What, specifically, does this mean?
Or what is the process by which something, such as a hand tool, becomes "double-insulated"?

AFAIK, this refers to insulated wiring contained within a non-conductive housing. Effectively, 2 or more layers of insulation between the user and anything live.

Sort of like a portable radio in a plastic cabinet, a hair dryer or even an electric drill in a plastic shell instead of a metal one.

The symbol for "double insulated" is two concentric squares.



This was a Taiwanese version of the symbol on a pair of speakers (found this one someone's audio review website).

Scroll down to "Double-Insulated Tools" FYI.
http://www.osha.gov/SLTC/etools/construction/electrical_incidents/powertools.html

The UK regs defines it as "Insulation comprising both basic insulation & supplimentary insulation.

Here is more info

Double Insulation as I understand it to be, means that there are 2 layers of insulation between the live part and surfaces which are normally touched by the user of an appliance, etc.
The same goes for flex's, although for some odd reason, TV's and the like only use cords with single insulation.

The electrical regs. in the U.K. have required double-insulated cords (flexes) on appliances since the mid 1970s. There are only one or two exceptions, such as fairy light strings.

So why then Paul do TV's, VCR's and Stereo's use single insulated flexes?.
Or is this just a Aust/NZ thing?.

All modern TVs, VCRs, bedside clock-radios, etc. sold throughout Europe are now fitted with double-insulated cords (brown/blue within an overall black/gray/white sheath).

I didn't realize that SPT-type cord was still used in Australia/N.Z. I thought it was still only common in NEMA-based countries.

Most of our light-duty appliances (TVs, radios, record players, fans) used to come fitted with 18-gauge SPT-1 cord.

In the past couple of decades there was a movement to equip things like TV sets, some hi-fi equipment, blenders, etc. with 18-gague SPT-2 cords. SPT-2 has thicker insulation. SPT-3 is the thickest you can get for parallel cord (at least that I've seen). SPT-3 is normally used for air conditioner extension cords -- normally they're built using 14-gauge wire.

Anyway....in the past - oh I'd say - five or six years, almost all UL-Listed electronic equipment (TVs, radios, tape recorders, turntables) started coming with the following:

NISPT-2 at 18AWG.

I think UL has been one of the ones reponsible for this -- the reason being the insulation is thicker, and less prone to getting nicked. UL-Listed fans and lamps are now being sold with 18AWG/SPT-2 cordage. The fans have had it for years. The lamps, only in the past two or three years or so.

The "NI" stands for Non-Integral. In other words, this is essentially flat SPT-2 cable that is encased in a tough, abrasion resistant thermoplastic jacket. Construction is similar to the thinner European version.

There are also some replacement cord-sets sold for cassette recorders that use NISPT-1 18AWG cord and some no-name cordsets that are actually made with .75 mm harmonized cordage (also double insulated).

Unfortunately, you can't buy NISPT cord in bulk at your local hardware store to replace the cord on your TV set that your dog chewed up.

SPT-2 cord in 18-gague is also pretty difficult to find in bulk. Certain mail-order places, however sell 18AWG/SPT-2 ready-made cordsets with moulded plugs (for replacement use or OEM)

If you're buying bulk zip-cord off the spool in most hardware stores and lighting stores, you're mostly limited to SPT-1 18AWG or SPT-2 16 AWG (used mostly in ordinary extension cords).

Sven, I have a 6-month-old DVD player with a linecord having no characteristic SPT-cord "grooves" between the 2 conductors. It must be a version of the NISPT-2 material. It seems like it will be more durable than what has long been conventional "zip cord".

It seems I remember two changes in US appliance cords. The more recent was increasing overall cord-insulation thickness—I believe there is some history of child injury from toddler “bitethough”.

An earlier change was increasing the dimensions of the skirt around the molded-plastic blade base on cord caps, to limit the chance of children’s smaller fingers contacting blades while energized. {My first 120V jolt from sticking fingers between cord-cap blades too many years ago is seared in my memory. It is my first recollection of being in immediate pain with no one else around—it didn’t make sense that I could really hurt from such an innocent act.}

Minor Aside — At http://ulstandardsinfonet.ul.com/catalog/testequippics1.html — notice the “UL Articulate Probe” and “IEC Flexible Test Finger”. [Note item prices (!) at http://ulstandardsinfonet.ul.com/catalog/testequip.html ]

I say we chuck all those 'double insulated' toys in some occupied Taiwanese hot tub

Sparky,

could you explain that comment?

Sven,

interesting info. It made me look up the HAR (European) and UL cords. Here are the specifications from a manufacturer:

H03VVH2-F vs. NISPT-2
Conductors: 2x0.75 mm2 vs. 18 AWG
Insulation thickness 0.5 vs. 0.73 mm
Jacket thickness 0.6 vs. 0.4 mm
Dimensions: 3.5x5.7 vs. 3.5x7.0
Rated voltage: 300V vs. 300V
Temperature: 70°C vs. 60°C or 105°C

(NISPT-1 is identical to NISPT-2 except for the insulation thickness being only 0.34 mm.)

The total insulation between the user and the copper is 1.1 mm in both cases. What makes the NISPT-2 wider than the HAR cord is that the conductors are thicker than the jacket. (I find it a bit counterintuitive to make the conductors thicker instead than the jacket when you make a thougher cord. But it makes sense if your starting point is SPT-1 and SPT-2.)

Question: What is the 105°C rated cord used for?

(The HAR cord is available in 90°C, but with a different designation.)

I have seen SPT2 on florr lamps, and SPT-1 on table lamps (ones bought a set, that was the case).

In our A/V system, with relatively new
components, except the TV, the newer components use the NISPT-2 cord, which have a black and white conductor inside

I think Steve is making a statement about the amount of cheap & nasty Far Eastern junk that's sold in our stores these days.

Black and white? Wow. I'm surprised that it doesn't come with brown and blue conductors -- I thought the USA was also migrating to harmonized cordage. And considering that most of the stuff (right down to the cordsets) comes from the Far East, you'd think they'd be using harmonized.

I've got a couple of tape-recorder cordsets from the dollar store here that are wired with H03VVH2-F -- with USA style male plugs molded on the end...

I'm echoing discussion that's already taken place in the color-code threads in the non-U.S. area, but this is really one area where I don't see any need for the U.S.A. to change at all just to be "harmonized" with the "Rest of the World."

right on Paul.......

especially since we've our own cheap/nasty junk

FWIW, I have at least one linecord which has Blue/Brown/Yellow-Green conductors, and most
of my PC supplies are wired with blue/brown wires inside. I suspect many of my 3 wire IEC linecords may use European colours also.