Trial 1
all 3 fans come to full speed within 45 min. After 3.5 h, the fans are
slowed to 75% speed for the remainder of the freezing period.
Trial 2
fans came to full speed slightly faster than trial 1. Fan speed was
halved after 7 h. Of these two trials, the first saved more energy and
would be the preferred option.
Trial 3
the three fans started at 30 min intervals. After 4 h the centre fan
was switched off, reducing fan power by 1/3. This method does not
require the use of VFDs.
The results for the three trials are shown on Table 4. Trial 1
performed the best reducing the maximum freezing time by an
hour (8%) and reduced total energy use by 22%, based on the room
performance prior to modifications.