Hot Gas Reheat Function and Purpose

Indoor air quality (IAQ) and occupant comfort are two of the most important factors for any HVAC system design.

One of the leading causes of poor IAQ and occupant discomfort is too much moisture in the air, commonly referred to as high humidity. IAQ problems associated with high humidity include mold growth, condensation, increased sickness, and allergic reactions. As for occupant comfort, the saying goes, “It’s not the heat; it’s the humidity.”

Improving indoor air quality and occupant comfort by controlling the humidity and the temperature will help with these problems, boost productivity, and even improve the general well-being of the occupants.

Controlling temperature and humidity over all load conditions takes some planning when designing your HVAC system. To do this properly, we must understand the purpose and function of Modulating Hot Gas Reheat.

Modulating Hot Gas Reheat consists of a reheat coil downstream of the evaporator coil, a modulating reheat hot gas valve, a modulating condenser hot gas valve, and a reheat controller. The evaporator coil cools the mixed air below the dew point and then reheats the air with the reheat coil. The modulating valves allow only the needed amount of reheat, creating a consistent supply of air temperature. Modulating hot gas reheat is the solution to controlling high humidity loads.

[antonkorolev]

Quick, straight to the point - as always! Thank you

[crazycontroller]

These short videos are really helpful. Straight to the point. Keep it up

[yokeleetan]

very good explanation.. thanks Tony.. it was really entertaining..

[brandonestrada]

Amazing explanation, are you able to email me those two diagrams of the refrigeration cycle? One without the reheat and the one with it. I need those for the paper I’m writing if your okay with it

[chrisroday]

Do they make kits to retrofit a unit to provide reheat? When calling for reheat does that lower the overall capacity of the unit?

[jonathancabreja]

Is it possible to disable that valve from operating?

[andrewcardenas]

Does the reheat coil require a metering device?

[daveg]

Excellent. Are you a professional HVAC educator?