Product Overview

Heat your pool fast and keep it comfortable all season with the Sta-Rite Max-E-Therm SR400NA. This 400,000 BTU natural gas heater is built for strong performance in a compact footprint, with a simple digital control panel and low-NOx design for cleaner operation.

Ideal For

• In-ground pools and spas needing rapid heat-up (large gallons, cool climates, frequent use)

• Replacing an older gas heater with a compact, high-output unit

• Homeowners who want a reliable heater with straightforward controls and serviceability

Key Features

• 400,000 BTU heating capacity for quick temperature recovery

• Natural gas model (NA)

• Low-NOx emissions design (meets many air-quality requirements)

• High efficiency operation (commonly listed around 84%)

• Rotating digital display for easier viewing on different equipment pad layouts

• Durable, corrosion-resistant cabinet designed for outdoor equipment pads

• Union connections for easier install/service (plumbing adapters may be required depending on your setup)

Benefits

• Get to swim/spa temps faster with high-output heating

• Maintain consistent comfort during colder nights and shoulder seasons

• Compact sizing helps when equipment-pad space is tight

• Low-NOx design helps reduce environmental impact and improves compliance in many regions

Specifications

• Model: SR400NA

• Fuel Type: Natural Gas

• Heating Capacity: 400,000 BTU/hr

• Electrical: 120/240V (per installation requirements)

• Heat Exchanger: Copper (standard)

• Approx. Dimensions (L x W x H): 31.94" x 25.15" x 30.03"

• Approx. Weight: ~138 lb

Note: Copper heat exchangers are standard for this model. If you have a salt pool or aggressive water chemistry, you may want a cupro-nickel/“HD” style variant instead.

Customer-Facing Q&A

Q: Is this heater for natural gas or propane?
A: SR400NA is Natural Gas. If you need propane, look for the LP version.

Q: Is 400k BTU too big for my pool?
A: 400k is ideal for faster heat-up and larger pools/spas. If you want help sizing, share your pool gallons and location/climate.

Q: Can I use this on a saltwater pool?
A: This model uses a copper exchanger. Many salt pools run fine with proper water balance, but for extra protection some owners choose a cupro-nickel/HD exchanger model.

Q: Does it work for both pool and spa?
A: Yes—this is a pool & spa heater. Your installer/automation controls how it switches between bodies of water (if applicable).