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electrical p anel;however, a ccessory
equipment suchas electronic airclean-
ersandhumidifiers may beincluded o n
thefurnace circuit. Although a suitably
located c ircuit b reaker canbeused asa
service s witch, a separate service s witch
is advisable. Theservice switch is nec-
essaryif reaching the circuitbreaker
involves becoming close tothefurnace,
or if thefurnace is located b etween the
circuit breaker andthemeans o fentry to
the furnace room. T hefurnace switch
(serviceswitch)should be clearly
marked, installed in aneasily accessible
areabetween t hefurnace andfurnace
roomentry,andbe located in sucha
manner to reduce thelikelihood t hatit
would bemistaken a s a lightswitch or
similar device.
Thepower r equirements
for allmodels:
120 VAC, 1 ®,60Hz., 1 2A.
Accessories requiring 1 20VACpower
sources s uchas electronic aircleaners
and humidifier t ransformers may be
powered fromtheST9103 E FT.Donot
usethedirect drive motor connections
as
a power source, since there isa high risk
of damaging t he accessories by expo-
sureto high voltage fromthe auto-
generating windings o f the direct d rive
motor.
Thermostat wiringconnections andair
conditioning contactor lowvoltage con-
nections a re shown in the wiringdia-
grams. S omemicro-electronic
thermo-
statsrequire a dditional controls a ndwir-
ing.Referto the thermostat manufac-
turer's i nstructions.
Thethermostat should be located ap-
proximately 5 feetabove t hefloor, o nan
inside waltwhere thereis goodnatural
aircirculation, andwhere thethermostat
wiltbe exposed t o average r oomtem-
peratures. Avoidlocations wherethe
thermostat wilt b eexposed tocold drafts,
heat f romnearby l amps a ndappliances,
exposure t o sunlight, heatfrominside
walt s tacks, etc.
Normal heatanticipator setting: 0.1 A.
Formoreprecise adjustment, the heat
anticipator maybe adjusted t o theam-
perage d raw oftheheating c ontrol circuit
as measured between t he"R"and"W"
terminals of thethermostat. To reduce
theriskofdamaging theheat a nticipator,
do not measure c ircuit w ithout f irstre-
moving oneof the two wiresfirst.To
determine the heating circuit a mperage
draw:
1. Disconnect oneof the "R"or "W"
wires f rom thethermostat terminal.
2. Connect an ammeter between t he
wireandthethermostat terminal to
which itwasattached.
3.
4.
5.
Note the amperage
reading when
the heating
contacts
are
closed.
(System switch must be on "HEAT" if
SOequipped.
Re-connect
the thermostat
wire. If
the thermostat is serving a combina-
tion heating and air conditioning sys-
tem, pay particular attention to po-
larity.
When the thermostat is reconnected
and re-plumbed, adjust the heat an-
ticipator
setting
to match the ob-
served amperage reading.
FAN TIMER BOARD AND LIMIT
CONTROL
The Electronic Fan Timer integrates con-
trol of all burner and circulator fan opera-
tions. This control is the central wiring
point for most of the electrical
compo-
nents
in the furnace.
The
Honeywell
ST9103 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 se-
lecting
the dipswitch
combination
dis-
played in Table 6. 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 Table 5.
Similarly
the
United
Technologies
1158-120 have an adjustable fan off time
of 2, 3, 4 or 6 minutes displayed in Table
6. The fan off delay time starts when the
burner motor 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
in-
stalled, pre-set and is not adjustable.
If a limit control opens, the Honeywell
ST9103 wilt 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 ener-
gized as welt. When the limit closes, the
control
initiates a two
minute
delay.
When this delay is finished, 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.
TABLE 5
Honeywell ST9103
Dip Switch
Blower Off Delay
Position
Time
1_
60 seconds
On
I
Off
off I
On
Off
I
Off
90 seconds
120 seconds
150 seconds
Dip Switch Position
1
2
3
4
Dff
Off
Dn
Off
Dff
On
Dn
On
Off
Off
On
Off
Off
On
On
On
TABLE 6
United Technologies
1158-120
Blower Delay
Times
On
I
Sec-I
ondsl
3o I
6o I
go I
120
I
i
Off
Minutes
2
i
3
i
4
i
6
Note: It is advisable
not to set the
fan on delay time for a time period
longer
than
90 seconds
on the
04MD-140A-16-FA
with
128,000
BTUH output.
Longer fan on delay
times
may result in nuisance
limit
trips.
CIRCULATING
AIR BLOWER
All 04MD-091A-12-FA
AND 04MD-140A-
16-FA furnace models are equipped with
a direct drive blower system. Direct drive
blower speed adjustments
are not nor-
mally required in properly sized extended
31enum duct systems.
The motor RPM
and air CFM delivery will vary automati-
cally to accommodate
conditions within
the usual range of external
static pres-
sures typical of residential duct systems.
Under-sized duct systems may require a
higher blower speed to obtain a reason-
able
system
temperature
rise.
Some
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