Carrier 48MA - Manual (Page 10)

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FROM NOMINAL
Fig. 7 — 48MA/50ME Room Capacity Multipliers
Power Wiring Data — The 50ME028, 460-3-60 unit
with 132 kw of electric resistance heat, has a 75.8
cooling circuit minimum wire ampere and a heating
circuit minimum wire ampere of 207.0. If any
module is operating on mechanical cooling (com­
pressor operating), one heating stage in each
module is locked out and cannot be energized.
This, a common feeder can be sized for minimum
wire ampere of 221 (see Fig. 37).
APPLICATION
Diversity — The size, shape and orientation of the
building — as well as the application and location
of zones, influence the degree of diversity that may
be applied to a multizone system.
Since the normal application of multizone units
involves zones where loads are shifting due to solar
energy, people, equipment and lights, diversity will
exist.
The Carrier modular multizones will be affected
by building diversity only on the refrigeration
system. When a particular zone (or zones) thermo­
stats are satisfied, a solenoid shuts off the zone
evaporator coil. This enables more refrigerant to
flow to other operating zone coils, creating a larger
capacity for that zone. However, the diversity will
lower the selected unit total capacities.
The 48MA/50ME ratings do not reflect diver­
sity but can be converted to diversity ratings by
using the capacity correction factors and formulas
in Table 3.
Table 3 — Capacity Correction Factor (CCF)
LOAD
DIVERSITY FACTOR
1.0 90 .80
TC (Unit)
SHC (Unit)
1 0
1 0 97
94 94
89
RTC (with diversity)
RSHC (with diversity)
[TC (CCF) - OATH]
(Diversity Factor)
[SHC (CCF) - OASH]
Diversity Factor
This is accomplished by rating the unit assum­
ing that no more than 9 of 10 zones would be on
at one time, 90% diversity. The same logic applies
to other diversity factors on an average basis, such
as 85 or 95%.
A rating with a diversity factor results in a
lower room SHF; therefore, a reselection at a
higher total unit cfm is advisable to take full
advantage of the building diversity.
Limitations
MODULE CFM LIMITS AND FAN PER­
FORMANCE — The cfm limits per zone are
1200 cfm maximum and 600 cfm minimum. The
1 0