How to troubleshoot a Start/Run Signal Failure Fault (RUN SIG FAIL): on A Murphy Centurion Plus –
A Start/Run Signal Failure fault occurs when the Murphy Centurion Plus panel does not receive input from the auxiliary contact circuit of the motor starter that the contactor is engaged. The Unit Start Fail Delay timer incorporated with this fault is to be set between 2 to 5 seconds. Once the Unit Start Fail Delay times out and the contacts have not been closed, it will display RUN SIG FAIL banner on the HMI.
There are a number of things to look for if this should occur. Below is a description of how the circuit functions, followed by illustrations from wiring diagram #52-30-9565. A number of different wiring diagrams are available, but this is dependent upon the program that is installed. Most Centurion Plus programs follow the same terminal numbers, etc. Be sure to match the diagram with the panel model number. The model number is located directly under the Murphy logo on the front silver sticker.
In this instance, 120 V control power is supplied from the step-down transformer (if equipped). If a step-down transformer is not included, 120 V power will be installed via a separate 120V circuit at TB1. From here, 120 V power energizes CR29 and passes through a 10 AMP fuse – (F10 & F11) for unit A & unit B motor starters respectively.
When a call for a compressor to run is initiated, a digital output signal – (A: DO1 B: DO9) is sent from the MX5 processor and will energize CR16 for unit A and CR8 for unit B. This provides TB6, terminals 3 – unit A and 27 – unit B, with 120 V to engage the starter contactor.
The MX5 has given a command to engage the motor starter; it is now monitoring a RUN SIGNAL from the motor starter auxiliary contacts. At this time, the Unit Start Fail Delay timer has been initiated. If all components are functioning properly within the motor starter circuit, CR25 – unit A and CR28 – unit B will be energized sending a digital input signal (A: DI45 B: DI32) to the CEN processor verifying this.
If a RUN SIGNAL FAILURE does occur, follow these steps to resolve the fault:
- Verify that motor starter AUTO/OFF switch is in AUTO position.
- All fuses are operative – these can be checked by setting a multi-meter to the continuity function to verify the element within is still intact.
- Each Phoenix Relay is equipped with an LED indicator when the relay is energized – verify relays are working properly during each of the processes.
- Check all wiring throughout motor starter circuit(s); verify that leads are landed properly at the correct terminations.
- If all components within the control panel function properly and a RUN SIG FAIL still exists, opening the motor starter cabinets will be the next step.
- Verify that 3 phase power is present, the overload is not tripped, and that all control wiring is secure at terminal block.
- Verify that auxiliary contacts located at the motor starter are functioning properly and moving freely.