Midco 400B-02 - Manual (Page 5)

CAUTION: Do not
add any power consum-
ing devices in the low
voltage circuit as over-
loading of the trans-
former can result. Do
not use Motor Relay to
operate any external
devices as the extra
load could damage the
relay contacts.
Note: If any of the original
wiring as supplied with the
conversion burner must be
replaced, it must be replaced
with type TFF wire or its
equivalent.
CAUTION: The available gas pressure should be within the limits shown in
the SPECIFICATIONS section. Excessive pressure will damage Combination
Valve and Regulator. If the supply pressure exceeds the 14.0" W.C. maximum, a
suitable intermediate main regulator must be installed ahead of the Main
Manual Shut-Off Valve shown in Figure 6.
The burner gas supply piping should branch off from the main line as close to the gas meter as
possible. Do not connect to the bottom of a horizontal section. Use new black pipe and malleable fit-
tings free of cutting and threading burrs or defects.
Provide a sediment trap, union and 1/8" pressure tap in piping close to burner as shown in Fig 6.
Use pipe joint compound approved for use with Liquid Petroleum Gases.
Piping must comply with local codes.
To obtain the maximum firing rate of 400 MBH, the NATURAL gas supply piping must be sized to
provide minimum of 5.0" W.C. pressure (11.0" W.C. PROPANE) to the inlet of the Combination Valve
when the burner and all other gas utilization equipment are on.
Note: If there is more than 1.0" W.C.
differential in the inlet pressure to
the burner compared to when all
other gas utilization equipment are
off, refer to Section IX, last para-
graph "CAUTION...".
CAUTION: Because it is
difficult to accurately control
pressure during supply pipe
leak test, it is recommended
that the Combination Valve
be disconnected. Exposing
the Combination Valve to pressures over 1/2 PSIG (14.0" W.C.) will damage the
valve and void all warranties.
DANGER: Explosion hazard.
Do not use oxygen for pressure testing.
An explosion could occur during initial start-up.
If the burner piping must be rearranged because of space limitations, be sure to carry out
the general arrangement shown in Figure 6. Install the Combination Valve in any position
except up-side down.
When the burner is installed in jacketed equipment, it is recommended that the
Combination Valve be left adjacent to the burner within the vestibule and the Main Manual
Shut-Off Valve be installed outside.
5
Figure 5: Wiring Diagram
Pipe
Size
3 /
4
1
1 1 /
4
1 1 /
2
250
400
400 300
350
400
400 200
200
350
400
400
200
300
400
400
200
300
400
400
Type
of Gas
NATURAL
PROPANE
NATURAL
PROPANE
NATURAL
PROPANE
NATURAL
Capacity-MBH
Length of Pipe
Table 2: Supply Pipe Capacities in MBH
10 20 40 60 100
V Electrical
Continued
VI Piping
(Terminal call-out may not be as shown)