defining terms

[--tom]

what is meant by strapping?
could you define the terms: common
phase
earthing TT
earthing TNC etc.

where would i find images of a residential earthing arrangement(s) and an isolater switch?
ps is it true that in the UK stainless steel sinks do not have to be bonded?
thanks

 

[plugwash]

i think strapping is a think braid used for very high integrity earths but i'm not sure

there are 3 earhing types used on normal resisdential and commercial installation in the uk

most uk electrics has 3 phases that are 2/3PI radians out of phase with each other and a neutral (probablly what is being refered to as common) in the centre the phase-phase voltage is sqrt(3) times the phase-neutral voltage

real life figures for uk installation are around 240V RMS phase-neutral and 415V RMS phase-phase

however we have agreed to this fake european harmonisation where the normal voltages become 230V and 400V respecitvely but with a huge tolerance of 10%

(i call it fake harmonisation because rather than change anything we simply agreed on a standard so wide almost everything would fall into it)

TN-S is the most common in the uk and imo the safest but has fallen out of favor with the recs due to it's higher cost of installation for them it can be recgnised generally by a main earth conencted either to the sheath of the service cable or the body of the service termination (just before the service fuse)

TN-C-S also known as PME is the normal method for new installs and involves linking your earth system to the cupply neutral the danger here is loss of neutral in the supply system and because of this it is vital that main equipotential bonding is up to standard large PME installs need larger main equipotential bonds than other earth types but theese are unlikely to be encountered in a domestic situation

TT is where you have a rod due to the high earth loop impedence of a rod you absoloutely must have all cuircuits rcd protected. in a domestic install it is normal to use a 100ma time delay for lights alarms etc and a 30ma normal rcd for everything elese

 

[Inspector]

'strappers' is the slang term for twin red cable between the switches in a two way or intermediate lighting circuit
a 'common' terminal is one which is common to the other terminals in the same circuit
phase is the live conductor which can be the red, yellow or blue phase.
a TT supply is one which has an earth electrode
a TN-S supply has the earth supplied by means of a sweated collar on the cable
a TN-C-S supply has the earth and neutral at the same potential and therefore they are linked

In the on site guide
True - bonding only required by regs in bathrooms

 

[--tom]

thanks for the informative replies. however, i still can't locate images on this site, what exactly should i search for?

 

[ban-all-sheds]

There are no images of "residential earthing arrangements" on this site, nor isolation switches, except where they crop up in peoples' posts, and I don't think you can search for those.

Many manufacturers (MK, MEM, Hager, Crabtree, M-G, and yea, even the scurrilous Wylex (wash my mouth )) have websites with images of isolation switches, as do a number of suppliers.

TLC is good for product photos, and they also have technical info (with drawings) on earthing schemes (but FWL doesn't rate that very highly).

 

[securespark]

Bonding indeed only required by regs in bathrooms (and main bonding of course) but some see bonding sinks & taps and any other extraneous metalwork in a kitchen as an absolute neccesity to avoid shock risk, while the IEE (in particular Paul Cook) think this will introduce hazards rather than reduce them.

 

[--tom]

Thank you all for your replies.

 

[Big_Spark]

Tom,

Try this on our website.

http://www.franklin-wood.co.uk/rewire_designing_and_planning_page6.htm

 

[ban-all-sheds]

So you're firmly in favour of bonding otherwise isolated metal objects, like baths and radiators connected by plastic pipes.

Hmm...