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User’s Manual 

Document 1317

H2372700-

 WARNING

If the information in this manual is not 

followed exactly, a fire or explosion may 

result causing property damage, personal 

injury or loss of life.

Do not store or use gasoline or other 

flammable vapors and liquids in the vicinity 

of this or any other appliance.

WHAT TO DO IF YOU SMELL GAS

• Do not try to light any appliance.

• Do not touch any electrical 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 fire department.

Installation and service must be performed 

by a qualified installer, service agency, or gas 

supplier.

FOR YOUR SAFETY:

 This product must be installed and serviced by a professional service technician, 

qualified in hot water boiler and heater installation and maintenance. Improper installation and/or operation 

could create carbon monoxide gas in flue gases which could cause serious injury, property damage, or 

death. Improper installation and/or operation will void the warranty.

 AVERTISSEMENT

Assurez-vous de bien suivres les instructions 

données dans cette notice pour réduire au 

minimum le risque d’incendie ou d’explosion 

ou pour éviter tout dommage matériel, toute 

blessure ou la mort.

Ne pas entreposer ni utiliser d’essence ni 

d’autres vapeurs ou liquides inflammables dans 

le voisinage de cet appareil ou de tout autre 

appareil.

QUE FAIRE SI VOUS SENTEZ UNE ODEUR DE GAZ:

• Ne pas tenter d’allumer d’appareils.

• Ne touchez à aucun interrupteur. Ne pas vous servir 

des téléphones dansle bâtiment où vous êtes.

• Appelez immédiatement votre fournisseur de

gaz depuis un voisin. Suivez les instructions

du fournisseur.

• Si vous ne pouvez rejoindre le fournisseur de

gaz, appelez le sservice des incendies.

L’installation et l’entretien doivent être assurés par 

un installateur ou un service d’entretien qualifié ou 

par le fournisseur de gaz.

User’s Manual

M

ASCOT

 ® 

ST

Wall-Mounted, Modulating  
Gas Condensing Water Heater 
Model MSTWW

199,000 BTU/hr

Natural Gas (NG) - Factory Configuration

Propane Gas (LP) - Field-Convertible

Summary of Contents for MASCOT ST MSTWW

Page 1: ...ses which could cause serious injury property damage or death Improper installation and or operation will void the warranty AVERTISSEMENT Assurez vous de bien suivres les instructions données dans cette notice pour réduire au minimum le risque d incendie ou d explosion ou pour éviter tout dommage matériel toute blessure ou la mort Ne pas entreposer ni utiliser d essence ni d autres vapeurs ou liqu...

Page 2: ...oper ventilation of interior components Do not obstruct or block a free flow of air to the water heater to ensure proper ventilation If desired clean the jacket surfaces with a dry cloth Do not use flammable cleaning materials If sidewall vented keep the vent terminal clear of obstructions do not snow against the vent terminal Clean the intake screen often and then develop an appropriate maintenan...

Page 3: ...witch 14 Gas Inlet 15 Gas Inlet Pipe 16 Freeze Protector Sensor 17 Domestic Hot Water DHW Outlet 18 Condensate Trap Cleanout Name of Component 19 Cold Water Inlet 20 Cold Water Inlet Filter 21 Manual Power Switch 22 DHW Temperature Sensor 23 Water Adjustment Valve 24 Condensate Trap Hose 25 Main Controller 26 Control Panel 27 Secondary Heat Exchanger 28 Flame Detection Sensor 29 Burner Case 30 Bur...

Page 4: ...oint LOW Range 95 120 F 35 49 C DHW Set Point HIGH Range 121 140 F 49 5 60 C D Toggle C F E Scroll Select Turn to scroll tap to select clockwise or counterclockwise The Control Display has a Control Dial E 4 buttons A B C D and a Liquid Crystal Display with 72 back lit segments This section of this manual gives instruction on how to navigate into the many functions of the Mascot ST and to change t...

Page 5: ...ll not allow changes when the lock mode is activated To exit the Lock mode press the button Numeric Display Domestic Hot Water Mode Lock Communicating Status and Installer Modes Flame Signal LAARS Heating Systems Page 40 SECTION 5 Control Display and Operation 5 1 Control Dial and Buttons Buttons Functionality PRESS Tap PRESS and HOLD 5 seconds A Display Power Turns Control Display ON OFF B Modes ...

Page 6: ...y is turned on the Control Display will go through a Start Up checklist and briefly show a sequence of diagnostic codes before entering into the Operating Mode It will then display the following information Indicate Example Current DHW temperature 125 F If the flow is present S24 If flame detected S37 Temperature sign Celsius or Fahrenheit letter C or F Communication state indicate C or F ...

Page 7: ... Fr Fan rpm Current fan rpm value C Lc Lock Mode Lock mode is used On or unused oFF d OP OP Temperature Current Operating Temperature E dH DHW temperature Current DHW temperature F Eh Exhaust Temperature Current Exhaust temperature h In Inlet Temperature Current Inlet Temperature L rt Running Time Display Running Time L rt 1 PH Power Supply Time Power Supply Time 100 hour increments 2 rh Burner Op...

Page 8: ...ochester NH 03867 603 335 6300 Fax 603 335 3355 1869 Sismet Road Mississauga Ontario Canada L4W 1W8 905 238 0100 Fax 905 366 0130 www Laars com Litho in U S A Laars Heating Systems 1503 Document 1317 Dimensions and specifications subject to change without notice in accordance with our policy of continuous product improvement Notes ...

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