Jandy JXi400N Gas Pool & Spa Heater
A large Gulf Coast pool, or a pool and spa combination, where the spa needs to be ready in under an hour and the equipment pad has no room to spare.
Gas heater
SKU JXI400N
- BTU input
- 399,000 BTU/hr
- Fuel / power
- Natural gas
- Thermal efficiency
- 84% thermal efficiency
- Heat exchanger
- Copper
- Warranty
- Parts: 1 year
- Controls & automation
- Onboard digital control with separate pool and spa setpoints; two- or three-wire remote, or an RS-485 connection to a Jandy AquaLink system. App control requires the AquaLink system and the iAquaLink app.
Modern Pool Heating Equipment Score
Our score for the equipment itself. It is not a Google or customer review rating.
How we rate heatersFull specifications
Every row below is taken from a manufacturer document. Anything the manufacturer does not publish is left out rather than estimated.
| Manufacturer model number | JXI400N (JXI400P propane; JXI400NN / JXI400PN cupro-nickel) |
|---|---|
| BTU input (firing rate) | 399,000 BTU/hr (marketed as 400,000 BTU) |
| Thermal efficiency | 84% (Jandy EnergyGuide label; 83% on the cupro-nickel JXI400NN) |
| Heat exchanger | Copper fin tube with polymer headers; cupro-nickel optional |
| Emissions | Low NOx; certified to SCAQMD Rule 1146.2 |
| Water connections | 2" PVC/CPVC unthreaded, or Jandy threaded union |
| Water flow | 30 GPM minimum, 100 GPM maximum |
| Gas connection | 3/4" NPT |
| Natural gas pipe sizing | 20 ft of 1", 95 ft of 1-1/4", 215 ft of 1-1/2"; 3/4" only for the first 5 ft from the gas valve |
| Inlet gas supply pressure | 4.0" W.C. minimum (natural gas), operating |
| Electrical | 120 VAC at under 5 A, or 240 VAC at under 2.5 A |
| Exhaust vent | 8" diameter Category I, 4" Category III |
| Minimum outdoor ambient | 40°F |
| Cabinet | 22.1" W x 21.6" D x 26.5" H — identical on every JXi size |
| Certification | CSA design certified; ANSI Z21.56 / CSA 4.7 |
| Controls and automation | Onboard digital control with separate pool and spa setpoints and a diagnostic menu; two-wire or three-wire remote, or a four-pin RS-485 connection to Jandy AquaLink RS, PDA and Z4. iAquaLink app control requires a Jandy AquaLink automation system. |
Why homeowners consider it
- 399,000 BTU/hr in a cabinet 22 inches wide. The JXi is the most compact heater in its output class on a typical Florida pad, and the body dimensions are the same as the 200,000 BTU model, so a big heater does not cost you a bigger footprint.
- 84% thermal efficiency on Jandy's own EnergyGuide label, level with the best current low-NOx gas heaters from Hayward and Pentair.
- There is a real cupro-nickel option in this size. JXI400NN (natural gas) and JXI400PN (propane) are cataloged cupro-nickel models, which is the corrosion upgrade worth having on a salt pool — with the caveat that Jandy labels the cupro-nickel version at 83% rather than 84%.
- It is built to make a same-pad swap easier. The top cover lifts off and rotates 180 degrees, so the flue and the control side can be reoriented to suit the existing plumbing instead of the plumbing being rebuilt around the heater.
- The RS-485 connection makes it a first-class citizen on a Jandy AquaLink system rather than something an automation panel switches on with a relay, and from there it is controllable in the iAquaLink app.
What to know before buying
- The published warranty is one year, parts only, with no labor coverage. On a 399,000 BTU appliance that is short — Hayward publishes three years parts on the Universal H-Series and Raypak publishes three years parts and labor on the AVIA. The five-year heat-exchanger term applies only when VersaFlo is factory-installed.
- Gas pipe sizing is the real constraint. Jandy's table gives a JXi400 only 20 feet of 1-inch natural gas pipe, 95 feet of 1-1/4 inch or 215 feet of 1-1/2 inch, and allows 3/4-inch pipe for a maximum of 5 feet from the gas valve. An existing line that fed a 250,000 BTU heater will usually not feed this one.
- Venting is bigger too: an 8-inch Category I vent connection against 7 inches on the 260 and 6 inches on the 200. That matters on any indoor or sheltered installation.
