COCOON THRMS-1-3900 Thermal Mass Duct Heater

The COCOON THRMS-1-3900 Thermal Mass Duct Heater is our highest-capacity Thermal Mass Duct Heater, engineered to deliver exceptional supplemental heating while stabilizing indoor temperature swings in the largest residential, commercial, industrial, and specialty HVAC applications.

Unlike conventional electric duct heaters that cycle between full heat and no heat, COCOON Thermal Mass Technology stores thermal energy and releases it gradually. This creates a smoother, more consistent flow of heated air that minimizes temperature fluctuations, enhances HVAC system performance, and delivers superior comfort throughout the conditioned space.

The THRMS-1-3900 is designed for the most demanding heating applications requiring maximum supplemental heating capacity, advanced zoning support, and optimized airflow balancing without the need for a complete HVAC system redesign. Whether serving large commercial buildings, industrial facilities, institutional spaces, or other high-load environments, it integrates seamlessly into existing ductwork while providing dependable, energy-efficient performance built to last.

Key Benefits

• Helps stabilize indoor temperature swings by smoothing heat delivery in the air stream
• Provides supplemental heating support for larger or uneven HVAC zones
• Reduces hot and cold fluctuations in delivered air for more consistent comfort
• Uses Thermal Mass Technology to store and release heat more consistently than standard electric duct heaters
• Improves overall comfort by supporting existing HVAC system performance rather than replacing it
• Designed for flexible installation in vertical, horizontal, or downflow configurations
• Integrates into existing ductwork with minimal system modification
• Compatible with grid power, solar, backup generators, and hybrid energy systems
• No venting required
• Suitable for residential, commercial, and specialty HVAC applications
• Engineered and manufactured in the United States

General Specifications

THRMS-1-3900-R-P12

Energy Source: Electric Grid, Solar, Wind, Hydro, Backup Generator, or Hybrid Energy Systems

Venting Required: None

Emissions: None

BTU Capacity: 183,222 BTUs

Active BTU: 110,553.4 BTUs

Stored BTU: 72,668.6 BTUs

Active KW: 32.4

Number of Circuits: 3

Number of Circuit Breakers: 3

Voltage: 208-240V / 480V

Hertz: 50 / 60

Full Load Amps: 45 each

Maximum Overcurrent Protection: 60 amps each

Minimum Circuit Ampacity: Per NEC and local codes

Circuit Ampacity: 58 Amps

Recommended Breaker: 60 Amps

Installation Orientation: Vertical, Horizontal, Downflow

Electrical Phase: Single Phase standard (Three Phase available, contact for availability)

Unit Dimensions: 18 x 24 x 54 in

Product Weight: 225 lbs

Shipping Weight: 245 lbs

Safety Listing: UL Listed File Number SA44706

Warranty Information

• 1-Year, 5-Year, and 10-Year Limited Warranty Options
• 10-Year Heat Exchanger Warranty
• See Warranty Documentation for Complete Details

Shipping Information

Shipping Method:
LTL Freight (Where Available)

Shipping Weight:
245 lbs

Country of Origin:
United States

Application Assistance

If you have questions regarding sizing, electrical requirements, installation configuration, or application suitability, our team is available to help determine the best COCOON solution for your project. Call us at +1 314-931-1004