Universal H-Series Low NOx Heater 400K BTU - NG ASME - H400FDNASME


Model # H400FDNASME

By Hayward Pool Products



Model # H400FDNASME

Warranty 3 Year

Product Description

New Hayward H-Series ASME gas heaters are designed and certified for commercial use. The flagship of our H-Series line, they combine industry-leading hydraulics, exceptional performance, energy efficiency, and reliability, with planet-friendly low-NOx emissions. Flexible connection options make them ideal for new or existing applications. Choose from 6 250,000, 400,000 and 500,000 BTU natural gas or propane models.


  • Patented Cupro Nickel Finn Plate heat exchanger with bronze header included as standard on all models
  • ASME pressure relief valve included as standard
  • Independent left or right side electric, water and gas connections
  • 2in x 2 1/2in CPVC plumbing fittings
  • Electronic lockout feature prevents unauthorized access to configuration settings
  • Easy installation and service via access of single front panel
  • Easy gas valve adjustment
  • Easy dual voltage conversion with fuse-protected circuit board
  • 3-Year limited warranty on parts and labor

Product Specifications

400,000 BTU
Digital Readout:
0-10,000 ft.
Heat Exchanger:
Cupro Nickel
Special Feature:
Low NOx Emissions / Commercial

?     Asked on 12/28/2016 by Fred tewell

what is the most likely cause of communication error or (CE) notice on the control console, THE SYSTEM IS NOT HOOKED UP TO THE POOL PANEL, it is manually controlled from the heater controls the book says a communication error between the pool control and the heater

A  Answered on 12/28/2016 by InyoPools Product Specialist Adam Y.

Good afternoon Fred, I would contact Hayward tech support to see if that code would register with any other problems or malfunctions. Hayward 1-800-657-2287

?     Asked on 7/17/2016 by SALEEM E BARHOUM

What is the reason for a Hayward H400 not to ignite? My heater ignites and stays on for 2 to 3 seconds and goes out. Please help

A  Answered on 7/19/2016 by InyoPools Product Specialist Lennox H.

HI Saleem, You will have to contact a service technician to troubleshoot your heater to find out why is not igniting.

?     Asked on 1/30/2016 by Ray

New Hayward H400FDNASME heater continues to give IF error and will not fire up.

A  Answered on 2/1/2016 by InyoPools Product Specialist Lennox H.

Hi Ray, Error code "IF" indicates Ignition Failure according to the Hayward Service and Installation Manual. I would recommend have a certified technician inspect your unit because that error code can be cause by several problem.

?     Asked on 9/8/2015 by

Error Code 56 ???

A  Answered on 9/9/2015 by InyoPools Product Specialist Brian M.

Error code 56, according to the tech at Hayward (908-355-7995)  is usually a bad display board.

?     Asked on 5/19/2015 by


A  Answered on 5/19/2015 by InyoPools Product Specialist Patrick P.

No the cover would stay on during heating.

?     Asked on 5/19/2015 by


A  Answered on 5/19/2015 by InyoPools Product Specialist Patrick P.

This heater uses a direct spark ignition meaning that the pilot is only lit while the heater is in use and does not use the older standing pilot light where the pilot is always on. Yes this heater is weatherproof.

?     Asked on 4/21/2015 by George

I want to install the Hayward Lownox heater on my pool but I live in the mountains at 3,000 foot elevation; do I need to buy a special high elevation heater?

A  Answered on 4/21/2015 by InyoPools Product Specialist Matt S.

Hello George, The Hayward Universal Low Nox are self adjusting up to 10,000 feet of elevation. Any installation above 2,000 feet will require a special restriction plate to be installed. Luckily, that plate comes standard with every heater so no need to purchase it separately.

?     Asked on 10/2/2014 by Guest

Heater model # H400FDN, can be used on pools of all different sizes? The larger the BTU's the quicker the pool will get warm

A  Answered on 10/2/2014 by InyoPools Product Specialist Patrick P.

The required size of a heater depends on the size of your pool or spa and how fast you want to heat up your pool. In the northern states you will probably want the larger heaters to compensate for the colder temperatures. Above ground pools use heaters from 55K to 130K BTUs. In ground pools and spa general run from 100K to 400K BTU. For an average 15' x 30' pool (15,000 gallons), a 300K BTU heater would raise your pool temperature 2 degrees per hour; a 400K BTU heater, 2.7 degrees per hour. For a 20' x 30' pool (20,000 gallons) the temperature rise for 300K and 400K heaters would be 1.5 and 2 degrees respectively. By contrast these same heaters would raise the temperature of an average size spa 30 degrees in 35 and 20 minutes respectively.

?     Asked on 10/8/2013 by Guest

Where can my heater be installed?

A  Answered on 10/8/2013 by InyoPools Product Specialist Patrick P.

There are specific venting requirements and clearance distances that must be met to ensure proper operation. Consult the owner’s manual for exact specifications for your model of heater.NOTE: Gas fired heaters should be diagnosed and repaired by trained personnel.

?     Asked on 1/17/2013 by Guest

Is a vent required for typical outside installation for the Hayward 150k Ng Lo Nox heater?

A  Answered on 1/17/2013 by InyoPools Product Specialist Patrick P.

For the Hayward  Lo Nox heater, you would not need to purchase an additional vent if you are using it outside. If you are installing the heater outside, we recommend you purchasing a heater cover. This will protect your heater from debris, rain, snow, heat- or pretty much anything that could get caught in your heater. The Weather-Out Pool Heater Cover  can be viewed on our website.

?     Asked on 10/18/2012 by Guest

What is the elevation rating for the Hayward H-Series Low Nox Heaters

A  Answered on 10/18/2012 by InyoPools Product Specialist Patrick P.

Per Hayward, the Hayward H-Series Low Nox Heaters have an elevation rating up to 7,700'

?     Asked on 10/10/2012 by Guest

What is the difference between an Electronic and Millivolt ignition?

A  Answered on 10/10/2012 by InyoPools Product Specialist Patrick P.

The basic answer is that Millivolt is the old style of ignition, using a standing pilot light. While the electronic ignition uses a spark start system like a gas grill. Electronic ignitions are more efficient in gas usage and also are better suited for high wind areas where a pilot light might get extinguished.

?     Asked on 1/16/2012 by Guest

Will a gas heater operate at the low speed of a dual speed motor?

A  Answered on 1/16/2012 by InyoPools Product Specialist Patrick P.

Probably not - Most gas heater will shut off at low GPM levels (20-40) to keep the heater cores from overheating - 20 for 200 BTUs, 40 for 400 BTUs. Depending on your pool system you might get these GPM levels at the low speed but generally these heaters must be run at the motor's high speed.

?     Asked on 12/29/2011 by Guest

How do you know if a pool heater is a propane heater or a natural gas heater?

A  Answered on 12/29/2011 by InyoPools Product Specialist Patrick P.

Typically in the product name we use the abbreviation of "LP" for propane or "NG" for natural gas. Click here for a full listing of our >Pool Heaters.