- Flow has to land between 30 and 100 GPM, and the water pressure switch is factory set to 7 psi. Set the variable-speed pump's heating speed accordingly rather than running the heater at the pump's filtration speed.
- Jandy's warranty excludes product bought through the internet or e-commerce platforms and requires a licensed, qualified installer. Confirm the purchase channel with whoever quotes you.
- Published outdoor operating ambient is down to 40°F, and Jandy asks for a protected outdoor shelter if the heater will run below freezing. That is rarely an issue here and often is further north.
Warranty, term by term
The warranty only matters on the parts that actually fail. Here is how this one splits up.
- Parts
- 1 year
Jandy's published limited warranty covers JXi heaters for one year from retail purchase. There is no labor coverage at all: the document states Fluidra's liability does not include costs for labor to service or repair the product. The five-year term applies to the heat exchanger only, and only when VersaFlo is factory-installed. The warranty does not apply to Jandy products purchased through the internet or other e-commerce platforms, and it applies only to products installed and serviced by a licensed, qualified pool professional. Anything installed outside a single-family dwelling drops to one year. Professional installation / authorized-channel requirements may apply.
Why the heat exchanger matters
The heat exchanger is the part of a pool heater that actually moves heat into the water, and what it is made of decides how long the heater survives Florida water chemistry. Here is what the four materials mean in practice.
- CopperThis heater
- The traditional material and the cheapest to build. It transfers heat well and is fine on a well-balanced chlorine pool, but it is the least forgiving of low pH, high chlorine and salt. On the Gulf Coast it is usually the first component to fail.
- Cupro-nickel
- Copper alloyed with nickel. It gives up a little heat transfer in exchange for much better resistance to unbalanced water chemistry and salt. On gas heaters this is the upgrade worth having in Florida, and some manufacturers now ship it as standard.
- NiTek (nickel alloy)
- A nickel-alloy exchanger used on some gas heaters as a corrosion-resistant alternative to copper. Positioned between cupro-nickel and titanium in both durability and price.
- Titanium
- Effectively immune to pool water chemistry, including salt. It is the standard on quality pool heat pumps and the reason a heat pump can sit on a salt pool for years without exchanger trouble. It is expensive, which is why you rarely see it on gas heaters.
Whatever the material, plumbing order matters just as much: a chlorinator or salt cell belongs downstream of the heater, never upstream.
How we scored it
- Warranty drives the score and drives it down. The published coverage is one year, parts only, with no labor — against 2 years parts and labor on a Pentair MasterTemp and 3 years parts with 1 year field labor on a Hayward Universal H-Series — and it is why our number sits well below the 4.6 starter score in the guide we work from. The guide's own warranty column says the same thing; we simply weight it at 25%.
- Durability gets 3.5 rather than 3: copper is the baseline, but a genuine cupro-nickel option exists in this size, the headers are polymer rather than cast iron, and the thermal regulator valve keeps the exchanger out of the condensing range that eats fin tubes.
- 84% thermal efficiency on Jandy's own EnergyGuide label is at the top of the conventional gas field, matched by Hayward and Pentair and ahead of Raypak's Digital line.
- Serviceability is a strength — compact cabinet, rotating top cover, swing-up raceway, parts stocked widely in Florida — with half a point off for the Rev G / Rev H parts split that catches out anyone ordering a flue sensor or power interface board.
- Controls score high because the RS-485 link into AquaLink is a real data connection, not a relay, and gives useful diagnostics as well as app control through iAquaLink.
- Value is mid-pack: good engineering and a compact footprint at an upper-mid installed price, undercut by the warranty term.
Real Modern Pool Heating installations
We have not published a job-site photo for this exact model yet. Installation photos on this site are only ever our own work, and we label each one as the exact model or as a representative install.
Installed locally, researched for everyone
Affordable Solar & Pool Heating, LLC installs and services pool heating in Sarasota, Manatee, Charlotte & Pinellas County, Florida. If you are outside that area this page is still yours to use — take the questions on it to your local contractor. Pool heater installation in Sarasota.
Other heaters worth putting beside it
Same job, different tradeoffs. Every one of these has its own verified spec page.
Jandy · JXiQ
Jandy JXiQ400NK Smart Gas Pool & Spa Heater
Model JXIQ400NK
- BTU input
- 399,000 BTU/hr
- Thermal efficiency
- 84%
- Heat exchanger
- Copper
- Warranty
- 1-Year Parts5-Year Heat Exchanger
- Wi-Fi / automation
- App Control via AutomationAutomation Compatible
A pool and spa owner who wants the heater itself to tell them, and their service company, what is going on — and who is already committed to a Jandy AquaLink system.
