Laars NEOTHERM NTV User manual

Document 1292
Modulating Boiler
Model NTH
Sizes 399-850 MBTU/h
Water Heater
Model NTV
Sizes 399-850 MBTU/h
Every reference
that you’ll need,
to service the
Commercial
NEOTHERM
®
Service Manual
for
NEOTHERM

Service Manual - NeoTherm 500
How to Use This Manual
i
How to Use the Troubleshooting Information
This manual is divided into ve main sections:
Section A - Troubleshooting Instructions
Section B - Troubleshooting Procedures
Section C - Combustion
Section D - NeoTherm Control System
Appendix
Start the troubleshooting process using the charts in Section A. The
instructions in Section A will lead you to more detailed procedures in
Section B.
Section C covers possible combustion problems and the combustion
setup procedure.
For details on the User Interface used on your unit, see Section D.
If the unit presents a Hold or Lockout message, you can get more infor-
mation from the listing in the Appendix.
Contact Laars Technical Support if you can’t diagnose the problem using
the information in this manual:
LAARS Product Support
Phone: [phone]
[phone]
Fax: [phone]

Service Manual - NeoTherm 500
ii
Finding Information in this PDF File
This manual includes a lot of detailed information, but none of this is
very useful to you unless you can nd it. We’d like to help you to nd the
information you need, quickly and easily.
There are four ways to locate information in this PDF* le.
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Table of Contents -
The Table of Contents is located at the beginning of the manual. (The
bookmark for Contents will take you there.) Use this to identify the sec-
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II

Service Manual - NeoTherm 500 iii
Safety Notes
Please read this section before beginning any
troubleshooting procedures.
If the information in this manual is not followed exactly, a re or ex-
plosion may result, causing loss of life, personal injury, or property
damage.
Necessary Training -
This product must be installed and serviced by a professional service
technician, qualied and/or licensed in hot water boiler and heater instal-
lation and maintenance. Any changes to safety-related conguration
parameters must only be done by qualied and/or licensed burner/boiler
operators and mechanics.
Carbon Monoxide Hazard -
Improper installation and/or operation could create carbon monoxide gas
in ue gases which could cause death, serious injury, or property dam-
age. Improper installation and/or operation will void the warranty.
Fire or Explosion Hazard -
Improper conguration can cause fuel buildup and explosion. Improper
user operation may result in death, severe physical injury, or property
damage. Do not store or use gasoline or other ammable vapors and
liquids in the vicinity of this or any other appliance.
What to Do If You Smell Gas -
If any odor of gas is detected, or if the gas burner does not appear to be
functioning in a normal manner, close the main gas shutoff valve. The
inlet gas pressure to the appliance must not exceed 13” w.c. (3.2 kPa).
• Do not try to light any appliance.
• Do not touch any electrical switch. Do not shut off the power switch.
Do not use any phone in your building.
• Immediately call your gas supplier from a nearby phone. Follow the
gas supplier’s instructions.
• If you cannot reach your gas supplier, call the re department, your
heating contractor, gas company, or factory representative.

Service Manual - NeoTherm 500
Electrical Shock Hazard
Electrical shock can cause severe injury, death or property damage. Only
a professional technician, trained in electrical safety, should work on
this unit. Whenever the troubleshooting procedures make this possible,
turn off the power to the unit before working inside the cabinet. The only
exceptions would be when it is necessary to test the voltages between
the points listed in this manual. 120V AC is present in this unit behind
the metal cover marked with the safety label. Be especially careful when
working on the unit if this cover has been removed. Always replace
the cover when the service procedure is complete. Before making any
changes, disconnect the power supply to prevent electrical shock or
damage to the equipment. It may be necessary to turn off more than one
power supply disconnect.
All electrical wiring is to be done in accordance with local codes, or in the
absence of local codes, with: 1) The National Electrical Code ANSI/NFPA
No. 70 - latest Edition, or 2) CSA STD. C22.1 “Canadian Electrical Code
- Part 1.” This appliance must be electrically grounded in accordance
with these codes.
Hot Water -
This unit can produce water which is hotter than 125°F (52°C). This can
cause severe burns instantly or death from scalding. Always shut off the
system and allow it to cool for one hour before opening any pipe connec-
tions that may contain hot water.
Children, disabled and elderly persons are at the highest risk of being
scalded. See the Installation and Operating manual for instructions be-
fore setting the temperature at the NeoTherm unit.
For NTV units - Adjust the outlet control (limit) or use temperature limiting
valves to obtain a maximum water temperature of 125°F (52°C). Instruct
all users to feel the water temperature before getting into the bath or
shower.
The NeoTherm unit is protected against over-pressurization. A pressure
relief valve is included with each NeoTherm unit.
Installation Codes -
All installations must be made in accordance with 1) American National
Standard Z223.1/NFPA54-Latest Edition “National Fuel Gas Code” or
2) CSA B149.1 “Natural Gas and Propane Installation Code” and with
the requirement of the local utility or other authorities having jurisdiction.
Such applicable requirements take precedence over the general instruc-
tions contained in this manual.
iv

