Carrier 5H - Manual (Page 21)

REFRIGERANT 12 AND 22 BOOSTER COMPRESSORS
Booster Application Data - The following data
supplements single-stage compressor application
data, and adds information pertaining to booster
application only. Refer to single-stage compres­
sor data for all other information.
Rating Basis - All booster ratings are given in
refrigeration effect and are based on;
1. Use of a liquid-suction heat interchanger. (It
is important to note here that all liquid-suction
interchangers should have a bypass connection
on the liquid side so that adjustment can be
made in the event that too much superheating
of the suction gas causes excessive heating of
the compressor. This is especially true in the
case of Refrigerant 22, which has a higher
compression exponent than Refrigerant 12.)
2. The liquid refrigerant at Point "A" (Fig. 15)
being at the saturation temperature corre­
sponding to the booster discharge pressure.
This is also often referred to as the "sat­
urated intermediate temperature."
This situation obtained when booster discharge
gas is condensed in a cascade (refrigerant-
cooled) condenser, or when using an open flash
type intercooler in a direct staged system.
When subcooling or the liquid takes place in a
closed type intercoooler then it is not possible
to bring the liquid temperature all the way
down to the saturated intermediate tempera­
ture because of the temperature difference
required for heat transfer thru the liquid coil.
In this case, the compressor rating must be
3.
decreased for each 10 F, that the liquid
temperature at Point "A" is above the sat­
urated intermediate temperature.
Use of only one-half the standard number of
suction valve springs per cylinder. All 5F,H
compressors are factory-assembled with the
standard number of suction valve springs;
therefore, one-half of the suction valve springs
per cylinder must be removed in the field for
booster application.
"R" Factors - In a multi-stage compression sys­
tem, the intermediate or high stage compressor
must have sufficient capacity to handle the low
stage (booster) compressor load plus the heat
added to the refrigerant gas by the low stage
machine during compression. Likewise, if an
intermediate stage compressor should be used,
the high stage compressor must have sufficient
capacity to handle the intermediate stage com­
pressor load plus the heat added to the refrigerant
gas by the intermediate stage machine during
compression.
To assist in the selection of higher stage
compressors. Tables 18 thru 20 present "R"
factors which depict the approximate required
relationship between stages at various saturated
temperature conditions.
To determine the required capacity of a higher
stage compressor, multiply, the lower stage com­
pressor capacity by the proper "R" factor from
either Table 18, 19 or 20. Any additional loads
handled at the intermediate pressure must be
added to this figure to arrive at the total higher
stage load.
Multi-Stage System Pointers - A staged system
is essentially a combination of two or more simple
refrigerant cycles. In combining two or more
simple flow cycles to form a staged system for
low temperature refrigeration, two basic types
of combination are common (Fig. 15).
DIRECT STAGING - Involves the use of compres­
sors, in series, compressing a single refrigerant.
CASCADE STAGING - Usually employs two or
more refrigerants of progressively lower boiling
points. The compressed refrigerant of the low
stage is condensed in an exchanger (cascade
condenser) which is cooled by evaporation of
another lower pressured refrigerant in the next
higher stage.
S U P E R S E D E S
SECTION 5F,H-1X
PAGES 1-42
DATE 11-63
SECTION
PAGE
DATE
5F,H-1XA
21
10-66