Hayward · Universal H-Series
Hayward Universal H-Series H400FDN Gas Pool Heater
Model H400FDN
- BTU input
- 399,900 BTU/hr
- Thermal efficiency
- 84%
- Heat exchanger
- Cupro-nickel
- Warranty
- 3-Year Parts / 1-Year Labor
- Wi-Fi / automation
- App Control via AutomationAutomation Compatible (Relay)
A large Florida pool, or a pool and spa combination, that needs to reach temperature on demand rather than hold it all season.
Raypak · AVIA
Raypak AVIA 404A Gas Pool & Spa Heater
Model P-R404A-EN-C
- BTU input
- 399,000 BTU/hr
- Thermal efficiency
- 84%
- Heat exchanger
- Copper
- Warranty
- 3-Year Parts & Labor
- Wi-Fi / automation
- Wi-Fi Built InAutomation Compatible (Relay)
A large Florida pool, or a pool and spa, where the owner wants spa-speed output and three years of parts and labor cover.
JXI400N questions
What size pool is a 400,000 BTU heater right for?
Large pools, and pool-plus-spa combinations where the spa has to reach temperature quickly. Output this high is about speed rather than efficiency — it will not cost more to run per degree, but it will get there faster, which is the whole reason to buy gas.
What is the difference between JXI400N and JXI400NN?
The heat exchanger. JXI400N is copper with polymer headers; JXI400NN is the cupro-nickel version. Jandy's EnergyGuide labels rate the copper model at 84% and the cupro-nickel model at 83%, so you trade one point of thermal efficiency for a more corrosion-tolerant exchanger.
Will it work on a salt water pool?
Yes, with the usual conditions. Plumb the salt cell or chlorinator downstream of the heater, never upstream, and keep the water balanced — Jandy's manual states plainly that damage to the heat exchanger by corrosive water is not covered by the warranty. If the pool is on salt or close to the water, the cupro-nickel JXI400NN is worth pricing.
Can I control it from my phone?
Through a Jandy AquaLink system, yes — the heater connects over RS-485 and appears in the iAquaLink app. The JXi has no Wi-Fi radio of its own, so without an automation system it is a local control panel plus an optional remote switch.
Does my existing gas line fit this heater?
Often not. Jandy allows only 20 feet of 1-inch natural gas pipe to a JXi400, and 3/4-inch pipe only for the first 5 feet from the gas valve. A line that was sized for an older 250,000 BTU heater usually has to be upsized, which is the single most common reason a gas heater swap costs more than the sticker price.
Do you install Jandy gas heaters in Sarasota?
Yes. We install and service Jandy gas heaters throughout Sarasota, Manatee, Charlotte & Pinellas County, Florida. The comparison content here is written for pool owners anywhere; the installation offer is local.
Is the JXI400N right for your pool?
We install and service pool heating in Sarasota, Manatee, Charlotte & Pinellas County, Florida. If you are outside that area, the comparison above is still yours to use — ask your local contractor the same questions.
Licensed & insured · Florida Certified Pool/Spa Contractor #CPC1460367 · Mon-Sat, 8am-6pm
Last verified September 17, 2026
Specifications and warranty terms are taken from the manufacturer documents below. Manufacturers revise these without notice, so confirm the current terms before you buy. If you spot something out of date, email us and we will fix it.
Sources
- Jandy — JXi Gas-Fired Pool and Spa Heater Installation & Operation Manual, H0574300 (rating plate BTU, gas and water connections, flow window, electrical, venting, ambient limit, cupro-nickel model list)
- Jandy / Fluidra — 2024 Product Catalog Addendum, Gas Heaters, 61356_SA (model-number key, firing rates, vent diameters, cabinet dimensions, current part numbers and Jandy's EnergyGuide thermal-efficiency labels)
- Jandy — USA & Canada Jandy Limited Warranty, H0333803 (1 year on JXi heaters, 5 years on factory VersaFlo heat exchangers, 2 years on heat pumps with 5 years compressor and exchanger, no labor, e-commerce exclusion)
Ratings on this site are the editorial opinion of Affordable Solar & Pool Heating, LLC, trading as Modern Pool Heating. How we rate heaters. Corrections: modernpoolheating@icloud.com.
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Mon-Sat, 8am-6pm · Licensed & insured · Florida Certified Pool/Spa Contractor CPC1460367