Jandy JXiQ 400K BTU Natural Gas Pool & Spa Heater with VersaFlo – JXIQ400NK

Key Benefits + Pool Heating Performance

• Powerful 399,000 BTU/hr natural-gas heating for compatible pools and spas
• Copper heat-exchanger tubes provide efficient heat transfer
• Factory-installed VersaFlo Integrated Bypass directs water through the heat exchanger only when heat is needed
• 84% thermal-efficiency rating
• Auto-sensing power input adjusts to a compatible 115V or 230V supply
• Low gas-pressure sensor helps prevent ignition when sufficient gas pressure is not detected
• Integrated sensors measure temperature rise to help optimize water flow and protect the heat exchanger
• Calculates estimated heat-up time and displays operating information on the large digital screen
• Bluetooth connectivity gives pool professionals access to real-time diagnostics through the Fluidra Pro App
• Automation-ready for compatible Jandy AquaLink systems and iAquaLink control
• Compact heater body fits on a 2-foot by 2-foot equipment pad
• Fully enclosed cabinet helps protect internal wiring from rodent damage

Jandy’s official materials identify JXIQ400NK as the copper, natural-gas model with polymer headers and factory-installed VersaFlo. The model carries a 399,000 BTU/hr firing rate and an 84% thermal-efficiency rating.

Quick Product Summary

The Jandy JXiQ JXIQ400NK is a 399,000 BTU natural-gas pool and spa heater with copper heat-exchanger tubes, polymer headers, and a factory-installed VersaFlo Integrated Bypass. Its smart sensors monitor gas pressure, water-temperature rise, and operating conditions to support proper performance and easier troubleshooting. This model is intended for pool and spa owners who need fast gas heating, smart diagnostics, automation compatibility, and a compact equipment-pad footprint. Before ordering, confirm the natural-gas supply, heater sizing, electrical service, plumbing layout, venting requirements, installation clearances, and local code requirements.

Best For

• Residential swimming pools and spas
• Larger pools requiring a 400K-class gas heater
• Natural-gas equipment installations
• Pool owners wanting faster water heating
• Systems using compatible Jandy AquaLink automation
• Variable-speed pump systems that can benefit from an integrated bypass
• Equipment pads where a compact heater footprint is important
• Replacing compatible heaters after plumbing, gas, venting, and electrical requirements are verified

Why This Matters

• Correct heater sizing affects heat-up time and fuel use
• The integrated bypass limits heat-exchanger flow when heating is not required
• Auto-sensing electrical input simplifies compatible 115V or 230V installations
• Gas-pressure monitoring helps identify conditions that may prevent safe ignition
• Temperature-rise sensing helps the heater evaluate water flow
• Copper heat exchangers require properly maintained pool-water chemistry
• Confirming the exact fuel type prevents ordering a propane heater for a natural-gas installation
• Professional installation helps ensure the gas, venting, water-flow, electrical, and combustion requirements are met

Jandy states that the VersaFlo bypass directs water through the heat exchanger only when heating is needed. The heater also includes gas-pressure, temperature-rise, and self-diagnostic features intended to support installation, operation, and service.

Common Signs You Need This / Use This When

• Your existing pool or spa heater has failed or become unreliable
• Your current heater takes too long to reach the desired temperature
• You are adding gas heating to a compatible pool or spa system
• You need a high-capacity natural-gas heater
• You want smart diagnostics and estimated heat-up-time information
• You want remote control through an existing compatible Jandy AquaLink system
• Your installer has confirmed that the gas supply and plumbing can support a 399,000 BTU/hr heater
• Your equipment pad has the required space, ventilation, clearances, and service access

Product Specifications

The official catalog confirms the model code, natural-gas configuration, copper heat exchanger, polymer header, VersaFlo bypass, dimensions, 399,000 BTU/hr firing rate, vent sizes, 84% efficiency, and professional-installation requirement. POOL360 confirms the UPC, approximate weight, voltage compatibility, and supplied connection components.

Compatibility / Fitment Notes

JXIQ400NK is the natural-gas model with a copper heat exchanger, polymer headers, and factory-installed VersaFlo. The model-number code is important:

• N identifies natural gas
• K identifies the copper heat exchanger, polymer header, and factory-installed VersaFlo configuration

Do not confuse JXIQ400NK with a propane model or a cupronickel heat-exchanger version.

Before ordering, have a qualified installer verify:

• Required heater capacity based on pool size and desired temperature rise
• Natural-gas meter and available gas-supply capacity
• Required gas-pipe diameter and total equivalent pipe length
• Electrical supply and circuit requirements
• Plumbing connection layout
• Available water flow
• Outdoor clearances or indoor venting requirements
• Combustion and ventilation air
• Equipment-pad size and service access
• Local permits and building, fuel-gas, electrical, and mechanical codes
• Compatibility with existing automation or remote controls

This is not a universal drop-in replacement for every 400K heater. Although the JXiQ offers flexible plumbing and retrofit features, the complete installation must be evaluated before purchase. Jandy’s installation manual requires sufficient gas supply, electrical service, water flow, ventilation, clearances, and code-compliant installation.

Installation / Use Notes

This gas-fired pool and spa heater must be installed and serviced by a licensed or otherwise qualified pool-equipment professional in accordance with Jandy instructions and applicable codes. The installer must verify the natural-gas supply, gas-line sizing, combustion air, venting, plumbing, electrical service, water flow, heater clearances, pressure-relief requirements, and equipment-pad location.

Do not attempt to convert, connect, vent, wire, or start this heater without the manufacturer’s instructions and the required professional qualifications. Incorrect gas or venting work can cause fire, explosion, carbon-monoxide exposure, property damage, serious injury, or death.

After professional startup, use the heater display or compatible Jandy automation to select pool or spa mode and the desired temperature. Maintain proper circulation and balanced water chemistry, and follow Jandy’s inspection and maintenance schedule to protect the copper heat exchanger.

Buy with Confidence

Benchmark Pool Supply provides practical pool-equipment knowledge to help customers identify the correct heater before ordering. We help verify important details such as fuel type, BTU capacity, heat-exchanger material, electrical service, automation compatibility, plumbing configuration, and installation requirements. For this model, confirm JXIQ400NK, natural gas, the copper heat exchanger, and the factory-installed VersaFlo configuration with your installer before purchase.