Multi-headed mains cable

Simple question.

Is this configuration of mains cable electrically safe with regard to appropriate fusing?

To my mind this type of mains cable increases the risk of electrical fire or electrocution in the event of equipment fault. This because each piece of kit connected to each cable branch will not be fuse protected with the correct rating of fuse. Much the same in fact as replacing the 5 amp fuse in an OEM mains cord with a dummy brass fuse (a mains tweak I've also seen described on hi-fi forums).

The fuse in the mains plug above needs to be based on the sum power consumption of the connected kit such that it does not blow during operation; with five pieces of kit 13 amps. The downside of this is if a CD player goes live at the point of switching when the power consumption of the CD player dictates a 5 amp plug fuse is required for failsafe operation; the 13 amp fuse will not blow (or will not blow quick enough).

I'm not aware of any CD players that have a power consumption greater than 1.5kW and therefore the correct fuse rating for failsafe operation is either 3 amp or 5 amp. The information available on local fire safety websites with regard to the correct fusing of electrical equipment reinforces this point.

Some IEC inlets are of course individually fused – but only some not all.

I did raise these concerns on another (naimless) forum on a thread about this configuration of mains cable but was accused of being an overly cautious troll and subsequently banned! A sad indictment on said forum but no skin off my nose. (There was also some comments regarding the audibility of mains fuse orientation – laughable IMHO but best left for the more obsessive types).

I do however think end-users need to be aware of these potential risks if the vendors do not take the responsible position of explaining such (if this is the case?). Hi-fi is great hobby but not one worth burning your house down for – or worse.

Any thoughts?

 

My thoughts? As long as all the individual components are fused then I cant see any problem.
As for the legal side I would have thought it was OK, its no differant to the Micromark Multiplug that is on general sale, and that must surely have all the nessesary kite marks.


Paul.

 

That's my point tho' Paul.

The individual components (CD player, amplifier, tuner etc) are not correctly fused. Essentially the same as removing all the plugs (and their appropriately rated fuses) from existing OEM mains leads of these components and joining the bare wires together. No correct failsafe fuse protection because the fuse in the mains plug is for sum power consumption.

I take your point about the Micromark plug. For the same reasons I'd avoid these aswell. The correct fuse rating is given with the simple formula I = P / V where I is current draw, P is power consumption (watts) and V voltage.

 

Most equipment has an internal fuse as well so you are pretty safe IMO

 

Its not much different to the hydra type mini plug setups. As long as all the equipment is drawing the same current I can't see a problem.....that though is not a real life scenario.

I think I'd pass on that one. Go for a rewired mains block....loosing all that nasty brass and replaced with a suitably rated copper wire.

 

Here in France, mains plugs do not have fuses or the ability to fit them. If something "blows", then I have to rely upon the internal fuse of each bit of equipment or failing that, the mcb/earth trip at the fuse board.
From that, it therefore follows that the plug fuse does nothing other than protect the cable itself, the French taking the view that this is best done at the fuse board. Incidently, in France there are no polarity rules for plugs either , only tradition and the sockets are all unswitched. I live in the Middle Ages with regard to electrical safety. God bless the French.

 

I cant see why it isn't safe, providing the fuse rating in the plug top is correct to cover the current capacity of the cable used.

 

I can't see the problem. A typical 100W hifi amp plus a CD, tuner, minidisc and record deck would not exceed 3 amps anyway so fit a 3 amp fuse in your hydra and it will be perfectly safe.

 

Perhaps I'm not explaining this very well.

The fuse in a mains plug needs to be rated for the power consumption (and hence current draw) of the piece of equipment connected to the mains supply. In the case of hi-fi equipment this invariably means a 3 amp or 5 amp fuse (apart from very meaty power amplifiers which may have a power consumption greater than 1.5kW).

In the case of a multi-headed 'hydra' the fuse in the mains plug needs to be rated for the total power consumption (and hence current draw) of all the pieces of equipment connected to each IEC plug.

