Middleby Marshall PS740 Series Gas Ovens P/N 60250 - Manual (Page 21)

17 P/N 60250 September 28, 2012
on the oven serial plate. The location of the serial plate is shown
in Figure 1-1 (in Section 1, Description).
A fused disconnect switch or a main circuit breaker (customer
furnished) MUST be installed in the electric supply line for each
oven cavity. It is recommended that the switch/circuit breaker
have Lockout/Tagout capability.
The supply conductors must be of the size and material (cop-
per) recommended. Refer to the wiring diagram inside the
machinery compartment of the oven. Electrical specifications
are also listed on the oven’s serial plate and in Table 1-3,
Electrical Specifications (in Section 1, Description).
The oven requires a ground connection to the oven ground
screw. For gas ovens, the screw is located in the electrical
junction box (see Figure 2-14). If necessary, have the electri-
cian supply the ground wire. Do NOT use the wiring conduit
or other piping for ground connections.
Incoming electrical power lines are fed through the strain-relief
fitting, shown in Figure 2-14. The electrical supply connections
are made inside the electrical junction box. The power lines
then connect to the oven circuits through safety switches
located inside the machinery compartment and each blower
motor compartment. These switches interrupt electrical power
to the oven when the Machinery Compartment Access Panel
is opened, OR when the rear panel is removed.
Connection
Refer to the wiring diagram inside the machinery compart-
ment of the oven to determine the correct connections for the
electrical supply lines. Connect the supply as indicated on the
wiring diagram.
CAUTION: The terms of the oven’s warranty require all
start-ups, conversions and service work to be
performed by a Middleby Marshall Authorized
Service Agent.
Figure 2-17. Utility Connection Locations for Gas Ovens
Strain-relief
fitting
Electrical Junction Box
(One per oven cavity)
Gas Inlet
(One per Single, Double,
or Triple Oven)
VII. GAS SUPPLY
CAUTION: DURING PRESSURE TESTING NOTE ONE OF
THE FOLLOWING:
1. The oven and its individual shutoff valve must be discon-
nected from the gas supply piping system during any
pressure testing of that system at test pressure in excess
of ½ psi (3.45 kPa).
2. The oven must be isolated from the gas supply piping
system by closing its individual manual shutoff valve dur-
ing any pressure testing of the gas supply piping system
at test pressure equal to or less than ½ psi (3.45 kPa).
3. If incoming pressure is over 14″ W.C. (35mbar),
a separate regulator MUST be installed in the line BEFORE
the individual shutoff valve for the oven.
WARNING: To prevent damage to the control valve regu-
lator during initial turn-on of gas, it is very
important to open the manual shutoff valve
very slowly.
After the initial gas turn-on, the manual
shutoff valve must remain open except
during pressure testing as outlined in the
above steps or when necessary during
service maintenance.
A. Gas Utility Rough-In Recommendations
The following gas system specifications are STRONGLY
RECOMMENDED. Deviating from these recommendations
may affect the baking performance of the oven.
Gas Meter
• One or two cavities: 750 cfh meter
• Three oven cavities: 1200 cfh meter
Gas Line
• DEDICATED LINE from the gas meter to the oven
• 2″ (50.8mm) pipe for natural gas
• 2″ (50.8mm) pipe for propane
• Maximum length: 2002 (61m). Each 90°elbow
equals 7″ (2.13m) of pipe.