Middleby Marshall Oven - Manual (Page 26)

2-26
SECTION 2
INSTALLATION
VIII. PREPARATION FOR VARIOUS GASES
Before proceeding to set up the oven for a specific gas, the
main gas supply valve and the electrical supply circuit breaker
should be turned off.
When preparing the oven for use of Group H or L Natural gases,
the orifice (Manifold) pressure should be adjusted to the values
shown in the chart on Page 1-1.
The main orifice and also the by-pass (low flame) orifice should
be changed for the specific gas type used as shown in the
following Table, also refer to Section IX, CHANGING ORIFICES.
FOR USE WITH NATURAL GAS
The input to the burner can be determined using the orifice
(manifold) pressure data or by the volume supplied using the
gas meter.
Using the orifice pressure data you must know the specific gas
quality used and when using the volume method you must
know the heat value (HuB) of the gas used (Obtainable from
your local gas supplier).
If you used the orifice pressure method, you should double
check the rated input using the volume method.
If the measured input does not correspond with the rated input,
check first that correct orifices are installed. If the orifice sizes
are as specified, check and correct the supply and orifice
pressures to obtain the correct input based on the gas meter
reading.
FOR USE WITH LIQUID (LP) GAS
When using liquid gas the converter in the multifunction gas
valve has to be turned end over end - 180° (Refer to Figure 2-
36). This takes the governor out of operation.