First on the list is the non-condensing AO Smith ATO-510-N. It’s one of the best tankless water heaters in AO Smith 510 series. This unit uses up to 199,000 BTUs to deliver a max flow rate of 10 GPM. This makes it well-suited for residential/commercial applications. As for its fuel efficiency, the AO Smith ATO-510-N use non-condensing technology to achieve an Energy Factor of 0.82.
The Unit at hand runs on natural gas but it supports two models (indoor and outdoor) to accommodate for your needs and preferences. This should be a big deal if you, just like me, prefer outdoor units over indoor ones because they are a lot safer that way.
Speaking of safety, this unit comes equipped with an anti-freezing circuit which prevents your pipes from freezing which is very useful especially for people who live in colder climates. The ATO-510-N also comes with an overheat cut-off fuse to prevent you from damaging the unit due to excess pressure. To avoid overheating, go with a basic ventilation system and save yourself the trouble (some sort of ventilation is also necessary for outdoor units).
When it comes to user friendliness, this unit is definitely a top ranker. Thanks to the inlet and outlet thermistors, you can constantly keep an eye on temperature instead of playing the guessing game every time you need to take a shower. That being said, this unit definitely stands out as one of your best tankless options.
Second AO Smith tankless water heater goes by the code name ATI-310-P, and and as you can tell, this model is significantly less powerful than the previous one yet it is still a solid competitor. With a continuous flow rate of 8.0 gallons per minute, this tankless water heater can provide enough hot water for a household of at least 3 bathrooms at ease, not to mention the regular house keeping requirements.
When it comes to safety features, the ATI-310-P is on point. The unit comes with a built-in freeze protection to prevent your pipes from freezing in cold weather, an overheat cut off fuse as mentioned earlier, inlet/outlet thermistors so you can always keep an eye on water temperature and last but not least a flame sensor which will warn you in case of fire.
The warranty life on this unit, like other AO Smith tankless water heaters, is worthy of a strong mention. This model comes with a 12 years long warranty on heat exchanger for residential applications and 5 years warranty on parts.
Last but definitely not least is the AO Smith ATO-110-N which is also a non-condensing model designed for residential and commercial use alike. This water heater can provide a continuous flow rate of 6.6 gallons per minute which is significantly compatible with most middle class users. The reason I’m saying that is because this model can easily take care of a house of 2-3 bathrooms, washing machine and a dish washer.
As with most AO Smith tankless water heaters, the ATO-110-N comes in two models: indoor and outdoor, both these models support propane and natural gas to accommodate for a wider range of users. Nevertheless, there is no difference between all of these models except the powering fuel, so make sure you pick the version you’re most comfortable with.
This tankless water heater is no different to its siblings when it comes to durability. Just like most AO Smith tankless water heaters, the ATO-110-N is very reliable and user friendly. Safety features are also pretty much alike to ensure your and your family’s well being. Namely, the built-in anti-freezing circuit, the overheat cut-off fuse, the flame sensor and the outlet and inlet thermistors for constant temperature monitoring.
Although the ATO-110-N is considerably cheaper than the stronger models, the manufacturer does not reduce the warranty life a bit. Thus, this model comes with a 12 years heat exchanger warranty for residential users (but you must make sure, you hire a licensed professional to install the unit) and 5 years warranty on parts.
In the end, the AO Smith regularly earns some of the most positive reviews all over the internet and that is not a coincidence. Their tankless water heaters are very durable and reliable, you just make sure you pick the one that suits your needs best and I assure you it will be your first and last heater.
If I had to pick some criticisms for AO Smith tankless watet heaters, it would be just the price. Their tankless water heaters cost a pretty penny.