Frequently Asked Questions

By installing a mast or external lightning protection on my building will it be sufficient to prevent damage to equipment inside my building?

No, as the electromagnetic effects and induction will still cause damage to equipment within the building. In actual fact, if you install external lightning protection, you will actually require lightning current arresters and surge arresters to be able to withstand the induced energy. Lightning striking up to 1km away can cause damage to sensitive electrical and electronic equipment.

How often can I expect a direct strike to my house?

An average 200m2 house in Gauteng, with a lightning flash density of 5 strikes per km, can expect to be struck less than once in 250 years. The same house can expect a surge to enter via the power and telephone cables at least 5 times a year thus power and telephone line protection are strongly recommended.

By installing surge arresters in my electrical distribution board will I never have damage again?

By installing surge arresters in your electrical distribution board you are dramatically reducing your risk of suffering damage via the power only, but not eliminating the risk.

Will the surge arresters in my electrical distribution board be damaged by a direct strike?

Most probably as they are only designed to withstand induced surges of up to 40kA. A direct strike has far more energy which could destroy the surge arresters but they will still offer some protection. Due to the fact that your risk of a direct strike is so small you should worry about the regular induced surges.

If the supply voltage increases to 250 Volts, will the surge arresters protect my equipment?

No, as they are designed to protect against high energy, high voltage surges and not to operate as voltage regulators.

Once the surge arrester has disconnected can it be re-set?

No, it needs to be replaced.

If the electrical distribution board has a fault current rating of 15kA must I use 20kA surge arresters?

The kA rating of the surge arresters has nothing to do with the fault current rating of electrical distribution board. You can fit a 40kA surge arrester in a domestic board with a fault current rating of less than 5kA. In larger panels with high fault current ratings you must pre-fuse the surge arresters to co-ordinate and protect the surge arresters.

Does it help to fit 2 x surge arresters in parallel to increase the surge handling capabilities?

Not really, as the surge arresters will not conduct evenly and thus by installing 2 x 40kA surge arresters does not mean that you can handle a surge of 80kA. You may be lucky to handle a surge of 65kA.

What is the difference between a surge arrester marked 40kA (8/20) and 65kA (4/10)?

These 2 x units are actually the same but (4/10) is half the energy of (8/20) and thus the manufacturer can claim higher kA ratings. To overcome this problem all manufactures must publish their surge handling ability at (10/350) for lightning current arresters and (8/20) for surge arresters.

If I install lightning current arresters Class 1 will I get a better level of protection than using surge arresters Class 2?

No, if you install Class 1 then they must be used in conjunction with Class 2 surge arresters to offer complete protection.

If I install only plug-in type surge arresters such as the Copa SurgeGuard range will I be protected?

The Copa SurgeGuard range is typically a Class 3 arrester and in terms of SANS 10142-1:2003 they should be used in conjunction with Class 2 surge arresters installed in the electrical distribution board.

Must I unplug my computer or modem if there is lightning and I have a Copa SurgeGuard TeleFax protector installed?

No, the Copa SurgeGuard is designed to withstand induced surges and it also requires the electrical plug to be plugged in to supply the earth discharge path.


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