8

I have a Sony TV that has OEM cable on the left. I want to replace it with a longer cable on the right. The new cable fits into the TV's slot but would not have the third prong.

Is this safe to do? Does the third prong of the new cable interact in any way with the other two? What are these cables called?

left OEM cable, right new cable

  • 2
    Answers have already covered the safety requirements here. If you really want an identical cable, then the appliance (TV side) is an IEC 60320 C17 connector, while the wall sideis dependent on what region you're in (probably CEE 7/16 or CEE 7/17 if you're in most parts of Europe, or NEMA 1-15 if you're in North America), with the easiest search term being 'IEC C17 to <whatever>' where '<whatever>' is whatever the relevant local standard is for wall sockets. – Austin Hemmelgarn Jul 24 at 12:35
8

Is this safe to do?

Yes.

Does the third prong of the new cable interact in any way with the other two?

The third pin is a protective earth connection, some appliances "class 1" require a protective earth connection to maintain single-fault safety. Others "class 2" do not.

The connectors are sensibly designed so you can use a cord with an earth for an appliance that does not need one, but not vice-versa.

What are these cables called?

The connectors are from the IEC 60320 series. The connector with an earth is a C13 while the one without it is C17. The corresponding inlets are C14 and C18 (normally the inlet has a number one higher than the corresponding cord connector).

Some of the more common connectors in the series have colloquial names, for example the C5/C6 is commonly referred to as "cloverleaf" or "mickey mouse", while the C7/C8 is commonly referred to as "figure 8". The C13 in my experience usually just gets referred to as an "IEC connector" or sometimes as a "kettle plug" (though this is ambiguous because actual kettles use the "hot condition" C15/C16). The 16A variants are usually referred to by their current rating "16A IEC connector".

I'm not aware of a colloquial name for the C17 connector though. In my experience it's a pretty rare connector. Most class 2 electronics are low enough power to use the "figure 8" connector and stuff like heaters tend to have fixed power cords.

I also suspect that the compatibility mentioned above means there is virtually no end-user market for C17 cords. Regular C13 cords are available everywhere and the economies of scale mean they are cheaper than C17 cords despite having higher material costs.

| improve this answer | |
  • I would call that plug a "PC power connector" since that's where I first saw them. – FreeMan Jul 26 at 19:44
32

The OEM cable does not have a ground or earth connection.

The cable on the right does.

So this will be a safe replacement for the original cable.

The ground connection will not be used and that wire in the cable is not connected to either of the other wires in that cable.

| improve this answer | |
  • 21
    @gatorback what information are you missing? the photo is clearly labeled. – Jasen Jul 23 at 10:49
  • 32
    I'm not clear what "danger" @gatorback is warning of here. These are both IEC power cables which are specifically designed so that you can use a grounded (i.e. the one on the right) in place of an ungrounded one (i.e. the one on the left) but not vice-versa. – jwh20 Jul 23 at 12:03
  • 12
    I suspect that if the cable standarization wanted to avoid this situation they would have made sure the shapes are incompatible. Oh wait, they did :) you can't use an ungrounded cable where the ground is required; but they allow the other way. – UuDdLrLrSs Jul 23 at 14:26
  • 18
    This entire SE is literally dedicated to electrical decisions by way of the internet, and by definition, safety is inherit. – user2259438 Jul 23 at 14:35
  • 2
    Note that on the back of the TV, there are 2 prongs sticking out into the power cable's receptical - they are the Neutral (N) and Line (L) (or Hot). There is no Earth (or Ground) prong sticking out. That means the TV is not designed to use the Earth connection. If you plug in your replacement cable, it will have a connection to N & L, and nothing will connect to E. The Earthing connection at the wall will connect to the mains wiring, and extend that connection to the inside of the plug at the TV, but no further. @gatorback please explain how this could possibly be unsafe! – FreeMan Jul 23 at 14:35
17

To answer the question of what these cables are called, they are IEC 60320 (commonly called kettle plugs) connectors. If you take a look at the "Appliance_couplers" section of the linked page you will see the left is c17/c18 (the male and female versions have different numbers) while the right is c13/14.

