Pentair MasterTemp 400 NG Gas Pool Heater
A large pool, or a pool and spa combination, on a pad that is already Pentair and an owner who wants heat on demand rather than an everyday running cost.
Gas heater
SKU MasterTemp 400 NG
- BTU input
- 400,000 BTU/hr
- Fuel / power
- Natural gas
- Thermal efficiency
- 84% thermal efficiency (input rated; 400,000 BTU/hr input)
- Heat exchanger
- Copper
- Warranty
- Parts: 2 years · Labor: 2 years
- Controls & automation
- Two-line LCD with separate pool and spa setpoints, fault history for the last five errors, runtime, cycles, stack flue temperature and flame status; RS-485 COM port for direct IntelliCenter control, 2-wire fireman's switch for IntelliTouch, EasyTouch, IntelliConnect or a time clock.
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 | MasterTemp 400, natural gas, P/N 460736 |
|---|---|
| BTU input | 400,000 BTU/hr input — the MasterTemp manual defines model size as BTU input in thousands of BTU/hr, so output is input times efficiency |
| Thermal efficiency | 84% (tested per ANSI Z21.56:19/CSA 4.7:19 2019, section 5.10) |
| Heat exchanger | Copper (cupro-nickel on the HD models) |
| Fuel | Natural gas (P/N 460737 is the propane version) |
| Emissions | Certified for low NOx emissions; CSA certified to CSA/ANSI Z21.56:19/CSA 4.7:19 |
| Water connections | 2" PVC slip unions, supplied with the heater |
| Water flow | 40 GPM minimum, 120 GPM maximum (bypass valve required above 120 GPM) |
| Gas connection and supply pressure | 3/4" pipe to the gas valve; 4" w.c. minimum and 14" w.c. maximum inlet; manifold factory set at -0.2" ±0.1" w.c.; sediment trap and manual shut-off required outside the cabinet |
| Gas pipe sizing (natural gas) | 1" to 20 equivalent ft, 1-1/4" to 100 ft, 1-1/2" to 200 ft (add 3 ft per elbow) |
| Electrical | 120 or 240 VAC, 60 Hz, single phase; 15 A circuit, 14 gauge field wiring; about 5 A at 120 VAC or 2.5 A at 240 VAC. Ships with the 240 VAC plug fitted. Not rated for 208 VAC. |
| Clearances | 6" from combustible surfaces on the top, exhaust side, header side and door panels; 3 ft between the top of the exhaust vent and any roof overhang; 36" from an air conditioner or heat pump |
| Dimensions and weight | 23.02" W x 21.0" D x 28.15" H; 136 lb carton weight |
| Minimum water temperature | Do not run continuously below 68°F water — condensation damage voids the warranty |
| Controls and automation | RS-485 COM port connects directly to an IntelliCenter Control System (up to 16 heaters, addresses 1-16; the heater's own buttons go inactive and its alarms appear on the IntelliCenter home screen). IntelliTouch and EasyTouch use the 2-wire fireman's switch terminals; Pentair's IntelliConnect guide wires a heater through its low-voltage dry contacts to the heater's external switch connection. Optional Smart Heater Bypass Kit P/N 462048. |
| Florida anchoring | Bolt Down Bracket Kit P/N 460738; Pentair states anchor clamps are required in Florida |
Why homeowners consider it
- It is the gas heater our techs see most often on Gulf Coast equipment pads, and that familiarity is worth real money: parts are stocked locally, and a tech who opens a hundred of these a year diagnoses one faster than an unfamiliar cabinet.
- 84% thermal efficiency, measured per ANSI Z21.56:19/CSA 4.7:19 section 5.10, is at the top of the conventional gas heater range and matches the best of the competing atmospheric and induced-draft units.
- Automation integration is the strongest in the gas category. The heater has an RS-485 COM port that connects straight into an IntelliCenter Control System, where the heater's own alarms appear on the home screen rather than blinking on a panel nobody looks at.
- The LCD carries genuinely useful diagnostics — the last five errors, total runtime, on/off cycles, live stack flue temperature and flame sensor status — so a service call can start with data instead of guesswork.
