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

Item No. 385629 | Manufacturer SKU: W3H400FDN
Item No. 385629 | Manufacturer SKU: W3H400FDN
Hayward  W3H400FDN Universal H-Series Low NOx 400K BTU Natural Gas Pool  Spa Heater
Hayward  W3H400FDN Universal H-Series Low NOx 400K BTU Natural Gas Pool  Spa Heater
Hayward  W3H400FDN Universal H-Series Low NOx 400K BTU Natural Gas Pool  Spa Heater Hayward  W3H400FDN Universal H-Series Low NOx 400K BTU Natural Gas Pool  Spa Heater
$3,599.00 Price reduced from $3,999.00 to

Hayward W3H400FDN Universal H-Series, Low NOx, 400,000 BTU, Natural Gas, Pool and Spa Heater delivering durability, reliability, and energy efficiency. More Details

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Hayward W3H400FDN Universal H-Series, Low NOx, 400,000 BTU, Natural Gas, Pool and Spa Heater delivering durability, reliability, and energy efficiency.
  • "Totally Managed" Flow saving energy by reducing pump run time
  • Silicon Nitride Ignition System
  • Cupro-Nickel Heat Exchanger ensures compatibility with almost all pool systems including salt pools
  • Low NOx certification
  • 83-84% industry-leading thermal efficiency
  • Patented header by-pass design
  • Corrosion resistance
  • Digital LED display
  • High and low voltage options (110V or 220V)
  • 3/4" Gas Connection at heater
  • Choice of left-side or right-side electric, gas and water connections (delivered right-side by default)
  • 2" or 2-1/2" plumbing connections
  • Important: Instructions for Accepting Your Freight Shipment

The Hayward Universal H-Series Natural Gas Pool and Spa Heater brings you quiet, efficient heating for your pool and spa. Hayward Natural Gas heaters are quiet, certified for low NOx emissions and eco-friendly making for a dependable, safe pool heater you can trust. Combining advanced technology with universal-fit flexibility, the Hayward H-Series is perfect for new or existing pool systems, delivering state-of-the-industry performance.

Hayward Universal H-Series Pool Heater Features
The Hayward Universal H-Series Natural Gas Pool and Spa Heater utilizes industry-leading hydraulic performance, reducing circulation pump run time while saving energy. The cupro-nickel heat exchanger provides exceptional corrosion resistance and erosion protection Ideal for today's salt-based electronic chlorination systems. Silicon Nitride Ignition System and Insulated Fire Tile® Combustion Chamber allow for fast dependable lighting while securely trapping the heat, delivering the most performance for every BTU. The digital LED display maintains water temperature, monitoring the heater's performance with self-diagnostic capability. The Hayward H-Series' Finn Plate cupro-nickel heat exchanger has special V-groove design for faster heating and longer life. Hayward Universal H-Series, Low NOx, 400,000 BTU, Natural Gas, Pool and Spa Heater delivers energy efficient heating to your pool's water that you can trust.

Hayward Universal H-Series - Versatility & Power

Using natural gas, the Hayward H-Series is reliable and boasts higher heating efficiencies. Being extremely versatile, Hayward Universal H-Series Heaters allow you to configure water, gas and electric connections on either the right or left side for unprecedented installation flexibility. Connecting your natural gas line is super easy to install with the Hayward H-Series built-in 3/4" gas connection. With a lightweight, low-profile, compact design, the Hayward Natural Gas Pool and Spa Heater installs with virtually all new and existing equipment pads.

Common Questions

What are the dimensions of the unit?
  • Heater Dimensions: 36-1/2" Width x 29-1/2" Depth x 24" Height
  • Weight: Approx. 210 lbs.
What Heat Exchanger type of the Hayward Universal H-Series Pool Heater?
  • Cupro-Nickel Heat Exchanger
Is this unit Low NOx?
  • Yes, this unit meets all state air quality regulations.
Plumbing Size?
  • This unit is plumbed 2" and comes with 2" unions for installation.
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Instructions for accepting your freight shipment


Dual Voltage
Installation is simplified with voltage that adapts to either 110V or 220V.
Universal Wiring Junction Boxes
High and low voltage connections are easy and convenient with left and right side junction boxes.
Hot-Surface Silicon Nitride Ignition System
Exclusive silicon nitride ignition system for dependable lighting and reliable operation.
Digital LED Control Panel
Electronic control display maintains water temperature; monitors heater performance with self-diagnostic capability
Insulated FireTile Combustion Chamber
Unlike older forms of insulation, FireTile securely traps the heat, delivering the most performance from each BTU.
Low NOx Emissions
Environmentally responsible; complies with all current California and Texas air quality emission standards.
Standard Cupro Nickel Heat Exchanger
Totally Managed Flow provides exceptional corrosion resistance and erosion protection. Ideal for today's salt-based electronic chlorination systems.
Superior Hydraulic Performance
Industry-leading hydraulic performance saves energy by reducing circulation pump run time.
State-of-the-Art Finn Plate Heat Exchanger
State-of-the-industry Finn Plate heat exchanger with special V-groove design for faster heating and longer life.

Product Type: Pool Heater
Heat Exchanger: Cupro-Nickel
Controls: Digital
Ignition: Electronic
Emission: Low NOx
Fuel Type: Natural Gas
Installation Type: Residential
Pool Type: Spa/Hot Tub
Eco-Friendly: Yes
Energy Efficient: Yes
Pool Type: In Ground
Voltage: 110V / 220V
Heat Output: 400,000 BTU
Manufacturer: Hayward
Elevation: 0 - 10,100 ft
Product Weight: 210 lbs.
Warranty: 3-Year
Product Dimensions: 36.5" Width x 29.5" Length x 24" Height

Three (3) Year Limited Warranty on Product, see Owner's Manual for a full description of warranty claims and coverage details.


* Freight charges may apply on oversized products. Shipping charges may apply on select products such as sand, salt, and D.E. Discounts do not apply toward shipping, handling and freight fees, taxes, the purchase of select items, or previous orders. Prices are subject to change without notice.