Service Manual - NeoTherm 500
Table of Contents
Section A - Troubleshooting - Start Here
Sect. Title................................................................................Page
A1 Troubleshooting - Start Here ............................................... 1
A2 Unit Will Not Fire - Blower is Not Running........................... 2
A3 Blower Runs Continuously, No Display ............................... 4
A4 Control Unit is in “Standby” Mode........................................ 5
A5 Changing Control Settings, Change Not Complete -
Unit with Original (White) User Interface ............................. 7
A6 Unit is Running, But Building is Still Cold ............................ 8
A7 Control Unit Says “Run”, But Boiler is Not Firing................. 9
A8 Open Safety Chain - Fault #63 ........................................... 9
A9 Unit Runs in High or Low Fire Only -
Unit with Current User Interface ........................................ 10
A10 Unit is Noisy....................................................................... 10
Section B - Troubleshooting Procedures
Sect. Title Page
B1 Quick Check of Components in the
Safety Chain ...................................................................... 11
B2 Troubleshooting the 24V AC Power Supply ...................... 15
B3 Checking the Safety Interlocks .......................................... 16
B4 Checking the Low Water Cutoff Switch ............................. 18
B5 Controller for Low Water Cutoff ......................................... 19
B6 Removing and Replacing the
Low Water Cutoff Switch ................................................... 20
B7 High Water Temperature Limit Switch ............................... 22
B8 Checking the Flow Switch ................................................. 22
B9 Testing the Flow Switch ..................................................... 23
B10 Removing and Replacing the Flow Switch ........................ 24
B11 Removing and Replacing the Gas Valve ........................... 26
B12 Checking the High Gas Pressure Switch........................... 29
B13 Checking the Low Gas Pressure Switch ........................... 30
B14 Testing the Low Gas Pressure Switch ............................... 31
v

Service Manual - NeoTherm 500
Table of Contents (continued)
B15 Removing and Replacing the High and Low Gas
Pressure Switches............................................................. 32
B16 Checking the Condensate Trap Water Level Switch ......... 35
B17 Testing the Condensate Trap Level Switch ....................... 36
B18 Removing and Replacing the Condensate Trap................ 36
B19 Checking the Air Pressure Switch -
Blower Proving Switch....................................................... 38
B20 Test Procedure for Air Pressure Switch ............................. 39
B21 Removing and Replacing the Air Pressure Switch ............ 39
B22 Checking the Blower.......................................................... 41
B23 Removing and Replacing the Blower ................................ 42
B24 High Stack Temperature Fault ........................................... 46
B25 Removing and Replacing the
Stack Temperature Limit Switch ........................................ 47
B26 Checking the System Sensor ............................................ 48
B27 Checking the DHW Sensor................................................ 48
B28 Inlet Water Temperature Sensor........................................ 49
B29 Removing and Replacing the
Inlet Water Temperature Sensor........................................ 49
B30 Outlet Water Temperature Sensor..................................... 50
B31 Removing and Replacing the
Outlet Water Temperature Sensor .................................... 50
B32 Testing the Temperature Sensors...................................... 51
B33 Troubleshooting the Outdoor Reset System ..................... 52
B34 Servicing the Transformer ................................................. 52
B35 Removing and Replacing the Pressure Relief Valve ......... 54
B36 Ignitor Assembly ................................................................ 55
B37 Flame Sensor .................................................................... 56
B38 Pump Fault ........................................................................ 57
vi