- Pentair publishes a heat-up estimate of 4 hours 58 minutes to raise a 20,000-gallon pool by 10°F, and 27 minutes to raise a 600-gallon spa by 30°F. Those are lab estimates, not guarantees, but they show what this size of gas heater is for.
What to know before buying
- The heat exchanger is copper, not cupro-nickel. That is fine with disciplined water chemistry, but on a salt pool, a coastal lot or a pool that runs acidic, the HD version (MasterTemp 400HD, P/N 460805) with a cupro-nickel exchanger is the better buy. You give up 2 points of efficiency for it.
- This is a 400,000 BTU/hr input appliance and the gas line has to be sized for it. Pentair's own table allows 1 inch pipe only to 20 equivalent feet on natural gas, 1-1/4 inch to 100 feet and 1-1/2 inch to 200 feet — and you add 3 feet of equivalent length for every elbow. An undersized existing line is the most common reason a heater swap costs more than the quote.
- Natural gas has to be available at the address. Large parts of Sarasota and Manatee County have no gas main, which pushes you to the propane version (P/N 460737) plus a tank and a delivery contract.
- Flow matters: 40 GPM minimum through the heater, 120 GPM maximum before a bypass valve is required. On a variable-speed pump the heating speed has to be programmed high enough to satisfy the water pressure switch.
- Pentair warns that running the heater continuously with water below 68°F causes harmful condensation, damages the heater and voids the warranty. Do not use a gas heater as freeze protection.
- The published warranty is 2 years parts and labor, and only through the right channel. Buy the same heater from an internet retailer and Pentair's warranty page drops it to 1 year parts only with no labor coverage.
Warranty, term by term
The warranty only matters on the parts that actually fail. Here is how this one splits up.
- Parts
- 2 years
- Labor
- 2 years
Pentair's published warranty table gives MasterTemp 2 years parts and labor when the heater is bought through a brick-and-mortar retailer, pool builder or pool service company AND installed by a qualified professional who charges a fee. A heater bought from an internet retailer is covered for 1 year parts only, with no labor. Pentair also publishes a bundle: install a qualifying pump, filter and heater together and all three go to 3 years. Registration is required. MasterTemp is a TradeGrade product, which is Pentair's professional-channel line. Professional installation and authorized-channel requirements 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 scores mid-range. Two years parts and labor is honest, workable coverage, but Raypak's AVIA and Pentair's own ETi line both publish three years parts and labor, and the drop to 1 year parts only for an online purchase is a real trap for homeowners.
- Durability is the weak spot on this particular SKU: a copper exchanger is the category baseline, not a coastal answer. The polymer cabinet and rodent-resistant escutcheons pull it back up half a point.
- 84% thermal efficiency sits at the top of the conventional gas band, and Pentair's own heat-up estimates (4 hr 58 min for +10°F on 20,000 gallons) show it recovers a large pool quickly.
- Serviceability is the best score on the card. This is the gas heater most often already on the pad in our market, parts are stocked regionally, and the LCD keeps a five-error history that turns a diagnostic visit into a repair visit.
- Controls score a full 5 because of the RS-485 COM port: with an IntelliCenter system the heater is a real network device, not a relay, and its faults show up on the automation home screen.
- Value is good rather than exceptional — you are paying for the ecosystem and the service network, not for the exchanger material.
- The computed score lands below the owner's 4.5 starter score for the MasterTemp line. The starter score covers the whole line including the cupro-nickel HD models; this SKU is the copper one, and the copper exchanger plus the 2-year term are what pull it down.
What third-party reviews say
eBay product page (marketplace listing, Pentair MasterTemp 400,000 BTU natural gas)
4.9/5 from 18 reviews
A marketplace aggregate on eBay's catalog page for this heater, not a manufacturer or installer sample. Eighteen ratings is a very small sample with no publication dates, so treat it as a supporting signal only — it is not a current, representative measure of the product. Pentair's own MasterTemp product page publishes no customer rating, and INYOPools' listing for P/N 460736 showed no reviews when we checked.
