NOTE: The "Flame" LED does not
come on during the time the igniter is
energized, but only after the system
goes into its flame monitoring phase.
FIGURE 91
HONEYWELL LED's
A WARNING: MAKE NO ATTEMPT
TO FIELD REPAIR/ MODIFY ANY
SOLID STATE CONTROL UNLESS
SPECIFICALLY AUTHORIZED BY
THE FACTORY. UNAUTHORIZED
MODIFICATIONS MAY CAUSE
DANGEROUS OPERATING CON-
DITIONS POSSIBLY RESULTING IN
ERRATIC FURNACE OPERATION,
EXPLOSION, PERSONAL INJURY
OR DEATH.
A
►
WARNING: THE HONEYWELL
CONTROL, PART NUMBER 62-
24044-01, IS ONLY TO BE USED
WITH THIS FURNACE, OR
CURRENT PRODUCTION 90%
HSI FURNACES. USING THIS
CONTROL ON OTHER FURNACES
MAY RESULT IN DANGEROUS
OPERATING CONDITIONS.
Lock Out Status
The control board reacts to
malfunctions in the system by going
into lock out.
FIGURE90
UTEC -920 and -927 LED's
In a soft lock out both green lights
are on. This could be described as a
waiting state. Reset the board either
by cycling the thermostat or the main
power disconnect off 5 - 1 0 seconds
and then back on. If the unit fails to
sense flame microamp current it
goes into soft lock out. This affects
only the heating mode. Cooling
calls through the "Y" and "G"
terminals operate normally. There
is no response to a fan "ON" call
through the "G" terminal only.
Soft lock out causes
1. Not detecting flame after four
ignition trials.
2. Four flame failures during one
heat call.
This control should not go into a
hard lock out. In a hard lock out the
"OK" light is off. No heating functions
operate. A hard lock out may or may
not be reset by cycling the line
voltage disconnect switch off 5-1 0
seconds and then back on. If the
problem persists the unit goes into
another hard lock out. This is usually
caused
by a hardware failure.
Hard lock out causes
1. Damaged microprocessor.
2. Failure of a control board
component
3. Failure of a built-in safety self-
check.
4. Failure of the flame sense
circuitry.
"Self Healing"
A unit could soft lock out if the heat
assisted limit control (HALC) opens
during, or after, a furnace run cycle.
The HALC breaks power to the gas
, valve and the board retries for
ignition. With an open HALC the gas
valve cannot open and the control
goes through its trials for ignition and
then locks out.
For this reason the new controls
have certain timing functions if the
furnace does not light after the first
or second retry for ignition, called
"self-healing." If the first or second
trial for ignition fails, the control then
runs the main blower for 180
seconds. This attempts to cool and
reset the HALC. The gas valve can
then open and restart the furnace.
All models use this "self healingtt
feature.
Low Thermostat Anticipation
Because of the circuitry in the board,
the thermostat circuit amp draw
could be as low as 0.1 0 amps. This
could be below the minimum heat
anticipator setting of some
thermostats. However testing shows
0.10 amps on a thermostat with a
0.25 or 0.30 amp minimum
anticipator setting causes very little
temperature overshoot.
Control Board Characteristics
The new controls have a newly
designed microprocessor. There are
different timing functions and
operations that previous IFC boards
did not have.
It has the "self healing" feature.
It makes four (4) tries for ignition
before locking out
The blower on time is 20
seconds after the gas valve opens
and its off delay is 90, 120, 160,
or 180 seconds after burner shut
down.
The UTEC -920 twinning
settings are with DIP switches in
the control center and by wiring
the two furnaces together. E2001
twinning settings are by
removing a metal jumper in the
control center and wiring the two
furnaces together. See the section
on furnace twinning.
Its flame sensitivity could be as
low as 0.5 microamps making it
much less subject to nuisance lock
outs.
It should NOT BE AFFECTED BY
MOMENTARY POWER
OUT AGES. A brief power outage
or electrical interference ("noise" )
causes the unit to reset WITH THE
"OK" LIGHT Off FOR ONE
SECOND ON THE UTEC AND 2.5
SECONDS ON THE
HONEYWELL. The furnace then
starts normally.
The "OK" light should never be
off for more than ONE OR 2.5
SECONDS at a time. If it is
REPLACE THE CONTROL.
Each control has a ONE HOUR
RETRY FOR IGNITION. If the
control goes into "soft" lock out, it
automatically retries for ignition
one hour later. This prevents total
loss of heat caused by a transient
condition.
77
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