When several AC, MC, or NMC cables are bundled together, what happens to the current-carrying capacity compared to when they are separated?

When several AC, MC, or NMC cables are bundled together, the current-carrying capacity is impacted due to heat dissipation requirements. When cables are bundled, they experience reduced airflow around them, which can lead to an increase in temperature.

In standard conditions, each cable has a specific current-carrying capacity when installed independently, based on the ambient temperature, insulation type, and thermal properties. However, when cables are grouped together, the collective heat generated from the flow of current cannot dissipate as effectively, which can necessitate a derating of each cable's capacity to prevent overheating.

Thus, it is generally accepted that when cables are bundled closely together, they actually carry less current compared to when they are installed separately, reinforcing the notion that there can be significant thermal effects that need to be considered in electrical installations. This means that in practice, the correct understanding is that the cables will carry less current than they would if they were spaced apart properly to allow for adequate cooling.