What is the purpose of reheat coils?
What is the purpose of reheat coils?
Reheat for dehumidification is simply cooling the air with the air conditioner to pull out the moisture. But instead of throwing the heat outside, the reheat coil simply puts that heat back Into the original air stream. It forces an air conditioner to act like a poorly designed dehumidifier.
How does reheat control humidity?
To prevent the temperature of the dehumidified air from over-cooling the space, the reheat coil heats the air before it leaves the unit. As the compressor turns on and off, the humidity will also fluctuate; while the compressor is on, the air is dehumidified and the space humid- ity drops.
Where are reheat coils located?
The secondary heat exchanger or “reheat coil” is almost always located directly above the blower making them prone to collecting more dust and debris than air conditioning coils. This is why it is imperative to access, inspect and clean these coils in order to properly clean the system.
When should I warm up my coil?
Reheat is used sometimes for humidity control, and sometimes for occupant comfort. The latter use happens when zone cooling loads are low and too much cold air is supplied to a space.
What is a reheat coil?
1. In an air-conditioning system, a coil which heats air in the supply duct to control its temperature. 2. A coil which is heated to control the temperature of air being furnished to individual zones, 1.
How do you size a reheat coil?
The Main Heating Coil Airflow is equal to the Design Heating Airflow.
- Main Heating Coil Airflow = 500 cfm.
- Leaving Coil Temperature = 122.3 F.
- Entering Coil Temperature = 55.9 deg F.
- Main Heating Coil Capacity = (1.0882) x (500) x (55.9 – 122.3) = -36,128 MBh.
- Reheat Coil Airflow = 500 cfm.
What does reheat mean in HVAC?
Reheat is the addition of heat to previously cooled air. Reheat is used sometimes for humidity control, and sometimes for occupant comfort. The latter use happens when zone cooling loads are low and too much cold air is supplied to a space.
What is a pre heat coil?
In an air-conditioning system, a coil used to preheat air which is below freezing to a temperature somewhat above freezing, in advance of other processing.
What is the face area of a reheat coil?
The one-row reheat coil has a face area equal to that of the evaporator coil. The thermostat is factory-mounted and controls the leaving air temperature by ±3.0° F (± 1.6° C) at varying evaporator conditions.
How does a vav with terminal reheat work?
The reheating is primarily or exclusively done at the zone level and is sometimes called VAV with Terminal Reheat. In general (e.g. for offices), this system works by having the central air-handling unit (AHU) cool all the air just to the point needed by the hottest zone with its VAV box wide open (maximum air flow to the zone).
Where does the reheat take place in a HVAC system?
This “reheat” process is often performed at the central air-handling unit (AHU). Temperature control in the zones is then performed by some combination of airflow control and additional heating or cooling. In the case of temperature control, a very common HVAC scheme is Variable Air Volume with Reheat (VAV-RH).
How does the reheat guide for DDC work?
reheat coil. Specifically: Reheat in Btu/hr = 1.08 x zone airflow in cfm x (zone discharge air temperature in °F – AHU supply air temperature in °F) This equation will indicate the reheat at any given moment. In a typical direct digital control (DDC) system, the flows and temperatures can be trended and the trend data can be used to determine
