Wire thhn, just like other building materials such as water pipes, it do not require frequent replacement during normal use. Usually, it is only considered during the second renovation whether to replace the thhn thwn wire, and there are even many users who do not replace the THHN THWN 2 wire during the second renovation.
According to the American standard, the service life of cable thhn shall not be less than 70 years. In other words, as long as the construction is carried out according to the specifications, the service life of thhn thwn wire can be almost the same as that of the decoration. Of course, the above refers to thhn copper wire, and the service life of thhn aluminum wire is slightly shorter. But this does not mean that the thhn wire can never be replaced. When the following three situations occur, it is necessary to consider replacing the thhn stranded wire.
The quality of thhn Wire has deteriorated. Not all thhn electrical wires on the market are qualified products. Once we buy a low-quality thhn cable, the troubles it brings us are endless: if the insulation layer is slightly damaged, it is leakage; A slight breakage of thhn conductor can cause overload; A slight adhesion of the connector can cause a short circuit... Occasionally, one or two circuit faults occur, which can be considered a coincidence. But if the line frequently malfunctions (1-2 times a year), we have to suspect the quality of the THHN wire. At this point, it is necessary to replace the cable thhn thwn throughout the house, which may cause line faults and inconvenience to users. This is only one aspect. On the other hand, if there is a problem with the protective device, it may also cause electric shock to personnel, burn equipment, or trigger a fire.
The selection cannot meet the demand. With the increase in the number of household appliances, the selection of wires is also changing. Looking back more than a decade ago, the combination of 16 AWG thhn wire solid and 14mm thhn wire was commonly used in home decoration. However, in today's home decoration, there are very few 16 AWG thhn wires, and instead a large number of cable 12 AWG thhn and even cable thhn 10 AWG wires are used. No one can say for sure what the future holds. Who knows whether the current on the power lines will increase (according to the current development direction, the current will only increase), decrease (due to the crazy research and development of environmentally friendly appliances, which may lead to a decrease in the current on the power lines in the future), or even eliminate the need for wires.
The most we can do now is to choose the best configuration we can see today - whether this configuration can meet the needs of the next few decades is not certain. So, if one day in the future, today's thhn wire selection is no longer sufficient, we will need to replace the thhn cable. The quantity cannot meet the demand. On the one hand, it is the number of electrical devices (switches, sockets), and on the other hand, it is the number of circuits (each switch in the distribution box is a circuit). When the quantity cannot meet the demand, it is necessary to increase or replace the thhn wire.
