Pentair MasterTemp® Digital IID ASME Natural Gas Low NOx Pool & Spa Heater 400K BTU
The Pentair MasterTemp® Digital IID ASME Natural Gas Low NOx Pool & Spa Heater 400K BTU delivers all the efficiency, convenience, and reliability of the MasterTemp platform — with ASME-certified construction required for many commercial pool installations. User-friendly indicator lights make system operation and monitoring a snap, and the compact design and super-quiet operation won't intrude on poolside leisure.
Built by Pentair with ASME certification, Digital IID ignition, Low NOx emissions, and 400,000 BTU natural gas output in the compact 23-inch MasterTemp cabinet. Backed by a 2-year warranty.
⚠️ Professional Installation Required. Pool heater installation involves gas line connections and electrical wiring. Always use a licensed contractor to ensure safety, code compliance, and warranty validity.
Key Features
ASME Certified Construction
Built to the most rigorous pressure vessel standards — required for many commercial pool installations.
400,000 BTU Natural Gas
Maximum-capacity heating in the ASME-rated MasterTemp platform.
Digital IID Ignition
Intermittent Ignition Device — reliable electronic ignition without a standing pilot light.
Low NOx Certified
Meets low emissions standards — green certified.
Digital Indicator Lights
User-friendly indicator lights for simple operation and monitoring.
Compact, Quiet Design
Same 23-inch wide MasterTemp cabinet — super-quiet operation.
Indoor and Outdoor Rated
Suitable for both indoor and outdoor pool and spa installations.
2-Year Warranty
Pentair warranty coverage.
Who It's For
- Commercial pool installations that require ASME-certified heater construction
- Applications where ASME is required by code but standard (non-HD) heat exchanger materials are acceptable
- Indoor and outdoor commercial pool and spa heating at 400K BTU
- Anyone who needs ASME certification without the additional cost of cupro nickel HD tubing
Specifications
Heating Performance
| BTU Input / Output | 400,000 BTU |
| Fuel Type | Natural Gas |
| Ignition | Digital IID (Intermittent Ignition Device) |
| Emissions | Low NOx |
| Max Flow Rate | 120 GPM |
Construction
| Control Type | Digital (Indicator Lights) |
Installation
| Gas Connection | 0.75 in |
| Voltage | 120V / 240V |
| Frequency | 60 Hz |
| Phase | Single |
| Application | Indoor / Outdoor / Pool / Spa |
Physical
| Product Weight | 149 lb |
| Cabinet Dimensions | 23 W × 28.2 D × 21 H in |
| Shipping Dimensions | 36 × 24 × 30 in |
Approvals & Warranty
| Certifications | ASME Certified |
| Energy Efficient | Yes (Green Certified) |
| Warranty | 2 Years |
What's in the Box
- Pentair MasterTemp Digital IID ASME 400K Natural Gas Heater
- Union Fittings
- User Manual
Warranty
The MasterTemp Digital IID ASME 400K comes with a 2-year manufacturer warranty from Pentair. Clearflow Pool Supply is an authorized Pentair dealer and will assist with any warranty service needed.
Downloads
Frequently Asked Questions
What is the difference between this (460775) and the 461021 HD ASME model?
Both are ASME-certified 400K BTU MasterTemp natural gas heaters with Digital IID ignition. The 461021 adds heavy-duty cupro nickel tubing specifically rated for low pH, high flow, and heavy use applications. The 460775 uses standard heat exchanger materials — appropriate when ASME certification is required by code but HD tubing isn't necessary for the water chemistry or application.
What does ASME certified mean for this heater?
ASME (American Society of Mechanical Engineers) certification means the heat exchanger was built to the most rigorous pressure vessel standards. Many commercial pool installations — hotels, fitness centers, aquatic facilities — require ASME-certified heaters per local code.
Does this heater require professional installation?
Yes. Gas heater installation involves connecting to a natural gas supply line, electrical wiring, and proper venting. A licensed contractor must perform the installation to ensure safety, local code compliance, and warranty validity.
Can it be used indoors?
Yes. The MasterTemp is rated for both indoor and outdoor installation. Indoor installations require proper venting per local code. Consult the operating manual and a licensed contractor for indoor venting requirements.