Bosch Therm C 1210 ES Review

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Explore the Bosch Therm C 1210 ES review and find the top features which make it the most powerful tankless water heater with the highest flow rate of all Bosch on-demand heating appliances.


Bosch Therm C 1210 ES was built as the condensing water heater so it can work with the ultra-high thermal efficiency, and at the same time successfully compete with other brands such as Noritz, Rinnai, Takagi...

Bosch condensing appliances use natural or propane gas to heat water directly and the flue gases to heat the incoming cold water, which results in lower exhaust temperature and use of PVC vents, instead of more expensive stainless steel.

High energy efficiency of 98% means that only a few percents of the heat is lost, while most of the energy goes toward heating the cold water. High performance also means lower emission and less pollution. Since the model was designed with the gas input of 225,000 BTU, it is not Energy Star certified (maximum power is 199,900 BTU to be eligible for ES program), but it can heat and provide lots of hot water, which can reach high 12.1 gallons per minute.

This model is also ASME certified, which ensures the high quality of materials and craftsmanship; and with the superior design Bosch is able to provide long 15-year warranty, which is longer the warranty than on most models from other manufacturers (12-year is the maximum).


Bosch Therm C 1210 ES

All tankless water heaters from Bosch, including the Therm C 1210 ES are designed to compact and small, which allows wall-mount installation, and with the sealed combustion chamber, installation almost anywhere inside your home.

As most of the modern tankless water heaters, Bosch Therm C 1210 ES does not use the pilot light to light the main burner but the electrode and electronic ignition. When the main burner is lit, thanks to its innovative design, maximum heat energy goes toward heating the water in the first heat exchanger, while the lost energy in the flue gases heats the incoming water in the second, aluminum heat exchanger.

The flue gases are further taken out through the direct vent system, installed either horizontally or vertically and with the concentric or dual pipe system.

Bosch Therm C 1210 ES is available as the indoor and outdoor model (with the optional outdoor kit), which gives more flexibility during the installation.

Modulating gas valve and its constant gas - air ratio control makes the water heater work in the range from the minimum gas input of 25,000 to the maximum of 225,000 BTU. And with the modulating water valve, the comfort is increased while the temperature control is improved.

It was said that this Bosch condensing water heater provides high 12.1 GPM which is enough for large homes with up to five showers. If there is a need for even more hot water, the Intelligent Cascading system allows connecting up to 24 units into the one system.

At the front of the unit, there is a control panel with the LCD display that shows the temperature, few indicators and error codes, for easy troubleshooting, ON/OFF and program/temperature control buttons. The wireless remote is optional and is used to control the temperature of the outgoing hot water.

Safety features

  • Built-in freeze protection, down to 5 F and only for short-term

  • ECO for overheat protection
  • Flame failure device (ionization sensor)

  • Outlet temperature sensor
  • Backflow temperature sensor

  • Flue temperature sensor
  • Water drop protection

  • Condensate drain


  • Temperature range: 100-140 F

  • Accuracy: +/- 2 F
  • Maximum vent length 63 ft.

  • Vent size: 3 or 4 inch
  • Maximum altitude 8,000 ft.

  • Minimum water flow to activate: 0.5 GPM

  • Water pressure: min 30, max 145 PSI
Bosch Therm C 1210 ES is a powerful tankless water heater that not only heats potable water in your home but can be used for space heating, for recirculation and instant hot water delivery and as the back-up in solar water heating.

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