4
Plenum Duct
The plenum duct can be run in practically any location
accessible for the attachment of the supply tubing (see
suggested layouts in Figure 1.2). The plenum is normally
located in the attic or basement, and it is usually more
economical to run the plenum where it will appreciably
shorten the lengths of two or more supply runs.
In some two-story split level homes, it may be
advantageous to go from one level to another with the
plenum duct. Whenever necessary, either between floors
or along the ceiling, the small size of the plenum makes it
easy to box in.
The fan coil unit is designed to operate with a total
external static pressure of 1.5 inches of water column
(minimum 1.2 - maximum 1.5). Excessive static pressure
increases the air flow in individual runs and may cause
some or all terminators to be noisy.
FIGURE 1.2: PLENUM/TUBING LAYOUT EXAMPLES
(FOR GUIDANCE ONLY)
UNIT NO. 1
UNIT NO. 2
FAN COIL UNIT
FAN COIL UNIT
NO MORE THAN
60% OF CAPACITY
ON ONE
S
IDE
3
0% MAX. OF CAPACITY
MINIMUM 24"
MINIMUM 24"
FIGURE 1.3: USE OF TEES
For systems designed with a bullhead tee installed as on
Unit No. 1 (Figure 1.3), the best results are obtained if not
more than 60
%
of the total number of system outlets are
attached to any one branch of the tee. For systems with a
branch tee installed as on Unit No. 2 (Figure1.3), not more
than 30
%
of the total number of system outlets should be
attached to the perpendicular branch of the tee.
The ESP-4860V has some additional plenum installation
requirements that the smaller systems do not. This is due
to the twin blower arrangement. The ESP-4860V
plenums can be considered and installed as if they were
attached to two separate units, but it is important that
both plenums have about the same number of supply
runs and that the supply runs be of similar length. If the
unit can not be installed in this manner, then an “H”
plenum should be used, as in Figure 1.4. This corrects
flow imbalances between the two plenums. Static read-
ings should be taken on both plenums 18” after the
crossover of the “H” plenum. No supply runs should be
installed between the unit outlet and the crossover.
Summary of Contents for ESPV2-109
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