This convention centre has several large event halls, exhibition space and food preparation areas. Disinfection and insect control has to be done in short windows between event changeovers.

The machine in use is a high-powered electric ULV unit, well suited to large enclosed spaces, but it must stay plugged in throughout use, which is a constraint in halls where sockets exist only around the walls.

The team solved the distance problem by joining several extension leads to reach about fifty metres, a common approach that looks harmless, until a burning smell rose mid-event.

What happens inside a lead that is too long

Every cable has resistance, and resistance increases with length. When current flows through resistance, voltage drops along the run, so the voltage at the far end is lower than at the socket.

On a small-gauge lead fifty metres long, the voltage at the far end can drop far more than most people expect, and the higher the current drawn, the greater the drop.

An electric motor does not simply do less work at lower voltage. It tries to maintain output by drawing more current, and that is where it becomes serious, because higher current means more heat in the windings.

On the day of the incident, the team noticed the airflow from the nozzle was weaker than normal from the very start, a clear warning sign that was interpreted as thick solution or a blocked nozzle.

Forty minutes before the burning smell

For the first forty minutes the machine worked, if weakly, so the team carried on and ran it at maximum speed to compensate for the poor airflow, adding still more current and heat.

The extension leads were heating too, particularly at the joints between them, where resistance is higher than in the cable itself. The team later reported that one joint was too hot to touch.

At the forty-minute mark, a burning insulation smell came from the machine. The team unplugged immediately, which was the correct decision and the reason this ended with a damaged motor rather than a fire.

The event organiser had to stop fogging in the remaining halls and delay their opening by two hours, directly affecting the schedule of the clients renting the space.

What we found when we opened the motor

With the motor removed, the smell of burnt insulation was obvious before the casing was even opened, and inside we found windings discoloured over a wide area, the signature of enamel insulation that has exceeded its temperature limit.

Measuring winding resistance across phases showed an imbalance, and insulation resistance to the frame was clearly below the safe threshold, which means this motor cannot be returned to service.

The brushes were unevenly worn with more arcing marks than normal on the commutator, a consequence of running at low voltage for an extended period.

On the control board we found heat marks at the incoming terminals and two discoloured components, which had to be replaced at the same time because parts that have overheated degrade internally even while still working.

What we repaired and what we set up instead

We fitted a new correct-model motor, because rewinding a motor of this size is rarely economic and never as consistent as new, and replaced the brushes and checked the bearings.

We replaced the heat-affected board components and the scorched incoming terminals, then cleaned and applied moisture-protective coating to standard.

We measured the machine's actual current draw at full load, calculated the correct cable size and maximum acceptable length, and produced a table the centre can use to select leads correctly.

Finally we recommended using one single lead of appropriate size rather than joining several, and fully uncoiling it before use, two habits that prevent nearly all incidents of this kind.

10 reasons customers choose World Health Disinfection

1. Actual current measured, not read off the plate

We measure current at genuine full load, because the measured figure is what determines the correct cable size.

2. Cable size and maximum length calculated for you

We calculate to standard voltage-drop practice and provide a table the team can use to choose a lead on the spot.

3. Correct-model motor rather than rewinding

An overheated motor usually has unseen damage, so a new correct-model unit gives a more certain and safer result.

4. Heat-affected board components replaced

Components that have exceeded their temperature limit degrade internally even while working, so we replace them together to prevent a repeat.

5. Insulation resistance measured for safety

We measure insulation resistance to the frame every time, because in occupied spaces current leakage is unacceptable.

6. Full-load testing before return

We run the machine continuously at full load and measure body temperature and current draw, to confirm everything is within limits.

7. Nozzle and solution system checked alongside

Weak airflow can have contributing causes in the nozzle or delivery system, so we check all of it to leave no hidden fault.

8. Handover with documentation for the facilities team

The team receives the current measurement, the extension-lead selection table and the list of parts replaced, for the building's maintenance system.

9. Service that fits a convention centre schedule

We time collection and return to changeover windows so tenants are not affected.

10. Nationwide pickup and return

We collect from and return to convention centres, hotels, factories, hospitals, schools and local authorities across Thailand.

Choosing the right extension lead for an electric fogging machine

The simplest principle is that further means thicker, not just longer, because voltage drop depends on both the length of the run and the cross-sectional area of the conductor.

Always use one single lead long enough for the job rather than joining several, because every joint is a high-resistance point and a hot spot, which is a direct fire risk.

Fully uncoil the lead from its reel before use every time. A lead still wound on its reel cannot dissipate heat and gets hot very quickly under a heavy load.

Check the plug and socket of the lead before use. Replace it immediately if you see scorching, melting or loose pins, because a poor contact is the most dangerous heat source of all.

Warning signs that the machine is not getting enough voltage

The first sign is weak airflow from the very start rather than airflow that gradually declines. If the machine is weak from the beginning with a clean nozzle, suspect the power supply first.

The second is a deeper, heavier motor note, the sound of a motor working harder than it should to maintain output.

The third is a warm or hot lead or joint. If it is noticeably warm to the touch, stop immediately and move to a thicker or shorter lead.

The fourth is lights in the area dimming slightly when the machine starts, which indicates that circuit is near its load limit. Move to a socket on another circuit.

Frequently asked questions

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