Description
The Hayward HS250FDN is a residential natural gas pool heater from Hayward, rated at 250,000 BTU, built to run on natural gas. It is designed for heating swimming pools and spas.
The Hayward HS250FDN is a natural gas pool heater rated at 250,000 BTU that runs on natural gas. Below we explain how it works, how to size it, what goes into a safe installation, and how to keep it running for years.
Quick Answer: What Is the Hayward HS250FDN?
The Hayward HS250FDN is a residential natural gas pool heater with 250,000 BTU/hr input. Gas heaters warm water quickly in any weather, making them ideal for spas, occasional heating and cooler climates.
Hayward HS250FDN Specifications
| Brand | Hayward |
|---|---|
| Equipment Type | Natural Gas Pool Heater |
| Model Number | HS250FDN |
| Input (BTU) | 250,000 |
| Fuel Type | Natural Gas |
| Application | Residential |
| ASME Certified | No |
Key Features of the Hayward HS250FDN
- 250,000 BTU input
- Runs on natural gas
How a Gas Pool Heater Works
Pool water from the filter flows through a heat exchanger, a bank of tubes typically made of copper or cupro-nickel. Below it, burners fire natural gas, and the hot combustion gases pass over the tubes, transferring heat to the water before it returns to the pool. An electronic ignition lights the burners only when the thermostat calls for heat, and safety switches confirm water flow, pressure and temperature before firing.
Because a gas heater creates its own heat rather than pulling it from the air, it works the same on a cold morning as on a warm afternoon. That makes it the go-to choice for spas, for pools that are heated only on weekends, and for climates with cool spring and fall weather.
Low NOx designs reduce nitrogen oxide emissions and meet strict air-quality rules in California and other regions. Check local requirements before you buy.
How to Size a Gas Pool Heater
It takes about 8.33 BTU to raise one gallon of water by one degree Fahrenheit. The basic formula is: BTU needed = gallons x 8.33 x temperature rise. Divide that by the heater's output (input BTU x efficiency) to estimate heat-up time.
Here is what roughly 205,000 BTU/hr of delivered heat means in practice. These estimates assume no heat loss, so real times will be longer, especially in wind or without a cover.
| Body of water | Estimated heat-up time |
|---|---|
| 10,000 gal pool, +10 F | 4.1 hours |
| 15,000 gal pool, +10 F | 6.1 hours |
| 20,000 gal pool, +10 F | 8.1 hours |
| 30,000 gal pool, +10 F | 12.2 hours |
| 400 gal spa, +30 F | 29 minutes |
For pools, surface area matters as much as volume, because most heat is lost from the surface through evaporation. Wind, shade and cool nights all increase the load. A solar cover is the single most effective way to cut heat loss and gas use. If you heat only occasionally or want fast spa heat, choose a larger heater; if you hold a steady temperature, a heater sized to your surface area and climate works well.
Good, Better, Best: Where the Hayward HS250FDN Fits
At HVAC365 we organize every category into a simple Good, Better, Best framework so you can compare options without wading through jargon. Within our natural gas pool heater lineup, this model sits in the Good tier: Essential features at a great value.
The Good tier is built around affordability and simplicity. You get dependable, proven equipment without paying for extras you may never use. It is a smart pick for straightforward replacements and budget-conscious projects.
Compare it with the other tiers in the same category. Whatever you choose, the equipment is brand new and covered by the full manufacturer warranty.
Installation and Gas Requirements
Gas heaters must be installed by a qualified professional following the manufacturer's manual and local codes. That includes correctly sized natural gas supply piping, proper clearances from walls, windows and overhangs, venting for indoor installations, and electrical connections. The heater is plumbed after the pump and filter and before any chlorinator, so concentrated sanitizer never flows through the heat exchanger.
Gas line size depends on the heater's BTU input and the distance from the meter or tank, so have your installer confirm it before the project starts. Many areas require a permit for gas work.
Maintenance Tips
- Keep water chemistry balanced. Low pH and high chlorine are the leading causes of heat exchanger corrosion.
- Keep the area around the heater clear of leaves, mulch, plants and debris, and keep insects and rodents out of the burner area.
- Clean the filter regularly; low flow can trip the pressure switch and stop the heater.
- Schedule an annual inspection of burners, ignition, gas pressure and venting.
- In freezing climates, drain the heater or use freeze protection when the pool is closed.
Gas Heat by Region
In northern states and higher elevations, gas heaters are popular because they heat quickly no matter how cold the air is, so you can open earlier in spring and swim later in fall. In the South, many owners pair a heat pump for the main season with a gas heater for the spa or for cold snaps. Natural gas is usually the lower-cost fuel where it is available; propane is the choice for homes without a gas line. Local air-quality rules may require low NOx models.
What's Included and Compatibility
This listing is for the Hayward HS250FDN (model HS250FDN). Venting kits, gas piping and automation interfaces are typically sold separately.
Built for Homeowners, Contractors and Property Managers
- Homeowners: use the pool math on this page, then reach out with your pool size, location and existing equipment. We will help you confirm the right model before you order.
- Contractors and installers: order quickly, follow every shipment with tracking, and reorder common equipment from the HVAC365 Contractor Portal.
- Property managers: standardize models across properties, plan replacements and control maintenance costs with help from our team.
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Frequently Asked Questions About the Hayward HS250FDN
How fast will the Hayward HS250FDN heat my pool?
With about 205,000 BTU/hr delivered to the water, it can raise a 20,000-gallon pool roughly 1.2 F per hour before heat losses. A cover and calm weather help it get there faster.
Natural gas or propane: which should I choose?
Choose the fuel you have at the home. This model runs on natural gas. Natural gas and propane versions are not interchangeable without the manufacturer's conversion parts and a qualified technician.
Gas heater or heat pump?
Gas heaters heat fast in any weather and suit spas, occasional use and colder climates. Heat pumps cost less to run in warm climates but heat more slowly and lose capacity as air temperatures drop.
How long do gas pool heaters last?
With balanced water chemistry, good flow and annual service, many heaters last 8 to 15 years. Poor water chemistry is the most common cause of early failure.
What warranty does it have?
It is brand new and covered by the Hayward manufacturer warranty. Warranty terms vary by model and application (residential vs. commercial); see the manufacturer's documentation or ask our team for details.