Five pieces of equipment (CD player, tuner, amplifier etc) each with a nominal current draw of 2 amps (typical) equates to a total current draw of around 10 amps. Therefore the fuse in the 'hydra' mains plug needs to be a 13 amp – anything less would be insufficient given the total current draw.

The problem with this, as previously mentioned, is that if a piece of hi-fi equipment that should have a 3 amp or 5 amp mains fuse develops a fault at the point of switching on (when such faults are most likely to occur) the 13 amp fuse in the 'hyrda' plug does not blow. Hence no failsafe operation.

 

as mentioned by others, so long as equipment has internal fuse there is no problem. A plug top fuse is really to protect the cable, in the case of fused components.

 

I'm afraid this simply isn't correct Penenace. The fuse in a mains plug is designed to reduce the risk of electrical fire or electrocution in the event of equipment fault. It has nothing to do with protecting a piece of cable (which is entirely expendable).

For those not sure about correct fuse ratings I'd suggest they check their local fire safety website.

In the case of internal fusing you are correct. But if, and only if, the IEC inlet is fitted with a correctly rated fuse.

 

Thats what i said (i think)

It was correct when i did my C&G 236.
The cable is not 'expendable' if the current drawn is greater than the current carrying capacity of the cable (or ~75% if cable is encased), there is danger of fire or shock.

 

Yes. In the case of hi-fi equipment that has a separately and correctly fused IEC inlet there is a failsafe when using a 'hydra' mains cable. But only in this case.

“expendable†in the respect that generally speaking human life is not!

 

It's my understanding, Mosfet, that the picture at the top of the thread is of a Graham's hydra, and that it is recommended for use exclusively with Naim equipment. It is also my understanding that all Naim gear have case fuses (which, I'm guessing, are correctly rated for the case involved) in addition to the fuses in the plugs at the end of the power leads, so, taking this into consideration:

...what is the problem with the use of said Hydra with Naim gear? I believe that Graham's have been making these for a number of years and have remained Naim dealers for all this time, so one can only assume that Naim are happy with the practice.

 

If each individual cable 'head' is current rated at a higher figure than the plug fuse what is the problem. If any one head suffers damage that caused it to draw a current higher than the fuse then the fuse will blow before the cable overheats and burns.
I would imagine that the main circuit board MCB or RCD will detect the fault and trip long before the plug fuse blows anyway.

 

I'm sure there is a point here in principle, like there is a risk of Sizewell B PWR nuclear station being hit by an asteroid, which it is not designed to withstand. But in practice I suggest the household members engage in some risk compensation, such as washing their hands more often, or looking more carefully when crossing the road.

 

There's no problem Goomer if this configuration of mains cable is used exclusively with equipment with separately fused IEC inlets. A point I made in the opening post and several times since.

Further if it can be said categorically that all Naim equipment is thus fused then again there is no problem.

I've purposefully not referred to Grahams directly and tried only to refer only to “configuration†rather than any specific brand. Unfortunately 'hydra' (the product that Grahams sells) is a good way to describe such a configuration.

 

If you consider the increased risk of house fire or electrocution to be negligible as a result of using this configuration of mains cable then you have nothing to be concerned about Steve. Either way it isn't a frivolous subject.

For those wanting a more authoritative view of correct fusing practice I'd suggest the local fire safety website.

 

Mosfet: You have MCBs don't you? The delay between one of those tripping and a plug fuse blowing is minute. Its the same as having a plug fuse its just further back down the chain. Most aftermarket mains cables I've seen come with a 13A in anyway as its the closest thing to a nail or something (which is obviously illegal). Plug fuses are unnecessary with an MCB system.

 

Sorry Anex, not strictly correct, a fuse is to protect against fire and or shock, a plug fuse max is 13amp, a ring main fuse or breaker is 30 amp, a rather large difference.
Brief explaination as im orf home now