Laars MASCOT LX User manual

Mascot LX Service Manual Document 1371
Service
Manual
for
Mascot LX
Service
Manual
for
Mascot LX
Modulating Boilers - Model MLXH
Sizes 50, 75, 100, 150, 175, and 220 MBTU/h
Water Heaters - Model MLXC
Sizes 125, 150, and 175 MBTU/h
Modulating Boilers - Model MLXH
Sizes 50, 75, 100, 150, 175, and 220 MBTU/h
Water Heaters - Model MLXC
Sizes 125, 150, and 175 MBTU/h

Mascot LX Service Manual
Table of Contents
i
Introduction
Sect. Title Page
How to Use the Troubleshooting Information ..................... 1
Identifying Your Unit............................................................. 1
Finding Information in this PDF File .................................... 2
Safety Notes ........................................................................ 3
Removing the Covers ......................................................... 6
Part Locations...................................................................... 7
Sensor and Switch Locations .............................................. 8
Access to Control Board...................................................... 9
Control Panel..................................................................... 10
Control Display .................................................................. 11
Operating Displays ............................................................ 12
Operating Displays - Examples ......................................... 13
 Notications,Blocking,Lockout,andErrorDisplays ......... 14
Changing Setpoints ........................................................... 16
Installer and Service Mode Displays ................................. 17
Section A - Troubleshooting Instructions
Sect. Title Page
A1 QuickCheckoutProcedure............................................... 19
A2 LockoutCodes................................................................... 22
A3 NoticationCodes ............................................................. 27
A4 UnitisRunning,butBuildingisStillCold........................... 29
A5 Short-Cycling ..................................................................... 30
A6 Unit is Noisy....................................................................... 31

Mascot LX Service Manual
Table of Contents (continued)
ii
Section B - Troubleshooting Procedures
Sect. Title Page
B1 Troubleshooting the 120V AC Power Supply .................... 33
B2 Troubleshooting the 24V DC Power Supply ...................... 35
B3 Inlet Water Temperature Sensor ....................................... 36
B4 Outlet Water Temperature Sensor ..................................... 37
B5 System Sensor ................................................................. 38
B6 DHW Sensor ..................................................................... 38
B7 Outdoor Sensor ................................................................. 38
B8 Flue Temperature and Flue Safety Sensors ..................... 39
B9 Testing the Temperature Sensors ..................................... 41
B10 Water Pressure Switch ..................................................... 42
B11 Blower Problems .............................................................. 43
B12 Air Pressure Switch .......................................................... 45
B13 Gas Valve ......................................................................... 47
B14 Condensate Trap .............................................................. 48
B15 Pressure Relief Valve ........................................................ 49
B16 Direct Spark Ignition ......................................................... 50
B17 Pump Problems ................................................................ 52
B18 Outdoor Reset ................................................................... 53
B19 Low Water Cutoff Switch .................................................. 55
B20 DHW Problems - Combi Units (MLXC) ............................. 57
B21 DHW Temperature Sensor ................................................ 58
B22 DHW Flow Sensor (Hall Sensor) ...................................... 59
B23 Three-Way Valve ............................................................... 60
B24 Flat Plate Heat Exchanger ................................................ 61
B25 Hot Water Problems - Indirect Tank (MLXH) ..................... 62
B26 DHW Problems - Indirect Tank with Aquastat (MLXH) ...... 63
B27 DHW Problems - Indirect Tank with Sensor (MLXH) ......... 64
B28 Cascade Setup .................................................................. 65
B29 External Modulation Control (BMS) ................................... 66
B30 Replacing the SIT Control Board....................................... 67
B31 Annual Service Procedure................................................. 69

Mascot LX Service Manual
Section C - Combustion Setup
Sect. Title Page
C1 About Correct Combustion ................................................ 71
C2 Combustion Adjustment Procedure ................................... 72
C3 Troubleshooting Combustion Problems ............................ 74
C4 Cleaning the Burner and Heat Exchanger ........................ 75
Appendix
Sect. Title Page
App1 SIT Parameter Codes........................................................ 77
 LockoutCodes................................................................... 77
 BlockingCodes.................................................................. 77
 NoticationCodes ............................................................. 78
Installer Mode Parameters ................................................ 79
App2 IgnitionandFiringSequence............................................. 82
App3 Wiring Diagrams ................................................................ 83
App4 Gas Conversion Procedure .............................................. 86
Table of Contents (continued)
iii

