How Does a Variable-Capacity Furnace Like The Lennox SLP99V Work?

The Lennox SLP99V is an example of a variable-capacity furnace, which provides home heating in a manner that promotes enhanced comfort, efficiency, and energy conservation compared to traditional fixed-capacity furnaces. While we will generalize about variable-capacity furnaces, the Lennox SLP99V can serve as a model example.

1. Variable-Speed Blower:

  • Even Air Distribution: The variable-speed blower motor can adjust its speed to more accurately control the flow of air throughout the home, ensuring consistent temperatures and reducing hot or cold spots.
  • Quiet Operation: Variable-speed blowers typically operate at a lower, steadier speed, which is usually quieter than the full-speed operation of traditional blower motors.

2. Modulating Gas Valve:

  • Precise Temperature Control: The modulating gas valve can adjust the heat output in small increments, maintaining the desired temperature with greater accuracy than traditional furnaces that simply turn on and off or operate at fixed levels.
  • Enhanced Efficiency: By closely matching the heat output to the current need, the furnace often operates more efficiently, potentially saving on energy costs.

3. Advanced Controls and Sensors:

  • Smart Thermostat Compatibility: Advanced control systems often allow for integration with smart thermostats, facilitating precise temperature control and programmability.
  • Self-Diagnostics: Some furnaces have self-diagnostics that monitor system performance, ensuring that the furnace operates efficiently and alerts you to any potential issues.

4. Zoning Systems:

  • Individualized Comfort: The furnace can work with zoning systems, allowing for different areas of the home to be heated to different temperatures, accommodating varied preferences and usage patterns.
  • Energy Savings: By only heating areas that are in use, energy is not wasted heating unoccupied spaces.

5. High-Efficiency Design:

  • Energy Savings: High-efficiency furnaces like the Lennox SLP99V convert a larger proportion of the energy in the fuel to heat, reducing waste and potentially lowering energy bills.
  • Environmental Impact: With reduced energy consumption, the furnace helps in lowering the household’s carbon footprint.

6. Air Filtration and Quality:

  • Improved Air Quality: Enhanced air filtration options can help to improve indoor air quality by removing particles and contaminants from the circulated air.
  • Humidity Control: Some advanced systems also manage indoor humidity, contributing to improved comfort and indoor air quality.

7. Durability and Reliability:

  • Longevity: High-quality components and smart diagnostics contribute to a longer life for the furnace, reducing the likelihood of unexpected breakdowns.
  • Consistent Performance: The regular self-checking and diagnostic capabilities ensure that the system maintains its performance across its lifespan.


Variable-capacity furnaces like the Lennox SLP99V offer a more comfortable and efficient home heating experience by precisely adjusting to the specific heating needs of a space, promoting even temperatures, supporting advanced control options, and often providing enhanced air quality and energy savings. They leverage advanced technology and design principles to adapt to the unique heating needs of each home and user, providing a tailored heating solution.

Why Choose ROX Heating & Air?

Choosing ROX Heating & Air for your home heating needs, like installing or servicing a variable-capacity furnace such as the Lennox SLP99V, is choosing impeccable quality and service. Here are a few points that stand out about ROX Heating & Air:

  • Expertise and Experience: With a team of certified and skilled technicians, ROX Heating & Air brings a wealth of experience to your heating solutions, ensuring that installations and servicing are conducted thoroughly and professionally.
  • Customer-Centric Approach: The firm places a paramount emphasis on customer satisfaction, providing not only top-tier heating and air solutions but also maintaining transparent, friendly, and reliable customer service.
  • Quality Assurance: ROX Heating & Air prides itself on delivering superior quality in both products and services, ensuring your heating systems are efficient, durable, and reliable.
  • Innovative Solutions: The company stays ahead in understanding and implementing the latest technologies and solutions in heating and air conditioning, thereby providing you with advanced, energy-efficient, and smart solutions for your home.

Sign Up for the Priority Comfort Club

The Priority Comfort Club by ROX Heating & Air is a membership program designed to offer an enhanced level of service and security for your HVAC systems. Here’s why you might consider signing up:

  • Priority Service: As a member, your service calls are prioritized, ensuring that your needs are addressed promptly and efficiently.
  • Maintenance Benefits: Enjoy regular, scheduled maintenance of your heating and air systems to ensure they operate at peak efficiency and to prevent unexpected breakdowns.
  • Exclusive Discounts: Membership brings you exclusive discounts on repairs, providing cost-saving benefits alongside reliable, professional service.
  • Peace of Mind: Regular check-ups and prioritized service mean you can have peace of mind knowing that your HVAC systems will perform optimally when you need them most.


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Priority Comfort Club

Become a member and enjoy the benefits of regular HVAC maintenance, including exclusive discounts, priority service scheduling, annual HVAC Maintenance, and peace of mind.  Colorado's Best HVAC Maintenance Membership Program.

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