Cummins/Onan — Voltage sensitive relay adjustment

Adjustments

From a Cummins/Onan owner's manual — check it applies to your exact model before use.

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Procedure

1. Provide an accurate ac voltmeter (not less than 1000 ohms per volt) of 0-150 volt range. Provide a 1000 ohm wire wound rheostat (2 watts or larger).
2. Install temporary jumper wire from N/O to C terminals.
3. Connect the voltmeter across the L1 and L2 terminals. Connect the rheostat in series with the L1 terminal and the wire which normally connects to this terminal.
4. Turn the temporary rheostat to its minimum resistance position, giving a high reading on the temporary voltmeter.
5. Remove the protective caps from the two adjusting controls of the relay. Note the factory marking of the control adjustments.
6. Turn the 'pickup' control to its clockwise limit. Turn the 'drop-out' control to its counterclockwise limit, then 1/4 turn clockwise.
7. Turn the 'pickup' control slowly counterclockwise to just the point where a click is heard, indicating that the relay points have closed.
8. Turn the temporary rheostat to drop the voltmeter reading until the relay contacts open.
9. Turn the temporary rheostat to raise the voltmeter reading slowly. Note the voltage at which the relay closes. This is the pickup voltage at which the load will transfer from Instapac to normal source
10. If the pickup does not occur at the desired simulated voltage turn the relay pickup control in the proper direction. Repeat steps 8 and 9.
11. Turn the temporary rheostat to give the desired voltage for transfer of load from normal line to Instapac.
12. Turn the 'drop out' control slowly clockwise to just the point where the relay contacts open. This will establish the point at which transfer is made from Line source to Instapac.
13. Scratch or paint a reference line to indicate the final adjustment of each adjusting screw, for future reference. Replace the protective caps.
14. Disconnect the temporary rheostat and voltmeter and reconnect wire removed in step 3.
15. Remove jumper wire from N/O and C terminals installed in step 2.

Source: Cummins/Onan owner's manual. Steps and values are as documented; always cross-check against the official manual and any later revisions for your exact serial number before servicing.

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