A possibly strange and foolish question.
I have available to me a twin, no earth lighting circuit on a 16 amp rcd. Does Naim equipment require an earth for safety reasons or does it need a shared earth on components to ensure the best possible sound?
I would say for safety reasons you can’t use it without an earthed mains supply. The Metal casework makes it potentially lethal if due to a fault, the casework becomes live. Keeping everything earthed to a single point is the SQ aspect but without an earth, this couldn’t happen either.
I think if you did use this circuit you are taking the first step towards winning a Darwin Award.
Naim equipment needs to be earthed.
Is that true though? An RCD or RCBO at 10ma is designed to protect the human against earth faults, ie no earth route in case of a live leakage path then the circuit is tripped.
The Naim grounding topology for SQ is a separate design that just happens to use the convenience of the existing earth in a UK supply.
What happens if the RCD has a fault and is slow in tripping or doesn’t trip? Unlikely I know but for safety, you don’t skimp, better to have another backup, the earth is that. Without the mains earth, how would you earth the kit?
There are many European countries with non earthed circuits. Formerly protected by nothing other than a ceramic wire fuse holder, Nowadays most codes are rcd/ rcbo.
Yes - class 1 appliances use the casework earth to provide a return path for fault currents. If you remove that connection, under a fault condition the casework could float at mains potential. When you, or a member of your family, pet etc. touch the casework, you provide that path for the fault current & only then would any protective device trip.
Faulty RCDs, RCBOs, GFCIs are not uncommon & (mostly) rarely tested. And if not fitted, you could be passing well over 30A of fault current through someone’s heart before a fuse ruptures/MCB operates. Depending on the circuit design of course.
It would be foolish to consider it - please don’t.
Regards
Neil.
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Many thanks NeilS.
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I am wondering why you asked the question as you seem to have made your mind up already.
No, never made up my mind. It is exactly why I asked. I like to understand what the potential ( no pun intended) issue is. Safety related or just related to being a UK based design parameter.
Neil has kindly given the technical information I required.
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I read a while back that DC Offset on your mains would result in older type RCDs not to trip at their designed rate (30mA in the UK). The latest RCD’s dont have that issue.
I believe rooms with no earth outlets most often were built so you didn’t have a low resistance earth connection. It’s when you start to mix non earthed sockets with earthed sockets in the same room you can get a problem. Up until 1994 it was only kitchens and bathrooms that used earthed outlets in most European countries. Meaning still today many many houses and rooms have no earth in the sockets.
An RCD will protect you against problems in both earthed and non earthed environments.
An RCD shall be checked 1-2 times per year by pressing the control button.
The earth is many times also needed to pass the EMC levels in the standard the equipment is built against.
Thanks but I think Neil has answered my query re Naim equipment.
My original query was prompted by me noticing that other metal cased amplifier/receivers that I have are only two pin. Pioneer, Yamaha and Sony. How they isolate internally is a mystery to me. Hence the question is it a safety issue or a UK design issue.
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Some equipment is double-insulated and does not use an earth wire on a mains lead. The Naim equipment is not like that and should not be used without an earth on the mains lead.
Use any equipment for your and others’ safety as intended and designed. It is not just a UK wiring quirk that can be ignored due to being in a different country. It is designed to have an earth so use it with one.
The equipment while fault-free will work without an earth but you will find out what happens when there is a fault and you or someone else becomes the earth. The devices in your consumer unit may help you survive but they also may not before enough electrical power crosses your chest and stops your heart.
As Mr Eastwood said, “Do you feel lucky punk?”
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Equipment with two pin connections is manufactured to an approved safety standard called Double Insulation.
Its designed/constructed much like it says, each electrical part has two layers of insulation separating it from the user.
In UK its known as Class II and regulated under BS7671.
Its labelled with the double insulation symbol which is a square inside another square.
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The answer is I believe both.
The mains earth is used as a ground reference for unbalanced signals… and also mains earth is for safety
I think a lot of people confuse ground and earth, or believe them to be one and the same thing….
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Indeed. There are in fact three. Signal ground, chassis ground, and earth ground. All have different symbols. Some disign link them. Some don’t.
As an electrical engineer once explained to me, grounding is complex and not always obvious. Anyone who thinks they know all about it has just proved they don’t.
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Chassis ground is connected to earth ground? With the switch on “chassis” you connect signal ground to chassis ground which is earth ground via the power cord?
When putting the switch on floating you split signal ground from chassis ground because another source already have this path from signal to chassis to earth ground and you want only one path.
In the case of Naim, I believe that is correct.
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