Mascot LX Service Manual
iv

Mascot LX Service Manual 1
How to Use This Manual
How to Use the Troubleshooting Information
This manual is divided into ve main sections:
Introduction - How to Use This Manual, Safety Notes,
Parts Identication
Section A - Troubleshooting Instructions
Section B - Troubleshooting Procedures
Section C - Combustion Setup
Appendix - Error Codes, Wiring Diagrams, etc.
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.
If the unit presents a Lockout message, you can get more information from the listing in Section App1 in
the Appendix.
This manual covers two versions of the Mascot LX:
• The standard unit (MLXH), which produces hot water for central heat only. (This type of unit can
also be connected to an indirect hot water tank.)
• The “Combi” unit (MLXC), which also produces domestic hot water using a built-in heat exchanger.
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]
Identifying Your Unit
Model Designation - M = Mascot
Series Designation - LX = Laars Heat Exchanger
Usage - H = Modulating Boiler
C = Combination Boiler and Water Heater
Conguration - W = Wall hung
Size - 50 - 220 MBH
Fuel - N = Natural Gas
P = Propane
Altitude - A = 0’ - 10,000’
Revision - 1 = First
Options Code - X = Standard
L = Low water cutoff
Pump Options - N = With pump

Mascot LX Service Manual
2
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 three ways to locate information in this PDF* le.
Bookmarks -
When you rst open this le on your computer, it will display a list of
“Bookmarks” along the left edge of the page. Scroll down the list until
you see the item you want. When you click on that Bookmark, the PDF
Reader will take you to that point in the manual. (If the Bookmarks do
not appear, you can display them by clicking on the small tab in the
middle of the left margin, and dragging toward the center of the screen.)
Search Functions Provided by PDF -
The PDF reader includes several ways of locating information. From the
line at the top of the screen, select Edit, then Find. Type in the item you
want to nd. The PDF Reader will take you to the rst occurrence of that
item. To go to the next occurrence, click on the right-arrow.
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-
tion of the manual you want to read, then use the Bookmarks to jump to
that section. (You can also scroll through the PDF le to get to the sec-
tion you want.)
*About PDF -
The U.S. Government developed the PDF format (“Portable Document
Format”) to provide an easy way to transfer information between comput-
ers without worrying about fonts, page size, etc. You can read a PDF le
using the Adobe Acrobat PDF Reader. You will nd that the Reader has
already been installed on most computers. You can also download a free
copy at this address:
https://get.adobe.com/reader/ l

Mascot LX Service Manual 3
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.

Mascot LX Service Manual
4
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 ex-
ceptions would be when it is necessary to test the voltages between the
points listed in this manual.
This unit includes the following electrical hazard areas:
Full line voltage is present behind the lower front panel. Be
especially careful when working on the unit if this cover has been
lowered. Always replace the cover when the service procedure is
complete.
Before doing any work inside the unit, disconnect the power supply to
prevent electrical shock or damage to the equipment. It may be neces-
sary 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 Hazard
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 Mascot LX unit.
For MLXC units - Adjust the outlet control (DHW setpoint or limit) or use
temperature limiting valves to obtain a maximum water temperature
of 125°F (52°C). Check local codes for details of the required mixing
valves. Instruct all users to feel the water temperature before getting into
the bath or shower.
The Mascot LX unit is protected against over-pressurization. A pressure
relief valve is included with each Mascot LX unit.
The condensate water can be hot, and is also slightly acidic.
Safety Notes (continued)

Mascot LX Service Manual 5
CAUTION
Capillary Tubes
The temperature gauge on the front of the unit is connected to its sensor
by a thin copper capillary tube. This tube is delicate, and can be dam-
aged if it is bent sharply.
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.
Safety Notes (continued)

Mascot LX Service Manual
6
Removing the Covers
The upper and lower covers can be removed by pulling the part straight
out and away from the unit. The center control panel cannot be re-
moved.
Upper inner panel -
2 screws
Lower inner panel -
2 screws
Center panel -
not removed

Mascot LX Service Manual 7
Part Locations
Intake air
vii
Water outlet pipe
(top)
Water outlet pipe
(bottom)
Air bleed vent
Pressure switch
Blower
Heat exchanger
Transformer
Condensate
trap
Circulator
pump
Three-way valve
(Combi units only)
Burner
(inside heat
exchanger)
Venturi
Gas valve
Water inlet
pipe (top)
Gas inlet pipe
(top)
Exhaust

Mascot LX Service Manual
8
Sensor and Switch Locations
Air pressure switch
Inlet water temp.
sensor
Water pressure
switch
Air vent
Water outlet temp.
sensor and safety
limit
Low water cutoff
switch (optional)
Flue temp. sensor
and ue safety
DHW water temp.
sensor
DHW ow sensor
(Hall sensor)
Combi units only
Three-way
valve -
Combi units
only

Mascot LX Service Manual 9
Access to Control Board
Lower metal panel folds down
High voltage terminal strip The controller circuit board is
located behind this cover.

