3–22 469 MOTOR MANAGEMENT RELAY – INSTRUCTION MANUALCHAPTER 3: INSTALLATIONFIGURE 3–24: 2-Wire RTD Lead CompensationThe compensation lead L2 is added to compensate for Hot (L1) and Return (L3), assumingthey are all of equal length and gauge. To compensate for leads RL1 and RL2, a resistorequal to the resistance of RL1 or RL2 could be added to the compensation lead, though inmany cases this is unnecessary.RTD GroundingGrounding of one lead of the RTDs is done at either the 469 or at the motor. Groundingshould not be done in both places as it could cause a circulating current. Only RTD Returnleads may be grounded. When grounding at the 469, only one Return lead need begrounded as they are hard-wired together internally. No error is introduced into the RTDreading by grounding in this manner.If the RTD Return leads are tied together and grounded at the motor, only one RTD Returnlead can be run back to the 469. See the figure below for a wiring example. Running morethan one RTD Return lead to the 469 causes significant errors as two or more parallelpaths for the return current have been created. Use of this wiring scheme causes errors inreadings equivalent to that in the Reduced RTD Lead Number application described earlier.FIGURE 3–25: RTD Alternate Grounding3.2.10 Output RelaysThere are six (6) Form-C output relays (see Specifications on page 2–6 for details). Five ofthe six relays are always non-failsafe; 6 SERVICE is always failsafe. As failsafe, the6 SERVICE relay is normally energized and de-energizes when called upon to operate. Italso de-energizes when 469 control power is lost and will be in its operated state. All other808719A1.CDR469 Motor ControlTerminal Box MotorHotCompensationRTD ReturnA1A2A3L1L2L3RcompRTD1RL1RL2+–808720A2.CDR469 Motor ControlTerminal Box MotorHotCompensationRTD ReturnA1A2A3L1L2L3CompensationHotHotCompensationRTD ReturnA4A5A6A7A8L4L5L6L7No connectionRTD1+–RTD2+–RTD3+–J1J2
