Troubleshooting; Servicing The Boiler; Diagnosing An Inoperative Boiler; Display Normal But No Dhw - NTI VM110 Installation And Operation Instructions Manual

Vmax I&O Manual

18.0 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 shutoff 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.

Diagnosing an Inoperative Boiler

1) Blank Display – perform the following steps:
 Ensure the boiler service switch located on the front of the boiler is in the ON (1) position.
 Ensure the main service switch (if applicable) is in the ON position.
 Ensure the circuit breaker in the electrical panel supplying power to the boiler in on.
 Measure across boiler terminals 16 and 15 (L1 120VAC and L2 NEUTRAL) for 120VAC, see Figure 12-2.
If 120VAC is present, check fuse located on the boiler controller, see Figure 18-1. If 120VAC is not
present, check wiring between the boiler and electrical panel for poor connections.
 Check the electrical connection to the display – connector is located behind display.
2) Display Normal but no heat to radiators – perform the following steps:
 Ensure there is a heat call from the thermostat (radiator symbol on the display will flash during a thermostat
demand). If uncertain about thermostat operation, place a jumper between the boiler's Thermostat
terminals. If the radiator symbol does not display, check outdoor sensor reading (User Menu reading 1-08),
and compare to the warm weather shutdown setting (Installer Menu setting 2-04); central heat call will not
activate if the outdoor temperature is above the warm weather shutdown setting.
 If the radiator symbol is flashing, but the boiler is not firing, compare the boiler outlet temperature
(temperature displayed on the main screen) with the Current target temp (User Menu reading 1-01). Boiler
will not fire until the outlet temperature drops below the Current target temp by the CH setpoint differential
(Installer Menu setting 2-02 – default setting = 9ºF).
o Ensure the central heating pump(s) is running – if not ensure it is wired to pump output CH PUMP or
BOILER PUMP.
o If Current target temp is insufficient, increase CH setpoints (Installer Menu settings 2-01 and 2-05).
 If the radiator symbol is on but not flashing, and the faucet symbol is flashing, then the boiler is actively
servicing a DHW demand; at which time no hot water will go to the radiators. If condition continues,
consider increasing the DHW setpoint (Installer Menu setting 2-07), or decreasing the DHW priority time
(Installer Menu setting 2-09).
3) Display Normal but no DHW – perform the following steps:
 VM110 and Indirect Tank with Tank Sensor, or VM110P:
o Verify DHW Mode is set to 1 (Installer Menu setting 2-08).
o Verify there is a Tank sensor wired to COMMON and DHW (boiler terminals 3 and 6), see Figure 12-2.
Tank sensor temperature, DHW temp, is viewed from User Menu reading 1-03.
o Compare DHW setpoint (User Menu reading 1-04) with the DHW temp (User Menu reading 1-03).
DHW Tank demand is generated when the DHW temp drops 4ºF below the DHW setpoint; after which
burner demand starts when the boiler outlet temperature (displayed on Main Screen) drops below the
│Troubleshooting
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