151B0801 R5 3/28/2006
8
MANUAL FAN.
When the manual fan switch on the
thermostat is on, energizing G only, the
blower will ramp to 50% of the selected
cooling/heat pump airflow.
SEE TABLE A.2 & A.3 FOR PROPER
DIP SWITCH SETTINGS. (HEATING
ONLY)
SEE CHART ON COVER OF BLOWER
CONTROL BOX FOR PROPER DIP
SWITCH SETTINGS FOR AIR
CONDITIONING.
DIRECT DRIVE
The
O4HD-***A-**-FA
furnaces are
equipped with a direct drive blower
system. Direct drive blower speed
adjustments are not normally required in
properly sized extended plenum duct
systems. The motor RPM and air CFM
delivery will vary automatically to
accommodate conditions within the usual
range of external static pressures typical
of residential duct systems. Under-sized
duct systems may require a higher
blower speed to obtain a reasonable
system temperature rise. Some older
duct systems were not designed to
provide static pressure. They typically
feature special reducing fittings at each
branch run and lack block ends on the
trunk ducts. These systems may require
modification to provide some resistance
to the airflow to prevent over- amping of
the direct drive blower motor. Selecting a
lower blower speed may correct this
problem.
Direct drive blower speeds are adjusted
by changing the "hot" wires to the motor
winding connections. Please refer to
wiring diagram in Appendix B or the
wiring diagram label affixed to the
furnace.
THE NEUTRAL WIRE
(normally the white wire) IS NEVER
MOVED TO ADJUST THE BLOWER
SPEED
.
DO NOT CONNECT POWER LEADS
BETWEEN MOTOR SPEEDS. THE
NEUTRAL WIRE MUST ALWAYS BE
CONNECTED TO THE MOTOR'S
DESIGNATED NEUTRAL
TERMINAL.
It is possible and acceptable to use a
single blower speed for both heating and
cooling modes. The simplest method to
connect the wiring from both modes is to
use a "piggy-back connector"
accommodating both wires on a single
motor tap. It is also acceptable to
connect the selected motor speed with a
pigtail joined to both heating and cooling
speed wires with a wire nut. As a safety
precaution against accidental
disconnection of the wires by vibration, it
is advisable to secure the wire nut and
wires with a few wraps of electricians
tape.
If the joining of the blower speed wiring
is done in the furnace junction box, tape
off both ends of the unused wire.
FURNACE CONTROLS
The Electronic Fan Timer integrates
control of all burner and circulator fan
operations. This control is the central
wiring point for most of the electrical
components in the furnace. The
Honeywell
EFT
has a fixed fan delay on
time of 30 seconds after the burner
ignites. The
United Technologies 1158-
120
has an adjustable fan on time that is
set by selecting the dipswitch
combination displayed in Table 5. This
fan on delay can be set at 30, 60, 90 or
120 seconds. This provides a delay
between the burner ignition and blower
start-up to eliminate excessive flow of
cold air when the blower comes on. The
Honeywell
ST9103
has an adjustable
fan off time of 60, 90, 120 and 150
seconds that is set by selecting a
dipswitch combination on the control
board displayed in chart 1. Similarly the
United Technologies 1158-120
have an
adjustable fan off time of 2, 3, 4,or 6
minutes displayed in Table 5. The fan off
delay time starts when the burner is de-
energized at the end of a call for heat.
Blower shutdown is delayed to remove
any residual heat from the heat
exchanger and improve the annual
efficiency of the furnace.
The electronic fan timer board works in
conjunction with snap disc limit controls,
which perform a safety function, and
breaks power to the oil burner primary
control, which shuts off the burner if the
furnace over-heats. The limit control is
thermally operated and automatically
resets. The limit control is factory
installed, pre-set and is not adjustable.
If a limit control opens, the
Honeywell
ST9103
will energize the circulating fan.
When the limit control closes the burner
is re-energized and the heating cycle
begins again.
If the limit control opens with the
United
Technologies 1158-120
electronic fan
control
,
the circulating fan will be
energized as well. When the limit closes,
the fan off timer will begin. At the end of
the fan off time cycle the burner will be
energized, initiating a normal burner
cycle.
The circulating fan start-up and
shutdown is immediate in the cooling
mode.
The heating mode “fan off” delay may be
field adjusted by manipulating the
dipswitches. See Table 5.
Table 5: Heating “Blower Off/On”
Timing
Honeywell ST9103
Dip Switch
Position
Blower Off Delay
Time
1 2
On On
60
seconds
On Off
90
seconds
Off On
120
seconds
Off Off
150
seconds
United Technologies 1158-120
Dip Switch Position
Blower Delay
Times
1 2 3 4 On
Sec.
Off
Min.
Off Off
30
On Off
60
Off On
90
On On
120
Off
Off
2
On
Off
3
Off
On
4
On
On
6
DISCONNECT THE POWER SUPPLY
TO THE FURNACE BEFORE
OPENING THE BLOWER ACCESS
DOOR TO SERVICE THE AIR FILTER,
FAN AND MOTOR. FAILURE TO
SHUT OFF POWER COULD ALLOW
THE BLOWER TO START
UNEXPECTEDLY, CREATING A RISK
OF DEATH OR PERSONAL INJURY.
DO NOT START THE BURNER OR
BLOWER FAN UNLESS THE BLOWER
ACCESS DOOR IS SECURELY IN
PLACE.
OIL BURNER
O4HD furnaces are equipped with
Beckett AFG Series oil burners. The oil
burner must align properly with the
cerafelt fiber chamber (firepot). The
cerafelt fiber chamber is initially quite
soft, but hardens and becomes quite
brittle after the first firing. The firepot is
held in place by a retaining bracket;
however, it is possible for the firepot to
shift if subjected to rough handling during
transit.
