehumidification sequence (de-energize the
reheat valve) until the cooling call is satisfied. If the
dehumidification call is still present when cooling call
is satisfied, the compressor will continue to operate and
the reheat valve is reenergized.
Any time there is a call for heating mode of operation
through circuit R-W1 the dehumidification mode will
cancel and the system will return to heating operation.
Dehumidification is delay 45-60 seconds on start up
after any heating cycle is complete.
Any time the indoor coil temperature falls below 32
degrees the compressor will be de-energized until the
coil temperature rises above 57 degrees.
If the room temperature falls below 65 degrees the
dehumidification mode will discontinue until the room
temperature rises above 72 degrees.
(Refer to Section 33 on Page 47 for specific electronic
sequence descriptions.)