Middleby Marshall PS740 Series Gas Ovens P/N 60250 - Manual (Page 22)

18 P/N 60250 September 28, 2012
B. Connection
Check the oven’s gas supply requirements before making the
gas utility connection. Gas supply requirement are listed on the
oven’s serial plate and in Table 1-4. Gas Orifice and Pressure
Specifications (in Section 1, Description).
Check the serial plate to determine the type of gas (Propane
or Natural) to be used with the oven.
Refer to the instructions in the gas hose package (included
in the Installation Kit) before connecting the gas line.
One gas line connection method is shown in Figure 2-18;
however, compliance with the applicable standards and regula-
tions is mandatory.
Inlet, regulated, and pilot gas pressure readings can be
taken using a digital tube manometer at the tap location shown
in Figure 2-19. Figure 2-19 shows the burner assembly and
Figure 2-21 shows the gas valve.
NOTE: The installation must conform with local codes or in
the absence of local codes, with the National Fuel Gas
Code, ANSI Z223.1-latest edition.
Certain safety code requirements exist for the installation of
gas ovens; refer to the beginning of Section 2 for a list of the
installation standards. In addition, because the oven is equipped
with casters, the gas line connection shall be made with a
connector that complies with the Standard for Connectors for
Movable Gas Appliances, ANSI Z21.69 (in U.S.A.), as well
as a quick-disconnect device that complies with the Standard
for Quick-Disconnect Devices for Use With Gas Fuel, ANSI
Z21.41 (in U.S.A.).
C. Gas Conversion
Where permitted by local and national codes, it is possible to
convert ovens from natural to propane gas, or from propane
to natural gas. Use the appropriate Middleby Gas Conversion
Kit for the specific oven model.
CAUTION: The terms of the oven’s warranty require all
start-ups, conversions and service work to be
performed by a Middleby Authorized Service
Agent.
D. PS740 Propane Conversion
Two items have to be changed, to change the oven to LP:
1. Replace main orifices.
2. Adjust main gas regulator per instructions below.
Disconnect the manifold union closest to the main burner, and
remove the manifold assembly (four screws). Slide out the
manifold assembly (leaving the ignition and sense wires con-
nected). Replace the main orifices.
Replace the main orifices on the manifold assemblies with the LP
units, and replace the manifold assembly. Reconnect the union.
E. Adjusting the Maximum Pressure Setting
1. Disconnect pressure feedback connection (if applicable).
2. Connect a suitable pressure gauge to pipe line or to outlet
pressure tap of gas control concerned, to measure burner
pressure (measuring point must be as near to burner as
possible).
Figure 2-19. Gas Burner Assembly
Figure 2-18. Flexible Gas Hose Installation
Gas Burner
Manifold Pressure Tap
To Gas
Supply
Pipe
90°
Elbow
Quick-
disconnect
device
Flexible
Gas Hose
Full-Flow
Gas
Shutoff
Valve
3/4″ gas
pipe nipple
3/4″-1/2″
gas pipe
reducer
Individual gas
connection
for each oven
cavity
1/2″ gas
pipe nipple
1/2″ gas
line tee with
pressure tap
3. Make sure that the appliance is in operation and the Mo-
duplus ® coil is energized with maximum current.
4. If maximum rate pressure needs adjustment, use an 8
mm wrench to turn adjustment screw for maximum pres-
sure setting (clockwise to increase or counter-clockwise
to decrease pressure), until the desired maximum outlet
pressure is obtained.
5. Disconnect electrical connection of the Moduplus ® .
6. Check minimum pressure setting and readjust if neces-
sary. (See Adjusting Minimum Pressure Setting for proper
adjusting procedure.)
7. Reconnect pressure feedback connection (if applicable).
8. If minimum and maximum pressures are set, wire the
Moduplus ® in circuit.
9. Close pressure tap screw.