Wire Gauge help needed please

[granddad gnome]

I have taken advantage of builders putting a trench along one side of my garden (app 80 Ft). So thought I should use said trench to put in a conduit pipe the full length as I wish to put in a separate power board at the bottom of the garden.

My idea is to have terminals for AC mains. as well as the end of a bus bar for track power (use DCC Massoth) also a terminal for uncontrolled DC for accessories etc. Question is Wire gauge to use. AC Mains. No problem. but what gauge do I use for a bus bar for DCC and also for the DC, and do I need a 15volt DC, or 12 volt DC supply for the uncontrolled accessories.

 

[Gizzy]

I suggest speaker cable (at least 14 SWG) would make a good DCC bus bar feed for Massoth? I would though ensure that is suitable for outside use despite being run in the conduit.

As to what supply voltage for the DC accessories, it depends on the expected voltage drop and the rating of the accessories you propose to use. I would run the cable in the conduit, connect to your supply, then measure the voltage at the begining and end of the cable before connecting any accessory. You could always use a 12V lamp as a simulated load....

 

[bobg]

I notice you've sensibly put a drawrope into the new bore (pipe).

What everyone forgets to do, is to make sure that when they pull the cable(s) in, they replace the drawrope at the same time. This is so that you can pull another cable (and drawrope) through the bore alongside the 'existing' at any time. It is standard B.T. practice. Trying to get another cable through an occupied bore without a drawrope, can be "fun"!

 

[Philbahn]

Wonder if you might need screened cable, running along sie AC mains might cause interference

 

[mbendebba]

Generally speaking, wire gauge is determined by how much current (amps) need to flow through it and over what distance, the more current and the further the distance the thicker the wire. For DCC, I use 14 gauge stranded wire. For DC accessories, I use 16 gauge stranded wire. I would use slightly thicker wire if the distance between source and appliance is greater than 40 feet.

Mohammed

 

[Madman]

Don't forget that whatever conduit size you think you need, double or triple it. I see that you already have your conduit installed. But if you can place another along side of the present one, you will thank me someday.

 

[minimans]

Something else you may need to consider, armoured/rodent proof cable....
Just incase one of our fury friends becomes helpful and decides to interconnect the various voltages......

I would pull two A/C cables and as many 14 gauge wires as I could fit through the conduit! you can use the Romex A/C cable for the DCC stuff as well if needed, just remember bigger is better in this case...........................Paul

 

[ntpntpntp]

... you can use the Romex A/C cable for the DCC stuff as well if needed..

But it will then be vitally important to clearly mark which cable is mains and which is DCC!

I'm not a qualified 'leccy man, but something feels a bit dangerous here. Not sure if I would allow the mains and low voltage cables to run anywhere near each other, just in case the wrong one was cut into or wired up. I think I'd rather run armoured mains cable in a totally separate route and/or conduit. Also mustn't forget aren't there rules about having to place warning tape or something on top of buried mains cable? I'm sure I read something about that.

 

[jacobsgrandad]

When we had our wiring for a local theatre redone involving mains votage and low voltage. Were told you should NOT run mains and low voltage in same conduit

 

[spike]

When we had our wiring for a local theatre redone involving mains votage and low voltage. Were told you should NOT run mains and low voltage in same conduit

This is not strictly true as you can run them together as long as all cables are insulated to the highest voltage present.....
?or each conductor in a multicore cable is insulated for the highest voltage present....
unless conductors of the two bands are separated by an earthed metal screen.......
or they are installed in separate compartments of a trunking or ducting system.....
or they are installed on a tray with a partition providing separation......
or a separate conduit or ducting system is provided for each band.

I believe the only exception is fire alarm cables.

 

[jacobsgrandad]

Thanks for the info

 

[spike]

Take a dozen sparkies and all of them will interpret the rules a different way.
If in doubt keep the cables of different bands seperated, in some cases this may not be achievable.

My 17th edition is a work and will take a look to see whats been changed, if anything.
When you look at the Regs it's easy to see why some get confused.
You may want to keep mains away from critical cables as there may/will be induction from
the mains to those circuits.

As to buried cables........ I will check this as well.
There is no requirement to bury SWA cables at any depth within BS7671
The only ref to buried cables comes under 522-8-10
this gives no reference to the depth at which cables should be laid but you may see 600mm used.
Buried cables, conduits, and ducts shall be at a sufficient depth to avoid being damaged by any reasonably foreseeable disturbance to the ground.
Use common sense here.

 

[granddad gnome]

Thanks Guys for all information. Have read it all and come up with the following.
I will lay in another conduit at the side of the one laid. These will be at a depth for approximately 50cm and covered with a tape Marked Mains power, this was obtain from my City Electric Branch. The mains cable which is armored is one the right. The other wire is armored also but is 10 core plus an earth. I am not sure of its gauge as I don't have one but my strippers say 1.5. The overall distance from main board to proposed secondary board is 63 feet. So I hope all this will be a good enough compromise.

 

[spike]

Just checked 17th regs on underground cables.
Reg 522.8.10
Except when in a conduit or duct a buried cable shall incorporate an earthed armour or metal sheath suitable for use as a protective conductor.
The cable location shall be marked with cable covers or suitable marking tape.
Cables should be buried to a sufficient depth to avoid damage by any reasonably foreseeable disturbance of the ground.

 

[Philbahn]

So you are running SWA and SY together .Have you got the glands to terminate the SWA. I think the multicore Sy will be ok without glands. BTW yes it looks 1.5mm

Thanks Guys for all information. Have read it all and come up with the following.
I will lay in another conduit at the side of the one laid. These will be at a depth for approximately 50cm and covered with a tape Marked Mains power, this was obtain from my City Electric Branch. The mains cable which is armored is one the right. The other wire is armored also but is 10 core plus an earth. I am not sure of its gauge as I don't have one but my strippers say 1.5. The overall distance from main board to proposed secondary board is 63 feet. So I hope all this will be a good enough compromise.

 

[granddad gnome]

So you are running SWA and SY together .Have you got the glands to terminate the SWA. I think the multicore Sy will be ok without glands. BTW yes it looks 1.5mm

My local Lecy tells me we will be OK with these. the first is to recycle for inside the train room, the 2 is the water proof box for the other end and the 3 is the glands to use to earth every thing up.