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There are two (2) types of devices used to
measure water column (W.C.) pressure.
They are the spring/mechanical type
gauge and the water column test gauge
(manometer). The use of the spring/
mechanical type of gauges is NOT
RECOMMENDED because they are very
easily damaged and they are not always
accurate. The preferred type of gauge is
the manometer because it is a simple
devise to use and is highly accurate. A
manometer is simply a glass or trans-
parent plastic tube with a scale graduated
in inches. When it is filled with water and
pressure is applied, the water in the tube
rises, showing the exact water column
(W.C.) pressure.
a. System Diagnosis
1) Gas Pressure
A gas pressure test should be taken at the gas valve pressure tap provided on every
gas valve to assure that the water column (W.C.) pressure is correct and consistent.
WARNING: Test all connections for leaks by brushing on a soapy water solution.
NEVER TEST FOR LEAKS WITH A FLAME!!!
a) Connect water column test gauge (manometer) to the gas valve tap (1/8” N.P.T.).
f. FLAME SENSOR FAULT - if there is a problem/fault within the flame sensing circuit or
the Flame Probe, the “red” L.E.D. (light emitting diode) indicator light flashes 2 blinks
(i.e., FLAME SENSOR FAULT) continuously until the problem/fault is corrected (fixed)
or until the HSI Module is reset manually.
2. TROUBLESHOOTING/SYSTEM DIAGNOSIS (detailed)
TROUBLESHOOTING (Service Checks)
S
YMPTOM Cause
1. N
O L.E.D. INDI CAT OR LIGHT A. MISWIRED
B. TRANSFORMER BAD
(24 volts)
C. FUSE/CIRCUIT BREAKER BAD
D. HSI MODULE BAD
2. GAS VALVE ON - NO HOT SURFACE IGNITOR A. DEFECTIVE HOT SURFACE IGNITOR
B. MISWIRED
C. HSI MODULE BAD
(check voltage at Hot Surface Ignitor)
3. HOT SURFACE IGNITOR ON - NO GAS VALVE A. GAS VALVE COIL OPEN
B. OPEN GAS VALVE WIRE (
MV1 or GND)
C. HSI MODULE BAD
(check for voltage between MV1 and GND)
4. FLAME OKAY FOR T.F.I. (TRIAL FOR IGNITION)A.DEFECTIVE HOT SURFACE IGNITOR
NO FLAME AFTER T.F.I. B. S2 WIRE BAD
C. POOR GROUND (GND) AT BURNER
D. POOR FLAME
(check flame current)