Patterson-Kelley MACH-05 manual Adjustment, Page

MACH® Series Gas-Fired Boiler Installation

Table 3-1 Combustion Reading For Setting Gas Safety Shut Off / Control Valves

	Nominal	High Fire Setting			Low Fire Setting
Fuel
	Gas Pressure	% O2	% CO2	% O2		% CO2
Natural Gas	7" W.C	5.0 + 0.2	9.0 + 0.2	5.2	+ 0.2	8.8 + 0.2
Propane	11" W.C	5.0 + 0.2	10.4 + 0.3	5.2	+ 0.2	10.3 + 0.3

Adjustment:

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.

Note: The MACH C300 and C450 boilers are each equipped with two gas safety shut off / control valves that operate in parallel. When making any adjustment to the valves, the adjustment must be performed on each of the valves equally.

Example: If an increase in the gas flow is required to lower the O2 level, turn each of the maximum flow restrictors equivalent amounts (i.e. ¼ or ½ turn each) and allow the analyzer readings to respond and stabilize before proceeding with additional adjustment. Adequate response time must be allowed for combustion readings to stabilize. This response time will be longer for low firing rates than for high firing rates.

High Fire Setting

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:

Using a slotted screw driver or 2 mm hex wrench, set the maximum restrictor (high fire screw – see the figure below, item “D”) on each of the gas safety shut off / control valves by turning clockwise or counterclockwise to achieve the desired CO2 or O2 level; see Table 3-1 for correct settings. (There will be a slight time delay between the adjustment and the response of the CO2/O2 measuring instrument).

Clockwise rotation decreases gas flow. Counterclockwise rotation increases gas flow.

Low Fire Setting

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:

Using a 2 mm hex wrench, adjust the pressure regulator offset adjustment (see the figure below, item “R”) to achieve the CO2 /O2 level prescribed in Table 3-1. Note that equal adjustments must be made to each of the valves. Adjustments to the offset pressure regulators should not exceed ¼ turn at a time before allowing the readings to respond and stabilize. Please 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.

"R"

"D"

C300/450 Adjusting Low and High Fire

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