Carrier 5H - Manual (Page 10)

5F20 And 5F30 (Fig. 4)
Major Elements of Control Systems:
1. Capacity Control Valve: The function of this
valve is to raise or lower the oil pressure
from the oil pump in response to the refrig­
erant suction pressure.
2. Power Element: The function of this element
is to supply the power necessary to operate
the valve lifting mechanism.
3. Valve Lifting Mechanism: This consists of a
sleeve and push pin assembly around each
controlled cylinder, designed to hold the suc­
tion valve open, or to permit the valve to re­
main in a normal operating position depending
on its actuation by the power element.
Principle of Operation o/ihe System-An increase
in suction gas pressure, which requires increased
compressor capacity, causes the needle valve to
close. Therefore, the lubrication oil pressure in
the power element increases. The increased oil
pressure in the power element moves the power
piston upward and the suction valve discs are
allowed to seat.
Table 9 indicates thé control oil pressure
at which the controlled cylinders start to and
completely unload.
The different points of control pressure on the
5F30 are obtained by using springs with different
loading rates in the power element.
Table 9 - Initial and Final Unloading Oil
Pressui-es - 5F20, 5F30
COMPR
CONTROLLED
CYLINDER
START TO
UNLOAD
OIL PRESS.
COMPLETELY
UNLOADED
OIL PRESS.
5F20 1 19.8 13 0
5F30
1
2
30.0
198
20.2
13 0
2. Hydraulic Relay: The function of this relay is
to feed the lubrication oil from the oil pump at
full pressure in sequence to one or more power
elements. This hydraulic relay is activated by
the control oil pressure from the capacity
control valve.
Power Element: This element supplies the
power to operate the valve lifting mechanism.
4. Valve Lifting Mechanism: This consists of a
sleeve and push pin assembly around each
controlled cylinder, designed to hold the suc­
tion valve open, or to permit the valve to remain
in a normal operating position depending on
its actuation by the power element.
Principle of Operation of the System - A decrease
in suction gas pressure, which necessitates a de­
crease in compressor capacity, causes the range
spring to open the capacity control modulating
valve. This allows the control oil to relieve from
the hydraulic relay and thus reduces the control
oil pressure in the relay. With reduced control oil
pressure the spring in the hydraulic relay moves
the piston and thus the lubrication oil from the oil
pump is prevented from flowing to the particular
deactivated power element. This relieves the oil
pressure from the power element allowing the
spring in the power element to move the lifting
fork and unload the cylinder. An increase in suc­
tion pressure reverses the action and loads the
cylinders.
5H120 Capacity Control (Fig. 6) - The 5H120
capacity control system is similar to that used on
the 5F40 to 5H80 compressors. Unloaded starting
and capacity reduction is obtained by holding open
the suction valves of a number of the cylinders. For
capacity control purposes,* a suction pressure
activated capacity control valve pilots a hydraulic
relay which loads or unloads the cylinders in pairs.
5F40 Thru 5H80 (Fig. 5)
Major Elements of Capacity Control System:
1. Capacity Control Valve: The function of this
valve is to raise or lower control oil pressure
to the hydraulic relay piston in response to the
refrigerant suction pressure. An increase in
suction pressure increases the control oil
pressure in the hydraulic relay.
Major Difference from the 5F40 thru 5H80
Capacity Control:
1. The hydraulic relay design provides a wider
pressure differential between cylinder cut-in
and cutout points. This hydraulic relay is a
small, easily removed cartridge rather than
an integral part of the pump end cover.
2. The surge chamber on the 5H120 is an inte­
gral part of the bearing head casting.
SECTION
PAGE
DATE 5F,H-1XA
10
10-66 Printed in U.S.A.
S U P E R S E D E S
SECTION
5F,H-1X
PAGES 1-42
DATE 11-63