Mascot LX Service Manual
10
Control Panel
Display screen
Power switch
Reset button
Outlet
temperature
Cancel button
OK/ Select button
Up arrow
Down arrow
Power switch -
This switches on power to the Mascot unit.
Up and Down arrows -
These can be used to step between display screens, or to change
values used by the unit.
Reset button -
Use this to reset the controller after a lockout.
OK/ Select button -
Use this to select one of the options, or to Save a changed value.
Cancel button -
Use this to return to the previous function without saving a new
value.
Temperature and pressure gauges -
These indicate the temperature and pressure at the water outlet.
(The values shown here are not calculated by the SIT controller.)
System
pressure

Mascot LX Service Manual 11
Control Display
This line shows
temperature at
sensors
This line shows
setpoints, fan
speed, or error
codes
Temperature
shown in °F or °C
Central heat
demand
External demand from
master or 0-10V
Domestic
hot water
demand
Service
mode
Summer mode (DHW
output only)
Boiler lockout
Now display-
ing outdoor
temperature*
Now display-
ing system
temperature*
Now display-
ing domestic
hot water
temperature*
Now displaying
stack temperature
Now display-
ing inlet tem-
perature**
Now display-
ing outlet
temperature**
Flame size indicates output -
20% to 100%
Burner
ring
rate
Setpoint is
shown as
temperature
* If the probe is present, the outline will be darkened. If the probe
is reporting the current value, the center of the symbol will be
lled in.
** If both arrow symbols are lled in, the unit is reporting “Delta T”
- the difference between the outlet and the inlet temperatures.

Mascot LX Service Manual
12
Operating Displays
Operating Mode Displays -
When the unit is operating normally, use the Up and Down buttons to rotate through the
following functions:
• Outlet temperature - The setpoint for central heat is adjustable. Range 45°F - 189°F,
default 130°F
* Inlet temperature
• Delta T (the difference between the outlet and inlet temperatures)
• Outdoor sensor (if the outdoor temperature sensor is installed
• Flue temperature
• Domestic hot water temperature (if this is a Combi model or is connected to an external
tank). The setpoint is adjustable. Range 68°F - 189°F, default 120°F
• System temperature (if a System probe is installed). The setpoint is adjustable. Range
45°F - 189°F, default 130°F.
• Burner rate (if the burner is lit)
You can also use the Up and Down buttons to step through these displays. The following
images show how to interpret these displays.
Operating Modes -
The control system uses four modes:
Operating Mode - While the unit is running, the controller will rotate between several stan-
dard displays.
User Mode - This mode allows the user to change some of the setpoints. To go to
User Mode, press and hold the OK/Select button for one second.
Installer Mode - This allows the installer to change all of the parameters used to install
and congure the boiler. To go to the Installer Mode, press and hold
the OK/Select and Down buttons for ve seconds. For details, see the
Appendix.
Service Mode - This mode should only be used by technicians who have been trained
in service procedures on the Mascot LX. For details, see Section C -
“Combustion.”

Mascot LX Service Manual 13
Outdoor temp. = 70°F
Flue temp. = 188°F
Domestic hot water temp. = 80°F
Outdoor temp. sensor
Flue temp. sensor
DHW temp. sensor
Central heat demand, temp. is 180°F at outlet sensor
System temp. display, temp. is 188°F
Outlet sensor
Central heat demand
System temp. sensor
- or -
Operating Displays - Examples
Outlet sensor temp. = 180°F
Inlet sensor temp. = 150°F
Delta T = 30°F
(difference between inlet and
outlet temps.)
Outlet sensor
Inlet sensor
Indicates both inlet and outlet sensors
Use the Up and Down buttons to cycle through the following screens:

Mascot LX Service Manual
14
Notication, Blocking, Lockout, and Error Displays
There are four other kinds of displays you may see while the unit is operating:
Note -
A “Notication” indicates a condition that is unusual, but will not prevent
the unit from operating. For a list of Notication codes, see Section A3.
Blocking -
A “Blocking” code also indicates an unusual condition that will not
prevent the unit from operating. During a “blocking” event, the unit is
correcting itself or moving toward normal operation. For a list of Block-
ing codes, See Section App1 in the Appendix.
Lockout -
A “lockout” is a serious condition that will prevent the unit from operat-
ing. Usually the code will give you a good idea of the cause of the
problem. Section App1 lists some troubleshooting suggestions based
on the Lockout codes.