Finned copper tube gas boilers & water heaters – Boiler Manual
33
Troubleshooting A Startup
Action
Check
Identify Source
Symptom
An Interlock is tripped.
Proceed to HeatNet
Control Manual
for
more details and
problem resolution.
1.
1. Is it a 24 VAC Interlock?
2. Is it a 120 VAC Interlock/
Alarm?
3. Internal Alarms
1. All 24 VAC Interlocks are
located on J11A and J11B.
Examples of 24 VAC Interlocks:
1.SPARE3
2. Variable Frequency Drive(VFD)
3. Low Water Cutoff(LWCO),
4. Gas Pressure
5. Spare 4
6. Operator OPLIM
7. Water Flow
8. Air Pressure from UV Sensor.
2. All 120 VAC interlocks/Alarms
are located on J5. These include:
1.FLAME SAFE ALARM (Ignition
CTRL ALARM)
2. Valve Alarm (IRI ALARM)
3. XS_FACTORY (Reserved
4. HIGH LIMIT
1. OPEN SENSOR
2. SHORTED SENSOR
3. COMBUSTION AIR DAMPER
1.Use a multimeter and check
for 24 VAC on J11A,J11B to
identify which interlock has
tripped. Reset the Interlock or
check for disconnected wiring
or shorts.
The Air Pressure from UV
Sensor interlock if displayed
will allow the boiler to
function, but it needs to be
functional while the boiler is
running for it to clear.
1. Use a multimeter on J5 to
to check for 120 VAC on
these interlocks (except the
HIGH LIMIT). The High Limit
Interlock is displayed when
there is no 120 VAC, since
the HIGH LIMIT breaks the
120VAC to the Ignition
Control.
NOTE: Stray Voltages
Greater than 8 VAC and less
than 18 VAC on these
interlocks can cause
intermittant operation. If this
is the case, check for back
fed voltages from field wiring.
Check sensor voltages at
J10A and J10B. The
Temperature sensor inputs
should be between 0 VDC
and 5 VDC measured across
the sensor. Example: At 77 °F,
the voltage would read 2.5
VDC.
The combustion air damper
prove switch must be wired
across SPARE 1 and must be
a "DRY" contact. Do not
apply a voltage to this input,
the input supplies it's own
voltage/current.
2.
