CERTIFICATE OF COMPLIANCE SERIES – PART 6
By Cecil Lancaster, ECA(SA) Regional Director, Bosveld region
The sixth in a 13-part series that gets back to the basics …
Cecil is a Registered Engineering Technician and holds an NHDip (Electrotechnical Engineering – heavy current); Installation Electrician (IE); and Master Installation Electrician (MIE). He is a member of the SA Institute of Electrical Engineers (MSAIEE); and member of the Chamber of Engineering Technicians (MCET). He is also an assessor for the Electrical Skills Education Training Authority (ESETA) and serves on some 20 SABS technical committees and workgroups and other committees and associations.
Cecil joined the ECA(SA) as an ordinary member in 1986, and as an employee in 2002, when he was appointed Regional Director of the Bosveld (Pretoria) region. Cecil is the Technical Advisor and Secretary for the ECA(SA) National Technical Committee and serves on most of the ECA(SA)’s National Committees.
Part 6: The Test Report. Section 2 – Installation (part 2 – technical information)
Question: What is the correct way of completing page 2, ‘Section 2 –Installation’ parts of the CoC?
Type of electricity supply system
Generally, we will find TN-S and TN-C-S in all but special cases; and the coding system is explained on page 340:
The star-point of a three-phase transformer or inverter or generator or other source, is connected directly to Earth. In a single-phase installation, it will be one end of the output winding.
Only TN-configured installations are allowed, except for a few special cases like the ‘Isolock-systems’ in medical locations and safety supplies.
The Neutral and protective (Earth) conductor enters the installation as separate conductors, generally the Earth and Neutral is connected only at the source (star-point of the transformer) and remain separate.
In a few instances a combined protective earth and neutral (PEN) conductor is used from the source up to a point, mostly the kiosk on the sidewalk, or even the post top of overhead lines, from where the Earth and Neutral are connected and then run as separate conductors to the premises.
Figure J2.2 (p 342) depicts the TN-S (Earth Neutral Separate) arrangement:
This is the preferred method in South Africa.
The Neutral and protective (Earth) conductor enters the installation as a single combined conductor, up to a point, usually the meter box on the side of the house or on the porch, where the Earth and Neutral are connected and then run as separate conductors into the rest of the installation.
Figure J2.1 (SANS 10142-1 page 341) depicts the TN-C-S (Earth Neutral Combined Separate) arrangement:
The differences are minimal, but studying the supply earth terminal on the right, you will notice the difference.
An example of a TN-C-S connection can be seen below. It is the bare copper earth conductor installed between the meter towards the top, and the consumer’s earth terminal towards the bottom right.
In this case the connection is made in a dedicated terminal seen in the centre of the picture, with the consumer’s earth terminal towards the bottom right, and the bare copper conductor between.
Please try to ignore the obviously illegal addition of the orange toggle circuit breaker and surfix.
Supply earth terminal provided:
Confirm that an Earth terminal has been provided.
Tick the correct answer – it must be ‘Yes’.
Examples of earthing terminals can be seen towards the bottom right-hand corner of both the above photographs. It can also be in the form of a conductor or ‘tail’ entering the meter box, distribution board or premises.
Characteristics of supply:
Tick the appropriate declared (system or design) voltage.
Note that it has relevance to the next item, ‘Number of phases’.
In a multi-phase installation, it will not be wrong to tick 230 V as well, as there will probably be some single-phase circuits as well.
If the design voltage is different, say 48 V, then tick ‘Other’ and remember to insert the voltage.
Number of phases:
Tick as applicable. Remember to ensure it ties up with the voltages above.
Determine by test and tick accordingly.
It can only be relevant if the installation is three-phase. If not, ignore or write ‘N/A’.
Either can be correct, the only requirement is that it remains the same at all three-phase points throughout. If the rotation is indicated on the DB, that is what it must be.
This is the design or system frequency and 99.9% of the time, it will be 50 Hz.
In a very few specialised installations, you may come across other frequencies, for example 1200 Hz in the textile industry and 400 Hz on airport runway aprons. If you are not familiar with these, stay away or phone a friend. Mark appropriately and, if ‘Other’, insert the value.
If d.c. tick that block.
Prospective short-circuit current at point of control (PSCC):
This is what causes damage to equipment and properties, and often results in fires:
At the point of control (main switch) of the installation, determine the value, and enter in the allocated space.
In instances where the installation contains more distribution boards, or more supplies, this test must be done for each, and a copy of the ‘Tests’ under section 4 must be completed for each. The actual reading should also be inserted into item 5 of the test portion of section 4.
There are three recognised methods of determining this value.
By far the easiest and best is to measure it, which can be done instantly with a compliance meter or while testing the earth loop impedance.
In instances where it is impractical to measure, or where this part is completed at the design stage, it can be calculated. It is, however, not recommended unless you are familiar with the methods, and all the information regarding transformer characteristics and every piece of conductor in line is available. It can take up to four folio pages of calculations. If you follow this route, be sure to attach a copy of the calculations to the CoC and keep a copy for your records as well.
The third option is to obtain it from the supplier.
