18
19
TnT RCD
User Manual
Wavecom
TnT RCD
User Manual
Wavecom
Technical Information
Visual Inspection
Visual inspection has to be done before any other test is carried out using the TnT RCD.
The visual inspection is carried out to ensure there are no physical faults with the appliance before testing.
The following list is an example of potential physical faults, but it is not exhaustive and the relevant standards
must be consulted to ensure a proper Visual Inspection is undertaken.
• There is no damage or component defects to the accessories, plugs, outlet sockets or connectors (physical).
• There are no cracks &/or abrasions.
• There are no exposed inner cores or conductors (flexible) and the supply cords are not twisted or distorted.
• Any Fuse / Over load protection components (if fitted) are checked.
• All labels, markings and warning indicators (of the maximum load to be connected to the device) are
legible and intact.
• The insulation is not damaged in any way i.e. melted, cuts or abrasions. There are no iron filings in the
insulation. There is no insulation tape on the lead.
• Any flexible cords and/or leads are effectively anchored (glands and grommets intact).
• All covers or guards are in place and secure as intended by the supplier/manufacturer.
• All safety devices and systems are in good working order. (i.e. overload latches & buttons).
• No dust &/or dirt obstructs any exhausts or ventilation outlets.
• All controls are working properly and are secure and aligned.
Important - If Result is a Fail:
If any Equipment fails
ANY
of the above, it should be deemed to have
FAILED
the Visual Test, and therefore
no other tests need be performed. If this is the case the Equipment should be tagged with a DANGER TAG and
removed from service.
It is recommended by the manufacturer and distributor of this product that it SHOULD
NOT BE RETURNED TO SERVICE. To do so would be considered unsafe.
Class 1 (Earthed Appliance) Construction
Single basic insulated and protectively earth equipment
This type of product design provides two safety barriers between all live conductors at dangerous voltages and
the equipment user.
The provision of basic insulation between exposed metal parts and live parts is the first barrier to provide
basic protection against electric shock.
The second safety barrier is by the connection of exposed (accessible) conductive (metal) parts to the
protective earthing conductor (earth wire) in the fixed wiring of the device/Installation.
The protective earthing terminal of the equipment must be marked with the word “earth” or the symbol “E” or
the symbol for Earth Terminal or Protective.
To perform this test, a continuous earth loop must be made between the exposed conductive material (metal)
and the TnT RCD appliance tester. This is done by means of connecting the earth lead with the crocodile
clip/probe attached to a GOOD earth point (paint & coatings will not provide effective connections) and the
appliance plugged into the TnT RCD appliance testers’ test socket. The Maximum allowable limit is less than
1.0Ω.
Class 2 (Double Insulated) Construction
Double insulated equipment
This method of construction employs two safety barriers comprising two layers of insulation between
dangerous voltages and the user of the equipment.
The first layer of insulation is formed around the live conductor and is termed ‘the Functional Insulation’.
The second layer of insulation is termed ‘the Supplementary Insulation’. In Class II equipment, protection
against electric shock does not rely on basic insulation only, but has additional supplementary insulation such
as double insulation or reinforced insulation provided, there being no reliance on precautions in the fixed
wiring of installation.
Class II equipment is marked with the words “DOUBLE INSULATION” or the symbol:
For double insulated under Safety Symbols:
Note 1 – Double Insulation is insulation comprising both basic and supplementary insulation.
Note 2 – Reinforced Insulation is a single insulation system with a degree of protection against electric shock, which is
equivalent to double insulation.
Testing of Electrical Equipment
Many testing personnel have some reservations in testing sensitive, electronic equipment using a 500V DC
insulation test. There is a perceived fear of causing internal damage from over voltage. With the introduction
on the TnT RCD Range of appliance testers, these concerns are alleviated.
The TnT RCD can safely test electronic equipment as the tests are carried from Active-Neutral (shorted by a
relay inside the tester) to Earth. In this mode no dangerous voltages pass through to the internal components
of the appliance, or Device Under Test (‘DUT’). If these tests are done using an Insulation Tester and the user
tests Active to Neutral, this could potentially cause damage.
Some changes may be required in certain configurations where fitted surge protection devices (MOV’s) in the
DUT may cause a failed test result. Applying 500V in this these situations can cause the surge protection
devices to trip, therefore conducting the applied voltage to earth, thus showing a failure of insulation. In these
instances the test voltage should be changed to 250V, then the DUT should be retested. If the DUT still fails,
check with the DUT Operators’ Manual or an electrician. (for details see - ‘Double Insulation Test’ 250/500VDC
to change test voltage).
Under these circumstances, it would be difficult for any damage to occur to either the surge protection device
or the DUT, as there is insufficient current generated by the TnT RCD.
