Universal H-Series Low NOx Heater 350K BTU - NG - H350FDN


Part # H350FDN

By Hayward Pool Products

  4.5 Average  



Part # H350FDN

Warranty 1 Year

Product Description

Universal H-Series Low NOx Heaters
For In-Ground Pools and Spas - Electronic Ignition Dual Thermostat

Now With Cupro Nickel Heat Exchanger!

NEW Hayward Universal H-Series Low NOx heater combines industry-leading hydraulic performance; environmentally responsible low NOx emissions and a standard cupro nickel heat exchanger with a low profile appearance, lighter weight design, independent left or right side electric, water and gas connections plus 2" x 2 1/2" CPVC union connections to provide the ultimate installation flexibility for new or existing equipment pads.

It also includes a forced draft system that constantly moves air through the combustion chamber at a precise flow rate. As a result, all outside weather variables that can affect the heating performance, such as wind conditions, are eliminated - without having to install a high-wind stack.

NOTE: The Hayward Universal H-Series heaters meet the NOx Emission standards set by the California South Coast Quality Air Management Commission for 2001 and the Texas Natural Resource Conservation Commission Code.


  • Forced draft system constantly moves air through the combustion chamber at a precise flow rate, eliminating all outside weather variables that can effect the heating performance, such as high wind conditions -- without a high wind stack.
  • Our patented single header "V" baffle design heat exchangers allow for long life, fast heating and virtually no condensation. All Hayward heat exchangers are now constructed with highly resilient Cupro Nickel for greater durability and longevity even in salt-based, high flow or aggressive water chemistry set ups.
  • Easy-to-read L.E.D. digital Control Panel provides digital temperature readout and diagnostics for quick identification of components that might need service.
  • New polymer header provides superior hydraulic performance to save energy and protect against the damaging effects of erosion from high flow conditions for improved reliability.
  • Designed for today's larger diameter plumbing systems with 2" x 2 1/2" CPVC unions.
  • 1 Year limited warranty
  • Now with Cupro Nickel Heat Exchanger

Overall Dimensions

Product Specifications

350,000 BTU
195 lbs.
33-1/4 in.
0-10,000 ft.
Heat Exchanger:
Cupro Nickel
Special Feature:
Low NOx Emissions

?     Asked on 8/12/2019 by

That does not answer my question I need to know if the heater holds a 2 pull 20 breaker or 30?

A  Answered on 8/14/2019 by InyoPools Product Specialist Michelle B.

Hello, Unfortunately, We would not know. We recommend contacting the manufacturer with that question. You can reach them at 908-351-5400.

?     Asked on 8/11/2019 by

Can you tell me if you know the size breaker this needs mine keeps tripping the breaker Are there any specs on it

A  Answered on 8/11/2019 by InyoPools Product Specialist Lennox H.

Hi. The breaker size will be based on the operating voltage 115 or 230 volts. 

?     Asked on 2/17/2019 by Don Z

I am thinking of upgrading from a Hayward 250btu to the 350kBTU above and want to make sure everything else - the electric and natural gas fittings - will move easily from the old heater to the new one. Can you confirm for me, please?

A  Answered on 2/17/2019 by InyoPools Product Specialist Lennox H.

Hi, Don Z. The electrical and gas line connection to the heater is the same; however, you may need to increase your gas pipe. Please refer to the Gas Supply and Piping chart which is on page 22 of the Hayward H-series LoNox Installation Guide

?     Asked on 5/3/2018 by

Trying to replace a Sta Rite 200 BTU heater (natural gas) with a Hayward Low knox 300 or 350Btu heater (natural gas). Is there any difference in their connection in terms of sizing of pipes or any other special requirement I should be concerned about?

A  Answered on 5/3/2018 by InyoPools Product Specialist Lennox H.

Hi. Yes, The gas connection to the heater will be 3/4", however, the gas pipe size will need to be changed if you're increasing the BTU. Overall you would want to look at clearances and each manufacturer has different installation requirements. Before purchasing go over the Hayward H-series LoNox Installation Guide

?     Asked on 1/16/2018 by gary

will a hayward h350fdn pool heater work on a 18x36 pool

A  Answered on 1/16/2018 by InyoPools Product Specialist Lennox H.

Hi, Gary. Yes, this H350FDN heater will heat an 18' x 36' pool. 

?     Asked on 6/19/2017 by

If I install this "Pool Heater Universal H-Series Low Nox 350K BTU NG - H350FDN" in a pool shed/house does it require venting?

A  Answered on 6/19/2017 by InyoPools Product Specialist Patrick P.

Yes venting will be required, and you would need this Hayward 350 Vertical Vent Kit.

?     Asked on 1/10/2017 by Mike

I need to replace my heater and would like to control it from my Aqualink RS pad in the house. Does this limit me to a Jandy heater, or will it work with other brands?

A  Answered on 1/10/2017 by InyoPools Product Specialist Adam Y.

No, There are plenty of compatible brands that will work with your system. They would just have to be wired for that.

?     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 10/8/2013 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 10/7/2013 by Guest

Is it possible to convert this heater from natural gas to propane?

A  Answered on 10/7/2013 by InyoPools Product Specialist Patrick P.

Yes, it is possible to convert this heater from natural to propane gas as there is a conversion kit for it. To view and purchase this kit you you will need to click here.

?     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.


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