Triangle Tube Keystone KW 399 399,000 BTU Input Condensing Water Heater - KW 399

The Triangle Tube Keystone KW 399 399,000 BTU Input Condensing Water Heater - KW 399 is a Triangle Tube Keystone condensing water heater designed for high-volume domestic hot water production. The KW 399 model is sized around the listed 399,000 BTU input class for large residential, commercial, or multi-unit water heating loads.

Keystone water heaters use a stainless steel heat exchanger, electronic PID modulating control with a large color touchscreen, sealed combustion, and pre-mix stainless steel burner technology. Triangle Tube documentation lists 95% to 97% thermal efficiency and 5:1 turndown for Keystone water heater operation.

Product Features:

• KW 399 Input Class: Model-specific Keystone water heater with 399,000 BTU input listed in the product name.
• 95%–97% Thermal Efficiency: Triangle Tube Keystone literature lists high condensing thermal efficiency for domestic water heating.
• 5:1 Turndown Modulation: Modulates down to 20% of full fire to better match changing hot water demand.
• Stainless Steel Heat Exchanger: Welded stainless steel heat exchanger construction supports durability in condensing operation.
• Color Touchscreen PID Control: Electronic PID control displays holds, alerts, errors, and diagnostic information in clear text.
• Sealed Combustion / Direct Vent: Supports horizontal or vertical direct venting with sealed combustion chamber design.
• 160 PSI Maximum Working Pressure: Engineering submittals list 160 psi maximum working pressure for Keystone water heaters.

Warranty

Keystone water heaters include manufacturer limited warranty coverage. Confirm current heat exchanger, controls, labor, and commercial-use terms with Triangle Tube documentation.