Stop combining network filters — here's why it's risky
Power filters protect our equipment from power surges and turn one outlet into several useful sockets. But when there are still not enough "outlets," the temptation to connect one filter to another can result in overheating, fire, and loss of warranty.
SlashGear writes about it.
What happens if two protective filters are connected in sequence?
Each network or surge protection filter is designed for a specific maximum load. When one filter is inserted into another, the main device connected directly to the wall is forced to "pull" the entire circuit, exceeding its permissible power. As a result, overheating, tripping of protection devices, or even ignition is possible.
Most filters are UL certified for stand-alone use only: they are not designed to work in a "chain". Instructions (if any) usually explicitly require that the filter be plugged into a wall outlet only. Violation of this rule voids the warranty on both the filter itself and the equipment connected to it.
Serial connection is so dangerous that it is considered a violation of OSHA safety standards in the United States and contradicts the National Electrical Code (NEC). Although you are not required to comply with these standards at home, the risks remain the same.
Does a double filter provide better protection?
In many cases, "the more, the better," but it doesn't work with network filters. A power surge — for example, from lightning during a storm — is absorbed by the filter's internal circuitry. The additional load from a second filter can prevent this circuit from working or make it completely ineffective. Instead of enhanced protection, you get weakened protection and a higher probability of damage to expensive electronics.
As a reminder, we wrote that even a single charger that is constantly connected to the mains consumes a small amount of electricity. But if there are several such devices in the house, the costs become significant, along with additional risks for adapters and fire safety.