Application data – Carrier ZONE-MIZER 50ME User Manual
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Refrigeration system
Psychrometrics — The 48MA/50ME units differ psychro-
metrically from the conventional multizones due to the
operation of the outdoor air coil. The coil in the Carrier units
cools and dehumidifies the outdoor air entering the unit thus
assuring that raw outdoor air is not passed along to the
zones. This air treatment by the outdoor air coil (and also by
the zone module evaporator coils) provides excellent low
load performance and precise temperature control to the
conditioned space. The only large load variation occurs on
the outdoor air coil where a thermal expansion valve is used.
This allows the use of simple capillary tube expansion de
vices on the zone coils. The zone coils cool and dehumidify
a mixture of return air and outdoor air — outdoor air at the
approximate dew point temperature of the return air.
The Psychrometric Chart illustrates this air treatment for
a typical set of conditions. As an example: 1000 cfm of
outdoor air at 95 F/75 F having 99 grains moisture content
enters the outdoor air coil and is cooled and treated so that
the air leaving the coil has 68 grains of moisture content.
The outdoor air coil under these conditions has a capacity
of 60,000 Btuh of which 39,000 Btuh is sensible. This is a
coil sensible heat factor of 0.65. By examining the room
conditions, it is evident that the outdoor air coil is very
effective in removing the latent load. At 75 F/50%, the room
content is 64 grains of moisture. The percent moisture
removed with respect to room conditions is:
% removed
Application data
The 1000 cfm of outdoor air at 68 grains is mixed with
8000 cfm of return air at 75 F/50% room conditions (64
grains). This mixture then enters the zone modules and is
cooled and dehumidified by the zone coil.
Heating
Gas heating system — In special applications where
natural gas supply is limited, modify units to operate under
derated input/output conditions. Derate the modular multi
zone by changing the zone module burner spuds as follows:
TOTAL MODULE
DERATED INPUT(%)
HIGH FIRE
100
90
80
SPUD SIZE
No 38
No 41
No 43
9 9 - 6 4
100 = -1^ = 88.5%
oO
Contact Carrier Service Department before derating to
the above limits.
Hot water/glycol heating system — Multizone hot
water/glycol heating systems are ideal for renovation of
existing buildings where a hot water heating plant is usually
available. Each zone module has its own high-capacity
PSYCHROMETRIC CHART — EXAMPLE
GRAINS OF MOISTURE/
LBS OF DRY AIR