Customer wants round back boxes and round sockets, round everything!

[Lucien Nunes]

what is your opinion on some electricians' objection to unswitched sockets because of the possibility of arcing? We hear this sometimes from installers who flat-out refuse to consider them.

At 13A, the switch is a nicety; it gets more important when you move up to 63 and 12A etc. but these are not relevant here. When you are used to switched sockets, relying on the socket contacts to break the load seems crude, but it works fine and most of the world does it. Even locales with highly evolved electrical regs that have historically used unswitched sockets have not found it worthwhile to introduce a requirement for a switch.

The arc is not serious on AC and a deliberate attempt to withdraw a plug usually makes for a reasonably controlled rate of contact separation. Arcing is much more serious if a plug is left just barely engaged into contact and can fizzle and burn for an extended period, which of course is just as likely with a switched socket as an unswitched one. I would not differentiate between kinds of load or application when fitting an unswitched socket. A laptop charger is as likely to make splash on inrush, as a heater on disconnection, neither is dangerous. But I would say installing unswitched sockets for general use is inconvenient when switched ones are so widely available and standard.

Historically some manufacturers made various attempts to address arcing when disengaging a plug, especially in the pre-war days of DC supplies, as the arc is not self-quenching on DC as it is on AC. Wylex used spring-loaded ball bearings to create a snap action that made sure the plug was either fully in or out. At least one manufacturer introduced shutters with the claim that these 'cut off' the arc as they closed (in addition to preventing insertion of foreign objects). Walsall actually incorporated an interlocked switch that operated automatically as you inserted the plug - you couldn't see or operate the switch yourself. But whether these were of any real value on AC, and not just sales features, is moot.

 

[wolfatswtch]

At 13A, the switch is a nicety; it gets more important when you move up to 63 and 12A etc. but these are not relevant here. When you are used to switched sockets, relying on the socket contacts to break the load seems crude, but it works fine and most of the world does it. Even locales with highly evolved electrical regs that have historically used unswitched sockets have not found it worthwhile to introduce a requirement for a switch.

Thank you for the really comprehensive and informative comment. I will save this and send it to any installer who says "unswitched sockets are not safe and/or illegal in the UK" - we've had a few of those over the years...

A laptop charger is as likely to make splash on inrush, as a heater on disconnection, neither is dangerous.

My laptop power supply always causes arcing when I plug it in anywhere.

But I would say installing unswitched sockets for general use is inconvenient when switched ones are so widely available and standard.

True, but there is also the aesthetic element to consider. Some of the designs we supply look much better with an unswitched socket (and in fact a couple of them are only available unswitched). For example the porcelain range the OP mentioned doesn't come as switched. I've been told by manufacturers that it's difficult enough to make a 13A BS1363 outlet cover in ceramic, let alone adding a switch!

 

[DPG]

Thank you for the really comprehensive and informative comment. I will save this and send it to any installer who says "unswitched sockets are not safe and/or illegal in the UK" - we've had a few of those over the years...


My laptop power supply always causes arcing when I plug it in anywhere.


True, but there is also the aesthetic element to consider. Some of the designs we supply look much better with an unswitched socket (and in fact a couple of them are only available unswitched). For example the porcelain range the OP mentioned doesn't come as switched. I've been told by manufacturers that it's difficult enough to make a 13A BS1363 outlet cover in ceramic, let alone adding a switch!

Aesthetic requirements should come definite second after actual requirements. Unfortunately form over function seems to be the way things are going with electrical accessories.