Hayward TriStar VS 950 "Check System" Voltage Errors Explained

The Key Voltage Messages

You may see Check System messages similar to:

• AC voltage too high
• AC voltage too low
• DC voltage too high
• DC voltage too low

Each of these has thresholds. The drive expects line voltage within a tight band around rated voltage and internal DC bus voltages in a corresponding range. When it detects otherwise, it posts the message and trips.

Step-By-Step Troubleshooting

Step 1: Confirm the message and reset

Owner-level:

1. Note the exact wording of the Check System message.
2. Press Stop/Resume to clear it once.
3. If it returns quickly or repeatedly, do not ignore it. Move on to electrical checks.

Step 2: Measure line voltage at the pump

Tech-level, with proper PPE:

1. Remove the wiring access cover at the drive.
2. Measure voltage between the two hot legs at the terminal block while the pump is running or attempting to run.
3. Compare the reading to rated voltage; anything more than about 10 percent off is a problem.

If voltage is:

• Consistently high: investigate supply configuration or tap settings.
• Consistently low: suspect long runs of undersized wire, excessive voltage drop, or shared loads.

Step 3: Track voltage back toward the panel

1. If the voltage at the pump is out of spec, measure at intermediate junction boxes, timers, and finally at the main breaker.
2. If voltage is good at the panel but bad at the pump, you have voltage drop or bad connections.
3. If voltage is bad at the panel, this is an electrical service issue that must be corrected upstream.

Loose lugs, corroded connections, and old timers are all suspects.

Step 4: Check for mixed or incorrect wiring

• Confirm that the pump is wired exactly as a 230 V single-phase load, not miswired with a neutral or mis-tapped transformer.
• Check that there are no shared neutrals or creative multi-wire branch circuits that create imbalanced voltage.

Any non-standard wiring should be corrected to match code and manufacturer expectations.

Step 5: Consider intermittent supply issues

If errors are rare and not repeatable:

• Ask whether there were storms, brownouts, or other known supply problems.
• Check the event log to see how often and how recently messages appeared.

You might have to put a meter or logger on the line for a while if you suspect intermittent service voltage issues.

Common Parts And Fixes

• Wire upgrades to larger gauge for long runs.
• New breakers, disconnects, or timers when existing ones are overheated or damaged.
• Rarely, drive replacement if internal DC conversion is failing and the supply is known good.

The pump is often the messenger here; killing the messenger without fixing the power will only cause the replacement to die early.

Model-Specific Notes

• The Diagnostics menu can show real-time input voltage status as within range, too high, or too low. Use this instead of guessing.
• Errors can be cleared with Stop/Resume or by power cycling, but that does not fix the underlying supply condition.

How To Prevent Voltage Error Callbacks

• Size conductors for both ampacity and voltage drop, not just code minimum.
• Avoid sharing the pump circuit with large intermittent loads like compressors or welders.
• Make sure all connections are tight and protected from corrosion.