CONQUEST 90 - Control Reactions

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CONTROL REACTIONS
1.
POOR EQUIPMENT
GROUNDING
• Results in erratic flame sensing
and nuisance soft lock outs.
Check for poor grounding of the
burners by measuring the
resistance from the common
transformer terminal to the sheet
metal of a burner. There should
be zero/low Ohms resistance.
Check the unit grounding by
measuring the resistance from
the furnace neutral wire to the
furnace ground wire (green or
bare copper).
2.
MAIN LIMIT OPENING
• Results in furnace shut down.
The gas valve closes, the
inducer fan and main blower run
until the limit resets. If the limit
does not reset, both blowers run
indefinitely.
• When the limit resets, the
inducer fan runs for 5 seconds
and stops. The main blower runs
for its pre-set off delay. After the
main blower stops, the inducer
fan starts and goes through a
normal ignition sequence.
3.
HEAT ASSISTED LIMIT
CONTROL (HALC) OPENING
• This shuts down the gas valve
or breaks power to the induced
draft blower. If the first or
second retry for ignition fails
after a burner interruption, the
IFC immediately starts the main
blower. The main blower runs
for 180 seconds. This should
reset the HALC. After it resets
the main blower stops, the unit
goes into its normal ignition
sequence.
4. OPEN PRESSURE SWITCH
• Upon a heat call the control
operates the induced draft
blower for 30 seconds before
starting the ignition sequence.
If the pressure switch contacts
do not close, the induced draft
blower continues to run for up to
60 seconds. After 60 seconds
the control goes into a five-
minute "rest." It retries for
ignition for 60 seconds again
after the 5 minute rest. It repeats
this cycle indefinitely.
• If the pressure switch opens for
more than 2 seconds during a
heating cycle, the control closes
the gas valve and starts another
trial for ignition. If the pressure
switch opens for less than 2
seconds the control takes no
action.
5. PRESSURE SWITCH CLOSED
ON START UP
• If the pressure switch contacts
remain closed, the control does
not attempt to start the furnace.
It waits, with the "OK" light on,
until the pressure switch
contacts reopen.
6. LOW/NO GAS PRESSURE
• With insufficient gas pressure
to generate a proper flame, the
control loses flame sensing and
goes into soft lock out.
7. IMPROPER POLARITY
• If the control or furnace is
wired improperly the control
lights the burners, but does not
sense flame current. It goes into
soft lock out after 4 trials for
ignition.
8.
VOLTAGE SPIKES
• Transient voltage spikes cause
the
controls to respond by
resetting, with the "OK" light
off for 0.5 second, and then
starts a normal ignition
sequence.
9.
VARIATIONS IN 60 HERTZ
FREQUENCY
• The timing of the ignition
sequence changes in proportion
to the frequency variation.
10.
MOMENTARY POWER
OUTAGES
• There is no effect if the outage
is less than 0.2 second or more
than 2.5 seconds. The unit
operates normally if the reset is
outside this range.
• The controls are designed so
that momentary power outages
do not cause lock out. The
control waits one to 2.5 seconds
and then restarts the furnace.
11. CAN THE NEW CONTROLS BE
COMBINED FOR TWINNING
• Yes, see the section on
furnace twinning.
• The "OK" light flashes if the
twinning wiring or procedures
are not correct.
►
NOTE:The UTEC 1012-927, -
928 controls use
only switch #3
for twinning.
Connect the
thermostat to the furnace
intended to be first stage. The
other furnace automatically
becomes second stage.
12. HUMIDIFER OPERATION
• The control powers the
humidifier through the "HUM"
terminal 5 seconds after the
blower starts on a heating
speed. It terminates humidifier
operation 30 seconds before the
blower stops.
NOTE:This does not apply to
UTEC 1012-925 controls.
13. INCOMPATIBLE THERMOSTATS
• If the control is connected to a
"power robbing" thermostat, the
induced draft blower (IDB) tries
to start during the off cycle.
Since this drains so much power
from the thermostat, the I DB
pulsates off and on. See
isolation relay, page 58.
14. With the thermostat "FAN"
switch set to the
"ON"position,
the control powers the blower
constantly through the
"FAN"
terminal on the board. On a call
for heat, the blower stops as the
furnace goes through its ignition
sequence. The blower runs on
its heating speed 20 seconds
after the gas valve opens. It
shifts back to the constant
speed after the heating speed is
timed off.
NOTE:This does not apply to
UTEC 1012-925 controls.
15. SENSING FLAME DURING
THE "OFF" CYCLE
If the control senses flame when
a flame should not be present,
the amber "FLAME" LED flashes
with the "OK" and "PWR" LED's
on. The furnace operates both
the main blower and inducer. It
does not allow the gas valve to
open.
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