Frequently Asked Questions

The term "cold water sandwich" effect is used to describe the introduction of cold water into the hot water supply line during frequent on/off operation of an instantaneous hot water heater. When present, this effect appears as a momentary drop in hot water temperature as it is discharged from a hot water supply outlet (i.e., shower, tub, or faucet). It’s a phenomenon that is present in the operation of all instantaneous and on-demand tankless water heaters, but is minimized with the high-tech design of Rinnai Tankless Water Heaters.

Rinnai Tankless Water Heaters are microprocessor–controlled, and when water flow ceases, they remain in a "ready-to-fire state" for approximately one minute. If water flow begins within the first minute following water flow stoppage, the water heater will fire back up within one to two seconds. This minimizes the "cold water sandwich" effect that would otherwise be experienced with a less innovative tankless water heater.

There are two types of periodic maintenance that your service technician can perform to keep your Rinnai Tankless Water Heater running smoothly:

The in-line screen filter should be checked periodically for debris (time between filter checks will be dependent on water quality).

The unit should be flushed periodically (time between flushes will be dependent on water quality) to keep the unit free of scale and lime. This process should be completed by a professional installer. Please contact an installer near you.

Please contact an installer near you.

The wait time to get hot water is primarily determined by the distance between the water heater and the point of use. Rinnai Tankless Hot Water Heaters produce hot water within a few seconds of first water flow from a cold start. However, you must purge all the cold water out of the pipe between the hot water heater and your point of use. For example, if your kitchen sink is 50 feet from the hot water heater and the water flow rate is one gallon per minute, it should take approximately 90 seconds for hot water to reach your sink.

Because of their small size, you can place Rinnai Tankless Water Heaters in locations that you could never place a tank. If you can place your hot water heater close to your primary points of use—such as your kitchen or master bath—you drastically reduce the wait time.

Make sure the tankless water heater is connected to gas, water and electricity supplies, and that the power is turned on and the gas is turned on.

During cold weather, when the exhaust temperature is much hotter than the outside air, the exhaust fumes condense producing water vapor.

The fan is designed to continue running for a short time after the flow of water stops. This is to ensure constant water temperatures during rapid starting and stopping, as well as exhausting any residual gas flue products from the unit.

We have specific tankless water heaters available that are certified for installation in Mobile and Modular Homes. These units include both our Luxury and Value Series units.

The fan is designed to continue running for a short time after the flow of water stops. This is to ensure constant water temperatures during rapid starting and stopping, as well as exhausting any residual gas flue products from the unit.

Rinnai Tankless Water Heaters typically require a ¾" gas line to provide a sufficient gas supply to the unit’s burner. However, if there is sufficient pressure and the gas line is short enough, there are some cases where a ½" gas line can be used, which is the most common size used in the United States and Canada. This can make switching from a tank-style water heater to a tankless water heater faster, easier and less expensive.

As with all tankless water heater applications, installers should check and abide by local gas-pipe size and licensing rules and codes.

Rinnai offers a limited Field Conversion Program. Kits for converting gas tankless water heaters from natural gas to propane or vice versa are available for most models. Please have your installer/service provider call 1-800-621-9419 to find out if your model qualifies and to obtain a detailed step-by-step conversion instruction kit.

These kits are available directly from Rinnai, and will be shipped only after the installer/service provider has contacted Rinnai’s technical support services and consulted one of our technical specialists, to ensure the installer/service provider performing the conversion is qualified to do so. The Field Conversion Program is available for products which have been installed and where gas type availability has changed. It will not be approved for use in conversion of non-sold inventory or mobile homes.

We do not offer a battery backup system—also known as an Uninterrupted Power Supply (UPS)—for our products. Please check with your local retail store for a UPS that may be suitable for your needs.

We do not make an electric model. There are several potential drawbacks to electric tankless water heater units: First, the power requirements of electric units large enough to provide hot water for a typical household can be prohibitive. For example, a unit that can provide three gallons per minute with an 80° F temperature rise would require about a 150 amp 230VAC circuit. This is about eight times the power required for a three-ton central air conditioning system.

