Slant/Fin CB-45 Installation And Operating Instructions Manual page 19

STEP B: CALIBRATE GAS VALVE
Note: This step will set the air/gas ratio for optimum
combustion. The purpose of this step is NOT to set input
rate. Follow Step A and/or Step C to adjust input.
1. With power off, set differential pressure gage on a level
surface and adjust to zero.
2. Locate blower outlet pressure fitting and gas valve
outlet pressure fitting. See figure 20.
3. Remove cap on blower outlet pressure fitting and
connect to high side of gage tubing.
4. Remove cap on gas valve outlet pressure fitting and
connect to low side of gage tubing.
5. Turn power on. Raise thermostat to start boiler.
6. Boiler should start after 20 seconds.Let run for about 1
minute.
7. Gauge reading should register a differential pressure
reading of 0. If so, proceed to line 11.
8. If gage reading is not at 0, re-adjustment is necessary.
Locate gas valve adjustment screw cap on top of gas
valve.See figure 20.
9. Remove gas valve adjustment screw cap by turning
counterclockwise with a screwdriver.
10. Position screwdriver into adjustment screw slot
carefully. Observe gage while adjusting and turn screw
slowly. Turn adjustment screw clockwise to decrease
reading if over 0 set point. Turn adjustment screw
counterclockwise to increase reading if under 0
setpoint.
Note: Remember that the gas pressure is on the low
side of the gage. Consequently, decreasing the
differential reading actually is INCREASING the gas
pressure reading, since the blower outlet pressure is
on the high side of the gage and not changing.
11. When reading is set correctly to 0, retighten the gas
valve adjustment screw cap tightly with screwdriver.
Double check gage reading.
12. Turn power off, disconnect both sides of gage from
fittings and replace service fitting caps hand tight.
STEP C: CHECK BOILER INPUT RATE
1. Turn power on. Raise thermostat to start boiler. Let
boiler run steady about 10 minutes.
2. At meter, observe number of M
boiler uses in 3 minutes. Be sure that only this
appliance is running on the gas meter at this time.
3. Consult gas supplier for heating value of gas
- usually 10,350 W/m
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25,875 W/m (2500 BTU/cu.ft.) for propane.
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4. Verify input using following formula:
m in 3 minutes X heating value X 20 = W/hr input
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(Cu.ft. in 3 minutes X heating value X 20 = BTU/hr input)
Example:
0.1274m X 10,350 W/m
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(4.5 cu.ft. X 1000 BTU/cu.ft. X 20 = 90,000 BTU/hr input)
5. If gas flow is not at the specified input rate, it is
necessary to adjust the air shutter to attain the correct
input rate.
(cu. ft.) of gas the
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(1000 BTU/cu.ft.) for natural gas,
X 20 = 26,400 W/hr input
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6. Locate the knurled adjustment knob on side of air filter
box. See figure 20.
7. Loosen air adjustment locking screw on knob. Do not
remove.
8. Turn knurled adjustment knob clockwise to reduce air
flow, and consequently, reduce gas flow and input rate
Turn adjustment rod counterclockwise to increase air
flow, and consequently, increase gas flow and input
rate.
Note: Make adjustments in small increments and re-
check input as in line 4.
9. When input is set properly, retighten the air adjustment
locking screw finger tight. Hold knurled adjustment
knob steady while doing this to maintain setting.
10. Restore operation to any appliance shut off for meter
clocking.
Notes on Input Rate:
1. Refer to the Input Rate Adjustment Specifications
Charts on page 20 for the appropriate input rate setting
on each model boiler for each venting application.
2. The procedure in Step A is adequate for setting the
input rate. If a gas meter is available, it can be used to
verify the setting or as an alternate method for setting
the input.
3. For altitudes above 610m (2,000 ft.), ratings shall be
reduced at the rate of 4% for each 305m (1,000 ft.)
above sea level.
4. Re-orificing for altitude change IS NOT necessary on
this Concept 21 boiler.
5. By maintaining the air flow differential pressure set in
Step A, this Concept 21 boiler will derate itself
accordingly, due to air and gas density reduction as
altitude increases.
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