Commercial Water HeatersGas Tankless
Laars NT2V0650 Commercial Water Heater Manual
Setup, everyday use, maintenance and troubleshooting for the 650,000 Btu/h commercial gas tankless water heater, with verified specifications.
- Input650,000 Btu/h
- Thermal efficiency97%
- Flow at 70 °F rise≈18.0 gpm
- FuelNatural gas
About the Laars NT2V0650
The Laars NT2V0650 is a 650,000 Btu/h commercial gas tankless water heater certified under the ENERGY STAR program. It is rated at an input rate of 650,000 Btu/h and a thermal efficiency of 97% and runs on natural gas. That efficiency is higher than 18% of the 210 Gas Tankless models in our database.
At 97% thermal efficiency this is a condensing water heater: it extracts enough heat from the flue gases that water vapor condenses inside the heat exchanger. That is why it uses plastic or stainless venting, needs a condensate drain and is typically vented with a fan.
It has an internal water volume of 6 gallons and a power-vent design.
Specifications
| Brand | Laars |
|---|---|
| Model number | NT2V0650 |
| Model name / series | NeoTherm XTR |
| Type | Gas Tankless |
| Fuel | Natural gas |
| Input rate | 650.0 kBtu/h |
| Thermal efficiency | 97% |
| Storage volume | 6 gal |
| Vent type | Power Vent |
| Vent pipe size(s) | 6 in. |
Safety information
- Installation, gas piping, venting and service must be performed by a licensed plumber, gas fitter or qualified heating contractor in accordance with the National Fuel Gas Code (NFPA 54) or CSA B149.1 in Canada, local plumbing and mechanical codes, and the manufacturer's installation manual.
- Incorrect venting or combustion air can cause carbon monoxide (CO) poisoning. Use only the vent materials, lengths and terminations the manual permits, and install CO alarms in the building as required by code.
- Do not store or use gasoline, solvents or other flammable vapors near the water heater.
- Water above 120 °F (49 °C) can scald. Where water is stored hotter for sanitation or Legionella control, install thermostatic mixing valves to temper water delivered to fixtures.
- Turn off the fuel or power supply and close the water valves before servicing.
Installation and first-time setup
Commercial water heaters must be sized to the building's peak hot-water demand and installed to the manufacturer's instructions. At 650,000 Btu/h, this model needs gas piping and a meter able to supply roughly 650 cubic feet per hour of natural gas (based on about 1,000 Btu per cubic foot) in addition to every other appliance on the line, at the inlet pressure listed on the rating plate.
- Plan the location
Place the unit on a level, noncombustible surface, near a floor drain, with the service clearances shown in the manual. Use a drain pan where a leak could damage the building.
- Connect the water piping
Install full-port isolation valves and unions on the cold inlet and hot outlet, plus service valves with hose ports so the heat exchanger can be flushed and descaled. Where a backflow preventer or check valve creates a closed system, add a properly sized thermal expansion tank.
- Connect the gas supply
Run gas piping sized for the full input rate, with a manual shutoff valve and a sediment trap (drip leg) ahead of the appliance gas valve. Leak-test all joints with an approved solution, never a flame.
- Install the venting
This model is listed for power-vent installation. Use only the vent and air-intake materials, diameters and maximum equivalent lengths in the manual (the certification lists 6 in. vent pipe), slope horizontal runs back toward the unit so condensate drains, support the pipe as specified and keep terminations clear of windows, doors, air intakes and snow lines.
- Connect the condensate drain
Route the condensate drain to a suitable drain through a condensate neutralizer where required by code or the manufacturer — condensate from gas combustion is acidic and can damage drain piping. Protect the line from freezing.
- Provide electrical power
Connect the electrical supply for the controls, igniter and blower as shown on the wiring diagram, with a service disconnect.
- Fill and purge
Open the water supply and a hot-water fixture to purge air from the heat exchanger before enabling the burner.
- Commission with a combustion analysis
A qualified technician should start the unit, verify gas pressure, check combustion (CO and CO2 or O2) at high and low fire with a calibrated analyzer and confirm all safety controls operate.
Using your commercial water heater
Setting the water temperature
Choose the storage or outlet temperature for the application and the facility's water-management plan. Common practice for Legionella control is to store water at 140 °F (60 °C) or higher and deliver it to hand sinks and showers through thermostatic mixing valves at a safe temperature. Commercial dishwashers usually need 140 °F supply water, with a booster heater for a high-temperature sanitizing rinse.
Flow capacity
A tankless water heater heats water as it flows, so capacity is a flow rate rather than a stored volume. Based on its input rate and 97% thermal efficiency, approximate continuous flow is:
| Temperature rise | Approximate flow |
|---|---|
| 40 °F | 31.5 gal/min |
| 70 °F | 18.0 gal/min |
| 100 °F | 12.6 gal/min |
Very low flows may not activate the burner; recirculation loops and multiple-unit (cascade) systems should be designed to the manufacturer's guidance.
