John Wood Tankless Water Heaters

John Wood tankless water heaterJohn Wood tankless

Consider the following facts and tips when selecting the best John Wood tankless water heaters for on-demand heating of potable water in residential and light commercial applications.

The article reviews model types, top features, and the benefits of the combined on-demand and condensing technology.

Top features and benefits

John Wood tankless water heaters are designed as the non-condensing and condensing, or low and high-efficiency models. Condensing models also offer the most advanced features, and with the high energy factor, are Energy Star compliant.

Besides domestic water heating, tankless models are also used with hot water tanks, recirculation systems, and combined water and space heating.

High efficiency

All the John Wood water heaters designed for on-demand water heating are using Takagi technology.

Models that utilize condensing technology are ultra-efficient that come with two heat exchangers; one made of commercial-grade copper and the second one made of stainless steel, making the units resistant to the aggressive water action and are more durable than the heat exchangers found on most of the tankless models.

Such a combination allows the usage of the latent heat from the flue gases for high thermal efficiency of over 90%. Non-condensing models can provide an energy factor of 0.82 and 0.83, which is lower than the efficiency found in condensing.

All models use electronic ignition for reliability and convenience and fully modulating gas valves allowing heaters to adjust the temperature and gas consumption based on the requirements. This is what reduces energy consumption while saving the consumers money.

Flexible venting

With the higher thermal efficiency, especially condensing models with the energy factor in the range from 0.91 to 0.95, there is less heat wasted through the flue vents. The products of combustion have a lower flue temperature, which allows venting with the approved PVC, CPVC, and PP pipes, for added flexibility and lower costs. The direct venting system provides excellent flexibility during installation, using the two-pipe system with the horizontal or vertical termination. If the two-pipe system is not a viable solution, a concentric vent kit can be installed.

If the non-condensing models are your option to buy, some models come with the built-in concentric venting system with the sealed combustion providing better protection.

The non-condensing models are power vented, but if it is needed can be convertible to direct vent with sealed combustion.

Fast hot water delivery

For homes where the higher demand for hot water is needed and with the stable temperature and fast delivery, you can use the FlowTHRU storage tank that is specifically designed to work with John Wood tankless water heaters for added comfort. For the supplemental heating, FlowTHRU storage tanks are equipped with one electric heating element, an adjustable thermostat, and a side connection to a circulation pump.

While the maximum water flow rate in residential applications of the most powerful unit is around 10 GPM, which is enough for up to 4 bathrooms, a much greater amount of hot water can be delivered by using the Easy-link and Multi-link, which is important in large applications. Condensing model JWT-540 and non-condensing JWT-510C are the only residential models that can use these two features, so up to 4 units can be connected into one system when using an Easy-link system and up to 20 units when using the Multi-link system.

A new model 540P is even equipped with the recirculation pump delivering hot water faster than the units without the pump, increasing the comfort for the users.

Advanced electronics

Condensing water heaters feature advanced electronics that provide an easy temperature adjustment right on the built-in screen, diagnostics, and features that help prevent scalding burns, also advanced safety features such as the internal freeze protection system.

All the condensing units are using advanced features such as the self-diagnostic system for your safety and convenience. An integrated controller allows you to change and monitor the temperature of the hot water and check other parameters and error codes if the problem exists. On non-condensing units, the error code will show up on the remote controller and computer board.

A remote controller is provided with the non-condensing models.

Feature highlights

  • Condensing models available
  • Ultra-Low NOx models available
  • Power and direct venting with the sealed combustion for indoor models are available
  • Maximum exhaust vent piping length is up to 100 ft.
  • Warranty - 15 years
  • Convenient automatic ignition
  • Safety: thermistor and hi-limit switch for the exhaust gas, freeze protection...
  • Some models use Easy-link up to 4 units without a multi-unit controller
  • Multi-Link connects up to 20 units into one system so that the power can modulate from 13,000 to 4.0 million Btu/hr
  • 240, 340, and 540 series are condensing models
  • Recirculation pump control mode available on 510 water heaters
  • Temperature adjustment from 100 to 140 F, or 100 to 185 F on 540 H models


Model/Features BTU
Water Flow
# of baths Remote controller
JWT-240H-N 15,000
0.95 6.6 99
2 Yes
JWT-320H-N 13,000
0.91 8.0 99
3 Yes
JWT-340H-N 15,000
0.95 8.0 99
3 Yes
JWT-520H-N 10,300
0.91 9.0 99
4 Yes
JWT-540H-N 15,200
0.96 10.0 99
4 Yes
JWT-110-N 19,500
0.82 6.0 99
2 Yes
JWT-310-N 11,000
0.82 8.0 99
3 Yes
JWT-510-N 11,000
0.82 10.0 99
4 Yes


If you are looking to buy a new water heater, or replace an old and bulky one with something smaller and compact, and get fresh hot water delivered anytime and in continuous supply without worrying that your shower will end soon, John Wood tankless is a brand to consider.

The tankless models are smaller but powerful, environment-friendly, and as the tank type can operate using both natural and propane gas, but providing more savings with the modulating power. They last longer, any of the components can be replaced, there is no stinky rotten egg odor problem, no corrosion issues, tank leaking, and the warranty is even longer – 15 years provided by the manufacturer. That is why the tankless is a good pick.

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