This is probably the one single item that most registered persons get wrong!
In many cases, we find that the registered person simply copies the short circuit withstand rating printed on the supplier’s breaker into the allocated space – this is wrong.
NOTE: What is printed on the breaker is the withstand rating of the installed breaker, not the PSCC of the installation! The PSCC should be smaller (able to be protected) than this withstand rating, which we will discuss shortly.
Main switch type:
There can only be one main switch to any installation, so select only one, and tick the block.
Bear in mind that there should be overcurrent protection for all equipment, including the main switch and the busbars or jumpers.
In cases where the main switch is or contains a circuit breaker or is a fuse switch, that will provide the overcurrent protection, just check the ratings.
If the main switch is a switch disconnector (isolator) or earth leakage switch disconnector, ensure that overcurrent protection has been provided. Remember that it can be anywhere in the circuit.
The ratings are also all relevant to that same main switch only:
Generally, a three-phase installation will have a three-pole device, and a single-phase installation a two-pole device.
This should be the case for new installations.
You may find in some installations that a four-pole device is used for a three-phase installation, this not wrong.
In some older installations, you may find that the main switch on a single-phase installation is a single-pole device. While this will not be acceptable for new installations, it may not be contrary to ‘reasonably safe’ for existing installations. In other cases, a three-pole device is used, generally to provide for ripple-control of the geyser. Generally, in such cases one pole is used for supply to the geyser only, supplied from the meters and through the ripple relay with a 4 mm2 conductor, a second pole is used for supply to the rest of the installation, from the same meters but not controlled by the ripple relay using a 6 mm2 conductor, and the last pole is then used for the common Neutral, mostly a 10 mm2 conductor back to the meters.
Insert the number of poles into the allotted space.
The current rating on the device goes into the next space. Ensure that if it is an overcurrent protection device, that it protects all equipment in the DB, and if it not, that it is suitably protected.
The next one is the short-circuit withstand rating, which is the maximum fault current the device is rated/designed to withstand without being damaged or causing damage to the rest of the installation. It will be the value printed on the unit, and generally be one of 2.5/3/5/6/7.5/10/15/20/25/30/35/40 or 50 kA.
At this point, double check that it is rated to withstand (exceeds) the PSCC we determined and inserted two lines above on the test report. Note that disconnecting devices mostly do not have such a (kA) rating.
As the fault level or PSCC will remain the same throughout the DB, ensure that all equipment is suitably rated. There may be instances where special arrangements have been implemented to reduce the PSCC inside the board, but it is specialised and not common, and if you are not sure about understanding this, get advice from an expert.
The standard rated earth leakage tripping current is 30 mA. If the installed unit is so rated, tick the block next to 30 mA.
You may find other ratings, such as 12, 15, 20 and 25 mA, mostly in older installations, and in special installations like agriculture, temporary and construction installations you may find 300 or 500 mA units.
In such cases tick ‘Other’ but be sure to insert the value into the next block. Note that these units may be acceptable, but when testing them, the same rules apply: it must not trip at 50% of its rating but must trip at 100% of its rating. Thus, a 20 mA unit must hold 10 mA, but must trip between 10 and 20 mA.
The last few items are simply questions to be answered, as follows:
Is there surge protection installed; Yes or No, tick the appropriate block. If no, move on, and if yes, ensure that it complies with 6.7.6 and Annexure I.
Is there a standby generator, inverter, UPS, solar system, or any other source of electricity connected? If no, tick ‘No’ and move on. If ‘Yes’, ensure compliance with 7.12, and that a copy of the Tests’ under section 4 set of this report is completed and all the tests done for every supply.
Is there any part of the installation that can be classed as medical as contemplated in 7.7 or hazardous per 7.14? If no, tick ‘No’ and move on. If ‘Yes’, ensure that the appropriate additional test reports issued by a master are attached.
You have to include the installation work and tests for that part in this test report, and the additional test report is required over and above.
If there is no part of the installation intended to operate at more than 1 000 V, tick ‘No’ and move on.
More information on this can be researched in the Electrical Installation Regulations of 2009, Reg 5(5).
If there is a MV part included, typically a step-up-step-down system, or feeder or a ring at more than 1 000 V, generally found in and as part of shopping centres, or a minisub such as used for housing estates, please ensure that the design has been approved by a competent person, and that a duly completed copy of the test/safety report from SANS 10142-2 is attached.
Note that both the competent person and the contractor must complete and sign sections of that. If all of that is in place, tick ‘Yes’.
This part of the installation also has to comply with SANS 10142-2.
If this is not a new installation and a new point of supply, tick ‘No’ and move on.
If this new installation is from a new point of supply which does not include a distribution network intended to supply five or more users (separate owners with own points of supply) such as in a sectional title townhouse complex, tick ‘No’ and move on.
If it is a new installation, from a new point of supply and this part of the project includes the distribution network intended to supply five or more users, ensure that a competent person is employed from the onset to ensure compliance and to sign off under 5.5 of the report. Tick ‘Yes’ and enter the name of the appointed person in the next line.
For more information on this refer to the Electrical Installation Regulations of 2009, Reg 5(6).