Hayward H400FDN Review & Rating

  • Hayward H400FDN Review
9.7 score
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Thermal efficiency of 84%

Easy-to-use LED control panel

Heats water by three to five degrees per hour

Also great for saltwater pool systems



Hayward H400FDN 400,000 BTU Review

The Hayward H400FDN is a universal, energy-efficient solution for heating any new or existing pool. With a state-of-the-art hydraulic design, it enjoys a best in class thermal efficiency of 84 percent, allowing it to effortlessly and efficiently heat a pool while running less.

The energy-efficient Hayward H400FDN also features a high-quality Cupro nickel heat exchanger, low NOx emissions, and the ability to be installed on most new or pre-existing pool equipment pads, making it easy to install and capable of heating your pool or spa for countless years of enjoyment.

Thanks to its forced draft system, it constantly circulates air through its Fire Tile combustion chamber at a specific flow rate, which also eliminates any outside weather variables that may negatively affect its performance. Therefore, the installation of a high-wind stack often needed for other models is not needed with the H400FDN.

To top it all off, the folks at Hayward decided to equip the H400FDN with an easy-to-use LED control panel as well, allowing you to comfortably and effortlessly monitor and control your heater with the touch of a button.

All in all, this pool heater is well-made, energy-efficient, and will provide you with a warm and inviting backyard oasis for years to come. Unless you have an Olympic-size pool, the Hayward H400FDN is a pool heater worth considering.

How It Works

While it has a number of great features, one of the Hayward’s best features is its polymer header, which is designed to make it one of the most efficient heaters on the market. In fact, the Hayward H400FDN is capable of heating water by three to five degrees per hour, meaning it can comfortably heat a typical pool in only three hours. In addition to heating faster than many other pool heaters out there, it’s also more efficient, saving you money on your electric bill each and every month.

Heating Size

As one of the best pool heaters around, the Hayward H400FDN is capable of working on nearly any pool or spa made today. Since it is designed as a “universal” model, it can fit in a multitude of locations and work with any pool. Therefore, it’s incredibly powerful and capable of heating large amounts of water.

How to Use It

Unlike old-fashioned pool heaters with knobs and buttons galore, this state-of-the-art pool heater is super easy to use. Not only does it have a modern and easy-to-use LED control panel, but it only has a few buttons to press as well. You definitely won’t need a manual to operate this modern heater.

Final Words

While not necessarily a low-cost pool heating solution, this heater is a great option for any pool or spa owner in search of a powerful, efficient, and reliable means of enjoying their swimming pool throughout the year. With unique features and a solid-construction, this well-made and thoughtfully designed pool heater is tough to beat.


Cupro Nickel Heat Exchanger – Like other Hayward Universal H-Series pool heaters, the H400FDN comes equipped with a Cupro nickel heat exchanger, making it incredibly corrosion resistant and ideal for modern saltwater pool systems.

Superior Hydraulic Performance – Thanks to its rock-solid, state-of the-art hydraulic pump design, the H400FDN provides superior performance with minimal run time. With a new and improved polymer header, its able to save energy and last a lifetime.

Cutting-Edge Finn Plate Design – The state-of-the-art V-groove or baffle design of the H400FDN’s Finn plate allows for faster heating, minimal condensation, and a longer lifespan.

Digital LED Display and Control Panel – Equipped with an easy-to-use LED display and control panel, the Hayward H400FDN is surprisingly user-friendly and fun to operate. In addition to effortlessly allowing you to fire it up at the touch of a button, the LED control panel also provides digital temperature readouts and runs self-diagnostic tests.

Dual Voltage – Thinking of everything in their quest to make this pool heater as user-friendly and easy to install as possible, the guys at Hayward made it adaptable to both 110V and 220V.

Hot-Surface Silicon Nitride Ignition System – Utilizing an exclusive hot-surface silicon nitride ignition system, the Hayward H400FDN is designed to start and operate reliably for years of worry-free enjoyment.

Low NOx Emissions – Unlike some pool heater models, the Hayward H400FDN produces low NOx emissions and complies with all current Texas and California emission standards.

What We Like

The Hayward H400FDN 400,000 BTU Pool Heater is the perfect solution for your pool heating needs. Ideal for most backyard pools, this powerful yet surprisingly quiet and efficient pool heater can effortlessly raise the water temperature of an 800-gallon pool by a whopping 30 degrees in under an hour, so you can enjoy a comfortably warm pool as soon as you dip your toes in the water.

In addition to its impressive heating ability, the heater is also incredibly efficient. Thanks to its cutting-edge hydraulic design, this powerful heater has an industry leading thermal efficiency of 84 percent, resulting in an energy savings of nearly 20 percent! Plus, it comes with easy-to-use LED controls, a state-of-the-art Finn plate and Cupro nickel heat exchanger, and Fire Tile combustion chambers, making the Hayward H400FDN one of the best performing pool heaters around.

The Limitations

For first-time pool owners, the cost of owning and operating the Hayward H400FDN may be a little surprising. That being said, it’s reasonably priced compared to similar models with the same heating abilities and much more energy efficient, making it one of the best heating options for medium to large-sized pools.

Although some reviewers have noted it being a little loud as well, it is actually quite quiet in comparison to other models. Every pool heater is going to make noise just like a pool pump when it’s turned on, but this pool heater is one of the quietest of the bunch.