Midco Unipower MPG Series - Manual (Page 10)

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The blower functions to supply a constant and positive supply of air for complete combustion.
Air volume is controlled by an adjustable shutter in the blower inlet.
No routine service is necessary on the blower other than occasionally cleaning the blower
wheel. If the blower wheel must be replaced, be sure to check the replacement for proper
rotation. The concave sides of the blades must face the blower outlet, and rotation of the wheel
must be toward the outlet. Motor sizes and specifications are given in Table 1. All motors contain
integral motor overload protection, usually manual, occasionally automatic reset.
Proof of blower operation is
provided by the diaphragm air
switch, which must close its contacts
and maintain them closed when the
blower is running. In case of
malfunction, the diaphragm air
switch must be replaced.
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A combination integrated redundant main gas valve with an integrated gas pressure regulator is
used on the standard MPG burner.
The gas pressure regulator is used to automatically reduce and maintain constant gas
pressure to the burner. To vary the outlet pressure, remove the seal cap for access to the
adjusting screw. Turning the screw clockwise will increase outlet pressure, counter-clockwise will
decrease outlet pressure.
Maximum and minimum allowable gas pressures are shown in Table 1.
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Note: All burners are equipped with dual valves. Burner construction for special codes and/or
insurance requirements such as Factory Mutual or Industrial Risk Insurers (GAP) may require
alternate construction. (Refer to Section XV Special Equipment.)
10
Part 1 Installation
XIII Main Automatic
Valves
XII Gas Pressure
Regulator
XI Blower and
Motor
Drawer Assembly with Flame Rod
Drawer Assembly with UV Scanner
Figure 9: Drawer Assembly MPG Burner
VIII Initial Start-
up /Adjustment
On-Off Burners
Continued
Orifice Orifice Drill Pilot Gas
Model Type Size " Size Pressure
On-Off A 0.11" #35 2.0"-3.5"
Low Fire Start B 0.076" #48 2.0"-3.5"
(Full Mod and
2-Stage)
Table 8: Pilot Gas Pressure Orifice Size
Open to 7/64" Gap