Hot Gas Reheat vs. Hot Gas Bypass - What's The Difference?

In this video, we discuss the difference between Hot Gas Bypass and Hot Gas Reheat. Two HVAC industry terms that are commonly misunderstood.

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Video Description:

HOT GAS REHEAT uses the high pressure, high temperature, compressor discharge gas to reheat the air leaving the evaporator coil. This is achieved by running the gas through a hot gas reheat coil using hot gas reheat valves. Hot gas reheat is typically used in dehumidification modes to meet the desired space sensible temperature set point.

Modulating hot gas reheat, the more advanced form of reheat, allows us to precisely control the HVAC system leaving air temperature. As opposed to the older style electric reheat, which works well but wastes a lot of energy. Advances in HVAC controls and technology in HVAC systems over the years have made hot gas reheat very popular.

HOT GAS BYPASS provides an artificial load on the evaporator by introducing a portion of high pressure, high-temperature gas to the evaporator/suction side of the system. An inexpensive and simple way to keep the HVAC system running without freezing the coil but a huge energy waster. The hot gas bypass valve is old technology used on a limited basis today quickly being replaces by modulating compressors or variable capacity compressors.

Thank you for watching and please let me know if you have any questions!

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[MechanicsAndCarpentry]

When you build reheat systems like this have you found a need to install a receiver in any instance?

[nickyengle]

Would you say that both systems presented can control Humidity?

[mattroorda]

Hey Tony, great presentation. Do you ever recommend hot gas reheat on multi-zone VAV RTUs? I can't quite understand how these two control sequences would work together in harmony.