What are the requirements, in your country,
for the installation of Flush-mounting Downlight fittings?.
We have a whole Code of Practice, for these types of lights, especially ELV Dichroics.
Your input please-

Pretty much what you would expect: The final connection to the light made with heat-resistant flex (unless the terminal block is otherwise designated as taking NM directly), insulation cleared around and above the lamp to prevent overheating, fitted to a non-combustible surface (i.e. not the straw & plaster ceiling that somebody wanted me to install some in!).

Man, if they only done it your way Paul,
Over here, the TPS, is fed straight into the
downlight fitting, no HR flex, no J-Box, no
nothing.
If I was wiring my own house, it would be done like you said.
Just a simple thing like clipping cables,
happen's very seldom over here.
It's just a big mess.

The connection method I described is the way it should be done (and, of course, the way that I do it! ).

Sadly, I see so many of these things incorrectly installed exactly as you say: NM-type cable straight into the fitting. I frequently see the things completely enclosed in fiberglass insulation as well. I don't doubt that John & David will tell you the same thing.

Here's a typical example (copied from another thread);

Oh, and this one was supposedly fitted by a "professional!"

By the way, I assume that your TPS is normal PVC-sheathed NM-type cable. Is TPS Tough Plastic Sheath? (We used to have an old TRS cable - Tough Rubber Sheath.)


[This message has been edited by pauluk (edited 12-15-2002).]

Yes Paul,
TPS, is short for Tough-Plastic-Sheathed
cable.
What is NM cable?.
I note that in your penultimate reply, you
mentioned a straw and plaster roof, is that the cieling lining?.
How do they cope in areas of Devonshire and
such, that have thatched roofs?.

Yes, the straw and plaster was the ceiling of the rooms, fitted below the joists.

Good point on the thatched roofs -- I've never had to work in one of those, so I haven't really had to think about it. I can't think of anything in BS7671 that refers to thatched roofs specifically; it would be covered by the general rules.

NM is the American designation meaning Non-Metallic; i.e. equivalent to your TPS or British "Twin & earth." Often known in the U.S. by the name Romex.

Hey thanks Paul, for your explanation of the NM type cable, makes sense, I suppose.
I never knew what Romex was.
Are there any other abbreviations that I should know about, relating to cable types?.

NYM is the german/austrian name for round Romex style cable, followed by number and size of conductors, e.g. NYM 3x1.5, the most commonly used cable type for any wiring, the number 3 means it's a blue conductor for neutral, black or brown for live and yellow/green for ground. Other common types are NYM 3x2.5 and NYM 5x2.5, NYM 4x1.5 is used for a 3way switch (common, 2 travelers and ground).

There is a whole range of American designations which are completely different from those used in the U.K. and Europe.

SPT-1 and SPT-2 are flat "zip-cord" or "figure-8" power cords, for example. You'll see SO, SJT, and SVT used to refer to some other jacketed power cords in thermoplastic or rubber.

THHN or THWN are PVC-insulated wires such as are commonly drawn through conduit.

Somewhere, I have a list of how to decode all the letters, but I can't lay my hands on it at the moment. One of our American friends might be able to oblige......

The ones I know offhand because I use them practically every day:

SPT-1, SPT-2 and SPT-3: Single Parallel Thermolastic - the number refers to the thickness of the isulation - 1 is the thinnest.

SPT-1 is usually for 18 AWG wire. SPT-2 can be used for either 18 or 16AWG wire. SPT-3 is usually for flat 3-conductor (2 plus earth) cord such as used on air conditioners.

This is also affectionally known as ZIP CORD, so when you see me use that term, this is what I'm talking about.

* A variation of SPT cord is NISPT - Non Integral Single Parallel Thermoplastic which is double insulated like the two-conductor flat European cord. This has only been on the American OEM market for a couple of years. Haven't seen it on the racks at hardware stores yet....it's usually used for the factory supplied cord for radios, TV sets and tape recorders and other such non-grounded audio/video equipment.

----
SJ: Service Junior

SJT: Service Junior Thermoplastic

* Both of these are double insulated with a round cross section. I believe SJ is rubber jacketed and SJT is thermoplastic jacketed. They are also filled with fiber and paper to strengthen it.
---

SVT: Service Vacuum Thermoplastic - extra flexible for use on vacuum cleaners, has a round cross section also.

---

HPN: Heater Parallel Neoprene (for flat-irons, electric fires, electric toasters, etc.)

--
XT: Christmas (think X-mas) Tree thermopastic - used for christmas tree wires

I just now found the list of all the UL cable designations for AC cords - it even has the insulation dimensions for the different SPT cords:

Go to this link!!
http://www.volexpowercords.com/technical_information/ul_cord_type_designations.html

In fact, this link has other interesting technical documentation:
http://www.volexpowercords.com/technical_information/

Both links are from Volex, a manufacturer of cordsets.

[This message has been edited by SvenNYC (edited 12-17-2002).]

Heaters usually have rubber sheathed (i.e SJ) cord, some types also simple SJT. Flat-irons still have cloth wrapped round cords, the single conductors are rubber sheathed. You hardly get the NISPT off the Rack here. You get 0.75 mm2 SPT1 and 0.75mm2 SJT w/o ground for these purposes.

The harmonised European cables have very long designations:

For example, H03VVF mean that it's Harmonised, 0.3 kV max, and has a round plastic sheat. H03VVH-2F is the flat two-conductor cable.

(The German NYM is called EKK in Sweden. The relabling doubles the price.)

"Harmonized" is one of the European Committees' favorite words, as anyone living in this part of the world will know!

The coding breaks down into seven categories.

Identification of designation:
H = Harmonized standards
A = Authorized national standards

Nominal voltage:
03 = 300/300V
05 = 300/500V
07 = 450/750V

Insulating materials:
V = PVC
R = Rubber
S = Silicone

Sheathing materials:
V = PVC
R = Rubber
N = Polychloroprene (PCP)
J = Glassfiber braid (GFB)
T = Textile braid
T2 = Textile braid with flame resistance

Special constructions:
H = Flat divisible cords (Figure-of-8)
H2 = Flat non-divisible cords
D5 = Central core (non-supported element)

Conductor form:
U = Solid wire
R = Stranded wire
K = Fine wire (for permanent installation)
F = Fine wire (for flexible cables)
H = Superfine wire
Y = Tinsel

Number of cores:
2 = 2 cores
3 = 3 cores, etc.

Notice that for this system to apply the first character has to be "H" for harmonized standard. It's curious that a supposed international standard then specifies that "A" can be used for varying "authorized national standards."

Wow!,
The mind boggles as to how far all these abbreviations can go.
Little wonder our Regulation Books are so thick these days, it's all the explanations,involved to decipher the codes.
What is your maximum temperature wire?,
where would this be used?


[This message has been edited by Trumpy (edited 12-23-2002).]