Second, the relative operating cost of electric tankless water heaters is much higher than gas water heaters. Based on national averages, electricity costs almost twice as much per BTU as natural gas. Even with propane, gas tankless water heaters are considerably less expensive to operate than those that run on electricity.

Rinnai Tankless Water Heaters operate using natural gas or propane and have an electronic ignition.

Rinnai Tankless Water Heaters are not UL certified, but are certified by CSA International to ANSI Z21.10.3 Standard Gas Water Heaters, Volume III, Storage Water Heaters with Input Ratings Above 75,000 Btu/h. However, the following internal electrical components are UL certified:

  • a. Transformer E (UL 1411)
  • b. Relay (UL 41515)
  • c. Wire & Conduit (UL 1430)

Yes. Rinnai Tankless Water Heaters feature freeze protection for outside temperatures as cold as -22° F (-30° C) for indoor models or as cold as -4° F (-20° C) for outdoor models when protected from direct wind exposure, as long as there is both power and gas supply to the appliance. The pipes feeding the unit MUST be heat-traced and insulated to provide freeze protection.

Rinnai strongly recommends the installation of an optional drain-down system on units installed outside in cold climates. This system, if installed, will allow all water inside the unit to drain out if there’s a power and/or gas outage or a component failure in the product. See the owner’s manual for optional drain-down system piping.

Please keep in mind that Rinnai Tankless Gas Water Heaters need to see a demand of over 0.4 to 0.6 gallons per minute of water flow through the hot side in order to ignite and 0.26 gallons per minute to stay in operation. If the flow rate falls below this level, the unit will turn off because it senses that hot water is no longer needed.

There are several possible solutions to minimum flow rate issues: lowering the temperature on the unit to a more comfortable temperature to avoid cutting in too much cold water; cleaning the inlet water filter on the cold water inlet of the unit (sediment buildup in the filter can decrease flow into the unit); cleaning or removing the aerators from showerheads or fixtures; or replacing low-flow showerheads or fixtures.

If you believe that this is not the issue, contact your original installer or plumber to service the unit.

The maximum flow rate that our tankless hot water heaters can produce depends on temperature rise — the difference between the set temperature of the unit and that of the incoming ground water. For instance, if you set the temperature of the unit to 120° F and the incoming groundwater temperature is 60° F, the temperature rise is 60°.

The lower the set temperature, and the higher the incoming groundwater temperature, the more hot water flow the unit can produce and vice versa. If sized correctly for your application, the unit(s) should not have a problem producing enough flow for your hot water needs.

The life expectancy of a Rinnai Tankless Hot Water Heater is up to 20 years. Actual performance will vary depending on water quality, usage rates, environmental conditions, and regular maintenance.

Unfortunately, our tankless water heaters cannot be used in houseboats or RVs. However, we have specific units available that are certified to be installed in Mobile and Modular Homes. These units include both our Luxury and Value Series units.

Rinnai Tankless Hot Water Heaters cannot be used for heating pools or spas. The chemicals used would damage the components of the water heater.

Rinnai recommends that tankless water heater installation should be performed by a licensed contractor who is trained to handle the plumbing, gas, electrical and venting aspects of a tankless water heater and is aware of all local and national codes. Having a non-licensed professional perform the installation can cause operational and performance issues.

Find a Rinnai Independent Dealer

Rinnai Tankless Water Heaters require 120 volts AC, 60 Hz and less than three amps.

No. Rinnai Tankless Gas Water Heaters have a direct-spark electronic ignition.

Yes. Venting of Rinnai Condensing Boilers through a stainless steel chimney liner is approved. Local codes will dictate the ability to use this type of system. Contact your Rinnai dealer for more details if needed.

Find a Rinnai Independent Dealer

For the Rinnai Q175 Combi Boiler, there is no minimum domestic hot water activation rate, since the domestic hot water is coming from a storage tank.

For Rinnai E Series models, a flow sensor activates domestic hot water at 0.4 gallons per minute or more.

Yes, but common venting is not yet approved and a custom-sized low loss header may be required for cascading units.

