Russell CAC 11 User Manual

MultiCon

Computer Room
Air Cooled
Condenser

Publication No. 401.5
September, 2009

5 Thru 164 Nominal tons

Variable Speed
Head Pressure
Control

3050 Enterprise St., P.O. Box 1030, Brea, CA 92822-1030 • Tel: [phone] • Fax: [phone]

Visit us on the Web: www.russellcoil.com

General

Russell’s

CAC/CBC air cooled condenser design allows less fluctuation in discharge head pressures when ambient
temperatures vary. Combining a variable speed, header end fan(s), with fans controlled by standard cycling techniques
provides a stable, energy efficient refrigeration system.

Features

MOTORS / CONTROLS

Header end Vari - speed motors are specifically
designed for P66 application.
Johnson P66 fan motor speed control:

Pressure sensing
230/1/60 or 460/1/60 power
Single or Dual system input
24V control voltage
Double wide condensers have 2 independent P66

controllers.
Fan cycle control, temperature or pressure sensing, on
remaining fans (if applicable).
Units can be wired for an external control power source
(24,115 or 208/230V) or control voltage can be
provided by an 0.15 KVA inter nal control voltage
transformer (24V only) unless otherwise specified.
Fan guards are epoxy coated and fabricated from
heavy gauge steel rod.

CAC models use only 3/4 HP single phase fan motors
with 24” fan blades, and be wired for single or three
phase input power.

CBC models use 3/4 HP single phase Vari - Speed fan

motor(s) and 24” fan blades on the header end fan sec
tions, and 1-1/2 HP three phase constant speed motors
with 30” fan blades on all other fan sections. These
models are only available for three phase input power
applications.
Units are available for 230/1/60, 230/3/60, 460/1/60, or
460/3/60 applications (see page 6 for definition)
[

Consult Factory

for 50 Hertz operation].
Motor assemblies are supported in all-welded, heavy
gauge wire support structures. The wire structures
are zinc - chromate coated for corrosion protection.

COILS

Coil fins are manufactured from die formed corrugated
Aluminum. The tubes are seamless ½” OD Copper,
arranged in a staggered pattern and mechanically
expanded into the fins and tube sheets for optimum
heat transfer efficiency.
Tube sheets are clean punched from 0.080” Aluminum
to resist wear at the tube.

Headers are produced from heavy wall Copper tubing,
and are brazed to the coil using a high temperature
brazing process.
All coils are leak tested in a illuminated test tank at a
pressure of 400 psig.
Heavy gauge galvanized steel casing and support
members.

OPTIONS

Flooded condenser control - available using three-

way modulating valves controlled by discharge pres­sure. Valves are shipped mounted.
Motor fusing - available on all models. Motors can be
fused individually or in pairs on double width units.
Sub-cooling - available as an integral part of the
condenser.

Disconnect switch - thru the door disconnect.

Fins - available in four options; Aluminum, Copper,

polyester coated Aluminum, and baked phenolic coated
Aluminum.
Multiple system circuiting - up to 4 separate systems
are available per unit.
Horizontal air discharge - available upon request for
all models. Contact Russell for details.

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Selections

For the proper selection of an air cooled condenser it is necessary
to know the total heat rejection of the condenser. The Total Heat
of Rejection (THR) is equivalent to the sum of the Net
Refrigerating Effect (NRE) plus the heat of compression added by
the compressor. The amount of heat added to the refrigerant will
depend on the style of compressor, open or suction cooled, and
the operating conditions of the system.

Whenever the THR values are available from the compressor
manufacturer they should be used in selecting a condenser.

For those cases in which the THR data is unavailable it can be
quickly estimated using the following equation and the appropriate
factor from Tables 1 or 2.

Eq. (1) THR = Compressor Capacity x Heat Rejection Factor
In those cases where the refrigeration system is of a multiple or

cascade style, the following equations should be used to estimate
the total heat of rejection.

Open Compressor

Eq. (2) THR = Compressor Capacity + (2545 x BHP)

Suction Cooled Compressor

Eq. (3) THR = Compressor Capacity + (3413 x KW)

Altitude at which a condenser is to operate will also affect its
capacity. In order to correctly select a condenser at a specific
altitude, use the following equation and the appropriate correction
factor from Table 3.

