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Integrated Modules
Integrated Modules
Troubleshooting
4-16
#826498 - Revision B - December, 2016
Connecting Manometer to MM15TF/S
Because of the construction of the MM15TF/S, the technician must supply a special inline “T” connection to fit into
the 3/8” gas line between the regulator and the inlet to the gas valve. This allows the pressure to be monitored
while the MM15TF/S burner is set at low and set at high.
Static Pressure
Static pressure is the gas pressure when there is no gas movement. Taking this pressure is not an effective diag-
nostic tool. Pressure equalizes across any regulator in the gas supply system. It is not possible to determine what
pressure should be recorded when checking any part of unit by static pressure.
Low Flow Pressure
Low Flow pressure is manifold pressure on a unit taken when there is minimum gas flow. This pressure provides an
idea if the unit regulator is operating properly. Low Flow pressure must be within
PLUS
0.5” WC and
MINUS
0.0”
WC of designated manifold pressure. Low Flow pressure is obtained on the CG152TF/S by lighting the 12k burner
on Low Simmer while the manometer is connected to the 9.2k burner Main gas line. Low Flow pressure is obtained
on the MM15TF/S by lighting the burner on the lowest setting with the manometer connected inline.
Example:
Low Flow manifold pressure reading taken with 12k burner on low simmer on Natural Gas was
5.4” WC. Low Flow pressure is good. It falls in the range of 5” WC (+)0.5” WC (-)0.0” WC.
Example:
Low Flow manifold pressure reading taken with 12k burner on low simmer on Liquid Propane
(LP) was 9.7” WC. Low Flow pressure is bad. Outside the range of 10” WC (+)0.5” WC (-)0.0” WC.
Maximum Flow Pressure
Maximum Flow pressure is the manifold pressure when all burners are turned to high. 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
0.5”.
Example:
Low Flow manifold pressure is 5.4” on MM15TF/S. 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 MM15TF/S-LP after gas company raised the supply pressure.
Maximum Flow pressure is 9.5” WC. Pressure drop is 0.5” - unit fails pressure test.
Common Reason for Pressure Issues
Most often excessive drop in pressure between Low Flow and Maximum Flow is caused by insufficient volume of
gas. Ensure the following items are to specification:
If a flexline is installed it must be at least 1/2” Internal Diameter (ID). Many times the line is 1/2” O.D..
•
Shut Off valve should be 3/4”. Most of 1/2” shut off ball valves are 3/8” through the ball.
•
Ensure 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 cooktop.
Supply line to the unit is not 3/4”.
•
Note:
If customer has multiple issues correct the flexline and shut off first before requesting customer replace the
gas line.
