Rinnai RH180 Hybrid Tank-Tankless Water Heater

Write / Read Reviews

Rinnai RH180 selection, use, and review of the main characteristics. Find out how Rinnai water heater combined technology provides great savings and flexibility.

The RH180 water heater is actually known as the automatic circulating heater that consists of one large conventional water tank and a tankless unit that is attached to.

The heat exchanger is located in the tankless unit where cold water is heated to the set temperature and from there it is transferred to the storage tank by the circulating pump.

Both tankless and tank part of the system have the same elements as they would have as separate systems; the heat exchanger, fan, electric board, sensors, electric ignition, also anode rod, dip tube…


Rinnai offers only one model that is designed with the 40-gallon tank capacity, but the first-hour rating is very high, 180 gallons per hour and recovery at 90 F rise is 89 GPH.


The unit is used for heating potable water in residential applications, also for filling large or whirlpool spa tubs, for example. It cannot be used for manufactured homes or outdoor installations.


Incoming cold and outgoing hot water pipes are attached to the tank water heater while the gas piping to the tankless unit, where the gas control valve is.

Fuel type

Rinnai RH180 is factory set to use natural gas but can be converted to use propane gas also, and the gas input, in this case, is slightly lower; 91,300 BTU vs. 87,300 BTU.


Rinnai RH180

Rinnai RH180 can only be installed indoor and it requires an adequate amount of air for gas combustion and dilution of flue gases.

Combustion air can be used either from inside or outside the building and the unit gets it through the combustion air screen located at the front of the tankless unit.
Per manufacturer’s instructions, the water heater must be terminated vertically to the outside of the building, while it is not certified for side horizontal vent terminations.

The electric blower is used safely to move the flue gases through the 4-inch vent pipe (or larger) that is attached to the tankless unit. Due to the high thermal efficiency of over 80%, it results in lower flue gas temperatures.

Temperature controller

The temperature controller is built-in into the front cover and it allows the temperature change in five settings: 1=110 F, 2=120 F, 3=130 F, 4=135 F and 5=140 F; while if there is a problem with the unit, the error code flashes (see the list of codes with the fix). The green led diode under the LCD display indicates when the water heater is in recovery mode. The buttons on the controller allow you to change the temperature, display the water flow and temperature of the incoming water.


Storage Tank (Gal) 40
Power (Btu/hr) 59,500 - 91,300
(47,600 - 87,300)
First Hour Rating (Gal) 180
Thermal Efficiency 80%
Venting 4" UL B-Vent
Temp. settings (F) 110-140
Noise Level (dB) 50
Weight (pounds) 168.5
Dimension (inch) 20-51-28


  • Flame rod

  • Combustion fan rpm check

  • Combustion air Carbon Monoxide sensor

  • Over current glass fuse

  • Remaining flame

  • Thermal fuse

  • Boiling protection

  • FVIR sensor that protects the heater from flammable vapors and the accidental ignition outside the combustion chamber

  • Freeze protection uses the pump to cycle warm water from the tank into the engine


Rinnai RH180 comes with the warranty of 10 years for the heat exchanger and 6 years on the storage tank.

Review, Ask and Comment

Pictures - courtesy of Rinnai WH company

Home > Rinnai gas water heaters > Rinnai RH180

water heaters

fireplace gas line