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ComfortStar Technical Bulletin 24V+485 AHU Wiring Connecting Guide – Scenario 1 (Recommend)

24V+485 AHU Wiring Connection Guide - Technical Bulletin No. TB230427-03
Scenario 1 (Recommended)

Learn how to correctly connect the AHU-SG2 Air Handler to a CPR or CPH Side Discharge Condensing Unit with the ComfortStar thermostat in Scenario 1 of the 24V+485 AHU Wiring Connection Guide (Technical Bulletin No. TB230427-03).

You can access this bulletin by clicking here or through the ComfortStar Tech Support Mobile App in the APP STORE or GOOGLE PLAY under technical bulletins.

  • In Scenario #1, connect the thermostat to HA and HB on the display board and the condenser cables to S1 and S2 on the main board of the AHU-SG2.
  • For the CPR or CPH Side Discharge Condensing Unit, attach S1 and S2 on the top terminal board, clearly marked.
  • Ensure all DIP switches are in the off position (switched to the bottom).
  • When the unit is powered on, the board should display 00.
  • Once the thermostat is activated, your settings will appear on the AHU-SG2 display board, and in Scenario 1, the blower motor will start running within seconds.
  • In this setup, the blower motor will run continuously even after the desired temperature is reached; only by physically turning off the thermostat can you stop the blower motor.

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EPA Proposes Ban on R-410A Systems Starting in 2025

EPA Proposes Ban on R-410A Systems Starting in 2025

This move is part of a larger effort to reduce the carbon footprint of the HVAC industry. While R-410A has been widely used as a refrigerant in air conditioning systems, it is a hydrofluorocarbon (HFC), which contributes to the depletion of the ozone layer and global warming. As such, the EPA has been encouraging the use of more environmentally friendly refrigerants, such as R-32 and R-290, which have a much lower GWP and are less harmful to the environment.

While the phase-out of R-410A may pose some challenges for the HVAC industry, it presents an opportunity for manufacturers to innovate and develop more sustainable solutions. It also presents an opportunity for building owners and operators to invest in more energy-efficient and eco-friendly HVAC systems, which can help reduce their carbon footprint and operating costs in the long run. Overall, the phase-out of R-410A is a positive step towards a more sustainable future. By reducing the use of harmful HFCs in air conditioning systems, we can help protect the environment and mitigate the impacts of climate change.

The reduction of HFC consumption is a significant step towards combating climate change. HFCs are potent greenhouse gases that contribute to global warming and the depletion of the ozone layer. By reducing the use of HFCs, the EPA/DOE plan aims to reduce carbon emissions and promote a healthier environment.

The plan also includes incentives for the development and use of alternative refrigerants that are less harmful to the environment. This will encourage innovation and investment in the HVAC industry, ultimately leading to more sustainable and eco-friendly solutions.

As for the SEER2 requirements, they will improve the energy efficiency of HVAC equipment, helping to reduce energy consumption and lower energy bills for homeowners and businesses. This will also have a positive impact on the environment, as less energy consumption means lower carbon emissions.

Overall, the EPA/DOE plan marks a significant milestone in the fight against climate change. By reducing HFC consumption and promoting energy efficiency, we can create a more sustainable future for ourselves and generations to come.

One way we can ensure that we continue to provide comfort for our customers is by being proactive about the changes in the HVAC industry. We understand that it can be difficult to keep up with all the changes and new regulations, which is why we are here to help. We want to make sure that our customers are aware of the new regulations regarding R410 refrigerant and how it could impact their HVAC systems. Our team of experts is available to answer any questions and provide guidance on how to prepare for this transition.

At the end of the day, our goal is to provide comfort at a great value, and that means staying up-to-date with the latest industry changes and trends. We are committed to helping our customers navigate this transition and ensuring that they continue to receive the highest level of comfort and service.

Using A2L refrigerants such as R32 and R454B as a replacement for R410A has been shown to have a significant impact on reducing greenhouse gas emissions. These refrigerants are also more energy efficient, which can help reduce energy costs for consumers. Choosing a system that uses A2L refrigerants can also have long-term benefits for the environment, as they have a lower global warming potential than other refrigerants. As we continue to prioritize environmental responsibility, is committed to providing reliable, efficient HVAC systems that meet or exceed SEER2 standards and comply with environmental regulations.

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With over 50 years of combined experience, our research and development team continues to develop products that adhere to the highest quality standards, while elevating the level of efficiency to protect our precious environment.

Our manufacturing facilities maintain the highest quality and reliability standards with ISO9001 and ISO14001. All our products are AHRI and ETL certified.  

Across the world, we are committed to bringing daily comfort into every facet of your lives. Whether it is your home, your child’s school, or your local grocery store, ComfortStar is there to ensure a pleasant environment, regardless of the climate.

Advances in Inverter technology have made mini-split heat pump systems among the highest efficiency heating and air conditioning systems on the market today. This technology allows us to modulate the frequency of a compressor according to the thermal load of the conditioned space; therefore, a compressor can reduce the amount of work it does to reach a desired set temperature.

This results in longer compressor life-span and most importantly, decrease in energy usage and increased energy savings.

Mini-splits are ideal when making additions to a home, since expanding existing duct work can be problematic in some situations. Ease of installation makes it very practical for light commercial applications, such as hotel rooms, office spaces, malls and hospitals.


Products Made With Industry Leading Innovation

Advances in Inverter Technology have made our mini-split heat pump systems among the highest efficiency heating and air conditioning systems on the market today.

We are proud to be recognized worldwide as a leader in providing reliable, energy-efficient, innovative, and cost-effective products.


🡆 R410a Systems: Environmental friendly refrigerant.
🡆 Inverter Controlled Compressor:
High efficiency variable speed compressor.
🡆 Gold Fin: Condenser Coil Coating enhances heat
exchange, improves hydrophilic performance and
protects against corrosion.
🡆 Active Carbon Electrostatic Fiber Filter:
Electrostatic fiber traps small dust particles, smoke and pet
dander to prevent allergies.
🡆 Built-In Low Ambient Control:
System can operate in cooling and heating mode even.
when ambient conditions decrease down to 5° F.
🡆 Follow-Me Remote Control:
Built-in sensor in remote control which measures
room temperature where the remote is located.