Pressure Actuated Capacity Control Adjustment; Variable Frequency Drives - Carlyle 06D Series Application Manual

CONTROL
SET POINT
ADJUSTMENT
NUT
VALVE
BODY
Pressure Actuated Unloader Valve
3.11 Pressure Actuated Capacity Control
Adjustment
Control Set Point - The cylinder load-up point is
adjustable from 0 psig to 86 psig (1 bar to 6.9 bar).
Refer to Figure 14. Turn the adjustment nut clockwise to
the bottom stop. In this position, the cylinder load-up
pressure is 86 psig (6.9 bar). Control set point is regu-
lated to desired pressure by turning the adjustment nut
counterclockwise. The number of turns can be deter-
mined from the curve in Figure 14. Each full turn coun-
terclockwise decreases the load-up point by approxi-
mately 7.2 psi (.5 bar). Approximately 12 turns changes
the pressure from 86 psig to 0 psig (6.9 bar to 1 bar).
Pressure differential between cylinder load-up point and
unload point is adjustable from6 psi to 16 psi (.41 bar
to 1.1 bar). Refer to Figure 15.
150 PSI (10.4 BAR) SYSTEM DIFFERENTIAL
(1.4) 20
LOAD — UNLOAD DIFF. PRESSURE
VS NO. OF TURNS
18
(1.2)
(1.1) 16
(1.0) 14
12
(.83)
(.69) 10
8
(.55)
6
(.41)
(.28) 4
2
(.14)
0 1 2 3 4
TURNS IN FROM BACKSTOP — CLOCKWISE
Figure 15 – Differential Set Point
Turn the adjustment screw counterclockwise to the
back-stop. In this position, the differential is 6 psi (.41
bar). Differential is set by turning the adjustment screw
clockwise. The number of turns to the desired differen-
SEALING CAP
(COVERS
PRESSURE
DIFFERENTIAL
ADJUSTMENT
SCREW)
DOTTED LINES INDICATE EXPECTED
TOLERANCE EXTREMES UNDER
NORMAL R-22 OPERATING CONDITIONS
5 6 7 8 9 10
tial can be determined from the curve. Each full turn
clockwise increases the differential by approximately 0.8
psi (.06 bar). Approximately 5 turns changes the differ-
ential from 6 psi to 10 psi (.41 bar to .69 bar).

3.12 Variable Frequency Drives

Variable Frequency Drives (VFD's) may be used with
Carlyle 06D/E refrigeration duty compressors and pro-
vide optimum capacity control while maximizing the
compressor efficiency. Some of Carlyle's 06D air condi-
tioning models may require modification of the internal
lubrication system to operate properly. The changes
required for the 06D A/C models are noted in Carlyle
Bulletin 95T-8 or contact Carlyle Application Engineering
if additional clarification is required. VFD's, when prop-
erly applied, provide very stable suction pressure control
and minimize compressor cycling. Additionally, Carlyle
reciprocating compressors attain their peak efficiency at
approximately 900 - 1100 rpm. Therefore, the use of
VFD's versus simply unloading or cycling compressors
will typically result in significant energy savings. The lim-
itations on the allowable speed ranges when using VFD's
are 30 to 60 hertz. Application of Carlyle 06D/E com-
pressors below 30 hertz may result in nuisance oil safety
switch trips due to reduced oil pressure levels.
Operation above 60 hertz may result in increased oil cir-
culation rates and compressor valve failures.
Due to the low discharge gas pulsation frequency of
reciprocating compressors (typically 30 to 180 hertz),
after system start-up the operational frequency band
should be swept to identify any high vibration areas due
to the compressor exciting frequency matching a natural
frequency of the piping or base. Any frequency bands
that result in excessive vibration must be programmed to
skip over.
Variable frequency drives should not be selected on
nominal HP but based on the maximum KW of the com-
pressor motor shown in Tables 5 thru 9 on pages 25
thru 28.
24