Slant/Fin CHS-399 - Manual (Page 35)

CHS Series Installation and Operation Instructions │ Slant Fin Corp.
35
Manifold Pressure - DO NOT adjust or measure the Manifold Pressure of the boiler.
Correct manifold pressure is factory set. Field adjustment could result in improper burner
operation resulting in fire, explosion, property damage or death.
Adjustments to the Throttle / Input Screw may only be made by a qualified gas
technician, while using a calibrated combustion analyzer capable of measuring CO
2
and
CO. Adjustments may only be performed if the gas line pressure is maintained above minimum levels
throughout the duration of the test, see Table 9-1. Failure to follow these instructions may result in serious
injury or death.
Adjustment
Throttle / Input Screw Adjustments - The boiler is equipped with a Throttle/Input Adjustment Screw, located
on the Gas Valve and Venturi Assembly. It is used to adjust the flow of gas leaving the gas valve entering the
Venturi and then the combustion air stream. Turn the adjustment screw in (clockwise) to reduce the flow of gas,
make combustion leaner, and reduce the concentration of CO
2
in the flue gases. To increase the CO
2
level and
flow of gas in the combustion air stream, adjust the Throttle screw out (counterclockwise).
CHS 85-250 Adjustments - The throttle screw for models CHS 85-250 is a multiple turn valve. Typical
adjustment required for Natural Gas is 0-1 full turns in or out from the factory setting. Typical adjustment for LP
Gas is 0-3 full turns in or out from the factory setting upon inserting the LP orifice as per the applicable Propane
conversion instructions. See Figure 9-1 for throttle screw location.
CHS 300-399 Adjustments - The throttle screw for the CHS 300-399 is a geared valve with a 4:1 ratio.
Adjusting the throttle screw 4 complete turns will return the valve to the original location, 2 turns from fully
open will completely close the valve. Typical adjustment required is 0-1/4 turn in or out from the factory setting.
See Figure 9-2 for throttle screw location.
Combustion Calibration - To calibrate burner operation, perform the following procedure using a calibrated
combustion analyzer capable of measuring CO
2
and CO from Natural and Propane Gas burning boilers:
1. Operate the unit at the maximum modulation rate, see Table 9-2.
2. Ensure the gas line pressure is maintained within tolerance, see Table 9-1.
3. While at the maximum modulation rate, measure the CO
2
and CO; adjust as necessary, using the Throttle
Screw, to be within the limits listed in Table 9-1.
4. Operate the unit at the minimum modulation rate (Table 9-2). Ensure the combustion remains smooth and
CO
2
and CO remain within the limits (Table 9-1). If not, do not adjust further, contact Slant/Fin for
assistance.
Flue Gas Analysis and Adjustment
Each CHS boiler is factory set to operate with Natural Gas, for boilers field converted to operate with Propane
Gas, a flue gas analysis and adjustment is mandatory. See Table 7-1 and Propane conversion instructions.
Failure to perform the flue gas analysis and adjustment detailed in this section may result
in erratic and unreliable burner operation, leading to reduced efficiency, increased fuel
consumption, reduced component life, heat exchanger combustion deposits, and general unsafe operation.
Failure to follow these instructions may result in serious injury or death.
Analysis – Perform flue gas analysis, and adjust throttle/input screw as required until CO
2
and CO levels are
within acceptable limits.
Throttle/Input Adjustment Screw
Increase gas
Turn Counter Clockwise Decrease gas
Turn Clockwise