U.S. Boiler Company X-2 Series Service manual

106636-01 - 10/15
9700609
Price - $5.00
For service or repairs to boiler, call your heating contractor. When seeking information on boiler,
provide Boiler Model Number and Serial Number as shown on Rating Label.
Boiler Model Number
X-20
Boiler Serial Number Installation Date
Heating Contractor Phone Number
Address
INSTALLATION, OPERATING AND
SERVICE INSTRUCTIONS FOR
X-2™ Series
Cast Iron Gas - Fired Boiler

27
X. Troubleshooting
A. BEFORE TROUBLESHOOTING
The following pages contain trouble shooting tables for
use in diagnosing control problems. When using these
tables the following should be kept in mind:
1. This information is only meant to be used by
a professional heating technician as an aid in
diagnosing boiler problems.
2. In general, these tables assume that there are no
loose or miswired electrical connections. Before
using these tables inspect all electrical connections
on the boiler to make sure that they are tight. Also,
check the wiring on the boiler against the wiring
diagram in Figures 8 and 9. Ensure that incoming
120 Vac power polarity is correct and that the boiler
is properly grounded. Further, ensure that the control
power supply is 24 VAC (minimum 18 VAC to
maximum 30 VAC) and polarity is correct.
4. All controls on the X-2 Series are tested at least
once in the manufacturing process and a defective
control or component is generally the least likely
cause. Before replacing a component, try to rule out
all other possible causes.
5. When checking voltage across wiring harness pins
be careful not to insert the meter probes into the
pins. Doing so may damage the pin, resulting in a
loose connection when the harness is reconnected.
Press “I” key on the control to change
from one parameter to the next. Each
setting will alternate between display
code (for example STA) and value.
When Err (error) is shown:
Value Description
4 Flame current lower than threshold
6 Flame Out of Normal Sequence
18 Electronics Failure
23 Flame Sensed During Pre-purge
32 Temperature Sensor Failure
55 Damper Failed to Open
56 Damper Failed to Close
57 Flame Rod Shorted to Ground
58 AC Line Frequency
59 Line Voltage Error
60 Thermostat input higher than threshold
61 Line Voltage Unstable
63 Soft Lockout – Recycles Exceeded
64 Soft Lockout – Internal Failure
Possible STA (status) values:
Figure 27: Using Control Display to Troubleshoot
Value Description
1 Standby
4 Pre-purge
6 Spark
7 Flame Proving
8 Running
10 Retry/Recycle Delay
13 Soft Lockout
14 Hard Lockout
15 Waiting for Limit to Close
16 Flame Present Out of Sequence
17 Self Test
18 Waiting for Damper to Open
19 Waiting for Damper to Close
20 Damper Failure to Open
21 Damper Failure to Close

28
X. Troubleshooting (continued)
Display Status Recommended Corrective Action
Blank Boiler or Control is not powered No 120 Vac Power at boiler, check breaker and wiring between breaker
panel and boiler
Err 4Flame Current Lower than Threshold Check pilot assembly. Refer to Troubleshooting Section, C6.
Err 6Flame Sensed Out of Normal Sequence Flame sensed out of normal sequence (before opening gas valve or after
closing gas valve). Check the gas valve for proper operation.
Err 18 Electronics Failure Cycle power to control. Replace control if problem persists.
Err 23 Flame Sensed During Pre-purge Flame sensed during pre-purge (before gas valve signaled open). Check
the gas valve for proper operation. Replace gas valve if problem persists.
Err 32 Temperature Sensor Failure
Temperature sensor or interface failure (open or short connection, increased
connection resistance, dual sensor mismatch) or control hardware failure.
- Check sensor is securely attached to control P7 connector.
- Check sensor wire is not damaged.
- If secure and in good condition, replace sensor.
- If problem persists, replace control.
Err 55 Damper Failed to Open Atmospheric Damper End Switch failed to close (end switch contacts stuck
open). Refer to Troubleshooting Section, C5.
Err 56 Damper Failed to Close
Damper open. Voltage should not be present on P6-5. Control, vent
damper or wire harness is defective. While the Err 56 is displayed by the
control, perform the following tasks:
• Remove the call for heat (adjust thermostat or remove wire from TT
terminals.
• Check for 24Vac between P6-5 and ground.
• If voltage not present, attempt to start boiler again.
• If 24Vac is present, unplug the vent damper harness from control.
• With wire harness unplugged, check for 24Vac between P6-5 (on Control)
and ground.
• If voltage present, replace the control.
• If voltage not present, failed vent damper or wiring harness.
• Check wiring harness for shorts or mis-wiring. Replace if defective.
• If harness not defective, replace vent damper.
Err 57 Flame Rod Shorted to Burner Ground
Flame Rod shorted to burner ground, this can result from excessive ue gas
condensation.
- Check for excessive condensate. Dry pilot. Adjust setpoint higher.
- Check for loose or damaged ignition wire.
Err 58 AC Line Frequency Error AC Signal is too noisy or frequency is incorrect. Check supply voltage.
Check Sensor for Common shorted to ground.
Err 59 Line Voltage Error AC voltage out of specication high or low. Check supply voltage.
Err 60 Thermostat Input Higher than Threshold Check thermostat wiring.
Err 61 Line Voltage Unstable Possibly too many heavy loads switching on and off cause erratic supply
voltage. Check supply voltage.
Err 63 Soft Lockout – Maximum Recycles
Exceeded
Maximum number of recycles exceeded. Refer to Troubleshooting Section,
C6.
Err 64 Soft Lockout – Internal Failure
The electronics has detected an error. This can be caused by an actual
controller internal fault or wiring fault:
- Check vent damper, cycle power with vent damper disconnected. If error
is cleared, reconnect the vent damper and refer to Recommended
Corrective Action listed under stA 20, damper failed to open.
- Check pilot assembly,
- If problem persists, replace the control.
B. USE CONTROL DISPLAY ERR (ERROR) NUMBER TO DIRECT TROUBLESHOOTING EFFORTS
If the control detects an error it will ash “Err” (error) followed by a number. Use this number to identify the boiler problem
and corrective action in the table below. If there is no Err display proceed to Paragraph C:

