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STAGGER SPACING — A frequently used layout method
is to stagger the units. This arrangement gives good cover-
age, solves the problem of drafts when units blow at each
other, and is low cost. It also gives good flexibility for future
partition changes. (Fig. 17.)
MAXIMUM UNIT SPACING — Interior zones use less air,
as low as 0.4 to 0.6 cfm per sq ft. Using the large capacity
37HS4 unit at 250 to 350 cfm each may cause units to be too
widely separated. This results in poor coverage and poor air
distribution.
A good solution is to use a larger number of lower ca-
pacity 37HS2 units at 150 to 190 cfm each.
The maximum distance between units parallel to each other
(blowing at each other) can and should be fairly great, 25 to
45 ft. (See Tables 4 and 5.) But the maximum distance be-
tween the ends of the units in the same row must be more
limited for good coverage.
The unit will effectively cover a strip whose width is 3 to
4 times the unit’s length. A 4-ft unit would therefore cover
an area whose width is 12 to 16 ft (maximum). See
Fig. 18.
The high induction ratio of the Moduline diffuser keeps
total room air motion up to acceptable levels when the cfm
per sq ft is low.
Step 3 — Consider Unit CombinationsAnd Run-
Out Duct
— When the preliminary office layout is com-
plete, the trunk or main duct can be laid on the floor plan.
We are now ready for positioning the units in the space ac-
cording to the load calculations and the design of the run-out
ducts.
The zone load calculation provides the cfm requirements
for each space. Using those requirements and the ceiling lay-
out, the unit location and run-out can be determined. Figure
19 shows a single Moduline unit located on the grid line in
the approximate center of the space. Figure 20 shows mul-
tiple units in an air series located in similar fashion.
RECOMMENDED UNIT COMBINATIONS — Tables 6-8
list the recommended combinations of Moduline terminals.
Each model (size) of Moduline terminal is shown in com-
binations of 2, 3, 4 and 5 plenum sizes. To illustrate the use
of the tables, consider the 37HS2 for a space requiring 550
cfm. Three units in air series will provide the capacity. (Note
that 550 cfm is below the max cfm limit of 660 shown in
Table 7.) Six combinations of 37HS2 units are available; all
will produce a good installation. However, some factors in-
fluence the choice:
If it is desirable to have common plenum sizes throughout
the space, the choice will be three 9 x 9-in. plenums.
The lowest inlet velocities will result in the least variance
of discharge cfm among the 3 units on one control.
If this is a consideration, the choice would be three 11 x 11-
in. plenums.
The lowest cost choice would be 9- x 9-in., 9- x 9-in., and
7- x 7-inches.
If the requirement of the space is for maximum cfm from
the unit combination, one of the larger plenum combinations
would be favored.
Conversely, a conservative design with small cfm per unit
can use the smaller plenum sizes.
The selection of plenum sizes will not affect the sound
level of the space; there is no measurable difference in the
recommended plenum combinations.
NOTE: The listing of recommended air series combinations
does not indicate that one controller will always handle the
combination; in some cases, a second controller may be re-
quired. Refer to Determine Controller Location section,
page 37.
Table 9 provides an overall limitation on cfm in the inlet
collar of units in air series.
Fig. 17 — Staggered Units
Fig. 18 — Unit Spacing
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