Power Outlet Danger
We tend to use electrical power without much thought. Unless there’s a power outage it’s easy to ignore. Have you ever given any thought to the danger posed by incorrect usage of electrical power in your office? And would you be surprised that “normal” electrical wiring can cause a fire? Why does this happen?
Top Causes

The National Fire Protection Association reports the top 5 causes of residential fires as:
- Cooking - 50%
- Heating equipment - creosote build-up in chimneys and the use of space heaters - 14%
- Electrical distribution or lighting equipment - 10%
- Intentional - 8%
- Smoking materials - 5%
The percentages would be different for office buildings. Cooking and fireplace fires would not be much of a factor. Electrical distribution or lighting equipment would be much more significant, as would space heater fires.
Increasing Demand
Power demands have increased a lot over the years. Older buildings – those built before 1990 – did not anticipate the pending explosion of PCs into the office. Each desk needed a data connection as well as a power outlet. Data wiring upgrades were required but wholesale overhauls of building power did not always follow suit.
These days we want to plug in our task lights, Zoom video lights, phone chargers as well as chargers for other personal devices. If the office temperature is not warm enough, we plug in personal space heaters. We don’t request electrical upgrades from the Facilities Department, we just make do; we use power splitters and power bars.
Load Limits
The Canadian and US electrical codes and best practice suggests that wiring gauge and electrical breaker size should be selected so that continuous electrical load for each circuit be limited to 80%. This is partly because breakers are not precision devices and no one wants breakers to trip when there’s no danger. That’s a nuisance.
The other reason is more concerning: when wires carry electricity, the wires heat up. When they carry more electricity and for longer continuous periods of time, they heat up more. Other factors can increase the temperature of the wires as well. These include:
- Higher ambient temperature
- Sunshine heating up an exterior wall cavity.
- Electrical cables surrounded by insulation
- Higher numbers of electrical cables grouped within a wall space
- Other wall cavity heat sources such as data cables connected to power over ethernet data switches
- Personal space heaters which can heat the wall cavity as well as the office space
Watch Out For…
Electrical wires, invisible in your walls, can begin to grow too hot in some locations. This can lead to a fire. Symptoms of an overloaded circuit include:
- Too many circuit breaker trips
- Dimming or flickering lights caused by too many devices using the same circuit, causing the voltage to drop
- An outlet or light switch that feels hot to the touch
Using the 80% load factor, a standard 15A 120V circuit should not carry more than a 12A steady load, with steady load defined as 1 hour or more in any 2 hour period. Remember that up to six outlets could share the same 15A circuit, so you might find that one circuit serves an entire office. You should do regular power audits to identify circuits that may be overloaded and consider splitting loads between more circuits.
If you’d like to discuss a power audit in your organization, or to comment on this article, please email me at ellen.
This article was published in the
July 2024
edition of The TMC Advisor
- ISSN 2369-663X Volume:11 Issue:5
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