Service Manual - NeoTherm 500
Table of Contents (continued)
Section C - Possible Combustion Problems
Sect. Title Page
C1 About Correct Combustion ................................................ 59
C2 Combustion Adjustment Procedure -
Units with Original (White) User Interface ......................... 60
C3 Combustion Adjustment Procedure -
Units with Current User Interface ...................................... 62
C4 Troubleshooting Combustion Problems ............................ 64
C5 Cleaning the Burner and Heat Exchanger......................... 65
Section D - Using the NeoTherm Control System
Sect. Title Page
D1 Identifying the User Interface on Your Unit ........................ 73
D2 Using the Original (White) User Interface.......................... 74
D3 Reacting to Lockouts on the Original (White)
User Interface .................................................................... 76
D4 Removing and Replacing the Original (White)
User Interface .................................................................... 77
D5 Using the Current User Interface....................................... 78
D6 Reacting to Lockouts on the Current User Interface ......... 84
D7 Removing and Replacing the Current User Interface........ 85
D8 When to Replace a SOLA Controller ................................. 86
D9 Removing and Replacing the SOLA Controller ................. 87
Appendix
Sect. Title Page
App1 Error Codes ....................................................................... 89
App2 Ignition and Firing Sequence........................................... 104
App3 Wiring Diagram................................................................ 105
vii

Service Manual - NeoTherm 500
viii

1
Service Manual - NeoTherm 500
A1
Troubleshooting - Start Here
For troubleshooting instructions, see these sections:
Section Symptom Page
A2 Unit Will Not Fire, Blower is Not Running 2
A3 Blower Runs Continuously, No Display 4
A4 Control Unit is in “Standby” Mode 5
A5 Changing Control Settings, Change Not Complete,
Original (White) User Interface 7
A6 Unit is Running, but Building is Still Cold 8
A7 Control Unit Says “Run” but Boiler is Not Firing 9
A8 Open Safety Chain - Fault #63 9
A9 Unit Runs in High or Low Fire Only,
Current User Interface 10
A10 Unit is Noisy 10
New installation,
never ran correctly
Old installation,
ran correctly
See “Quick Check of Components
in the Safety Chain and
Firing Sequence” - Section B1
Is this a new
installation?
Did the unit ever
run correctly?
What changed?
Operating conditions?
Did you change any control settings?

2Service Manual - NeoTherm 500
Unit Will Not Fire - Blower is Not Running
A2
No
Yes
Check 120V AC electrical power.
Display is lit?
See Section B2 -
“Troubleshooting the 24V AC
Power Supply”
No
Check for correct “call for heat” signal.
(5-6 on TB7)
See Section B22
“Checking the Blower”
See Section B19
“Checking the Air
Pressure Switch”
Blower-related
problem?
Disconnect sensor for Outdoor Reset
(if used)
No
System operates
normally? Yes See Section B33
“Troubleshooting the Outdoor
Reset System”
(continued)
Yes
Yes
Short contacts:
Central Heat: 5-6 on TB7
DHW: 5-6 on TB6
Original user interface shows:
Check, Pre-Purge, Run = Normal operation
Current user interface shows:
Heat demand or DHW = Normal operation
Has call for heat? No

3
Service Manual - NeoTherm 500
Unit Will Not Fire - Blower is Not Running A2
cont.
Check programming in controller -
temperature settings, outdoor reset, etc.
See table of code numbers
in Appendix.
Problem indication
from controller? Yes - Code number
supplied
No
See Section A4
“Control Unit is in Standby Mode”
Controller stuck in
Standby mode?
No
Replace the SOLA controller.
See Section D8, D9
Settings OK?
Yes
Yes
Adjust regulator.
Check with
gas company.
Incoming gas
pressure is
OK?
No
Yes
Correct the settings.
No

4Service Manual - NeoTherm 500
Blower Runs Continuously, No Display
A3
In this condition, the blower is running continuously, but the display is
completely blank.
If unit continues to operate normally -
temporary condition
If breaker trips again -
See Section B2
Reset 24V breaker
switch under trans-
former. Resets?
Yes
No
Check the 24V power supply.
See Section B2.

5
Service Manual - NeoTherm 500
Control Unit is in “Standby” Mode
In certain situations, the controller on this unit can go into “Standby”
mode. The Boiler pump is running, so the unit sees a “Call for heat.”
There is no lockout or hold, but something is preventing it from going to
“Run” mode.
A4
No
Check for:
- Call for heat?
- System is up to set-point temp. - no need
for more heat?
- If warm weather shutdown is enabled:
Outdoor air temperature too warm?
Normal
operating
condition?
In certain situations, the controller on this unit can go into
“Standby” mode. The Boiler pump is running, so the unit sees a
“Call for heat.” There is no lockout or hold, but something is
preventing it from going to “Run” mode.
No
Unit operates
normally?
Disconnect outdoor temp. sensor
Yes See Section B33
“Troubleshooting Outdoor Reset”
No
Unit operates
normally?
Set Anti-Short-Cycle to minimum value (white display = 0, current display = 1 min.)
Yes Correct settings for Anti-Short-Cycle
(continued)
Yes

