nvent 910 Series Installation, Operating And Maintenance Instructions page 55

Terminal No.
19
20
21
22
8
9
10
11
The RTD manufacturer will typically color code the leads with the source and sense being the
same color, and the common a different color. Ensure that the RTD extension wire shield is
terminated at one end only, normally using the terminal block provided at the terminal board.
IMPORTANT: Some manufacturers use the common Black-White-Red triad color code for the
RTD connections. Usually, the RED lead is the common connection (same as the White-white
Red color scheme) and the White and Black connections may be used interchangeably.
2. Seemingly Incorrect Temperature
If you feel that the indicated or displayed temperature is not correct, the controller and the
RTD can be quickly checked for correct operation.
To verify the RTD:
TURN THE POWER TO THE CONTROLLER OFF BEFORE PROCEEDING!!
• Disconnect the RTD wiring from the input terminals.
• To calculate the temperature indicated by the RTD, measure the resistance from source
(white wire) or sense (white wire) to common (red wire) and subtract the resistance
measured between source and sense. This will give a compensated resistance value that
can be cross-referenced to one of the RTD tables found in Appendix E or Appendix F.
Compare the measured resistance and cross-referenced temperature value obtained from
the RTD table to the indicated or displayed value. These should agree to within the accuracy
standards of the HTC and the RTD.
IMPORTANT:
• Ensure you refer to the correct RTD table for the type of RTD you are using.
• Ensure that the TS TYPE setting matches the type of RTD that you are using.
To verify the Controller:
TURN THE POWER TO THE CONTROLLER OFF BEFORE PROCEEDING!!
• Disconnect the RTD wiring from the input terminals.
• Connect a 100 Ω resistor across the source or sense terminal and common. Insert a jumper
between the source and sense terminals.
• Apply power to the controller. The indicated or displayed temperature should be about 32°F (0°C)
depending on the actual resistance of the test resistor if TS TYPE is set to 100 Ω Platinum.
3. Unstable or Bouncing Temperature
An erratic indication of temperature can be caused by several factors external to the
controller, however a bouncing temperature of a few degrees should not be confused with
incorrect operation. The controller's accuracy and resolution will result in an indicated
temperature change of a couple of degrees if the measured resistance temperature falls
between two discrete values (this is sometimes referred to as quantization error).
If the bounce or instability is excessive, check:
• Wire used for extension of the RTD should be three-wire, twisted and shielded with the shield
grounded at the controller only. Each of the three lead wires must be of the same gauge.
• The ideal installation has a separate conduit for the RTD leads (if they have been extended).
It is not usually a problem to run low signal levels in the same conduit as the power leads
even in high power applications, as long as the RTD wire is a twisted, shielded type with an
insulation rating equal to or greater than the highest voltage in the conduit.
Description
Shield
TS 1 Source (WHT)
TS 1 Sense (WHT)
TS 1 Common (RED)
Shield
TS 2 Source (WHT)
TS 2 Sense (WHT)
TS 2 Common (RED)
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