Trinity boiler troubleshooting

If you use a boiler to heat your house and/or provide hot water, you may face technical problems one day. They occur due to improper maintenance, installation, etc. If you have noticed an issue, turn it off right away and examine it. Use the troubleshooting table below.

ER1 On Display“Water Temperature Excessive” Sentry has sensed a water temperature in excess of 250°F at the water temperature thermister.1. If the boiler is extremely hot chcck for adequate water pressure and circulation, contact NTI for assistance.
2. If not hot, check for sources of grounding or shorting (i.e. water) at the thermister electrical connections, check wiring from Sensor to Sentry Control.
3. Replace thermister if the resistance is not in the correct range.
ER2 On Display“Water Temperature Thermister Short Circuit”See ER1.
Sentry has sensed a short circuit in the water temperature thermister circuit.
ER3 On Display“Water Sensor Open Circuit” Sentry has sensed an open circuit in the Water Sensor circuit.1. Check wiring to Water Sensor for open circuits or shorting to ground (i.e. water). (Note: ER3 will be displayed if temperature sensed is less than 0?F.)
2. Replace Water Sensor if the resistance is not in the correct range.
ER4 On Display“24V Limit Error” Sentry has sensed a lack of 24V on the outlet of the Sentry burner relay (Bl).The error locks the boiler out for one hour before retrying ignition.
1. Reset power, if error goes away the problem is intermittent and was likely caused by a tripped limit that has automatically reset, check for adequate water pressure and flow rate. Allow the boiler to cycle and verify proper operation including outlet water temperature and flue temperature. If operation is unsuccessful and the error reoccurs continue to step 2.
2. Ti 100-200’s are equipped with a low water pressure switch on the boiler return that requires a minimum of 10PSI to complete the 24VAC ignition circuit. Ensure there is a minimum of 15PSI on the boiler outlet prior to the primary circulator; ensure the boiler is plumbed in primary-secondary fashion. Rcplace water pressure switch if plumbing and pressure is correct and if it measures an open circuit.
3. Check for continuity through the 24VAC limit wiring and manifold and stack limits, replace limits or wiring that are not a closed circuit.
ER5 On Display“DHW Time-Out” The ER5 option is ON and the Sentry has sensed that the DHW call has lasted longer than 2.5 hours, thus removing priority from the DHW call.Reset the ER5 error by resetting the power or cycling the DHW call.
Check for proper operation of the DHW call.
1. Combi’s are equipped with a DHW flow switch; ensure it is not sticking in the elosed position when there is no DHW flow. If so, remove it and free it of any debris and check for proper operation, replace if necessary.
2. For non-Combi boilers, operating with an indirect water heater, check for proper boiler water circulation during a DHW call, and check for proper operation of the indirect water heater’s Aqua-stat.
3. For applications with prolonged DHW draws, turn the ER5 option OFF.
ER6“Flame Lock Out” Sentry has sensed a lack of 24V to the gas valve during operation or a Fenwal ignition lockout.There is a problem in the ignition sequence; it could be causcd by a faulty igniter, flame sensor, gas valve or improper line pressure or combustion. Check ignition sequence to determine which component is not functioning. (Sentry will retry ignition sequence 1 hour after ER6 code originally occurs or if control is reset)
If a 3-Flash error occurs on the Fenwal controller prior to locking out on an Er6, proceed to “Three Flashes on Fenwal”.
Burner shuts off before set- point temperature is reached (and burner light goes out)Reset calculation being used to lower HI setting.If OD probe is being used, the HI setting will be calculated using formula, adjust RES setting as necessary.
Thermostat is satisfied1. If the thermostat demand light is turning off, the thermostat has satisfied.
2. If DHW temp light is turning off; the Aqua-stat or call for DHW has been satisfied.
ER9Internal Controller FaultIndicates that the Sentry control has lost communication with an internal processor, contact NTI for assistance.
ASO Indicates that the Air Switch is Open“Air Switch Open” This is displayed when the boiler is expecting the air switch to be closed by a differential pressure generated when the combustion blower turns on.1. Are the vinyl tubes connected between the air switch and the ports on the inlet pipe? Negative side of switch connects to the port on the 1-1/2” PVC elbow.
