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Testing of fixed installations.

Testing of fixed installations.

Testing of fixed installations.

I was wondering about the required frequency of inspection and testing of low voltage fixed electrical installations in buildings. In the UK there is no prescriptive requirement (that I am aware of), other than to comply with the reqirements of health and safety legislation, especially the Electricity at Work Regulations, to ensure the maintenance of safety in systems. It would then be up to the duty holder to assess any requirements with respect to the frequency of inspection and testing. Is there definite prescriptive requirements in other countries?



RE: Testing of fixed installations.


I spend a little time working in Eastern Europe and South America. The idea of testing electrical installations is very little understood, and I generally have to teach people everywhere I go. For example RCD tests, and earth loop tests are not often carried out nor is test equipment available. Most of the time test equipment is limited to insulation tests (old wind up megger), or continuity tests where they use a DVM. I tend to get equipment sent out from the UK to check installations I do.

A very interesting system is in Peru where they use three wire (even on unbalanced loads) 220V ph-ph where you have two phase conductors as the circuit. Earthing was via a separate earth rod array with maximum resistance of 5 ohms. 20A MCB's were used throughout but would almost never trip on an earth fault. This was in a 24 storey modern building. When I asked the design consultant why they used such systems they answered that the 4-wire system caused MCB's to trip out. What else are they supposed to do on an earth fault!!

I think that over the years I have found the UK wiring regulations inspection and testing to be basically one of the best LV wiring standards in the world.

RE: Testing of fixed installations.

It has been my experience that the manufacture of the equipment that has designed, built and installed the equipment should recommend the required inspection and maintenace of their equipment for the reason of Health and Safety. I would call the manufacture if the information is not already available and ask them what is required. If someone at your facility gets hurt because you did not follow the manufactures recommendations your company could be legally responsible.

Christopher Caserta

RE: Testing of fixed installations.

We tend to test general fixed electrical installations every 5 years.

If the installations are in hazardous areas this reduces to 6 months or 12 months depending on the hazardous area classification.

Do UK local authorities or Insurance Companies make any recommendations?

RE: Testing of fixed installations.

Essentially it is up to the inspecting engineer to make appropriate recommendations with respect to time intervals. However, other bodies, indeed like insurance companies, licencing authoraties etc, will have their own requirements.
As I said originally, there is no prescriptive time interval other than a requirement to ensure that the electrical "system" is safe.
Your post about Peru is interesting. Where does the 5ohms come from? What is the voltage to earth? 127? A 4 wire system should have ne affect on the mcb.



RE: Testing of fixed installations.


Basically with a 3 wire system the ground current return to the source (the transformer or generator) is via the phase-earth conductor and earth rod mat i.e. in this case the earth loop impedance includes the 5 ohm resistance of the mat plus the phase-earth conductor impedance.

For a 4 wire system, the earth mat plays no role in the return current to the source. The earth loop impedance includes the phase-earth conductors back to the source only.

Consider an IT or TT system for example. If you draw it out and include a source, you will see what I mean.

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