LAARS Mighty Max HH (Sizes 320M - 400M) - Installation, Operation and Maintenance Instructions - Manual (Page 22)

Page 22
LAARS Heating Systems
Figure 16. Gas Offset Pressure - Natural Gas.
Figure 17. Gas Orifice Differential Pressure - Natural Gas.
Figure 15. Unfired Venturi Differential Pressure - Natural
Gas.
7. After setting all pressures, turn the heater off and
replace each shutoff valve with the factory
installed threaded plugs. The venturi has now
been adjusted for proper operation.
3.7 Venturi Adjustment - Propane Gas
The field checkout involves measuring gas and
venturi pressures, and observing the flame through the
sight glass. If necessary, the gas input rate can be
measured by timing the gas meter.
Use a single, inclined manometer or digital
manometer with a 4.0 inch water column range. Install
shutoff valves at the gas orifice (regulator outlet) tap
(red), at the venturi inlet tap (blue) and at the venturi
throat tap (yellow). After installing the shutoff valves,
be certain they are closed (see Figure 18).
1.
With the heater off, connect the positive side of
the manometer to the shutoff valve on the venturi
inlet tap (blue). Open the shutoff valve.
2. Loosen the nut on the blower damper to allow
for adjustment. Turn the boiler on so that the
blower is running and the boiler is not firing. In
this unfired condition, adjust the damper until the
venturi inlet pressure (blue tap) is 1.2 inches
water column.
3. Approximately 40 seconds after the blower starts
the gas valves will open. The boiler is now
firing. If the heater is not running, check all
manual gas valves and heater safety devices.
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