Specifications
78
4. Calculate the line side error ratio using the following
equation:
* in POWER screen.
5. Shut down the chiller.
6. If the Line Side Error Ratio is greater than ± 0.02 adjust
the ICVC reading by adjusting the MOTOR CUR-
RENT CT RATIO in the ISM_CONF screen. This
screen can only be accessed when the chiller is not run-
ning.
Change CT Ratio
1. New MOTOR CURRENT CT RATIO = Present MO-
TOR CURRENT CT RATIO multiplied by (1+ Line Side
Error Ratio).
To access the ISM_CONF screen:
2. Press .
3. Press .
4. Enter the password 1111.
5. Select ISM (STARTER) CONFIG DATA.
6. Enter password 4444.
7. Select ISM_CONF.
8. Change present MOTOR CURRENT CT RATIO to new
ratio using calculation above.
9. Press to the softkey to save changes.
10. Press the softkey to exit the ISM_CONF screen.
11. Repeat ISM Current Calibration Check.
VFD Current Control Calibration Check
1. With the TARGET VFD SPEED at 100%, load the chill-
er so that the ICVC default display shows 75% to 100%
under the ICVC default screen display title AMPS %. A
higher load is preferred.
2. Access the current on the keypad of the VFD. Determine
the Load Side Current Ratio, using the equation below.
Next, access the VFD LOAD FACTOR on the Capacity
Control screen. Calculate the Load Side Error Ratio using
the equation below:
3. If the load side error ratio is greater than ± 0.02, adjust the
VFD LOAD FACTOR by changing the VFD CUR-
RENT LIMIT on the Setup 2 screen.
a. The new VFD CURRENT LIMIT = old VFD
CURRENT LIMIT multiplied by (1+ Load Side
Error Ratio).
b. Recheck the VFD Current Control Calibration.
c. Release the Speed Control by accessing the TAR-
GET VFD SPEED control.
Press .
Press .
Press .
(Refer to Override Operations section on page 19.)
Protecting the VFD Configuration
1. Select parameter P.051 from the VFD keypad.
2. Press the softkey to access the parameter. A zero
will be displayed.
3. Use the arrow key to increment the value to 26. This is
the password number.
4. Press the softkey to save the value. P.051 will by
displayed.
NOTE: Parameter programming is disabled when the
PASSWORD LED is on and enabled when the PASS-
WORD LED is off.
5. Select parameter P.006 from the VFD Keypad.
6. Press the softkey to access the parameter.
7. Use the arrow key to increment the value to 107. This
is the password number to restrict displaying the remain-
ing P, and all of the H and r parameters.
8. Press the softkey to save the value.
MODIFY SURGE LINE CONFIGURATION POINTS IF
NECESSARY (Machines with serial number prior to
1410Qxxxxx) (See Fig. 36) — If configuring a chiller with a
Four Point Hot Gas Prevention curve and settings are not avail-
able, calculate Maximum and Minimum load points as follows.
Use the minimum load point values for MINIMUM LOAD
POINT (ΔT1/ ΔP1) only. Use the maximum load point values
for all three points: LOW LOAD POINT ((ΔT2/ ΔP2) MID
LOAD POINT (ΔT3/ ΔP3) and FULL LOAD POINT (ΔT4/
ΔP4). This will result in a 2 point surge curve. When adjusting
this curve when surge prevention comes in too early or too late,
adjust as a 2 point curve but remember to adjust the LOW, MID
and HIGH LOAD points by the same amount.
Hand Calculate Maximum Load
— To calculate the maxi-
mum load points, use the design load condition data. If the
chiller full load cooler temperature difference is more than 15 F
(8.3 C), estimate the refrigerant suction and condensing tem-
peratures at this difference. Use the proper saturated pressure
and temperature for the particular refrigerant used.
Suction Temperature:
42 F (5.6 C) = 37 psig (255 kPa) saturated
refrigerant pressure (HFC-134a)
Condensing Temperature:
98 F (36.7 C) = 120 psig (1827 kPa) saturated
refrigerant pressure (HFC-134a)
Maximum Load T4:
54 – 44 = 10º F (12.2 – 6.7 = 5.5º C)
Maximum Load P4:
120 – 37 = 83 psid (827 – 255 = 572 kPad)
Error Ratio =
Amp Meter current –
ACTUAL LINE CURRENT*
Amp Meter current
Load Side
Current Ratio
=
VFD Actual Load Amps (from VFD)
VFD CURRENT LIMIT (in SETUP2)
Load Side
Error Ratio
=
VFD LOAD FACTOR – Load Side Current Ratio
Load Side Current Ratio
ENTER
SERVICE
SAVE
EXIT
MENU
STATUS
COMPRESS
ENTER
ENTER
ENTER
ENTER
A
B
C
Delta T
(INC)
(∆T1/∆P1)
(∆T2/∆P2)
(∆T3/∆P3)
(INC)
Delta
P
(∆T4/∆P4)
Fig. 36 — Four Point Surge Prevention Curve
a19-1867