re-heating coil

Hi all;

I´ve seen this term (re-heating coil) in an evaporator´s catalogue as an optional. Can anybody tell me what that means?

Best regards

Miguel

They are sometimes called terminal re-heat coils and are used in air conditioning applications where the evaporator's main duty is moisature removal.

When the desired wet-bulb condition is achieved and to give the design relative humidity, the off coil dry bulb may be too low. heat is then added after the cooling coil to temper the delivery temperature. It is possible to have them both in operation at the same time
It's not often used unless real humidity control is needed.

The best illustration can be seen if you plot it on a psych chart.

Sometimes an electric heating option is offered with some small split systems instead of cooling for the winter months. This is not the same thing.

Hope it helps
________
Yamaha Virago 750 history

Argus' reply is succinct and accurate. But here is perhaps another way to explain it, as one does often have to explain it to somebody not in the industry:

When you want a lower RH than normal comfort cooling provides, you need to let the air conditioner run longer so it can continue to extract moisture even after the desired dry bulb (thermometer) temperature is achieved. By warming up the air after the air leaves the evaporator coil, the air conditioning unit can continue to run on its thermostat and wring more moisture out of the air that passes over it.

Not quite true Dan

Reheat is used after cooling to bring either the temperature up because the cooling has reduced the temperature too much or it is used to expand the cool air to reduce the humidity (same moisture content in an expanded air volume = less humidity):D - it doesn't really wring more moisture out! - just another way of saying the same thing!