Operating controls
Modern condensing commercial water heaters use electronic controls with a display for setpoint, diagnostics and lockout history. Lockouts after repeated ignition failures are a safety feature — find and correct the cause rather than repeatedly resetting the control.
Care and maintenance
| When | What to do |
|---|---|
| Every month | Check for leaks and error history, and confirm vent and air intake terminations are clear. |
| Every 6–12 months | Descale the heat exchanger by circulating an approved descaling solution through the service valves; scale builds faster with hard water and high temperatures. Clean the inlet water filter screen. |
| Every 6–12 months | Inspect and clean the condensate trap and drain, and replace neutralizer media when it is depleted. |
| Every year | Have a qualified technician inspect the burner, igniter and flame sensor, clean the combustion air filter or screen, inspect the vent for leaks and support, and repeat the combustion analysis. |
Follow the maintenance schedule in your manufacturer's manual — intervals depend heavily on water hardness and usage — and keep a service log; it is often a warranty requirement.
Troubleshooting
Check fuel or power, water valves and settings first. Anything involving gas controls, combustion, venting or electrical components should be handled by a qualified technician.
| Problem | Possible cause | What to try |
|---|---|---|
| No hot water, control in lockout | Gas supply off or low pressure; blocked vent or air intake; blocked condensate drain; failed igniter or flame sensor. | Check that the gas valve is open and other gas appliances work; clear vent terminations; check the condensate trap; note the code and call a qualified technician. |
| Not enough hot water | Demand exceeds flow capacity; setpoint too low; mixing valve misadjusted; scale on the heat exchanger. | Compare peak demand with the capacity tables above; check setpoint and mixing-valve settings; descale the heat exchanger. |
| Water temperature fluctuates | Flow below minimum activation; scale; undersized gas supply. | Increase minimum flow or adjust recirculation; descale; verify gas pressure at full fire. |
| Water leaking from the condensate line area | Blocked or disconnected condensate trap or drain. | Clear and reconnect the trap and drain; check the neutralizer for clogging. |
| Error code displayed | Brand-specific diagnostic code. | Error codes are not standardized; consult the code table in your manufacturer's manual before resetting. |
Energy use and running costs
Heating 1,000 gallons of water by 70 °F (for example, from 50 °F to 120 °F) takes about 583 thousand Btu. At 97% thermal efficiency the Laars NT2V0650 burns roughly 6.0 therms to do it — about $9.02 at an assumed natural gas price of $1.50 per therm.
| Hot water per day | Gas per year | Cost per year |
|---|---|---|
| 250 gal | 549 therms | $823 |
| 500 gal | 1,097 therms | $1,646 |
| 1,000 gal | 2,194 therms | $3,291 |
| 2,000 gal | 4,388 therms | $6,582 |
At full fire the burner uses 650,000 Btu/h, or about 6.5 therms per hour ($9.75 per hour of continuous firing).
Frequently asked questions
What is the input rate and efficiency of the Laars NT2V0650?
It is rated at 650,000 Btu/h input with a thermal efficiency of 97%, so about 631,000 Btu/h ends up in the water at full fire.
How many gallons per minute can the Laars NT2V0650 supply?
Calculated from its rated output, roughly 18.0 gallons per minute at a 70 °F temperature rise, or 31.5 gpm at 40 °F.
How is the Laars NT2V0650 vented?
It is listed for power-vent installation with 6 in. vent pipe. Power-vent units use a blower to push flue gases out and draw combustion air from the room, so the space needs adequate combustion air. Use only the materials and lengths in the installation manual.
Can the Laars NT2V0650 run on propane?
It is certified for natural gas. Ask the manufacturer whether a propane version or conversion kit is available.
How much does it cost to heat water with the Laars NT2V0650?
At 97% thermal efficiency, heating 1,000 gallons by 70 °F takes about 6.0 therms — roughly $9.02 at $1.50 per therm.
Is the Laars NT2V0650 ENERGY STAR certified?
Yes. It appears on the ENERGY STAR list of certified commercial water heaters, with a certification date of July 2023.
Sources and disclaimer
Specifications on this page come from the ENERGY STAR certified commercial water heaters dataset published by the U.S. Environmental Protection Agency (record certified July 18, 2023), retrieved October 7, 2026.
The setup, operating, maintenance and troubleshooting guidance is written by ManualHarbor's editors for this specific product type and configuration. It is an independent guide — not a reproduction of the manufacturer's manual — and ManualHarbor is not affiliated with Laars. Always follow the safety instructions, installation requirements and warranty terms supplied with your unit, and contact Laars or an authorized service provider for warranty repairs and replacement parts.
Running-cost figures use assumed U.S. average utility prices and are estimates for comparison only. See our editorial methodology for details.
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