Wednesday, July 4, 2012
“Reheat” is the term used by air conditioning engineers to describe the process of reheating supply air of a variable volume air conditioning system. In a variable volume system, all rooms get the same cool air from a main air handler.
If one or more of those rooms gets too cold, the air is locally heated to make the space comfortable. This reheat can be done with either electric heating coils or with hot water heating coils. Electric coils are less expensive to install but use electricity rather than gas (used to heat the hot water) as a fuel source.
In California, the use of electricity is strongly discouraged by the Title 24 energy code. Thus, electric reheat is prohibited in California.
There is an exception, however. When the Title 24 calculations are done in conjunction with other factors such as boiler piping loss, electric heat may meet the energy code. It would appear that the USGBC did a full energy model proving electric heat to be an efficient energy choice. And MEP Ninja was “shocked” to make this discovery.
Mark D. Robison, PE
