Installation and Operation Instructions Matrix
20.0 TROUBLESHOOTING
Observe the following precautions when servicing the boiler. Failure to comply with
these may result in fire, property damage, serious injury or death.
Servicing the Boiler
Disconnect or shut off all energy sources to the boiler: 120VAC power, water and gas.
Identify and mark wires before disconnecting or removing them.
Never bypass electrical fuses or limit devices except temporarily for testing.
Use proper personal protective equipment (PPE) i.e. eye protection, safety footwear.
These procedures should only be performed by qualified service personnel, when abnormal operation of the
boiler is suspected. The boiler incorporates a sophisticated microprocessor based control which normally
responds appropriately to varying conditions. If the boiler operation appears to be incorrect, or it is not
responding at all to a demand for heat, the following is suggested to determine and correct the problem.
Before undertaking any troubleshooting procedures it is highly recommended to have
available a digital multimeter(s) capable of measuring AC and DC volts, Amperes,
Resistance (ohms) and Continuity.
Check 120VAC at the Boiler
First, verify the following:
There is 120V being supplied to the boiler:
o The circuit breaker in the electrical panel supplying power to the boiler is not tripped.
o The service switch (if applicable) is in the ON position.
There is a heat call from the thermostat:
o The thermostat is placed at a sufficiently high setting to create a call for heat to the boiler.
To check for the presence of 120VAC at the boiler follow this procedure:
Remove the junction box cover.
With an AC voltmeter set on the appropriate scale, measure the voltage across Line and Neutral (Black and
White wires).
If 120VAC is not detected, check the electrical service as suggested above. If the service is verified, inspect
the circuit wiring from the panel to the boiler for broken or disconnected conductors.
Table 20-1 Troubleshooting Chart
Boiler Control (Red Face)
“Water Temperature Excessive”
Sentry has sensed a water
temperature in excess of 250ºF at
the Water Sensor.
1. If the boiler is extremely hot check for adequate water
pressure and circulation, contact NTI for assistance.
2. If not hot, check for sources of grounding or shorting at
the Water Sensor electrical connections, check wiring
from Sensor to Boiler (Red) Control.
3. Replace Water Sensor if the resistance is not in the
correct range. (See thermister resistance charts in Figures
20-1 and 20-2)
“Water Sensor Short Circuit”
Control has sensed a short circuit
in the Water Sensor circuit.
“Water Sensor Open Circuit”
Control has sensed an open circuit
in the Water Sensor circuit.
1. Check wiring to Water Sensor for open circuits or
shorting to ground. (Note: ER3 will be displayed if
temperature sensed is less than 0F.)
2. Replace Water Sensor if the resistance is not in the
correct range. (See thermister resistance charts in Figures
20-1 and 20-2)
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