Delfield Prep Table Error Code uLo: Line Voltage Too Low
ULo on a Delfield NP prep table means the control sees a supply voltage below 96 volts. The manual gives no operator action for it. Call a technician to check the circuit.
High: low supply voltage can keep the compressor from starting properly and may damage it.
- Code
- ULo
- Maker
- Delfield
- Equipment
- Prep tables
- Applies to
- 4400/4500 Series NP refrigerated prep tables with R290 temperature control (4424NP-4472NP, D4424NP-D4472NP, ST4424NP-ST4472NP and variants)
What does Delfield error code ULo mean?
The R290 control keeps an eye on the incoming line voltage. A supply below 96 volts shows as uLo on the display, which the manual describes as line voltage too low. The only cause it lists is a supply voltage below 96 V. A compressor starting on a low supply draws more current and can struggle to get going, which is a reason the control watches this value. No operator step is given. The alarm follows the same timing as the others on this control. It sounds for about 10 seconds, is silent for 50, repeats for 15 cycles and then goes quiet, and the code remains on the display until the voltage returns to range. Because this is a reading of the supply, the cause is typically outside the table, such as overloaded wiring, a long extension run or a voltage drop on a circuit shared with other equipment.
Affected models and control systems
The manual covers the 4400 and 4500 Series NP refrigerated prep tables with the R290 temperature control, including the 4424NP to 4472NP, D4424NP to D4472NP and ST4424NP to ST4472NP sizes and their variants.
Code numbers and their meaning can change between control generations. We match the full model and control before acting on a code.
What you may notice
- ULo on the display
- Alarm tone for about 10 seconds each minute
- Lights dimming when the compressor starts
- Compressor clicking without running smoothly
Possible causes
Listed in Delfield's documentation
- Supply voltage below 96 V
Other likely causes — what usually sits behind error code ULo on this control. A technician confirms which one it is before any part is replaced.
- Long or undersized cord or branch wiring causing a voltage drop under load
- Receptacle shared with large equipment such as a fryer hood or dishwasher booster
- Loose or burnt connection at the plug or receptacle
Safe checks before calling for service
- Check that the table is plugged directly into a wall receptacle and not through an extension cord or power strip.
- Look at the plug and receptacle for discoloration or heat marks and leave them alone if you see any.
- Ask whether other heavy equipment shares the circuit and was running at the time.
- Leave the table off if the alarm keeps returning.
- For the service call, note when uLo appears and what else was on at the time.
How a technician diagnoses error code ULo
- Read uLo and measure the receptacle voltage with a meter, both idle and while the compressor starts.
- Check the voltage drop along the circuit and the condition of the plug and receptacle.
- Compare the circuit's size and load with the table's nameplate requirements.
- Confirm that the control's voltage reading matches the meter.
- Correct the supply and verify that uLo clears.
- Measuring voltage on a live circuit and tracing branch wiring needs a meter and electrical training.
- Overheated plugs or receptacles are a fire hazard that should only be handled by a technician or electrician.
- Running a compressor repeatedly on low voltage can damage it.
How error code ULo differs from similar codes
ULo triggers below 96 volts. Its counterpart uHi triggers above 140 volts.
Technical reference
- Document
- Prep Tables & Compact Refrigerators, 4400 & 4500 Series: Specifications, Installation, Operation & Maintenance Manual
- Edition
- Part Number 9295093A, 11/25 (page footers 10/25)
- Models / control
- 4400/4500 Series NP refrigerated prep tables with R290 temperature control (4424NP-4472NP, D4424NP-D4472NP, ST4424NP-ST4472NP and variants)
- Section
- Section 3 Operation, control table p. 24
- Checked
- October 2026
We use the maker's document to read the code and do not reproduce it. Always confirm the complete model and control before applying these steps.
Related Delfield prep table error codes
Why would voltage be low in a kitchen?
Shared circuits, long runs and loose connections can all drop the voltage under load. The manual lists only the low supply as the cause.
Will uLo go away by itself?
The code stays on the display until the voltage returns to range.
Should I keep the table running?
The manual gives no action. Because low voltage is hard on a compressor, it is safer to leave the table off and call.
Need help with Delfield error code ULo?
A technician confirms the cause on site and gives you the price in writing before any work starts.