4
OPERATION
1. Call for heat. Burner motor and ignition are energized.
Air is in the low-fire position. The low-fire oil valve ad-
mits oil at 100 psi to the nozzle and its spray ignites,
burning clean with proper air/fuel ratio.
2. If demand exceeds low-fire, the damper motor
is energized through a high-fire operating control
(aquastat, airstat, pressuretrol, or outdoor thermo-
stat). As the damper motor approaches a half open
position, the auxiliary end switch energizes the high-
fire valve on the fuel unit, closing the by-pass port,
and increasing the nozzle pressure to 300 psi. Thus
the full fire with open air burns clean with high CO
2
and high efficiency.
3. As the high-fire input begins to exceed the demand of
the high-fire operator, the operating control de-ener-
gizes the damper motor. As the damper motor returns
the air shutter to low-fire, the auxiliary end switch in
the damper motor de-energizes the high-fire valve
which drops the nozzle pressure to 100 psi.
4. If the demand exceeds low-fire, the high-fire operat-
ing control would again call for more heat as in Step 2
and then Step 3.
5. If, after returning to low-fire, the load should drop to
below the low-fire output, the operating limit would
shut off the burner completely.
It is important that the installation of the oil burner,
piping and fittings, safety devices, controls, elec-
trical wiring and equipment be done in accordance
with national and/or local regulations of the author-
ities having jurisdiction over such installation.
If adjustment to the damper motor is needed, please
reference the included supplement (Part# MNSQN71)
for all settings and operation.
NOZZLE SPECIFICATIONS
The 60° P Hago nozzle is the standard nozzle and usu-
ally provides the best fire. Substitutions are sometimes
recommended in specific packaged boilers.
Following is a list of nozzle specifications for packaged
boilers presently using the 702CRD burner:
Burnham Series V907 - V910: 70° B, Delavan
Burnham Series V911: 60° PLP Monarch
H. B. Smith Series 18: 9-11 Section, 45° P Hago
H. B. Smith Series 19: 7-11 Section, 60° P Hago
Weil-McLain 488, 488R: 60° PLP Monarch
Weil-McLain 588: 70° P Hago.
Other makes of nozzles may or may not prove satisfac-
tory.
For special applications, other specifications might pro-
vide a more desirable pattern.
FORCED DRAFT FIRING
Due to the back pressure in forced draft units, the max-
imum firing rate of a burner is reduced. The greater the
pressure, the lower the maximum GPH capability
becomes. Table 4 shows this. Note that the Table stops
at 0.70 inches W.C., the maximum recommended back
pressure for the 702CRD burner.
The combustion head settings for forced draft firing
would be somewhat greater than those shown in Table 3
which is for zero pressure or natural draft.
*
* The “low-fire” pump pressures shown are recommended. If higher low-fire
inputs are desired for a given situation, the low-fire pressure can be increased
only up to 200 PSI. Higher low-fire pressures will require higher low-fire air
openings.
** The “high-fire” pressure is set at the factory to 300 psi. This is the maximum
UL rating for the fuel unit, so higher pressures are not recommended.
HOW TO ADJUST THE COMBUSTION HEAD
The retention ring position ahead of the throttle ring is
adjustable from zero (flush) to 1
1
⁄
4
inches (Dimension
Figures 7 and 8). Turning the adjusting screw (clock-
wise) increases the distance “A” ahead. This distance
is indicated by llfting the housing cover and reading
the scale on the nozzle line across the corners on sides
of the channel guiding the nozzle line. Each division is
1/16- inch.
Refer to “A” dimension (Table 3) for corresponding
nozzle selection. Example: 702CRD burner firing at 6.80
GPH high-lire setting, Column “A” reads 1/8-inch.
TABLE 3
NOZZLE DATA AND COMBUSTION
HEAD SETTINGS
Nozzle
Size
Low
Fire
Pres.*
Low
FIre
Rate
GPH
Heat
Setting
“A”
(inch)
Low
Fire “X”
Air
Open (inch)
High
Fire
Pres.**
High
Fire
Rate
3.50
100
3.50
0
3/8
300
5.95
3.75
100
3.75
1/16
3/8
300
6.38
4.00
100
4.00
1/8
3/8
300
6.80
4.50
100
4.50
3/16
3/8
300
7.65
5.00
100
5.00
1/4
3/8
300
8.50
5.50
100
5.50
5/16
3/8
300
9.35
6.00
100
6.00
7/16
7/16
300
10.20
6.50
100
6.50
5/8
7/16
300
11.05
7.00
100
7.00
7/8
1/2
300
11.90
7.50
100
7.50
1
1
⁄
4
1/2
300
12.75
TABLE 4
MAXIMUM FIRING RATES (GPH) – FORCED DRAFT