Condenser; Capacity Correction (Antifreeze); Condenser Airflow; Correct Unit Capacity - Carrier 30GTN Product Data

Application data (cont)

Condenser

Altitude correction factors — Correction factors must be
applied to standard ratings at altitudes above 2000 ft (610 m)
using the following multipliers:
ALTITUDE CAPACITY
ft m
0 0
2000 610
4000 1220
6000 1830
8000 2440
10000 3050
Condenser airflow — Airflow restrictions on units with
standard fans will affect the unit capacity, condenser head
pressure, and compressor power input. Correction factors to be
applied for external static restrictions up to 0.2 in. wg (50 Pa)
are as follows:
EXTERNAL STATIC
in. wg Pa
0.0 0.0
0.1 25
0.2 50
High ambient temperature
High outdoor ambient chiller start-up and operation (fully
loaded) is possible for standard 30GTN,GBN chillers at
ambient temperatures up to 125 F (52 C) at nominal voltage. In
some cases, where return water temperature is expected to
exceed 60 F (15.5 C), an accessory kit may be required.
Low ambient temperature operation
With certain field provisions as described below, units will start
and operate down to 0° F (–18 C).
NOTE: Minimum load on chiller must be above minimum step
of unloading.
Antifreeze solution — Inhibited ethylene glycol or other
suitable corrosion-resistant anti-freeze solution must be field
supplied and installed in all units for unit operation below 32 F
(0° C). Solution must be added to fluid loop to protect loop
down to 15° F (8° C) below minimum operating ambient
temperature. Concentration should be based on expected
minimum temperature and either "Burst" or "Freeze"
protection levels.
Provide sufficient volume in the chilled fluid loop — At least 6
gal per ton (6.5 L per kW) of refrigeration is the recommended
minimum for a moderate system load.
Freeze versus burst protection — If chiller operation is not
required during winter/off season, lower glycol concentrations
based on "burst" protection criteria may be considered. Often
use of burst protection results in lower fluid costs and has less
impact on chiller cooler capacity and flow rate. Consult glycol
fluid manufacturers for burst protection recommendations and
fluid specifications.
CAPACITY COMPRESSOR
MULTIPLIER POWER MULTIPLIER
1.00 1.00
0.99 1.01
0.98 1.02
0.97 1.03
0.96 1.04
0.95 1.05
CAPACITY COMPRESSOR
MULTIPLIER POWER MULTIPLIER
1.000 1.00
0.986 1.01
0.968 1.03

Capacity correction (antifreeze)

Inhibited ethylene glycol (or other suitable brine) should be
used in installations where subfreezing temperatures are
expected. Unit performance data must be corrected for the
addition of inhibited ethylene glycol as shown in following
example. Correction factors can be derived from curves in the
Inhibited Ethylene Glycol Performance chart at right.
Additional performance information on this and other fluids is
available in Carrier's Electronic Catalog (E-CAT) software
program. "Slush" and "Burst" concentration may also be
considered for winter shutdown protection and unit operation is
not required.
Example: English — Where a 5 F outdoor temperature is
anticipated, determine concentration of inhibited ethylene
glycol to protect system to –10 F ambient temperature at zero
flow.
Enter the solution crystallization point curve (at right) at –10
F; read that 40% concentration of inhibited ethylene glycol is
required to prevent crystals from forming in solution.
Consider the 30GTN110 unit from the Selection Procedure
example on page 53 (refer to correction curves at 40%
solution).
Correct unit capacity — On the capacity correction curve in
chart on page 47, read 0.95.
Corrected capacity = 0.95 x determined capacity
= 0.95 x 112.6
= 107.0 tons
Correct cooler water flow — On the cooler flow correction
curve on page 47, read 1.15.
Chilled water flow (at corrected capacity)
= 24 x corrected cap. in tons = U.S. gpm
temperature rise F
= 24 x 107.0 = 183.4 U.S. gpm
14°
Chilled water flow (40% solution) = 1.15 x 183.4
Correct cooler pressure drop — On cooler pressure drop
correction curve on page 47, read 1.33.
On cooler pressure drop curve on page 49, for 210.9 gpm, read
pressure drop = 8.1 ft water gage. The pressure drop for 40%
solution = 1.33 x 8.1 = 10.8 ft water.
Correct compressor power input (kW) — On power correction
curve below, read 0.97 correction factor at 40% ethylene glycol
concentration.
Power input from Selection Procedure example
= 126.1 kW.
Corrected power input = 0.97 x 126.1 = 122.3 kW
20
= 210.9 U.S. gpm