Midco Unipower A-Series - Manual (Page 8)

VI Electrical
VII Gas Piping
■ ■ ■ ■ The burner when installed, must be wired and grounded in accordance with local codes or in
the absence of local codes, with the National Electric Code ANSI/NFPA No. 70-latest edition.
In Canada, refer to CSA Standard C22.1, "Canadian Electrical Code Part 1" and/or local
codes.
Refer to the separate wiring diagram included with this burner for specific wiring
details. The wiring diagram number for your burner is listed on the front cover of this
manual.
■ ■ ■ ■ When wiring, be sure that the electrical power take-off is connected to a permanently live
circuit and that the burner is electrically grounded. Use copper conductors not lighter than those
given in Table 4.
■ ■ ■ ■ Standard Unipower A-
Series burners are equipped
with Honeywell Flame
Safeguards.
■ ■ ■ ■ The RM7895 Flame
Safeguard provides pre-purge
and intermittent pilot
operation. See Section I
Specifications for application.
When mounting the chassis,
be sure electrical power has
been turned off. Check all
plug-in components for
security.
■ ■ ■ ■ The RM7840M Flame Safeguard provides pre- and post-purge and interrupted pilot operation.
See Section I Specifications for application. Burners over 2500 MBH are equipped with a high-
low gas pressure switch which prevents operation if gas line pressure exceeds or falls below
certain preset limits.
■ ■ ■ ■ For further information on both flame safeguards, see Part 2 Service.
■ ■ ■ ■ Where safe operation of the burner depends on factors external to the burner, an interlock
must be included which will prevent or delay burner operation until safe conditions exist. For
example, in the case of a motorized flue pipe damper or mechanical flue exhauster, the initial call
for heat must first energize the damper or exhauster motor, with burner start-up following only
when the above components are in effective operation as monitored by flow or draft pressure
switches in the flue pipe. If burner operation is made dependent on damper or exhauster control
relays, the system must "fail safe" so that malfunction or failure of these components will not
result in unsafe operations of the burner. See wiring diagrams for proper location of auxiliary
controls.
■ ■ ■ ■ For the usual low pressure gas supply system, i.e. 5" to 14" W.C., use Table 5 to find the
recommended gas line size.
■ ■ ■ ■ Piping follows normal practice and should be arranged as shown in Figure 12 with a drip leg at
the end of the vertical drop. The piping must be firmly supported independent of the
burner.
■ ■ ■ ■ The burner is shipped with the main and pilot valve train completely assembled except for the
manual gas valves and regulators which should be mounted in a location convenient to the
burner. If the main gas train must be rearranged because of space limitations, maintain the
relationship of the components.
■ ■ ■ ■ The gas line
pressure must be
within the limits
given in Section I
Specifications. If
higher than normal
gas delivery pressure
is encountered, as is
the case in many
industrial plants, the
gas line size may be
reduced to allow for
a greater pressure
drop (use the
multipliers given in
Table 5 for the
allowable size
variations) however, the size must be sufficient to deliver burner rating pressure.
Motor
H.P. Fuse Wire
115/1/60
Fuse Wire
230/1/60
Fuse Wire
230/3/60*
1 /
3
1 /
2
3 /
4
1 1 /
2
2
30A
30A
45A
65A
75A
#14
#14
#12
#10
#10
#14
#14
#14
#12
#12
15A
15A
25A
35A
40A
—
—
#14
#14
#14
—
—
15A
15A
20A
Table 3: Fuse and Wire Sizes
* When 3 phase motor is used, the 120V. 1 phase control circuit
should be fused for 10A minimum and wired with #14 conductors.
Figure 12: Gas Piping Schematic
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