Technical Reference

Manual Tuning
For optimum control performance, tune the 1500 to the themal system. The tuning
settings here are meant for a broad spectrum of applications; your system may have
somewhat

different

requirements.

Refer to the key flow

charts,

diagrams and
defini-
tions on Pages 42
-
61
for prompt location and description. Repeat this tuning
procedure for both Channel 1 and 2.
1
NOTE:
When tuning in
the Heat mode, use H where
X appears.
When tuning In the Cool mode, use C where
X appears.
1.
Apply power to the Series 1500 and enter a set point in the Change Data Mode
(CHG DATA). Next, go into the Change Parameter Mode (CHG
PARA),
and
enter (1) at

the GA parameter. Using the MODE, UP/DOWN

and ENTER keys,
set the operating parameters initially:
l Proportional Band:
1X
Pb=O
l Cycle Time:
!1
1X CT=5
.
Reset:
l 1 X
RS
=
0.00
l Dead Band:
1X
db=O
.
Rate:
1X
RT
=
0.00
l Caiibration
Offset:
1X
CA
=
0
l Rate Band:
1X
Rb
=
3.00
To tune a parameter relating to heat, set the set point above ambient temperature,
for cooling, set the set point below ambient temperature. Allow actual process
tern-
perature to stabilize at or near set point. The ACTUAL display indicates when
the
load is stabilized near set point.
2.
3.
4.
5.
6.
Proportional Band Adjustment: Gradually increase Pb until the ACTUAL display
temperature stabilizes to a constant value. The temperature will not be right on
set point because the initial reset value is 0.00 repeats per minute. The ACTUAL
temperature will stabilize below the desired set point. (When Pb
=
0,
RS,
Rb,
RT,
and
Ct
are inoperative, and the 1500 functions as a simple ON/OFF
control
with a
3°F/1.7°C
switching
differential.
Reset Adjustment: Gradually increase

RS

until the ACTUAL display temperature
begins to oscillate or “hunt.” Then slowly decrease
RS
until the ACTUAL display
stabilizes again near set point. NOTE: This is a slow procedure, taking from
minutes to hours to obtain optimum value.
Rate Adjustment: Increase
RT

to 1 .OO min. Then raise set point by

20°
to
30°F/
11° to
17°C.
Observe
the system’s approach to set point. lf the bad tempera-
ture overshoots set point, increase
RT
to 2.00 minutes.
Cycle Time Adjustment: Set CT as required. Optimum system controls is always
achieved with faster cycle times.
However, if a mechanical
contactor
or
solenoid
is switching
power
to the load, a longer cycle time may be desirable to minimize
wear on the mechanical components. Experiment until the cycle time is consis-
tent with the quality of control you want.
Calibration Offset Adjustment: You may want your system to control to a tem-
perature other than the value coming

from

the input sensor.
If
so, measure the
difference (as much as
±90°F/±50°C)
between that temperature, perhaps at
another point in the system, and the process value showing in the alphanumeric
display.
Then
enter the amount of CAL Offset
YOU
want
Calibration offset adds
or
subtracts
degrees from the value of the input signal.
Tuning, Chapter
4
WATLOW
Series
150O
User's
Manual
59