Checked September 17, 2026View the source
These are other people’s numbers, quoted as published. They are not folded into the Modern Pool Heating Equipment Score and they are not in this page’s structured data. How we rate heaters.
Real Modern Pool Heating installations
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.
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.
Jandy · JXi
Jandy JXi400N Gas Pool & Spa Heater
Model JXI400N
- BTU input
- 399,000 BTU/hr
- Thermal efficiency
- 84%
- Heat exchanger
- Copper
- Warranty
- 1-Year Parts
- Wi-Fi / automation
- App Control via AutomationAutomation Compatible
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.
Pentair · MasterTemp HD
Pentair MasterTemp 400HD Heavy Duty Gas Pool Heater
Model MasterTemp 400HD
- BTU input
- 400,000 BTU/hr
- Thermal efficiency
- 82%
- Heat exchanger
- Cupro-nickel
- Warranty
- 2-Year Parts & Labor
- Wi-Fi / automation
- Automation Compatible
A large salt-water or coastal pool, or a pool and spa that gets used hard, where the exchanger material matters more than the last two points of efficiency.
MasterTemp 400 NG questions
Is the MasterTemp 400 rated by input or by output?
By input. Pentair's manual states plainly that the model size is the BTU input in thousands of BTU per hour, so a MasterTemp 400 draws 400,000 BTU/hr of gas and puts 84% of that into the water. When you compare it against a heater advertised by output, you are not comparing like with like.
What size pool does a 400,000 BTU heater suit?
Large pools and pool-plus-spa combinations. Pentair estimates 4 hours 58 minutes to lift a 20,000-gallon pool by 10°F and 27 minutes to lift a 600-gallon spa by 30°F, both under lab conditions. Surface area, wind exposure and whether the pool is screened move the real result more than gallons do, so we size it against the pool rather than from a chart.
Is a copper heat exchanger safe on a salt water pool?
It can be, with disciplined chemistry and the salt cell plumbed downstream of the heater — but it is not the material we would choose for a salt pool or a coastal lot. Pentair's own answer is the MasterTemp HD, which uses a cupro-nickel exchanger and is described as standing up to low pH, high flow and heavy use. It gives up two points of efficiency to do it.
Will it work with my pool automation?
Better than most gas heaters. It has an RS-485 COM port that wires directly to an IntelliCenter Control System, where the heater's alarms appear on the home screen and its own buttons go inactive. IntelliTouch, EasyTouch, IntelliConnect and a plain time clock all use the 2-wire fireman's switch terminals instead.
What does the warranty actually cover?
Pentair's warranty page gives MasterTemp 2 years parts and labor when it is bought from a brick-and-mortar retailer, pool builder or pool service company and installed by a qualified professional who charges a fee. Bought from an internet retailer, the same heater gets 1 year parts only with no labor. Register the product, and ask about Pentair's bundle terms if you are replacing a pump and filter at the same time.
Do you install Pentair gas heaters in Sarasota?
Yes. We install and service Pentair gas heaters throughout Sarasota, Manatee, Charlotte & Pinellas County, Florida. The comparison content on this page is written for pool owners anywhere; the installation offer is local.
Is the MasterTemp 400 NG 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
- Pentair — MasterTemp High Performance Heater product page (models, part numbers, efficiency)
- Pentair — MasterTemp 400 natural gas SKU page (P/N 460736)
- Pentair — MasterTemp Pool and Spa Heater Installation and User's Guide (BTU input, gas pressure, flow, clearances, electrical, error codes)
- Pentair — 2025-2026 Pool Product Catalog, Heaters & Heat Pumps section (June 2025)
- Pentair — High-Performance Pool & Spa Gas Heaters brochure (efficiency, exchanger, dimensions, heat-up times)
- Pentair — Pool product warranty information (parts, labor, compressor, exchanger terms and channel conditions)
- Pentair — IntelliConnect Control and Monitoring System Installation Guide (how a heater is wired to IntelliConnect)
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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