Hayward – W3H400FDN Universal H-Series, Low NOx, 400K BTU, Natural Gas, Pool & Spa Heater

The Hayward W3H400FDN Universal H-Series stands at the top of residential pool heating performance. Delivering an impressive 400,000 BTU output, it is engineered for large pools and spas requiring fast, efficient temperature rise. Built with Low NOx combustion technology, it exceeds industry air quality standards—making it an environmentally responsible solution.

Designed for long-term reliability, the heater features a durable cupro-nickel heat exchanger that defends against corrosion from saltwater and chemically treated pools. Its digital control panel provides seamless operation and precise temperature accuracy. Whether upgrading an existing system or installing new equipment, the W3H400FDN offers unbeatable heating power.

Key Features

• 400K BTU High-Performance Heating — Heats large pools and spas quickly

• Low NOx Emissions — Cleaner combustion that meets stringent environmental regulations

• Cupro-Nickel Heat Exchanger — Enhanced durability against corrosion and chemical wear

• Energy-Efficient Design — Reduces operational costs while maximizing comfort

• Universal Installation Capability — Compatible with most existing plumbing and systems

• User-Friendly Digital Controls — Set and maintain precise water temperature with ease

• Rugged Polymer Headers — Maintain strong water flow and long-lasting structure

• Reliable Ignition System — Trouble-free startup in all climates

Benefits

• Extends swimming season with rapid, powerful heating

• Lower gas consumption and improved energy savings

• Ideal for saltwater systems and harsh pool environments

• Easy-to-operate interface for residential users

• Long-term durability reduces maintenance costs

• Flexible design works for retrofits and new builds