Bryant LOW-BOY 367AAN User Manual
Page 9
3. In order to ensure proper draft through furnace, a baromet-
ric draft regulator (supplied with furnace) must be installed
as close to outlet of furnace as possible.
In order for this device to function properly, barometric
damper must be mounted with hinge pins horizontal and
face of damper vertical. (See instructions included with
damper.) The draft regulator should be adjusted after
furnace has been firing for at least 5 minutes, and set
between -0.025 and -0.035 in. wc. (See Table 4.)
4. The over-fire draft, which is taken through observation door
(located in center line above burner in front panel of
furnace), is a measurement necessary to determine if there
is a blockage between oil burner and flue outlet.
There should be a total pressure drop of between 0.020 and
0.05 in. wc through furnace as shown in Table 4. The
over-fire draft must be set within the range shown in Table
4.
A reading outside the range shown in Table 4 (for example
+0.1 in. wc) would indicate that furnace is in an extremely
high-pressure condition in primary section. This condition
may be caused by any of the following problems:
a. Excessive combustion air due to air band being too wide
open.
b. A lack of flue draft (chimney effect) or some other
blockage, such as soot, in secondary section of heat
exchanger.
c. Use of an oversized nozzle input.
d. Pump pressure over 105 psig.
5. The CO
2
and stack temperature instruments enable you to
obtain data required to determine thermal efficiency of
furnace.
6. An oil filter should be installed as close to burner as
possible with ALL oil burners and is essential on lower
firing rate burners. We recommend the use of a low
pressure drop oil filter such as the General Filter, Inc. model
#1A-25A or equivalent.
7. The oil pressure regulator is factory set to give nozzle oil
pressures of 100 psig. The firing rates noted on nameplate
may be obtained using nozzles listed in Table 5.
8. On a new installation, air entrapped in oil line leading from
tank to nozzle must be thoroughly purged in order to
prevent excessive after drip. The oil pump is provided with
a special fitting which allows purging of any air between
tank and oil pump. The proper procedure for performing
this operation is as follows:
a. Place a piece of clear plastic 1/4 in. diameter tubing over
purge fitting on oil pump.
b. Start oil burner, then open purge fitting and allow burner
to run until purge tube is completely free of air bubbles.
c. Tighten purge fitting. Allow oil to run to nozzle and fire
burner.
d. If purging takes longer than 15 sec and no flame has
been established, burner stops. Push reset button on top
of primary control to restart burner.
e. For detailed information on operation of primary control,
refer to instructions included with furnace.
After all the setup procedures mentioned above have been com-
pleted, the burner should be allowed to operate and an inspection
mirror should be used to observe the flame pattern at tip of nozzle.
Any irregularities such as burning to 1 side or pulsating flame
patterns should be corrected by changing nozzle.
III.
FAN ADJUSTMENT CHECK
This furnace is equipped with a 4-speed direct-drive motor to
deliver a temperature rise within range specified on rating plate,
between return and supply plenums, at external duct static pressure
noted on rating plate.
WARNING:
When operating furnace in heating mode,
static pressure and temperature rise (supply-air tempera-
ture minus return-air temperature) must be within those
limits specified on rating label. Failure to follow this
warning could lead to severe furnace damage.
Adjust fan speed ACCORDING TO OIL INPUT SELECTED so
that temperature rise is within rise range specified on rating plate.
(See Table 6.) Consult wiring diagram for speed changes on
direct-drive motor.
To adjust fan off time, set DIP switches on control board to obtain
desired timing. (See Fig. 5.)
→
TABLE 4—FURNACE DRAFT CONDITIONS
(IN. WC)
FURNACE
INPUT
(BTUH)
FLUE
DRAFT
MINIMUM
OVER-FIRE
DRAFT
MAXIMUM
TOTAL RESTRICTION
THROUGH
HEAT EXCHANGER
70,000
-0.025
0.010
0.020 to 0.035
91,000
-0.025
0.020
0.030 to 0.045
105,000
-0.025
0.025
0.035 to 0.050
119,000
-0.025
0.025
0.035 to 0.050
140,000
-0.025
0.025
0.035 to 0.050
154,000
-0.025
0.025
0.035 to 0.050
→
TABLE 5—BURNER INPUT AND NOZZLE SIZE
(AT 100 PSIG PUMP PRESSURE)
FURNACE
INPUT
(BTUH)
FIRING
RATE
GAL/HR (US)
BECKETT OIL BURNER
Model
Nozzle
70,000
0.50
AFG-F3
0.50 gph
70-W
91,000
0.65
AFG-F3
0.65 gph
70-W
105,000
0.75
AFG-F3
0.75 gph
70-B
119,000
0.85
AFG-F3
0.85 gph
70-B
140,000
1.00
AFG-F3
1.00 gph
70-W
154,000
1.10
AFG-F6*
1.10 gph
70-W
* Requires field supplied and replacement burner firing head.
→
TABLE 6—SPEED SELECTION
UNIT
SIZE
FURNACE
INPUT
(BTUH)
RECOMMENDED
BLOWER
SPEED
036105/
060120
70,000/119,000
Med-Low
91,000/140,000
Med-High
105,000/154,000
High
→
Fig. 5—Fan Off Time DIP Switch Settings
(Black Box Represents Switch Position)
A95115
1
2
60 Sec
1
2
90 Sec
DELAY OFF DIP SWITCH SETTINGS
1
2
1
2
1
2
120 Sec
1
2
150 Sec
—9—
→