Patterson-Kelley MACH-05 ユーザーズマニュアル

 

Page  27 

MACH C750, C900 & C450  

TORX® T40 or 5 mm hex wrench 
3 mm or 7/64 in hex wrench 
Combustion analyzer 
 
The MACH  C750,C900 and C1050  boilers are 
equipped with a Honeywell  combined gas/air control 
and gas safety shut off  control valves.  The valve 
functions in parallel with the variable speed 
combustion blower to supply the correct gas air ratio 
for optimum performance and efficiency.  The 
combustion blower speed is controlled automatically 
and determines the amount of negative pressure felt at 
the gas safety shut off / control valves.  The gas/air 
regulator adjusts gas flow to maintain the proper 
pressure at the outlet nozzle of the associated valve. 

 

There must be sufficient load to operate the boiler at 
high fire to perform the following adjustments.  Start 
the boiler and observe proper operating parameters for 
the system.  
 

 

 

Set boiler to the “Test Mode High”, as described 
above, to achieve maximum firing rate of the boiler. 
Check combustion readings using a combustion 
analyzer.  If combustion readings are not in 
accordance with Table 3-1, adjust as follows: 

Remove the flat, round, blue plastic cap from the 
cover. Using a 3mm (7/64”) hex wrench, turn the 
adjustment screw counterclockwise to increase or 
clockwise to decrease gas flow and achieve the desired 
CO

2

 or O

2

 level; see Table 3-1 for correct settings.  

(There will be a slight time delay between the 
adjustment and the response of the CO

2

/O

2

 measuring 

instrument. Adjust the settings in small increments and 
allow the combustion readings to stabilize before 
readjusting. When desired adjustments are complete, 
reinstall the blue plastic cap on the cover. 

 

Set boiler to the “Test Mode Low”, as described 
above, to achieve minimum firing rate of the boiler. 
Check combustion readings using a combustion 
analyzer.  If combustion readings are not in 
accordance with Table 3-1, adjust as follows: 

Remove the cap on the gas regulator using a slotted 
screwdriver (See Fig. XX). This will expose the offset 
adjustment screw.  
Using a TORX® T40 or a 5 mm hex wrench, carefully 
adjust the low fire gas setting to achieve the CO

2

 /O

2

 

level prescribed in Table 3-1.   
Note: The rotation of the Low Fire adjustment is 
opposite of the High Fire as follows: Clockwise 
rotation increases gas flow, counterclockwise rotation 
decreases gas flow. 
Adjustments to the offset pressure regulators should 
not exceed ¼ turn at a time before allowing the 
readings to respond and stabilize.   
After proper low fire offset adjustment is made, 
reinstall the slotted cap on the regulator.  
 
Following all gas valve adjustments, check for proper 
light-off and verify correct fuel/air mix and 
combustion quality throughout the entire firing range 
(from lowest to highest fan speed). 
 

 

 

 
 

 

 

High fire adjustment 

Low fire adjustment