6mm cable for a hifi?

[HappyHippyDad]

Evening all.

A customer has asked for a dedicated radial circuit to feed 4 2g sockets.

He has asked for the cable to be rated at 45amps as he said at times the hifi equipment may reach this current. He is very specific that he wants the cable rated at this as a minimum.

He has asked for the 6mm to be terminated into an enclosure by the hifi which then feeds out in 2.5mm 'individually' to each of the sockets which are right by the enclosure (like an old spider circuit for lighting).

My plan was to use a 45A MCB for the circuit as the 2.5mm cable supplying the sockets will not need overload (O/L) protection and fault protection will be offered by the 30mA RCD (TT). Reference method will be 'C'.

I'd be interested in any opinions on this as it is a different style of circuit to 'normal' and those shown in appendix 15, but as stated fault protection is in place, O/L protection in place for the 6mm cable and protection against O/L can be omitted for the 2.5mm cable feeding the sockets (433.3.1 (ii)).

Cheers.

 

[M-Ty]

Flog him the rest of the reel to feed his 'speakers.

 

[HappyHippyDad]

That puts paid to your idea of running it outside then!

Thats what I've told the client. I've suggested running it indoors either in trunking or taking up the carpet/floorboards above but he has declined both of these options. So the next option is to run the SY in conduit outside.

I do have a further question, if ever you do have a cable going into an outside box and you have used a stuffing gland (for flex) or the proper gland for SY and you want to have this cable in conduit, how do you attach the conduit to the box or at least do something so that the conduit is not open at the top. I thought perhaps the shroud could be placed around the gland as normal and then over the conduit, not ideal but better than letting any water get into the conduit with SY cable in it?

 

[HappyHippyDad]

Is 6mm² too big now or is it the more finely stranded sound of SY that is wanted? As can be seen from my little fuse experiment in post 16, it will run happily on one strand of 4mm² SY.

This sounds like preparation for a big sell. If they advise to get a special circuit installed and the customer does so, when they try to push a £500 IEC lead they have already defeated the counter-argument that the installation cable is too poor for the special lead to make a difference.

Aha, the penny just dropped, SY sounds more... transparent!

He now seems less interested in reaching the 45A mark which I have made him aware that 4mm SY will not be suitable for and more interested in specifically using SY cable (due to advice from the specialist shop!).

 

[rolyberkin]

I have some genuine snake oil if your customer is interested! Cures all and if he rubs it on himself whilst listening to his hi fi it will sound better!

 

[Kamikaze]

Just sell him a Niobium-Titanium cable. A 2.5mm² cooled to -271.3°C by a closed liquid-helium system is good for over 1000A. He will be able to run everybody’s Hi-Fi in the street of it….lol.:joker:

 

[davesparks]

Thats what I've told the client. I've suggested running it indoors either in trunking or taking up the carpet/floorboards above but he has declined both of these options. So the next option is to run the SY in conduit outside.

I do have a further question, if ever you do have a cable going into an outside box and you have used a stuffing gland (for flex) or the proper gland for SY and you want to have this cable in conduit, how do you attach the conduit to the box or at least do something so that the conduit is not open at the top. I thought perhaps the shroud could be placed around the gland as normal and then over the conduit, not ideal but better than letting any water get into the conduit with SY cable in it?

I've never really considered how to terminate conduit in that scenario as its not an installation method I have ever yet considered using.
I would want to know why they are specifying SY and then find an alternative which does provide the properties they want as well as being suitable for external installation.
I suspect it's some BS about the shielding on SY, so I'd point out that conduit is a better shield in itself than the braid on SY.

 

[HandySparks]

I do have a further question, if ever you do have a cable going into an outside box and you have used a stuffing gland (for flex) or the proper gland for SY and you want to have this cable in conduit, how do you attach the conduit to the box or at least do something so that the conduit is not open at the top. I thought perhaps the shroud could be placed around the gland as normal and then over the conduit, not ideal but better than letting any water get into the conduit with SY cable in it?

If it's running in conduit, why would you need a gland for the cable? Just fit the conduit to the box as normal and poke the cable through it as though you were using singles.

 

[HappyHippyDad]

If it's running in conduit, why would you need a gland for the cable? Just fit the conduit to the box as normal and poke the cable through it as though you were using singles.

That's what gets done alot with SY Handy, but how do you effectively earth the braiding without using the correct gland? I've seen it twisted around abit and put in a terminal block which then gets attached to the earth but it looks a bit shoddy.

 

[davesparks]

If it's running in conduit, why would you need a gland for the cable? .

To correctly terminate the braid

 

[HandySparks]

That's what gets done alot with SY Handy, but how do you effectively earth the braiding without using the correct gland? I've seen it twisted around abit and put in a terminal block which then gets attached to the earth but it looks a bit shoddy.

To correctly terminate the braid

What I was envisioning was to keep the external conduit unbroken, but terminate the SY into glands inside the property where there are no issues with water getting into conduit. Easier to do it this way than if it was SWA, being more flexible.

 

[HappyHippyDad]

What I was envisioning was to keep the external conduit unbroken, but terminate the SY into glands inside the property where there are no issues with water getting into conduit. Easier to do it this way than if it was SWA, being more flexible.

Ah, misinterpreted you Handy, sorry! Not a bad idea, however the cable will go directly through the wall of the property into the back of another enclosure (or possibly socket).

 

[davesparks]

Ah, misinterpreted you Handy, sorry! Not a bad idea, however the cable will go directly through the wall of the property into the back of another enclosure (or possibly socket).

It'll have to not go directly in to the back if you do it that way.
The customer cannot specify an industrial type control cable and then not expect to see an industrial looking installation!

 

[HappyHippyDad]

It'll have to not go directly in to the back if you do it that way.
The customer cannot specify an industrial type control cable and then not expect to see an industrial looking installation!

Yes, hence having to gland in the external box and back to the problem of neatly and effectively keeping the conduit in place and free from water.

 

[davesparks]

Yes, hence having to gland in the external box and back to the problem of neatly and effectively keeping the conduit in place and free from water.

Personally I would just say no to installing it externally, I won't compromise the design for the sake of pandering to nonsense.

 

[shanky887614]

nah the customer will be the usual run of the mill idiot. offer him some monster gold plated hdmi cables for £100 a pop and he will bite your hand off, explain to him there cheap as you dont have the packaging XD.

its the same as some pc psu years ago, you needed to use a 500watt if you needed 250watts or they would burn out as they were rated way higher than they could actually output