Product Overview

Date: Bid Date:
Project #: Location:
Project Name: Engineer:
Contractor: Prepared By:
Contractor shall supply and install Qty.: Laars Model No. MSTWW (size) modulating condensing tankless water heater(s).
The tankless water heater shall be a Laars Mascot ST Model MSTWW (size) 199 rated at the input and output shown on the schedule.
The tankless water heater shall modulate 10-100% of full re. The unit(s) shall be design-certied to comply with the current edition of the
Harmonized ANSI Z21.10.3/ CSA 4.3 Standard for Gas Water Heaters, Storage Water Heaters, Circulating and Instantaneous.
The tankless water heater shall be listed with the U.S. Department of Energy as an Energy Star appliance. The tankless water heater shall be
listed with AHRI (Air Conditioning, Heating and Refrigeration Institute). The tankless water heater shall have a minimum energy factor of 0.96.
The water tube heat exchanger shall be stainless steel, rated for 150 psi (1034 kPa) working pressure. Heat exchanger shall be accessible
for visual inspection and cleaning of internal surfaces. The tankless water heater shall be fully condensing design with built-in condensate
drain and trap. The heat exchanger shall have a limited 12-year warranty.
Tankless water heater(s) shall provide domestic hot water ow rates, at 77°F (25°C) temperature rise of:
- 199 MBH = 4.7 gpm (18 l/m)
A Hall Effect ow sensor shall initiate the call for domestic water.
Each tankless water heater shall be test red and all safety components tested, at the factory.
The tankless water heater shall be sealed combustion. Chamber shall include a sight glass for viewing ame.
The tankless water heater jacket shall be a unitized shell nished with acrylic thermoset paint.
The tankless water heater shall have a condensate trap that does not need to be primed and will not allow ue gases to pass back through unit.
The tankless water heater shall operate on 3.5-13" w.c. gas pressure.
The tankless water heater shall use a premix metal ber burner and a zero governor gas valve to burn cleanly, with NOx emissions not
exceeding 20ppm. The tankless water heater shall meet the emissions requirements of SCAQMD.
The tankless water heater shall be designed for vertical or horizontal Category IV venting:
- Up to 50 equivalent feet with 2" diameter in PVC, CPVC, Polypropylene or stainless steel vent material
- Up to 100 equivalent feet with 3” diameter in PVC, CPVC, Polypropylene or stainless steel vent material
Air may be taken from the room, or ducted directly to the tankless water heater:
- Up to 50 equivalent feet with 2" diameter in ABS, PVC, CPVC, Polypropylene or galvanized pipe
- Up 100 equivalent feet with 3” diameter in ABS, PVC, CPVC, Polypropylene or galvanized pipe
Unit shall be 120VAC, single phase, less than 4 Amps (including mounted pump) for connection to a 15A breaker. The control circuit shall
be 24VAC. A 3 ft. length 14 AWG plug-in line cord is included for connection to 120VAC/15A receptacle.
The tankless water heater shall have built-in gas leakage detection capabilities such that when gas is detected for greater than 5 seconds,
or three times within 10 minutes, the tankless water heater will lock out for safety purposes.
The tankless water heater control shall be an integrated electronic PID temperature and ignition control with LCD, push buttons and dial
and shall control the tankless water heater operation and ring rate. The tankless water heater display shall be visible without the removal
of any jacket panels.
The control shall monitor ue gas temperature and shall stop the tankless water heater from ring if temperature is excessive.
The control shall easily allow the user to force the tankless water heater into minimum or maximum ring rate, for tankless water heater
setup and diagnostic purposes. Control shall have menu structures for user mode and installer mode.
Allowable control adjustments shall include: tankless water heater temperature setpoint and °F or °C display
Control diagnostics shall include, at a minimum, the following: ignition failure, grounded ame rod, sensor errors (open or shorted), and fan
speed proving rate failure.
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Mascot ST
Residential
Tankless Water Heater
Models MSTWW 199, Indoor
Specication