Rinnai's cascade controller can address up to eight Rinnai Heating Boilers. Five controllers will also cascade together for a total of 40 units.

In closed-loop (not domestic hot water) applications, an ASME approved 30-psi pressure relief valve is included with every Rinnai Condensing Boiler. However, since the maximum allowable working pressure of the boiler's heat exchanger is rated by ASME up to 45 psi, the installer can replace the 30-psi PRV to suit the needs of the application.

Rinnai E Series Boilers are limited to 30 psi maximum PRV due to their internal expansion tank.

At this time, it is not recommended to common vent multiple Rinnai Condensing Boilers.

Delta T is defined as the difference between incoming groundwater and a water heater's (in this case, a boiler's) set temperature. Delta T helps determine the flow range of a boiler.

A Rinnai Condensing Boiler will always try (through the pump or the BTU output) to maintain its default and most efficient temperature, which is 36° F. If its Delta T does not stay between 18° F and 45° F, burner operation will temporarily cease and a warning (or error) code will be displayed. Please understand this is only on the boiler side of the operation. The system or secondary loop will likely have a different Delta T based on system design. With a low loss header, the Delta T of the boiler and secondary loop do not have to match.

The size of the expansion tank depends on the size of the overall system. Rinnai E Series Boilers come equipped with an integrated expansion tank in anticipation of smaller overall systems, while Rinnai Q Series Boilers come with a slightly larger expansion tank.

Your Rinnai dealer can help ensure you have the right expansion tank for your system.

Find a Rinnai Independent Dealer

Rinnai Condensing high-efficiency Gas Boilers are designed to fire and circulate the pump as needed to help prevent freezing. This does not, however, guarantee the entire heating system is protected, and can depend on the overall system design in your application.

Rinnai Boiler Heating Systems require 120 volts/5 amps of power. Contact your Rinnai dealer with questions regarding your power supply. To find a dealer near you, click here.

Yes. A low loss header—also referred to as a hydraulic separator —is included with every Rinnai Boiler. The low loss header isolates the boiler from the rest of the system to protect the components within the boiler (heat exchanger, pump, etc.) and to optimize overall performance, efficiency and longevity for the Rinnai Boiler.

In most cases, an outdoor reset sensor is recommended for and is included with all Rinnai Condensing Boilers.

Rinnai Condensing Boiler heat exchanger tubing is made of 316 stainless steel—selected for resistance to corrosion.

Your Rinnai dealer can help you evaluate what size Rinnai Home Heating and Water Heating Boiler is right for your space by conducting an industry-standard heat loss calculation. Boiler selection will also be dependent on overall system design, type of heat delivery, etc.

Find a Rinnai Independent Dealer

Your Rinnai dealer can help you evaluate what size Rinnai Home Heating and Water Heating Boiler is right for your space by conducting an industry-standard heat loss calculation. Boiler selection will also be dependent on overall system design, type of heat delivery, etc.

Find a Rinnai Independent Dealer

No results were found.

Rinnai Direct Vent Gas Wall Furnaces require 120 volts AC, 60 Hz and 121 watts.

Rinnai recommends that direct vent wall furnace installation should be performed by a licensed contractor who is trained to handle the plumbing, gas, electrical and venting aspects of a direct vent wall furnace and is aware of all local and national codes. Having a non-licensed professional perform the installation can cause operational and performance issues.

Find a Rinnai Independent Dealer

No. Rinnai Direct Vent Wall Furnaces are natural gas or propane furnaces that have an electronic ignition.

Rinnai Direct Vent Wall Furnaces are approved for mobile homes and manufactured homes; however, they are not approved for RVs.

Rinnai Direct Vent Wall Furnaces are beige. However, model numbers ES38 and EX22C are also available in white.

Rinnai Direct Vent Wall Furnaces are not UL certified, but are certified by CSA International to ANSI Z21.86 Standard Vented Gas-Fire Space Heating Appliances. However, the following internal electrical components are UL certified:

  • a. Transformer (UL QL66-532NA)
  • b. Limit Switches (E52529)
  • c. Wire & Conduit (UL 1430)