29
X. Troubleshooting (continued)
C. USE STA (STATUS) NUMBER TO GUIDE TROUBLESHOOTING
The control will ash “STA” followed by a number. Use this number to identify the boiler problem in the table below:
2. Circulator is On, But Boiler is Off
Display / Status Recommended Corrective Action
STA1
Circulator
Pre-purge
Burner off
Circulator on
The boiler is warm and circulator is providing residual boiler heat to building:
Check boiler temperature
- The boiler will not start until boiler water temperature is less than the Setpoint (SP) minus differential (df)
- If boiler water temperature is higher than Start Temperature (ST_, default = 140 F) and the Circulator Pre-
purge (PP_, default = 2 minutes) time has not expired, boiler start will be delayed until water temperature
drops or time expires. To permit the boiler to start sooner increase Start Temperature parameter. Refer
to Operation Section for additional information.
4. Circulator is On But Damper is Not Open
Display / Status Recommended Corrective Action
STA15
Limit Open
Waiting for Limit to Open.
- Check Blocked Vent Switch, in the event of a blocked vent or poor draft condition, the blocked vent switch
will open interrupting power to control P5-4. The main burners will be extinguished immediately and the
circulator will remain on until the thermostat is turned off. The source of blockage must be corrected by
trained and skilled personnel from a qualied service agency before resetting switch.
Blocked Vents are caused by a collapsed chimney resulting in full or partial blockage, chimney cross
sectional area too small, height insufcient or cold chimney causing sustained poor draft. Always follow
the recommendations in Section I, Figure 1 and Section IV, Venting.
- Check Flame Rollout Switch, in the event of excessive blockage of the boiler section ue passageways
is developed the ame rollout switch will open interrupting power to control P5-4. The main burners will
be extinguished immediately and the circulator will remain on until the thermostat is turned off. If the
ame rollout switch is activated, do not attempt to place the boiler in operation. The source of the
blockage must be corrected and the identical ame rollout switch replaced by trained and skilled
personnel from a qualied service agency.
- Check External Limit.
3. Boiler is On, But Circulator is Off
Display / Status Recommended Corrective Action
StA 8
Burner on
Circulator off
Domestic Hot Water (DHW) Priority Forcing Circulator Off
- When there is a DHW heat request wired to the Control’s DHW terminal the System Circulator will be
“forced off” for the duration of the DHW heat request. When the DHW heat request ends the System
Circulator “force off” is removed, the circulator can respond normally. When the Priority Time, (PT_)
Parameter is set to “off” the System Circulator is not “forced off” for a DHW call for heat.
Wiring / Circulator Issue:
- Check wiring for loose connection, miswiring
- Check circulator
1. Boiler and Circulator Off
Display / Status Recommended Corrective Action
STA1
Standby
Burner off
Circulator off
The boiler has not detected a call for heat (tt = off and dh = off).
Check that the thermostat:
- When a thermostat call for heat is detected control display “tt” will show “on”
- Make sure thermostat is calling for heat and contacts (including appropriate zone controls) are closed.
Check for loose connection.
Check the DHW demand:
- When a domestic call for heat is detected “dh” will show “on”
- Make sure the DHW aquastat contact is closed. Check for loose connection.

