Middleby Marshall Oven - Manual (Page 29)

2-29
SECTION 2
INSTALLATION
4. Replace cover screw on adjustment valve and turn off main
gas supply valve.
5. Record the reading obtained from the gas meter and
calculate obtained gas flow. Compare this to the indicated
flow in the CHART OF ORIFICE SIZES, GAS PRESSURES,
NOMINAL INPUT RATINGS AND GAS FLOW on Page 1.
6. Note the following comments and procedures to assure
correct gas supply pressure and adjusting the gas valve to
obtain proper orifice (manifold) pressure.
XI. VARIATIONS OF RATED SUPPLY
PRESSURES
Special attention should be given to the supply pressure and
gas flow pressure at the supply connection to the oven. The
nominal supply pressure for gas family Group 2 (natural gas)
should be 20 mbar.
If the supply pressure is lower or higher than the rated (nominal)
pressure then the reason should be investigated and the gas
supplier contacted.
If the supply pressure is lower than 17 mbar’s or higher than 25
mbar’s then the oven should be shut down and the gas supplier
notified. No adjustment of the oven controls should be made
and the oven should not be operated.
TO CHECK GAS SUPPLY PRESSURE:
1. Close main gas supply valve.
2. Remove supply (inlet) pressure measuring stud screw from
gas valve and attach the manometer to the stud.
3. Open main gas supply valve and restart oven with
temperature control at maximum setting.
4. Measure inlet (supply) pressure. For all natural gases this
should be between 17 and 25 mbar’s.
5. Turn oven off, close main gas supply valve, remove
manometer from stud and tighten cover screw in to pressure
measuring stud.
ORIFICE (MANIFOLD) PRESSURE METHOD:
1. Turn off main gas supply valve.
2. Remove pressure measuring stud screw located at the
“out-flow” (closest to gas burner) of the gas valve and attach
a manometer.
3. Remove cover screw from the gas valve pressure (governor)
adjustment valve.
4. Open main gas supply valve and start oven according to
supplied instructions with the temperature control at
maximum setting.
5. Once oven is in operation, adjust pressure valve (governor)
to the orifice pressure value as shown for the specific gas
in the Gas Specifications Table.
6. Turn oven off, close main gas supply valve, remove “U” tube
manometer and tighten cover screw into pressure measuring
stud.