An experimental study of energy consumption and thermal comfort for electric and hydronic reheats

This paper compares the performances of electric and hydronic reheat modes for variable-air-volume units using experimental data for a building. The comparisons are made based on the daily energy consumption associated with each reheat mode and comfort performances within a building zone. Data are collected from a full-scale heating, ventilating, and air conditioning system. Weather conditions are considered and the corresponding energy distributions are evaluated. The results showed that the energy for the air handling unit using hydronic reheat is lower than that using electric reheat by about 24% when the air handling unit is operated in either the mechanical or mechanical and economizer cooling mode and 33% for the economizer cooling mode. The reheat energy for the variable-air-volume units using hydronic reheat is lower by about 75% than for electric reheat for either the mechanical or mechanical and economizer cooling mode and 54% for the economizer cooling mode. The main reason for the low-energy consumption using hydronic reheat is attributed to the lower requirement for the minimum air flow across the reheat coil. Electric reheat provides a slightly cooler comfort environment than that for hydronic reheat.