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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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Common Venting

The epitome of stremlined installation

With Rinnai Common Venting (CVent), up to eight Tankless Water Heater (TWH) units share the same CVent system—which means significantly fewer wall or roof cuts, less labor, and longer vent lengths than ever possible with single-unit TWH venting. The system is also fully CSA-certified and uses polypropylene PP—a more reliable venting material for the job, able to withstand exhaust temperatures up to 230° F.

Clean, easy, cost-saving install:

  • Vent lengths up to 100’ with seven TWH units; 41’ with eight TWH units
  • Easy push fit joints—no cement or glue required
  • Non-return valve prevents backflow of exhaust gases into idle tankless water heaters
  • In-line or back-to-back installations; horizontal or vertical termination
  • More options than ever before for indoor installations
  • Reduces wall penetrations

Along with our existing common venting options, Rinnai has five common vent solutions including:

  • Room Air for the U.S.
  • Direct Vent with side wall intake and vertical exhaust for the U.S. and Canada*
  • Direct Vent for Canada

In a common vent room air configuration, multiple unit installations like the Tankless Rack System (TRS) use the air in the room for intake air and therefore require only one vent penetration for the exhaust. This means one less cut, saving time and money for system installation. Room air can be used only in applications that utilize the approved Rinnai common vent method.

For more flexibility, common venting can now be done in different plane configurations with a vertical exhaust vent and horizontal air intake.

Both of these new solutions use Rinnai’s existing 8” venting material and are now approved for markets that require ULC S636 for venting.

* Exhaust must terminate vertically.

Single-unit vent solutions:

The dual venting configuration on the top allows for maximum flexibility for installers and dealers — one Concentric vent or two PVC/CPVC pipes can be used for venting.

  • Concentric Polypropylene
  • Dual-pipe PVC/CPVC
commercial venting optionscommercial venting options

* C199 only.

Common venting kits and accessories

Product Sizing Disclaimers

  • You must reference the Common Vent Installation Manual before making the final selection of vent components which are applicable to your Installation.
  • All intake parts except the intake termination and PVC adapter are field sourced by the installer and are not provided by Rinnai.
  • If spacing between water heaters is GREATER than 20.5” (center line to center line), the installer must purchase a vent extension and cut to the appropriate length. Refer to the manual for further instructions.
  • The length of each additional vent extension must be included in the maximum allowable vent length.
  • Maximum equivalent length cannot exceed 100 ft for 7 units or less or 41 ft for 8 units.
  • For water heater quantities outside the scope of this document, please contact Rinnai Applications Engineering Department.
  • CVent is not approved for use in Canada.

CVent elbows equivalent lengths:

45° = 3 ft, 90° = 6 ft



Performance-enhancing accessories can add even more flexibility to precisely engineered Rinnai Tankless Water Heaters.

Digital temperature control

Rinnai units are digitally controlled for a precise temperature set-point. The MCC-91 controller is needed for temperatures above 140° F to 185° F for Ultra and Luxury models (not required for C199).

Condensate neutralization tank (103000067)

The condensate produced by condensing tankless water heaters is acidic and has the potential to harm the environment and sewer system. Rinnai’s Condensate Neutralization Tank will neutralize the condensate to a more neutral pH level before it is discharged to drain.

Maintenance indication switch (MIS) (103000037)

The MIS is used to connect Rinnai Tankless Water Heaters to a central building management system (BMS), which then notifies the building or facility manager if a unit is experiencing a critical error code. This helps to minimize downtime associated with non-operating units and ensures any problem with individual or multiple units is quickly resolved.

Multi-system controller (reu-msb-m: master controller; REU-MSB-C1: tankless to tankless cable; REU-MSB-C2: MSB-M connection cable)

Connect up to 25 TWH units for your most demanding applications. Controller: rotates unit activation to ensure that each gets equal run-time, greatly extending the overall life of the system.

Ezconnect® Cable (REU-EZC-1-US)

Electronically connects two units so they function as one hot water source.