30
SELECTION PROCEDURE (WITH 50TC*A07 EXAMPLE)
I.
Determine cooling and heating loads.
Given:
Mixed Air Drybulb
80
_
F (27
_
C)
Mixed Air Wetbulb
67
_
F (19
_
C)
Ambient Drybulb
95
_
F (35
_
C)
TC
Load
69.0 MBH
SHC
Load
51.0 MBH
Vertical Supply Air
2100 CFM
External Static Pressure
0.66 in.wg
Electrical Characteristics
230--3--60
II.
Make an initial guess at cooling tons.
Refrig. tons = TC
Load
/ 12 MBH per ton
Refrig. tons = 69.0 / 12 = 5.75 tons
In this case, start by looking at the 50TC*A07.
III. Look up the rooftop’s TC and SHC.
Table 12 shows that, at the application’s supply air
CFM, mixed air and ambient temperatures, the
50TC*A07 supplies:
TC
Load
= 73.7 MBH
SHC
Load
= 54.4 MBH.
IV. Calculate the building Latent Heat Load.
LC
Load
= TC
Load
-- SHC
Load
LC
Load
= 69.0 MBH -- 51.0 MBH = 18.0 MBH
V.
Calculate RTU Latent Heat Capacity
LC = TC -- SHC
LC = 73.7 MBH -- 54.4 MBH = 19.3 MBH
VI. Compare RTU capacities to loads.
2,3
Compare the rooftop’s SHC and LC to the building’s
Sensible and Latent Heat Loads.
VII. Select factory options (FIOP)
Local code requires an economizer for any unit with
TC larger than 65.0 MBH.
VIII. Calculate the total static pressure.
External static pressure
0.66 in. wg
Sum of FIOP/Accessory static
+0.14 in. wg
Total Static Pressure
0.80 in. wg
IX. Look up the Indoor Fan RPM & BHP.
Table 33 shows, at 2100 CFM & ESP= 0.8,
RPM = 1268 & BHP = 1.52
X.
Determine electrical requirements
Table 52 shows the MCA and MOCP of a
50TC*A07 (without convenience outlet) as:
MCA = 30.5 amps & MOCP = 45 amps
Min. Disconnect Size: FLA = 30 & LRA = 157.
LEGEND
BHP
— Break horsepower
FLA
— Full load amps
LC
— Latent capacity
LRA
— Lock rotor amp
MBH
— (1,000) BTUH
MCA
— Min. circuit ampacity
MOCP — Max. over---current protection
RPM
— Revolutions per minute
RTU
— Rooftop unit
SHC
— Sensible heat capacity
TC
— Total capacity
NOTES
:
1. Selection software by Carrier saves time by performing
many of the steps above. Contact your Carrier sales rep-
resentative for assistance.
2. Selecting a unit with a SHC slightly lower than the
SHC
Load
is often better than oversizing. Slightly lower
SHC’s will help control indoor humidity, and prevent tem-
perature swings.
3. If the rooftop’s capacity meets the Sensible Heat Load,
but not the Latent Heat Load.
4. Indoor Fan Motor efficiency is available in Table 46. Use
the decimal form in the equation eg. 80% =.8.
50TC
Содержание 50TC Series
Страница 23: ...23 CURBS WEIGHTS DIMENSIONS CHASSIS 1 C08529 Fig 1 Dimensions 50TC 04 07 50TC ...
Страница 25: ...25 CURBS WEIGHTS DIMENSIONS CHASSIS 2 C08531 Fig 6 Dimensions 50TC 08 12 50TC ...
Страница 27: ...27 CURBS WEIGHTS DIMENSIONS CHASSIS 3 C08533 Fig 11 Dimensions 50TC 14 50TC ...
Страница 84: ...84 C08536 Fig 25 2 Stage Cooling Typical Power Diagram 50TC ...
Страница 86: ...86 C08576 Fig 27 2 Stage Typical Wiring Diagram 50TC ...