2. Check for blockage on the intake and exhaust vents.
3. If fan is running the air switch may be faulty, ensure it is set at 0.2”wc.
4. If fan is not running, check 120V wiring to blower, if ok remove low voltage harness from blower, if blower fails to start, replace blower, if blower does start problem may be with blower or Sentry control.
ASC Indicates that the Air Switch is Closed“Air Switch Closed” This is displayed when the boiler has turned the blower off and is expecting the air switch to be open.1. Is the fan running? If so check for 24V between B and D terminals. If 24V is not present replace transformer.
2. If fan is not running then the Air Switch is stuck closed.
a. Check to ensure switch is set at 0.2”wc.
b. Check vinyl tubes to air switch for moisture, clear if necessary and check venting termination for proper clearance (moisture in tubes is generally cause by cross- contamination of the exhaust to the air inlet).
c. Remove the white wire from the air switch, if ASC persists replace the Sentry 2100 controller, if an ASO message is display replace the air switch.
Two Flashes on Fenwal“Flame Fault” The Fenwal controller senses flame prior to ignition sequence.If the combustion sequence is normal, and there is no flame prior to ignition, the Fenwal control is defective, and must be replaced.
Three Flashes on Fenwal“Ignition Lockout”Check the condensate drain for blockage - a blocked condensate drain will flood the combustion chambcr and cause this error.
Reset and observe ignition sequence:
1. If the burner ignites then goes out within 2-3 seconds:
a. If the boiler is newly installed, check the polarity of the 120VAC power supply - reversed polarity will cause this error.
b. Ensure the cable is connected to the flame sensor.
c. Check for proper sustained gas line pressure.
d. Check venting and combustion chamber for blockage - clean combustion chamber.
e. Replace flame probe.
f. Replace Fenwal controller.
2. If the igniter glows but the burner does not ignite:
a. Check for proper sustained gas line pressure.
b. Check venting and combustion chamber for blockage - clean combustion chamber.
c. Replace igniter.
d. Replace Fenwal controller.
3. If the igniter does not glow:
a. Replace igniter.
b. Replace Fenwal controller.
Boiler will not stay lit.Indicates lack of a flame signal. In order to stay running the flame signal must be at least 0.7 nAmps1. If the Burner light on the Sentry is going out, go to “Burner shutting off’.
2. Check the condensate drain for blockage - a blocked condensate drain will flood the combustion chamber and cause this error.
Boiler bangs or hissesBangs or sounds like a kettle while burner is running indicates insufficient flow1. Ensure the plumbing is installed as per this manual. Check to see if pumps are operating properly and water pressure is above 15psi. This problem can lead to boiler overheating!
2. Boiler may be plugging-up with scale or magnetite, clean with Femox DS-40 Descaler and Cleaner (NTI PN: 83450).
3. If glycol is being used the concentration may be to high, recommend using a concentration lower then 35%. De-rate unit by reducing the maximum modulation rate (HFS) and/or the maximum water temperature (LO and HI)
Boiler Lights rough or pulsatesTypically an imbalance in the Air to gas ratio
2. Check venting and combustion chamber for blockage - clean combustion chambcr.
3. Check for proper sustained gas line pressure.
4. Momentarily remove the intake pipe from the boiler during ignition, if unit lights smoothly with intake pipe disconnected reconnect and check for proper combustion.
Fan appears to be creating a noise in the houseSlight vibration can cause noise in the residence (This is not a warranty issue)Use flexible gas line to isolate the vibration noises between the gas valve and the line.
Don’t hang gas lines from floor joists.
Use rubber insulators with gas line supports.
Making a rubbing noise. ((This is not a warranty issue))If gas valve is not held when the gas nipple is connected, the force of tightening the fitting can damage the valve, and warp the fan housing. If pipe is used, the gas line must not create any forces to the valve, either vertically (weight of line), or horizontally (misaligned connection)
Display Goes BlankNo power to control, blown control fuse or control failure1. Reset power, if display comes back on contact NTI for assistance.
2. Ensure 120VAC is being supplied to the boiler.
3. Check the internal fuse in the Sentry - to access the internal fuse, remove the front decal to reveal the screws securing the face plate cover. If fuse has blown replace with equivalent.
4. Replace Sentry 2100 controller.