WIRING CONNECTIONS
After the unit has been mechanically mounted, it is ready to be wired. All
wiring connections are made to the rear screw terminals. When wiring the
unit, use the numbers on the label and those embossed on the back of the case,
to identify the position number with the proper function.
All conductors should meet voltage and current ratings for each terminal.
Also cabling should conform to appropriate standards of good installation,
local codes and regulations. It is recommended that power supplied to the unit
(AC or DC) be protected by a fuse or circuit breaker. Strip the wire, leaving
approximately 1/4" (6 mm) bare wire exposed (stranded wires should be
tinned with solder). Insert the wire under the clamping washer and tighten the
screw until the wire is clamped tightly.
Caution: Unused terminals are NOT to be used as tie points. Damage to the
controller may result if these terminals are used.
SIGNAL WIRING
Thermocouple (T48)
When connecting the
thermocouple, be certain that
the connections are clean and
tight, refer to Figure 4 for
terminal connections. If the
thermocouple probe cannot
be connected directly to the
controller, thermocouple
wire or thermocouple
extension-grade wire must
be used to extend the
connection points (copper
wire does not work). Always
refer to the thermocouple
m a n u f a c t u r e r ’ s
recommendations for mounting, temperature range, shielding, etc. For
multi-probe temperature averaging applications, two or more thermocouple
probes may be connected to the controller (always use the same type).
Paralleling a single thermocouple to more than one controller is not
recommended. Generally, the red wire from the thermocouple is negative and
connected to the controller’s common.
RTD (T48)
When connecting the
RTD, be certain that the
connections are clean and
tight, refer to Figure 5 for
terminal connections. RTD
sensors have a higher
degree of accuracy and
stability than thermocouple
sensors. Most RTD sensors
available are the three wire
type. The third wire is a
sense lead for canceling the
effects of lead resistance of
the probe. Four wire RTD
elements may be used by
leaving one of the sense
leads disconnected. Two wire RTD sensors may be used in either of two ways:
A) Attach the RTD to terminals #8 and #10. Install a copper sense wire of the
same wire gage as the RTD leads. Attach one end of the wire at the probe
and the other end to terminal #9. Complete lead wire compensation is
obtained. This is the preferred method.
B) Attach the RTD to terminals #8 and #10. Install a shorting wire between
terminals #9 and #10, as shown in Figure 5, RTD Connection. A
temperature offset error of 2.5°C/ohm of lead resistance exists. The error
may be compensated by programming a temperature offset.
Note: With extended cable runs, be sure the lead resistance is less than 15
ohms/lead. For thermocouple or RTD runs longer than 100 feet, convert the
signal to a current near the temperature probe. Current or 20 mA loop signals
are less susceptible to noise and signal loss than long thermocouple or RTD
runs. The RLC ITMA and IRMA DIN rail modules are designed for these
applications. By converting the temperature signal, the P48 can be used in
place of a T48.
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Figure 4, Thermocouple Connection
Figure 5, RTD Connection