Hayward Universal H-Series W3H400FDN pool heater, front viewHayward Universal H-Series Natural Gas 400,000 BTU Low NOx Pool Heater, W3H400FDN In stock$5,09900 Web Price
Hayward Universal H-Series W3H400FDN pool heater, front view
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Hayward Universal H-Series Natural Gas 400,000 BTU Low NOx Pool Heater, W3H400FDN

Ask a questionMPN W3H400FDN
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Quick overview

  • Natural gas This is the natural gas model. The propane version of the same heater is a separate Hayward part number.
  • 400,000 BTU The top output in the Universal H-Series range, sized for larger pools and faster heat up.
  • Low NOx Built to Low NOx requirements, which many jurisdictions ask for on a new gas heater installation.
  • Universal H-Series Hayward positions the line around installation flexibility for the service professional.
  • Two part numbers on record Cataloged as W3H400FDN and also listed as H400FDN, so either number points here.
  • Freight delivery A complete gas heater travels on a pallet rather than by parcel carrier.
Full description and specifications ↓

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Product details

The Hayward Universal H-Series is the 400,000 BTU natural gas pool heater in Low NOx form, part W3H400FDN. It is the largest output in the residential H-Series range.

Why the Universal H-Series

Hayward built the Universal H-Series around the installer. The line is aimed at energy efficient, high output heating that adapts to the equipment pad it lands on, which is why it turns up so often on service replacements rather than only on new builds.

Fuel and emissions

This heater burns natural gas. If your pad runs on propane, the propane version is a separate model, so check the gas supply before ordering. The Low NOx rating matters too: a number of regions only allow Low NOx gas heaters on new installations, and this unit is built to that standard.

Part numbers and delivery

You may see this heater listed as W3H400FDN or as H400FDN. Both point to the same 400,000 BTU natural gas Low NOx unit. It ships by freight on a pallet, so allow for a delivery appointment.

Specifications
Brand Hayward
Manufacturer part number W3H400FDN
Also listed as H400FDN
Series Universal H-Series
UPC 0610377387255
Type Gas pool and spa heater
Fuel Natural gas
Heat input 400,000 BTU/hr
Heat output 336,000 BTU/hr at 84 percent
Thermal efficiency 84 percent, by Hayward
Ignition Hot surface
Heat exchanger Cupro nickel
Emissions Low NOx, meets SCAQMD Rule 1146.2
Electrical 120 or 240 V, single phase, 60 Hz
Amp draw 5.5 A circuit; 15 A maximum breaker
Water connections 2 in x 2-1/2 in CPVC unions
Warranty 1 year on parts, no labor, by Hayward for its Open Line (W3) models
Elevation To 10,100 ft unmodified, natural gas
Dimensions 24 in high, 34 in wide, 29.5 in long
Unit weight 195 lb
Shipping weight 214 lb
Manufacturer status Hayward lists the W3H400FDN as discontinued, replaced by the W3HS400FDN
Ships Freight

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Questions and answers

What people ask about this product, answered by our pool techs.

What is the difference between H400FDN and W3H400FDN?
The sales channel and the warranty, not the heater. W3H400FDN is the Open Line number, which Hayward approves for sale online and in stores. H400FDN is the Expert Line number for the same size and fuel, sold through stores and pool professionals. This listing is W3H400FDN.
Is the Hayward W3H400FDN discontinued?
Hayward's own site lists the W3H400FDN as discontinued and names the W3HS400FDN as its replacement. This listing is the W3H400FDN.
What does the LO code mean on a Hayward H400FDN?
A water pressure switch, vent pressure switch or temperature limit switch fault, by Hayward's troubleshooting guide. Our pool heater error code guide covers LO and the other codes.
What are the specifications of the Hayward H400FDN?
400,000 BTU/hr input on natural gas at 84 percent thermal efficiency, a cupro nickel heat exchanger, low NOx, 120 or 240 V, and 2 inch by 2-1/2 inch CPVC unions. The cabinet is 24 inches high, 34 wide and 29.5 long, and the heater weighs 195 lb.
What warranty does Hayward give the W3H400FDN?
One year on parts, with no labor coverage. That is Hayward's warranty for its Open Line, the W3 part numbers it approves for sale online. Hayward's longer parts and labor warranties belong to its Expert Line numbers, which it sells only through stores and pool professionals.
Where is the manual for the Hayward H400FDN?
Under Downloads on this page, as the Installation Manual. It is Hayward's Universal H-Series installation manual, and covers the H150FD through H500FD heaters in natural gas and propane.
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