FAQ and useful documents

[Crossy]

Last updated 13 April 2014

This FAQ is a Work in Progress so check back regularly for updates, if you can't find the answer here start a thread.

First off, some light reading

This document from PEA is an excellent introduction to how their inspectors want to see new installations wired, it has incoming wire sizes for various types of service and correct (Thai) implementation of MEN, but do read (ok look at the pictures) in conjunction with Forkinhades' safety thread, download it here:- http://www.crossy.co.uk/Handy%20Files/groundwire.pdf

There is in fact a real Thai electrical regulations book, you can buy it here for 300 Baht http://www.eit.or.th/book_detail.php?id=17&gid=2. It's actually very comprehensive, but concentrates on industrial and HV installations, unlike BS7671 and AS3000 which talk about domestic.

These documents from Aida Engineering are training on the above standards, worth a look even though in Thai.

http://www.crossy.co.uk/Handy%20Files/egat_ch1.pdf
http://www.crossy.co.uk/Handy%20Files/egat_ch2.pdf
http://www.crossy.co.uk/Handy%20Files/egat_ch3.pdf
http://www.crossy.co.uk/Handy%20Files/egat_ch4.pdf
http://www.crossy.co.uk/Handy%20Files/egat_ch5.pdf
http://www.crossy.co.uk/Handy%20Files/egat_ch6.pdf

Useful Thai Electrical Links

• Plugs, Sockets, Adaptors, Extensions, Power Blocks and the like.
• Wire Colour Coding
• Circuit Types and Recommended Cable Sizes
• Grounding and Protection
• Bathrooms and other moist areas
• HELP! My rented house has only 2 pin outlets
• Got a remote water pump, find the correct cable, Calculate Voltage Drop for long cable runs.
• Consumer unit Configurations (IEE 17th edition) http://www.tlc-direct.co.uk/Technical/DataSheets/Hager/Hager_17.pdf (New)
• And some interesting reading about MCBs http://www.neweysonline.co.uk/MCBs/Static.raction (New)

Frequently Asked Questions

Q. What is an RCD, and how do I know if I have one.
A. An RCD is a 'Residual Current Device' (I know that helps a lot).

An RCD detects whether electric current is going somewhere it shouldn't (through you) and disconnects the supply preventing electrocution.

You may know it as a Safety Switch / ELCB / RCCB / GFI / GFCI / Safe-T-Cut / Trip all are effectively the same device although 'ELCB' is normally reserved for the early 'voltage operated' devices which are now outlawed in most of the world as being unreliable.

An RCBO combines the functionality of an RCD with an MCB and so provides over-current and earth leakage protection.

The dead give-away as to whether you have an earth leakage protective device is the presence of a 'Test' button, these devices need to be tested regularly to keep them functional.

OK everybody, lets all go and push our RCD 'Test' buttons now

Dark in here, isn't it??

The UK Electrical Safety Council has some good stuff on RCDs http://www.esc.org.uk/public/home-electrics/rcd-faqs/ nice simple stuff for the common man.
This ABB document has similar information http://www.crossy.co.uk/Handy%20Files/ABB%20RCD%20doc.pdf
And another this time from the DTI http://webarchive.nationalarchives.gov.uk/+/http://www.dti.gov.uk/homesafetynetwork/pdf/rcd.pdf
Even more on RCDs http://www.neweysonline.co.uk/RCD/Static.raction (New)

And for the techies this Beama doc has the nitty-gritty http://www.crossy.co.uk/Handy%20Files/rcd_handbook_dec_2010_49836.pdf


Q. What is this 'Safe-T-Cut' I keep hearing about?
A. We should really call it a "Safe-T-Cut RCBO" in this instance. Safe-T-Cut are a Thai manufacturer of various electrical equipment, however their name has become synonymous with front-end whole-house RCBO devices which are a simple way of adding earth leakage protection to an existing installation quickly and without major disruption.

Any (ok, almost any) Thai electrician will understand what you want when you ask him to fit a Safe-T-Cut.

Their website is here http://www.safe-t-cut.com/

A typical Safe-T-Cut whole house RCBO looks like this;-



Note that these devices have an adjustable trip current as well as a 'Direct' position, when in use the lowest current that the unit will reliably remain 'on' at should be selected. 'Direct' disables the earth leakage protection and should only be used to get the power back on in an emergency situation.

Q. Does my RCD (Safety Switch / ELCB / RCCB / GFI / GFCI / Safe-T-Cut / Trip) need a ground to operate?
A. This one comes up a lot.

An RCD senses the difference between the current in the Live conductor and the current in the Neutral conductor, any difference greater than the trip current is assumed to be going where it shouldn't (through you) and the device operates.

This means that the RCD does not actually NEED an earth or an earthed system to function and provide protection from potentially fatal shock.

BUT

Say a device that should be grounded (say your water heater) is operated without a ground and then develops a L-E fault causing the metalwork to become live.

With no ground connection the heater sits there innocently awaiting the first mug to come along and touch the metalwork at which point a current flows to earth through the victim and, hopefully, the RCD operates and saves his life.

If the same device has been correctly grounded, when it develops the L-E fault the current immediately flows to earth and operates the trip, no need for a victim to act as part of the circuit.

Why does this matter, the RCD operated both times? The 30mA trip current chosen internationally for domestic RCDs is a trade-off between being too sensitive (and tripping all the time) and being fatal. 30mA for 30ms is generally accepted as being non-lethal to 90% of the healthy adult population, the elderly, very young or sick may have a lower tolerance and could actually be killed even though the RCD operates.

Get that heater earthed.

More coming soon.