Mini-Therm Gas-Fired Hydronic Boiler w/ Pump, 150,000 BTU Input, 126,000 Heating Capacity

Mini-Therm JX150 – Gas-Fired Hydronic Boiler for High-Efficiency Residential Heating

The Laars Mini-Therm JX150 is a Category I gas-fired, hot water boiler engineered for residential applications. It features a low-mass, copper-tube heat exchanger, enabling fast temperature response and reduced standby loss. This model delivers 150,000 BTU/hr input with a heating capacity of 126,000 BTU/hr, and is rated at 84% AFUE under standard conditions.

The JX150 is factory-equipped with multiple control features, including a spark-to-pilot ignition system, integral low water cutoff, outdoor reset, warm weather shutdown, and domestic hot water (DHW) priority control for indirect tanks. The boiler carries the ASME “H” stamp and includes a 30 psi relief valve, making it compliant for residential hydronic systems where code-mandated pressure protection and safety controls are required.

System Integration and Control Features

• ASME H-Stamped Heat Exchanger: Copper fin-tube design with cast iron headers
• Integrated Outdoor Reset: Automatically adjusts boiler setpoint in response to outdoor air temperature
• Warm Weather Shutdown: Built-in function disables boiler operation above a programmable ambient threshold
• DHW Priority Mode: Prioritizes indirect domestic hot water heating over space heating when needed
• Digital Display Interface: Provides real-time temperature and fault status
• Low Water Cutoff: Integral safety device prevents dry firing

Technical Specifications

• Input: 150,000 BTU/hr
• Output: 126,000 BTU/hr
• Efficiency: 84% AFUE
• Relief Valve: 30 psi, factory-mounted
• Ignition Type: Intermittent spark-to-pilot
• Electrical: 120V, single-point connection with field interlocks
• Vent Type: Atmospheric, Category I

Installation Notes

The Mini-Therm JX150 is designed for indoor installation in a controlled mechanical space. Proper venting and combustion air provisions are required per local code. The boiler must be installed level and plumb, with correct piping practices for low-mass systems to prevent short-cycling. All field wiring should follow NEC and applicable mechanical code requirements. Gas supply must meet the minimum inlet pressure specified by Laars technical documentation to ensure proper combustion.

Professional Use Context

The JX150 is suitable for single-family residences with hydronic baseboard, panel radiator, or in-floor radiant distribution systems. Its compact size and single-side service access make it appropriate for retrofit applications with limited mechanical room space. Designed with a contractor-friendly layout, all service points including controls, gas valve, and circulator connections are front-facing for simplified maintenance.