It looks like from the table the plug on the right is for class I appliances while the cable on the left is rated for class II appliances. In general electrical connectors are built with physical safeties such that they cannot be used in situations where their use would cause damage (this of course doesn't apply to hack-job scenarios like if the end-user were to grind out the safety tab to use a c13/14 connector when a c15/16 is required)

Selection of a coupler depends in part on the IEC appliance classes. The shape and dimensions of appliance inlets and connectors are coordinated so that a connector with lower current rating, temperature rating, or polarization cannot be inserted into an appliance inlet that requires higher ratings. (i.e. a Protection Class II connector cannot mate with a Class I inlet which requires an earth); whereas connecting a Class I to a Class II appliance inlet is possible because it creates no safety hazard.

CLASS I CONNECTORS

These appliances [Class I] must have their chassis connected to electrical earth (US: ground) by a separate earth conductor (coloured green/yellow in most countries, green in India, USA, Canada and Japan). The earth connection is achieved with a 3-conductor mains cable, typically ending with 3-prong AC connector which plugs into a corresponding AC outlet. The basic requirement is that no single failure can result in dangerous voltage becoming exposed so that it might cause an electric shock and that if a fault occurs the supply will be removed automatically (this is sometimes referred to as ADS = Automatic Disconnection of Supply).

A fault in the appliance which causes a live conductor to contact the casing will cause a current to flow in the earth conductor. If large enough, this current will trip an over-current device (fuse or circuit breaker (CB)) and disconnect the supply. The disconnection time has to be fast enough not to allow fibrillation to start if a person is in contact with the casing at the time. This time and the current rating in turn sets a maximum earth resistance permissible. To provide supplementary protection against high-impedance faults it is common to recommend a residual-current device (RCD) also known as a residual current circuit breaker (RCCB), ground fault circuit interrupter (GFCI), or residual current operated circuit-breaker with integral over-current protection (RCBO), which will cut off the supply of electricity to the appliance if the currents in the two poles of the supply are not equal and opposite.

CLASS II CONNECTORS

A Class II or double insulated electrical appliance is one which has been designed in such a way that it does not require a safety connection to electrical earth (ground).

The basic requirement is that no single failure can result in dangerous voltage becoming exposed so that it might cause an electric shock and that this is achieved without relying on an earthed metal casing. This is usually achieved at least in part by having at least two layers of insulating material between live parts and the user, or by using reinforced insulation.

In Europe, a double insulated appliance must be labelled Class II or double insulated or bear the double insulation symbol: ⧈ (a square inside another square).

Insulated AC/DC power supplies (such as cell-phone chargers) are typically designated as Class II, meaning that the DC output wires are isolated from the AC input. The designation "Class II" should not be confused with the designation "Class 2", as the latter is unrelated to insulation (it originates from standard UL 1310, setting limits on maximum output voltage/current/power).

| improve this answer | |
  • I think this is spot-on. The first quoted paragraph really has the direct answer to the question. – UuDdLrLrSs Jul 23 at 14:27
  • Today I learned that my electric kettle came with a C15-ended cord, but the receptacle is only C14. I'm guessing that despite the fact that a C13 fits, I shouldn't be using it? – stannius Jul 23 at 16:12
  • @stannius That's actually a really good question, and I don't know! Initially my guess would be if the kettle itself has a c14 receptacle a c13 could work; I would guess assuming your kettle design has approval by whatever electrical safety board your country has then you're good to use c13 as they would be rating the recepticle physically attached to the kettle, not whatever cord it ships with, but I would say it's easier to be safe than sorry. ¯\_(ツ)_/¯ – Sidney Jul 23 at 16:27
  • 1
    Unfortunately, IEC connectors failed to consider a rather serious danger. The plugs should have included a notch in one location when the far end of a cable is a 120V plug, and in another location when it's a 240V plug, and sockets for devices that only accept 120 or only 240, or must have a switch set to select voltage, should have been designed to only accept the proper type of cable (devices that accept either voltage interchangeably could accept either type of cable interchangeably). – supercat Jul 23 at 19:20
  • @supercat agreed, a lot of PCs have (or had) a manual switch to indicate the expected voltage – UuDdLrLrSs Jul 23 at 20:18

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.