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Commercial Tankless Water Heater

Commercial Water Heating Solutions

Sometimes the difference between "open for business" and "closed for repairs" is the reliability of a water heating system.

That's why for decades, a full spectrum of commercial applications - from retrofit to new construction and light to heavy - have trusted Rinnai Tankless Water Heaters. Because the system configures to your needs and to every kind of space, every usage demand is the perfect Rinnai fit - and that makes it easy to do business.

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Multi-System Configuration

Mastering The Art of Taking Control

Thanks to our flexible venting options and Tankless Rack System, as well as solutions that are custom designed (with and without storage), you can use multiple units together to provide anywhere from 15,200 to 4.9 million BTU – enough to replace even large boilers.

In this diagram, 10 tankless water heaters are electronically connected. Each bank of five is controlled by a Multi-System Control Board. These boards are connected to each other with Multi-System C2 cables. One Multi-System Control Board will serve as the master control for the entire system.

M MSB-M control board
A Connector Cable A (part of Multi-System Control Board kit)
C1 Multi-System C1 Cable – used for connecting water heaters within a banked system (up to 5 TWH)
C2 Multi-System C2 Cable – used for connecting multiple multi-system control boards (up to 5 TWH)

Illustration applies to use of Multi-System Controller with and without the Rinnai Tankless Rack System.

* Includes: Control Board; Cable A (23 in / 585 mm), Cable B (9.8 ft / 3 m), brackets, ties, and screws.

** Includes: Cable B (9.8 ft / 3 m), brackets, ties, and screws.

Includes: MSB Cable A (13.1 ft / 4 m), terminal connectors

The Rinnai Tankless Wall-Hanging Rack

The end of emergency replacement hassles

Capacity in a whole new form

Shipped fully assembled in a variety of configurations, the new Rinnai Tankless Wall-Hanging Rack (TRW) arrives ready to install, and ready to impress.

A complete and fully modular solution, the TRW features a sturdy, pre-assembled rack with multiple Rinnai Tankless Water Heaters already mounted and connected to each other. Together, the units have enough capacity to suit light commercial water heating requirements, replacing tank-style water heaters with one simple, energy-efficient solution.

  • TRW racks are stocked by distribution, making them perfect for emergency replacement
  • Quick and easy installation with included wall-hanging bracket
  • Lightweight steel box frames
  • TRW racks come with two to three tankless water heaters per rack, which can be combined with up to 25 models and provide up to 4.9 million BTU
  • Indoor or outdoor installations
  • Fits, fully assembled, through standard 32-inch doorways and on elevators
  • Modulation technology with turn-down ratios of up to 327:1 to ensure hot water delivery and efficiency
  • Use with or without storage tank and/or recirculation loop
  • Wi-Fi Ready

Rinnai Tankless Rack System (TRS)

STREAMLINED SOLUTIONS for Simpler Installations

Now you can harness all the benefits of tankless water heating technology, preassembled and ready to replace the boiler in your commercial water heating system.

Built with superior quality and reliability, Rinnai’s Tankless Rack System™ offers the perfect BTU upgrade of an old-style domestic water boiler that is reheating storage tanks. On retrofit applications, often times you can keep your existing tank and pump and simply replace with the lower cost and better performing TRS.

Pre-assembled with one connection point for gas, water, electrical and the condensate drain, the Rinnai Tankless Rack System (TRS) offers two new features* that simplify installation while reducing labor time and cost.

Multi-Unit Power Duplex Receptacle:

  • Allows for ease of wiring a central power source for multiple tankless units (the junction box is conveniently located on the outside of the frame for easy installation to new or existing power)
  • Located underneath the middle frame support
  • UL approved

Common Condensate Drain:

  • Assembled 3/4” Schedule 40 PVC
  • Assembled with a slope that is adjustable in either direction

The TRS installs in place of an old-style boiler and provides built-in redundancy by banking individual tankless water heaters to insure your hot water supply keeps flowing even if a unit is down. The TRS comes standard with our new condensing C199 tankless water heater that boasts a 96% thermal efficiency and a heat exchanger built for the demands of commercial applications.

Simulated TRS With Storage Installation Shown

Flexible installation is another TRS strong suit. It fits through a standard 32” doorway, has various venting options including PVC and the Rinnai Common Vent system, and can be mounted indoors or outdoors, either floor-standing or wall-mount.

By offering a significantly lower upfront capital investment and reduced annual maintenance costs, the overall cost of ownership can be lower vs. the same BTU boiler. Couple that with the Rinnai reputation for unsurpassed quality and technical support – plus the added benefit of having the Rinnai Commercial Solutions Team help with free sizing and application engineering – and the TRS is the business- friendly replacement for even the largest boilers.

Simulated TRS With Recirculation Installation Shown


Tank size: capacity of water in gallons inside storage tank as stated by manufacturer
Recovery pump: pump that will circulate water from tank to TRS during recovery period
Recovery Flow Rate: flow rate in GPM at which volume inside tank is being recovered
Recovery GPH: the water heater’s ability to replenish hot water as it’s drawn from the tank
Recovery efficiency: the ratio of energy delivered to the water to the energy content of the fuel consumed by the water heater
First Hour Delivered (Gal): useable volume of water that can be drawn in one hour and is determined using the following formula: First Hour Delivered (Gal) = Recovery GPH +Tank capacity x 0.70
Temperature rise: temperature difference in °F between the TRS set point and the incoming water temperature

TRS / TRW Highlights

  • 96% thermal efficiency
  • Commercial ENERGY STAR® certified
  • Direct replacement for domestic boilers
  • Power receptacle and common condensate drain included on TRS interior models*
  • Indoor / outdoor / wall / floor mount installations
  • Multiple venting options
  • No ASME inspection required
  • Available factory-direct preventive maintenance


This chart should be used only when the existing or specified system is known. Select TRS model to the left of chart. Use existing or specified storage tank with TRS selection. Reference chart to left for recovery GPH performance. To calculate “First Hour Delivered” add 70% of existing or specified tank volume to recovery GPH.

Product Sizing Disclaimers

  • This Sizing Reference Guide and all information contained herein is based on the proper installation and use of (1) a series of Rinnai tankless water heaters which are piped to a storage tank and (2) an adequate and properly-sized Recovery Pump that will recover the storage tank (i.e., that will circulate water from the Rinnai tankless water heaters into the storage tank) thereby allowing the Rinnai tankless water heaters to properly heat the water for the storage tank.
  • This Sizing Reference Guide is intended to be used as a guide only and not as a replacement for a professionally-engineered project. For additional information, please refer to the Rinnai Tankless Rack System Manual or contact the Application Engineering Department at Rinnai America Corporation by calling (866) 383-0707.
  • Multiple TRS should be installed in parallel using a secondary manifold from the building’s cold and hot water supply. You should reference the particular section of the TRS installation manual for piping multiple racks.
  • The building’s circulation pump must be controlled by an aquastat, timer, or both.

*Power receptacle and common condensate drain come standard on the following floor-standing, interior TRS models: TRS03, TRS36, TRS03IL/LW, TRS04, TRS46, TRS05, TRS06. Exterior TRS models will not have a power receptacle, but will ship with a condensate drain.