Carrier ZONE-MIZER 50ME - Manual (Page 13)

CAPACITY VS CFM CHANGES
ZONE NO. OF RSL/ZONE % DEVIATION % CFM CHANGE
jUNIT TOTAL
CFM3 CAPACITY
I multiplier
UNIT
NOMINAL
RTC/ZONE
ADJUSTED
NO. MODULES PEAK LOAD (RSL/NOM UNIT RSHC) FROM NOMINAL UNIT RTC
... 1 1 16,935 16,935/19,720 .86* -20 720 i 9 X 23,556 21,200
2 1 22,505 22,505/19,720 1.14 +20 1080 1 11 X 23,556 25,912
3 1 22,505 22,505/19,720 1 .14 +20 1080 1 11 X 23,556 25,912
4 3 59,160 59,160/3 X 19,720 = 1 00 0 2700 i 1 0 X 3 X 23,556 70,668
5 1 19,720 19,720/19,720 1.00 0 900 ! 1 .0 X 23,556 23,556
6 1 22,505 22,505/19,720 1 .14 : +20 1080 1 11 X 23,556 25,912
7
2 33,870 33,870/2 X 19,720 = 86 -20 1440 1 .9 X 2 X 23,556 42,400
10 197,200 9000 j 235,560
RSHC — Room Sensible Heat Capacity RSL — Room Sensible Load RTC — Room Total Capacity
ZONE COOLING CAPACITY MULTIPLIERS
%
CFM CHANGE*
+ 35
+ 20
+ 10
0
-10
-20
-35
ROOM TOTAL
CAPACITY
(RTC)
1.15
1.10
1.05
1.00
0 95
0 90
0 85
ROOM SENSIBLE
HEAT CAPACITY
(RSHC)
1.14t
1 07t
1.00
0 93
0.86
0.79
*Must not be greater than 1200 cfm nor less than 600 cfm per module,
tlf resulting RSHC is greater than RTC, then RSHC equals RTC
Outdoor Air Sensible Heat (OASH)
OASH = 1.09 (OA cfm) (toa - troom)
Room Total Capacity (RTC)
RTC = Unit TC - OATH
Room Sensible Heat Capacity (RSHC)
RSHC = Unit SHC - OASH
Leaving Air Temperature (LAT)
T A T + + R S H C
LAT = room temperature - ^ Q'^f^
Determine Heating Capacity:
The specified requirement for electric heat dictates the
selection of a 50ME028 unit with a kw option that meets
or exceeds the heating load.
The Electric Resistance Heater Data table (page 30) indi­
cates that the 028 unit has heating capacity options of 66,
88 and 132 kw. The 132 kw option is selected as it provides
adequate heat for this application. The kw/zone and
number of heat stages available are:
Zone No. Load
Zone Heating
Capacity
Stages
of Heat
1 10.0 kw 13 2 kw 3
2 12 9 kw 13 2 kw 3
3 12 9 kw 13 2 kw 3
4 32 5 kw 39 6 kw 9
5 12 3 kw 13.2 kw 3
6 12 9 kw 31 2 kw 3
7 23 7 kw 26.4 kw 6
Total 117 2 kw 132 0 kw 30
Stages of heat are controlled individually in the small zones
or collectively in large zones to provide flexible and
continuous control for each zone.
Determine fan requirements
For 48MA/50ME operation, cfm range per module is 600
to 1200 cfm. Lower flow volumes are permissible if only
first stage of heat is operated. Volumes above 1200 cfm
may cause water blow-off during cooling.
Since the various unit zones operate at different air
quantities and different external resistances, identify the
zone having the highest static pressure requirement for
the supply duct and supply outlet.
Usually, the longest duct run to the last outlet, with the
greatest number of offsets and elbows, has the greatest
static pressure requirement. Assume a duct friction analysis
has been made and the cfm and static pressure are:
Zone No. CFM ESP (in. wg) No. Modules CFM/Module
1 720 6 1 720
2 1080 8 1 1080
3 1080 5 1 1080
4 2700 6 3 900
5 900 4 1 900
6 1080 4 1 1080
7 1440 5 2 720
Totals 9000
The total unit (028
10
or 030) cfm is 9000. Zones 4 and 7 have
3 and 2 modules, respectively, “ganged” together to comply
with the limitation of 1200 cfm per module
The cfm for Zone 2 is 1080 with an ESP of 0.8 in. wg. This
module appears to possess the highest friction loss. There­
fore, the main fan static pressure is established at 8 in. wg
ESP.
Enter Fan Performance table at 9000 cfm, .8 in. wg ESP
and read: 1020 rpm and 5.4 bhp. The 028 indoor fan motor
data shows the standard 10 hp motor with a maximum bhp
of 11.5. Therefore, 5 4 bhp for this selection is satisfactory.
In the Physical Data table, 2 pulley selections are available
with the 028: Pulley A, shipped mounted; Pulley B, shipped
in the blower compartment. Pulley A has a fixed pitch and
at 1095 rpm is close enough to the required cfm and should
be used. Pulley B at 1230 rpm allows selection of the unit
at higher cfm’s and static pressures.
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