30
X. Troubleshooting (continued)
6. Circulator is On, Damper is Open But Boiler Fails to Start
Display / Status Description
STA 10
Retry / Recycle
Delay
The Boiler is in “Retry Delay”:
- The burner failed to light (no ame signal). After a 5 minute delay, Control will attempt to light the burner
again. There is no limit to the number of retries.
Recycle Delay
- The burner loses ame during running mode, (“STA 8”). After a 10 second delay, Control will attempt to
light the burner again. If the burner loses ame during running mode, “STA 8”
during the next six recycles, Control will progress to a soft lockout.
STA 13
Soft Lockout
When a soft lockout occurs, boiler will shut down. Boiler automatically restarts once condition that caused
the lockout is corrected and the one-hour time delay is completed. Boiler can be restarted sooner than the
time delay by using Adjustment Mode and selecting the reset button (see Adjustment Mode instructions) or
by cycling power. Soft Lockout is caused by one of the following:
- Err 63, Maximum Recycles Exceeded – The burner lost ame during running mode, “STA 8” six times in
a row. Refer to recommended corrective actions on next page to help determine the cause of the
problem.
- Err 64, Internal Failure, refer to Error code listing for recommended corrective action.
- Err 23, Flame sensed during post-purge (before gas valve signaled open). Check the gas valve
for proper operation. Replace gas valve is problem persists.
STA 14
Hard Lockout When a hard lockout occurs boiler shuts down.
STA 16
Flame Out of
Sequence
If ame is detected in pre-purge Control goes to Flame Out of Sequence Before trial, “Sta 16” and “rr 23”
is reported. The control gives a ame 10 seconds to disappear. If ame goes away, control resumes heating
cycle from the beginning. If it doesn’t “rr 23” is cleared and “rr 6” is reported. When ame is off
control goes to Soft Lockout and “rr 6” is cleared. Check the gas valve for proper operation.
5. Circulator is On But Damper is Not Open
Display / Status Recommended Corrective Action
STA 20
Damper Failed
to Open
The control is waiting for the damper to open. Damper end switch has failed to close (end switch contact is
stuck open). Combustion can never take place unless the damper blade is in the fully open position. Check
the following:
- During status “STA18" or “STA 20” the control terminal “P6 - 5” (yellow wire) is energized.
- Check for loose connection between control and vent damper, check damper harness.
- Check for obstruction in path of damper
- When damper is open (end switch closed) control terminal “P6 – 2” should receive power from the vent
damper.
- Place jumper between control terminal P6-5 and P6-2. If error 55 does not clear, replace control.
- Defective harness or vent damper.

31
X. Troubleshooting (continued)
Display / Status Recommended Corrective Action
StA 10
Retry / Recycle
Delay
StA 13
Soft Lockout
1. No Spark
a. Can you hear sparking while STA 6 is displayed?
- If there is no spark noise replace the control.
b. If you can hear spark noise check the following:
- Loose connection in ignition cable or ground wire
- Continuity of ignition cable
- Break in ignition cable insulation
- Loose ground connection
- Break in pilot ceramic insulator
- Incorrect pilot spark gap
2. No Pilot Flame
a. If pilot does not light check the following:
- All manual gas valves are open
- Supply tubing is not plugged, kinked or leaking
- Gas line pressures are good
- Gas line is purged of air
- Pilot orice is not plugged (pilot gas is owing)
- Condensate quenching pilot
Note: It may be necessary to recycle the “call for heat” more than once to clear the pilot
supply tubes of air.
b. If no gas ow check the following:
- 24 volts across PV and MV/PV at gas valve, if voltage ok replace defective gas valve
- Check for break in wiring harness to gas valve
- 24 volts across control connector P5–2 and P5–5, if no voltage at control replace defective control
3. Spark does Not Stop When Pilot Lights
If the spark does not stop when the pilot lights check the following:
- Loose connection in ignition cable or ground wire
- Continuity of ignition cable
- Clean ame rod
- Pilot electrode porcelain cracked
- Pilot ame covers ame rod and is steady and blue, if not adjust pilot ame
- Low gas pressure at gas valve inlet
- Defective control
4. Main Flame Does Not Light
If the main burners do not light check the following:
- Check orice size and/or blockage
- 24 volts across control terminals P5-8 and P5-5? If no voltage while in STA 7 defective control.
- 24 volts across MV and MV/PV at gas valve? Check for break in wiring harness to gas valve
- Defective gas valve
6. Circulator is On, Damper is Open But Boiler Fails to Start (continued)
D. FOR MODELS EQUIPPED WITH IDL 1200 LWCO:
1. If the AMBER Light is On and the boiler is lled with water: The amber "LOW WATER" light indicates the control
is not sensing water in the boiler. If you are certain that the boiler is lled with water, remove the sensor from the well.
Make sure that the metal clip is protruding enough to come in contact with the inside of the well tube. Check that the well
does not have any heat transfer grease or other contaminants that may interfere with the metal sensor head contacting the
well. If this does not resolve the problem, remove the well and examine for excessive residue build-up. Clean as needed
and re-install.
2. If the AMBER Light is blinking: If the LOW WATER light is blinking, the IDL1200 is nearing the limit of its water
detection range. This can occur as a result of a poor connection between the metal sensor head and the inside of the
copper well or as a result of excessive residue build-up on the exterior of the well. To address this situation, follow the
steps above under 'If the Amber Light is On.'