A practical guide for Red Deer and Central Alberta shops on why lights flicker when welders, compressors, pumps, motors, or other equipment start — and when to call an electrician.
If the lights in your shop dim or flicker every time a compressor, welder, pump, hoist, saw, or other piece of equipment starts, it is more than an annoyance. A brief change in brightness can be a normal sign of a large load starting up, but repeated or severe flickering can also point to voltage drop, loose connections, overloaded circuits, undersized wiring, or issues with motor starting equipment.
For commercial, agricultural, and light-industrial buildings around Red Deer and Central Alberta, flickering lights are worth paying attention to because they often show up before a larger failure. The cause might be simple, but it should be checked before it leads to nuisance breaker trips, damaged lighting drivers, motor problems, or downtime.
Motors and certain types of equipment draw more current when they first start than they do while running. This is called inrush current or starting current. A motor that runs comfortably once it is up to speed may pull several times its normal current for a short moment during startup.
When that sudden demand passes through panels, feeders, branch circuits, breakers, disconnects, transformers, and wiring, the voltage can dip briefly. Lights are often the first thing people notice because LED drivers and fluorescent ballasts react quickly to voltage changes.
Shops, farm buildings, pump houses, and outbuildings often have longer electrical runs than a typical office or retail space. If the feeder or branch circuit is long, heavily loaded, or not sized for the equipment now being used, voltage can sag when a motor starts. This is especially common when equipment has been added over time without reviewing the overall electrical layout.
Some motors start directly across the line, meaning they receive full voltage immediately. This can create a noticeable current surge. Depending on the motor size, the supply capacity, and what else is running at the same time, that surge can cause lights to blink or dim.
In some applications, a soft starter or variable frequency drive may reduce the starting impact. Whether that is the right solution depends on the equipment, duty cycle, environment, and control requirements.
Loose lugs, aging splices, worn disconnects, damaged receptacles, and deteriorated connections can all create resistance in the circuit. When equipment starts, that resistance can show up as heat, arcing, voltage drop, flickering lights, or intermittent operation.
This is one of the more important possibilities to rule out. A loose connection is not just inefficient; it can become a fire hazard or damage equipment.
In three-phase shops and light-industrial spaces, load balance matters. If one phase is carrying more than the others, or if multiple high-demand loads are grouped in a way that strains part of the system, lighting and equipment can behave unpredictably.
A panel may also be close to capacity during certain parts of the workday, especially when heat, ventilation, compressors, lighting, chargers, pumps, and production equipment run together.
LED lighting is efficient, but not all LED drivers respond the same way to voltage changes, harmonics, or electrical noise. A voltage dip that an older fixture barely showed may be obvious with certain LEDs. If only one area of lighting flickers, the issue may involve fixture quality, driver compatibility, a shared neutral, switching, dimming, or the specific circuit feeding those lights.
A small, momentary dim when a large motor starts may not be unusual. However, you should have the electrical system checked if you notice any of the following:
These symptoms can indicate a supply issue, connection problem, overloaded circuit, motor issue, or control problem. Waiting until something fails completely can lead to more expensive repairs and lost production time.
Electrical troubleshooting should start with measurements, not guesses. Depending on the situation, an electrician may check voltage at the panel and at the equipment, measure startup current, inspect connections, review breaker and wire sizing, look at phase balance, and check whether the lighting circuit is being affected by a specific load.
For motor-driven equipment, the inspection may also include contactors, overload settings, starters, VFDs, disconnects, control wiring, and the mechanical load on the motor. Sometimes the electrical system is being blamed when the equipment itself is hard to start because of a mechanical issue.
There is no single fix for flickering shop lights because the right repair depends on what is causing the voltage disturbance. The solution may be as straightforward as repairing a poor connection or moving lighting to a more appropriate circuit. In other cases, it may involve feeder upgrades, panel changes, load balancing, improved motor controls, a soft starter, a VFD, or changes to how equipment is sequenced during startup.
The important point is to identify the cause before replacing lights or equipment. Swapping fixtures may not solve the problem if the real issue is voltage drop, loose wiring, or an overloaded supply.
Grasse Electric helps commercial, agricultural, and light-industrial customers in Red Deer and Central Alberta troubleshoot electrical problems involving lighting, motors, controls, panels, and equipment power. If your shop lights flicker when equipment starts, a proper inspection can help prevent nuisance problems from becoming costly downtime.
Contact Grasse Electric to book electrical troubleshooting for your shop, garage, farm building, or light-industrial facility.
Written by Todd Grasse, Red Seal Journeyman Electrician, Grasse Electric — Red Deer, Alberta. Published September 21, 2026.
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