Product Overview

The Hayward Universal H-Series Propane Gas Heater W3H400FDP is a powerful 400,000 BTU pool and spa heater designed to deliver fast, dependable, and efficient heating for residential in-ground pool and spa applications. Built on Hayward’s Universal H-Series platform, this heater combines strong propane heating performance with Low NOx emissions, flexible installation features, and durable construction for long-lasting pool comfort.

Featuring a cupro nickel heat exchanger, electronic ignition, digital controls, and a forced-draft combustion system, the W3H400FDP is engineered to provide reliable heat-up performance while helping protect against corrosion caused by challenging water chemistry conditions.

Powerful Propane Heating for Pools and Spas

The Universal H-Series 400K BTU propane heater helps raise and maintain comfortable water temperatures for pools and spas. Whether used to extend the swimming season, warm cooler water, or provide fast heat recovery for an attached spa, this heater delivers strong on-demand heating when properly sized and professionally installed.

Its 400,000 BTU output makes it a strong choice for larger residential pools, pool/spa combinations, and applications requiring faster heat-up times.

Built for Low NOx Performance

The Hayward Universal H-Series Low NOx heater is designed to help reduce nitrogen oxide emissions while delivering dependable heating performance. This makes it suitable for many areas with stricter clean-air requirements.

The W3H400FDP uses propane gas / LP fuel and should only be installed with the proper propane supply, regulator, gas line sizing, ventilation, electrical setup, and code-compliant installation.

Flexible Universal Installation Design

The Universal H-Series platform is designed for adaptable installation and easier replacement. Its compact cabinet, connection flexibility, and service-friendly layout make it a strong option for both new equipment pads and heater replacement projects.

This heater is commonly selected for larger residential in-ground pools, spas, and pool/spa combinations where propane fuel is required and high BTU heating performance is needed.

Key Features

• Genuine Hayward Universal H-Series propane gas heater
• 400,000 BTU heating capacity
• Propane gas / LP fuel configuration
• Low NOx emissions design
• 120/240 V electrical compatibility
• 60 Hz, single-phase operation
• Designed for residential in-ground pools and spas
• Cupro nickel heat exchanger for enhanced corrosion resistance
• Excellent choice for saltwater pools when water chemistry is properly maintained
• Forced-draft combustion system for consistent performance
• Electronic ignition system with no standing pilot
• Digital LED control panel with temperature display
• Built-in diagnostics for easier troubleshooting
• Universal-style design for flexible installation
• Compact, low-profile cabinet
• Independent left- or right-side water, gas, and electrical connections
• 2" x 2.5" CPVC union plumbing connections, where supplied
• Designed for new installations and heater replacement applications

Product Benefits

Fast Heating for Larger Pools

The 400K BTU output delivers strong heating performance for larger residential pools, spas, and pool/spa combinations, helping customers enjoy comfortable water temperatures faster than lower-BTU models.

Propane Gas Convenience

Propane heating is a practical solution for homes that do not have natural gas service but still need powerful, on-demand pool or spa heating.

Corrosion-Resistant Heat Exchanger

The cupro nickel heat exchanger helps resist corrosion and premature wear caused by unbalanced water chemistry, saltwater systems, and demanding pool environments.

Cleaner Low NOx Operation

The Low NOx design helps reduce emissions and supports use in many areas with stricter air-quality requirements.

Easy Operation and Diagnostics

The digital LED control panel makes it simple to adjust water temperature, monitor heater operation, and support easier troubleshooting.

Flexible Replacement Option

The Universal H-Series design helps make the W3H400FDP a practical replacement choice for many existing pool heater installations.

Ideal For

This heater is ideal for:

• Larger residential in-ground pools
• Attached spas and pool/spa combinations
• Applications requiring faster heat-up performance
• Homes using propane gas / LP fuel
• Saltwater pools with properly balanced water chemistry
• Replacing an older propane pool heater
• Pool owners wanting stronger heating performance than lower-BTU models
• New equipment pad installations
• Installations requiring 120/240 V compatibility
• Areas where Low NOx heater performance is required

Compatibility

The Hayward W3H400FDP is designed for propane gas / LP pool and spa heating applications. It is commonly used for residential in-ground pools and spas when properly sized for the pool volume, desired temperature rise, plumbing flow, and local climate conditions.

Before ordering, confirm:

• Fuel type: Propane gas / LP
• Heating capacity: 400,000 BTU
• Electrical requirements: 120/240 V, 60 Hz, single phase
• Propane supply and regulator requirements
• Gas line sizing and supply pressure
• Pool size and desired heat-up time
• Plumbing flow rate requirements
• Ventilation and installation clearance requirements
• Local gas, plumbing, electrical, and building codes
• Professional installation requirements

This heater should not be used with natural gas unless the heater model is specifically configured for natural gas.

What’s Included

• One Hayward Universal H-Series Propane Gas Heater, 400K BTU
• Digital control system
• Cupro nickel heat exchanger
• Electronic ignition system
• Factory-installed heater components
• Manufacturer documentation, where supplied by packaging

Propane tank, propane regulator, gas line components, venting materials, electrical whip, plumbing fittings, equipment pad materials, and installation labor are not included unless specified separately.

Specifications

Customer-Facing Q&A

Q: What type of fuel does the Hayward W3H400FDP use?
A: The W3H400FDP uses propane gas / LP.

Q: How many BTUs is this heater?
A: This heater is rated at 400,000 BTU.

Q: What voltage does this heater require?
A: The W3H400FDP is designed for 120/240 V, 60 Hz, single-phase electrical operation.

Q: Is this heater for pools or spas?
A: This heater is designed for residential in-ground pools and spas when properly sized and installed.

Q: Does this heater have a cupro nickel heat exchanger?
A: Yes. The W3H400FDP features a cupro nickel heat exchanger for enhanced corrosion resistance.

Q: Is this heater compatible with saltwater pools?
A: Yes. It can be used with saltwater pools when the pool water is properly balanced and maintained.

Q: Is this a natural gas heater?
A: No. This model is configured for propane gas / LP. Do not use it with natural gas unless the heater model specifically supports natural gas.

Q: What does Low NOx mean?
A: Low NOx means the heater is designed to produce lower nitrogen oxide emissions, helping meet clean-air requirements in many areas.

Q: Does this heater require professional installation?
A: Yes. Gas pool heaters should be installed by qualified professionals according to local gas, electrical, plumbing, and building codes.

Q: What is the barcode for this product?
A: The UPC / Barcode is 0610377387279.