1. INTRODUCTION TO T&T ELECTRICAL WIRING CODE TTS 171: PART 1: 2002
By GEORGE SAMPSON
ELECTRICAL INSPECTOR III
GOVERNMENT ELECTRICAL INSPECTORATE

2. What is the T&T Wiring Code?
Revised edition of TTS:
REQUIREMENTS FOR THE ELECTRICAL WIRING OF BUILDINGS AND EQUIPMENT
More Comprehensive
Additional technical information.

3. WHO BENEFITS? AREAS Designing Planning
Electrical Fraternity members and clients
AREAS
Designing
Planning
The actual installation of a wiring system

4. SCOPE COVERS: Installations up to 600 volts NOT COVERED:
Installations operated by Authorities for
the Generation & Distribution of
electrical power such as:
Powergen
InnCogen
T&TEC

5. ENFORCEMENT HOW? The CEI is the authority with jurisdiction
Interpretation
Enforcement of this standard

6. CONFLICT
If ever, any conflict arises between TTS 171 and any other standard, the CEI shall be the sole arbitrator and his decision shall be final

7. WHAT’S NEW? The terminologies are in harmony with international standards Examples
2002
1978
Ground
Earth
Grounding Conductor
Earth Continuity Conductor
Grounding Electrode Conductor
Earthing Lead (MEC)
Receptacle Outlet
Socket Outlet

8. WHAT’S NEW ? ( Cont’d )
Ground Fault Circuit Interrupter & Ground Fault Protection of equipment are also new to the list of definitions.

9. ANNEX C Revision of TTS 1978 ( Table 21 )
Guidelines on sub-circuit requirements for:
Residential
Commercial
Industrial Installations

10. Simple Formulae and Worked Example for voltage drop calculation ( section D.1.7.3)
New to this standard
It was included to assist with the application of the Voltage Drop Tables

11. ANNEX E Maximum conductor fill for Conduits & Boxes
Consider a practical case:
Install the following conductors within a common raceway:
6 x 1.5mm sq.
8 x 2.5mm sq.
4 x 6.0mm sq.
6 x 4.0mm sq.

12. Comply with section 6.2.7 A space factor of 40% is not to be exceeded.
The cables are not to be damaged.
No more than two ( 2 ) 90 degrees bends are allowed along the conduit work.

13. DISTRIBUTION AND PROTECTION (Section 4.1.1)
Every consumer’s installation shall be adequately controlled by a service disconnect. i.e. Main Switch or Circuit Breaker
Does this requirement apply to systems utilizing standby power from a Generator?

14. The CEI requires that all wiring systems are to comply with section 4
The CEI requires that all wiring systems are to comply with section whether they utilize a standby Generator or not.
In addition, those with standby power must incorporate suitable Transfer Equipment.

15. Why Transfer Equipment?
This is to prevent the inadvertent or accidental interconnection of the normal (T&TEC) and the standby ( Generator) sources of power.

16. HIGHLIGHTS FROM OTHER SECTIONS OF THE CODE

17. MARKINGS
Section requires each piece of electrical apparatus and material to bear such markings to identify it
To ensure its suitability for the particular application

18. Examples of Markings
Manufacturers’ name, trademark, or other recognized symbols of identification
Rated load in amperes
Rated frequency or frequency ranges in hertz
Whether for continuous load or intermittent

19. Consequences of failure to conform to technical data
Persons could receive a severe electric shock
Explosion or fire may occur
Serious injury may occur from a fall or flying objects
Electrocution is also a very, very real possibility

20. The foregoing are sufficient reasons to be meticulous when selecting equipment and materials.

21. GROUNDING ELECTRODE CONDUCTOR & GROUNDING CONDUCTOR

22. Why should we give the Grounding Electrode Conductor and the Grounding Conductor the respect they deserve?

23. Three basic reasons for grounding
Limits the voltage caused by lightning, or by accidental contact with conductors of higher voltages.
Stabilizes the voltage under normal operating conditions - to maintain the voltage at one level relative to ground so equipment connected to the system is subjected only to that potential difference.
Facilitates the operation of over current devices such as fuses, circuit breakers or relays under ground fault conditions.

24. Selection and application of:
The Grounding Electrode Conductor and the Grounding Conductor deserves our keenness attention
Sizes of grounding conductors
( Sec 9.5 )
See Current Ed. Of NFPA 70 Tables
and

25. APPARATUS IN GARAGES (Section 8.5)
Where motor-driven vehicles are:
Stored
Serviced
Repaired
All apparatus shall, unless of a totally enclosed or flameproof type, be installed at a minimum height of 1200mm ( 4ft ) above the general floor level.

26. SEGREGATION OF CIRCUITS (Section 5.23 )
Lighting and power cables operating at voltages above extra-low ( i.e.exceeding 50 V a.c. or
120 V d.c. whether between conductor or to ground).
Shall not be drawn into the same conduit or duct as cables of extra-low voltage or of radio systems.
Unless the latter are insulated for the higher voltage present.

27. Note:
Failure to observe these guidelines
may result in Electromagnetic
Induction (EMI ) and disruption of
the extra-low voltage equipment.

28. RACEWAY INSTALLATIONS (section 6.1.1)
Conduit works shall be completed before any cables are drawn in.
Ends shall be reamed and bushed to avoid abrasion.
Inspection boxes shall remain accessible throughout the life of the installation.

29. TESTING AND INSPECTION (Section 10 )
To determine what malfunctions are possible
To determine what protection is necessary and sufficient
To minimize the ill-effects of such malfunctions

30. Section 10.1.1 Requires that every new installation and
any alteration to an existing installation
shall be inspected and tested to ensure
compliance with TTS 171

31. Inspection and Testing
Involves:
Visual examination of workmanship
Verification of polarity (I.R.test)
Effectiveness of grounding
Continuity
A verification of polarity shall be made to ensure that all fuses, circuit breakers and single pole control devices, are connected to live conductors only.

32. Since ground fault protection relies on operation of fuses or circuit breakers, the resistance or impedance between the electrode and the remote end of every grounding conductor, shall not exceed 1 ohm.
Where metal conduit forms part or whole of the grounding conductor, the above shall also apply.

33. Electrical Metallic Tubing ( EMT )
Shall be protected against any risk of mechanical damage.
Not to be exposed to rain, dripping water, condensation, oil, corrosive substances and hazardous location.
Not bend, as to damage the tubing or to effectively reduce its internal diameter.
Not be buried directly in the ground.

34. CONTROL OF MOTORS (Section 8.12.2)
Each motor and its control equipment shall have a disconnecting means.
For remote disconnecting means:
an additional means of isolation adjacent to the motor shall be installed OR
a lockout device shall be installed adjacent to the motor
The remote means of isolation shall be able to be locked in the off-position.

35. Conclusion Section 3.1.2 reads in part:
This standard contains minimum provision considered necessary for safety, but is not to be regarded as a design specification or an instruction manual for untrained persons.

36. THE END