Eq. (4) THR Corrected =THR Design x Altitude Correction Factor

Selection Example

Given:

Altitude 5000 ft.
Ambient Temperature 90°F
Evaporator Temperature 20°F
Maximum Condensing Temperature 110°F
Refrigerant R-22
Compressor Capacity (NRE) 225,000 BTUH
Compressor Type Suction Cooled

Assume compressor THR is not available

Calculate:

1. Total Heat Rejection

2. Design temperature difference

3. Russell condenser size

4. Actual system TD

5. Actual condensing temperature

Solution:

1. Calculate the system THR from Table 2, a suction cooled
compressor, at 110°F condensing temperature and 20°F evap­orator temperature, will have a heat rejection factor of 1.33.

THR = Compressor Capacity x Heat Rejection Factor
THR = 299,250 BTUH

THR Corrected “Altitude” = THR x Altitude Corr. Factor
THR Corrected “Altitude” = 336,656 BTUH

2. Design TD = Condensing Temp. - Ambient Temp.
Design TD = 20°F

3. Select condenser size:
From page 4 locate single width CAC section of the page.
Then using the TD of 20°F calculated in Step 2, go to the
appropriate column and select a condenser whose THR equals
or exceeds that of which we calculated in Step 1; 336,656
BTUH.
A model CAC -37 with a THR of 366,000 BTUH will meet the
required conditions.

4. Eq.(5) Actual TD = Design TD x Design THR

Actual Condenser Capacity at Design TD

Actual TD = 18.4°F

5. Eq.(6) Actual Condensing Temp. = Actual TD + Ambient Temp.

Actual Condensing Temp. = 108.4°F

HEAT REJECTION FACTORS
TABLE 1 - OPEN COMPRESSOR

EVAP

. CONDENSING TEMPERA TURE

TEMP. 90° 100° 105° 110° 115° 120° 125° 130°

-40° 1.45 1.48 1.52 1.56 1.58 1.61

-35° 1.42 1.45 1.47 1.51 1.54 1.57

-30° 1.39 1.41 1.44 1.47 1.50 1.53

-25° 1.37 1.39 1.41 1.44 1.46 1.49 1.52

-20° 1.34 1.37 1.39 1.41 1.43 1.45 1.48 1.51

-15° 1.31 1.34 1.37 1.38 1.40 1.42 1.45 1.47

-10° 1.28 1.31 1.33 1.37 1.38 1.40 1.42 1.45
0° 1.24 1.28 1.29 1.32 1.33 1.35 1.38 1.41

10° 1.21 1.24 1.26 1.28 1.30 1.31 1.34 1.36
20° 1.18 1.21 1.23 1.24 1.26 1.28 1.30 1.32
30° 1.15 1.18 1.20 1.21 1.23 1.24 1.26 1.28
40° 1.13 1.15 1.17 1.18 1.19 1.20 1.22 1.24
50° 1.11 1.13 1.14 1.15 1.16 1.17 1.18 1.20

TABLE 2 - SUCTION COOLED COMPRESSOR

EVAP. CONDENSING TEMPERA TURE
TEMP. 90° 100° 105° 110° 115° 120° 125° 130°

-40° 1.67 1.71 1.75 1.79 1.84 1.90

-35° 1.63 1.67 1.70 1.73 1.78 1.83

-30° 1.58 1.62 1.65 1.68 1.72 1.77

-25° 1.54 1.58 1.60 1.64 1.67 1.71 1.76

-20° 1.49 1.53 1.56 1.58 1.63 1.66 1.70 1.75

-15° 1.46 1.50 1.52 1.54 1.58 1.62 1.65 1.69

-10° 1.42 1.46 1.48 1.50 1.53 1.57 1.62 1.64
0° 1.36 1.40 1.42 1.44 1.47 1.50 1.54 1.56

10° 1.31 1.34 1.36 1.38 1.40 1.43 1.47 1.49
20° 1.26 1.29 1.31 1.33 1.35 1.37 1.40 1.43
30° 1.22 1.25 1.26 1.28 1.30 1.32 1.35 1.37
40° 1.18 1.21 1.22 1.24 1.25 1.27 1.30 1.32
50° 1.14 1.17 1.18 1.20 1.21 1.23 1.25 1.27

TABLE 3 - Altitude Correction Factor (ft.)

Altitude Sea Level 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000

Factor 1.0 1.029 1.052 1.076 1.101 1.125 1.151 1.177 1.204 1.231 1.260

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