6Service Manual - NeoTherm 500
A4
cont. Control Unit is in “Standby” Mode (continued)
Example:
High flue temperature trips
High Stack Temp. Sensor.
Unit will not run for 20 min.,
then automatically resets.
Controller reacting
to a temporary problem?
No
Units with original (white) user interface -
See Section A5
“Changing Control Settings,
Change Not Complete”
Were you changing
the control settings? Yes
No
See Section B3
“Checking the Safety Interlocks”
Problem with
safety interlock
circuit?

7
Service Manual - NeoTherm 500
Changing Control Settings, Change Not Complete
Original (White) Interface
NeoTherm units were produced using two types of user interfaces. (See
Section D1 to identify the kind of interface used on your unit.) These
instructions apply to units with the original (white) user interface.
In certain situations, the controller used in this unit can go into a “Stand-
by” mode. There is no lockout or hold, but the unit still will not run.
This can happen if you begin to change one of the control settings, but
do not nish the process. For example, let’s say you want to change the
DHW setpoint from 180° to 175°. You use the menus to go to the item
for the DHW setpoint, then enter the new number – “175.” At this point,
you are supposed to press the Done button to send the new setting to
the controller. However, if you do not press Done or OK, the control-
ler will go into the Standby mode. The setting for the DHW setpoint will
remain at the old setting (180°), because at this point the controller still
has not received the new setting. More importantly, the unit will not re
because it is still waiting for that new setting. There is no indication of
this on the User Interface.
To recover from this, you need to return to the point where you were
making the change, and enter the new setting again. In this case, you
would step through the menus until you returned to the item for the DHW
setpoint. Enter the new number again (175°), then press Done. At that
point, the controller will leave the Standby mode, and the unit should
begin operating normally.
In order to troubleshoot this kind of situation, ask yourself, “What was I
just doing?” Were you trying to change a control setting? Which one?
You probably need to return to that setting, enter the new value again,
then remember to press Done.
A5

8Service Manual - NeoTherm 500
Unit is Running, But Building is Still Cold
A6
Yes
No
Clear it
Air inlet is
blocked?
Clean
Air intake
inside unit is
plugged?
Yes
No
Clean, blow out
(Gas/air mixture is correct,
but not enough gas/air
mixture is supplied.)
Dirty fan? Yes
No
Burner and/or
heat exchanger
plugged?
Yes
See “Cleaning the Burner and Heat Exchanger”
Section C5

9
Service Manual - NeoTherm 500
Control Unit Says “Run,” But Boiler is Not Firing
In this condition, the panel is lighted, so you know the unit has power.
The Boiler pump is running, so you know the unit is receiving the call
for heat. The blower is running, the unit has spark, and the gas valve is
operating correctly.
Open Safety Chain - Fault #63
This fault indication can point to several different problems:
• Blocked condensate drain
* Blocked exhaust vent
• High or low gas pressure
• Low water in system
• Problem with circulator pump
Fault #63 is a bit like the “Check Engine” light in a car - it indicates a problem, but
does not identify the problem. To identify the specic problem, see Section B3 -
“Checking the Safety Interlocks.”
A7
A8
No
Example:
Stack temp. limit trips,
automatically resets after 20 minutes.
Until this happens, the display says
“Run” but the unit will not fire.
Unit is operating
correctly - recovering
from a trouble
condition?
No
Check safety
interlocks
(Sect. B3)
OK?
Replace the SOLA controller
See Section D8, D9

10 Service Manual - NeoTherm 500
On systems using anti-freeze –
This can occur if the concentration of anti-freeze is too high. At concen-
trations above 35%, localized boiling can occur, and this can produce
noise.
Unit is Noisy
A10
On systems using the Current user interface –
To see if the unit is locked into high re or low re -
From the Home screen, press “i” to go to the “Info/Install” screen. High-
light “Test” and press “OK.” In the Test menu, highlight “Manual Burner
Operation” and press “OK.” Be sure “Firing Control” is set to “Auto.” If it
is not, log in using the password “lnt”, and change the setting to “Auto.”
Unit Runs in High or Low Fire Only
A9