Gas Pressure Testing - Wolf Rangetop Service Manual

Troubleshooting Guide
Gas Pressure Testing (continued)

GAS PRESSURE TESTING

Testing gas supply pressure to a unit is a critical tool in properly
diagnosing a problem. Gas supply pressure issues are
common, and many times they are the root cause of recurring
issues. On SRT units, each burner has an individual spark
module. There are no fuel-to-air ratio adjustments. Intermittent
sparking issues, flame quality issues, and ignition issues that
affect all burners are almost always related to gas pressure or
the supply regulator. Because there are also three different sizes
of burner assemblies on each unit, pressure issues can affect
different sizes of burners in different ways. Check gas pressure
using only the method listed, so that the recorded pressures
can help diagnose a specific issue.
Natural Gas Specifications
The supply pressure to the inlet of the unit regulator must be
between a minimum of 7" water column (wc) and a maximum of
14" wc.
The outlet of the regulator must be 5" +.5" wc/-0.0" wc.
The maximum pressure drop from maximum flow to low flow
must be less than .5" wc.
Liquid Propane Specifications
The supply pressure to the inlet of the unit regulator must be
between a minimum of 11" wc and a maximum of 14" wc. The
outlet of the regulator must be 10" +.5" wc/-0.0" wc.
The maximum pressure drop from maximum flow to low flow
must be less than .5" wc.
Connecting to the Unit Manifold
To check pressure on a SRT unit:
1 Uninstall the unit.
2 Remove the burner pan.
3 Assemble the burners.
WARNING
Do not over-tighten the burner assembly
screws. The burner is designed to have the
burner pan between the burner assembly and
the orifice holder. A small amount of gas
leakage is normal during testing.
4 Disconnect the main gas tube from a 9.2K orifice holder,
and connect the manometer to the main gas tube. Set the
burner to High.
Static Pressure
Static pressure is the gas pressure when there is no gas
movement. Taking this pressure is not an effective diagnostic
tool. Pressure will equalize across any regulator in the gas
supply system. It is not possible to determine necessary
pressures when checking any part of the unit by static pressure.
828990 REV. A
Sealed Burner Rangetop with Wok Service
Low Flow Pressure
Low flow pressure is manifold pressure on the unit taken when
there is minimum gas flow. This pressure will provide an idea if
the unit regulator is operating properly. Low flow pressure must
PLUS
be within
designated manifold pressure. To find the low flow pressure on
SRT units, light one of the 9.2K burners in the simmer range,
while connected to the other 9.2K burner main gas line.
Example:
Low flow manifold pressure reading taken on a
SRT unit's 9.2K burner using natural gas was 5.4" wc. Low flow
pressure is good. It falls in range of 5" wc - 5.5" wc.
Example:
Low flow manifold pressure reading taken with
right front burner on low simmer on a SRT unit with liquid
propane (LP) was 9.7" wc. Low flow pressure is bad. Outside of
range of 10" wc - 10.5" wc.
Maximum Flow Pressure
Maximum flow pressure is the manifold pressure when all
burners are on the High setting. It is normal for the pressure to
drop slightly. The difference in pressure from the low flow
pressure to the maximum flow pressure must be less than .5"
wc.
Example:
Low flow manifold pressure is 5.4" wc on a SRT
unit. Maximum flow manifold pressure is 5.2" wc. Pressure test
is good. Pressure drop was 0.2" wc, and low flow was 5.4" wc.
Unit is not experiencing a gas pressure issue.
Example:
Low flow pressure is 10" wc on a SRT unit after
the gas company raised the supply pressure. Maximum flow
pressure is 9.5" wc. Pressure drop is .5" wc. Unit fails pressure
test.
Common Reasons for Pressure Issues
Most often, an insufficient volume of gas is the cause of an
excessive drop in pressure between low flow and maximum
flow. Make sure the following items are to specification:
▪ If a flex-line is present, it must be at least
diameter (ID) and no longer than 3 feet long. Many times,
1
the line is / " OD.
2
Shut-off valve should be
▪
3
valves are /
8
Make sure the supply pressure stays at or above the
▪
minimum supply pressure at full load. Full load is when all
gas appliances in the home are on including the rangetop.
Supply line to the unit is not
▪
Note: If the customer has multiple issues, correct the flex-line
and shut-off first before requesting that the customer replace
the gas line.
UNINSTALL THE UNIT
1 Turn off the power to the unit.
2 Remove the unit from the installation.
25
service.subzero.com
MINUS
.5" wc and 0.0" wc of the
1
3 1
/ ". Most of the
4
" through the ball.
3
/ ".
4
Manual
/ " internal
2
/ " shut-off ball
2