Haas NGC Alarm 160: Low Incoming AC Line Voltage at power-up, what to check?

Question

I'm getting Alarm 160 Low Incoming AC Line Voltage on our Haas NGC mill right at power-up. It's been happening since we moved the machine to a new bay. What should I check first?

Top answer · Written by InduQT from the fault guide and manufacturer manuals cited below · Oct 28, 2026

Alarm 160 on a Haas Next Generation Control (NGC) indicates that the incoming AC line voltage to the machine is less than 80% of the expected value. This condition prevents the machine from operating until corrected. The Power Fault Detect Module (PFDM) is responsible for detecting this low voltage.

Likely causes and checks

1Transformer taps set incorrectly for the shop supply

Points to it: The machine's transformer taps might be configured for a higher supply voltage than what is actually provided by your shop. This is a common issue after a machine has been moved or newly installed.
Check: Have a qualified electrician compare the transformer tap setting with the measured supply voltage, referencing the machine's installation documentation.

2Low or sagging plant supply

Points to it: The overall plant supply voltage might be low or experiencing sags, especially when other large loads start up or during periods of high demand, such as spindle acceleration.
Check: Have the supply voltage measured at the machine's disconnect under load and compare it against the machine's specified rating.

3Supply wiring or connection problem

Points to it: There could be an issue with the incoming supply wiring or connections, leading to a voltage drop on one or more phases, particularly under load.
Check: With the machine locked out, visually inspect the incoming terminals and the disconnect for any signs of loose or overheated connections.

Next check: Given that the alarm started after the machine was moved and appears at power-up, the most likely cause is incorrect transformer tap settings. You should have a qualified electrician verify the transformer tap settings against the measured supply voltage according to the machine's installation documentation.

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