Parallel Conductors.

[Rampage]

Going slightly off piste on my D&V Project again.
I'm thinking of running parallel conductors for an electric gate supply 'just to learn about it'.

After reading the BGB it seems quite simple, in that the sum of two smaller cables will be the Iz of the circuit as long as the cables are roughly the same length, material, type, CSA and no branches or separate isolators!
Also, the In can be rated according to the current carrying capacity of both cables as long as they are protected against mechanical damage. Or, separate MCB's can be used for each conductor.


Is it really that simple?

The supply it's feeding is an electric gate, so I guess the thermal constraints could be worked out based on the gate only using power for 30 seconds(?) at a time so that a single cable would survive if the worst came to the worst.

Assuming you used twin and earth(!) for this. Would you run both Lines in one cable and the neutrals in the other, or not, or wouldn't it matter?

Many thanks.
Chris

 

[Guest123]

Isn't one of the parameters of the project that the installation has to be cost effective too??

 

[Rampage]

It's not mentioned!
It might be saving money by using 2x 1.5mm2 as opposed to one 6mm2, although the cost of the extra MCB and mechanical protection might counter-act that

I mentioned I was using a 3-phase cooker the other day and nothing was said!

 

[Engineer54]

In your case, it may not be a cost effective alternative, to using a correctly sized single cable.

Generally, you would consider a parallel circuit on very long runs, or where there is a high current requirement or indeed in many cases, where both are involved.

One thing many electricians and engineers alike, often neglect to consider when deciding on installing parallel runs, especially when the larger cables are involved. That is the connections at both ends... This can be a real headache, and will often require ACB/MCCB terminal extensions, which is fine, ...if there is enough space for them, and the dressing of the cables!!!

So Yes it is very simple and straight forward, if everything is in your favour, but it can also get very involved, with other provisions needing to be made, in order for a parallel circuit to work!!!

 

[GLENNSPARK]

i noticed you mentioned running 2 lines in the same cable......i would run it as line and neutral with the CPC between.......

 

[Engineer54]

i noticed you mentioned running 2 lines in the same cable......i would run it as line and neutral with the CPC between.......

Frankly, .... i don't know how he could of even asked that question!! I think he'd best stick to single cable installations for the time being!! lol!!!

 

[Paul.M]

If your going to use 1.5mm for a gate, consider start up currents for both cable and mcb.

 

[Rampage]

Frankly, .... i don't know how he could of even asked that question!! I think he'd best stick to single cable installations for the time being!! lol!!!

I was wondering about induction. I'm still not too sure on how induction works, I need to read up on it. If you don't ask you never find out.
Also 523.7 BGB Part 1 a: 'the conductors in parallel are multicore cables'
Which, while eating dinner and rushing reading about parallel cables assumed it meant the same cable!

 

[Rampage]

Thirdly if a cable was to get damaged I though it would be better if one with 2 Lines got cut through rather than a Line and Neutral which would leave a circuit with only half the current carrying capacity.

 

[tigerpaul]

You mention 2 cables with an mcb for each one... so to isolate the circuit you need to switch off BOTH mcbs? Never heard anything like it!

You mention 2 T+E cables and then using both cores of one for Line and both cores of the other for Neutral???

No this sounds dodgy to say the least.

 

[tigerpaul]

Not knocking you though mate, if you dont ask these questions you dont get the feedback. and at least your taking a good interest!

 

[Engineer54]

Thirdly if a cable was to get damaged I though it would be better if one with 2 Lines got cut through rather than a Line and Neutral which would leave a circuit with only half the current carrying capacity.

Stick to what you know!! ...Because it's quite evident, you don't know anywhere near enough about parallel supplies. ....i'm just hoping this is a virtual job your talking about, and not one in the real world...

 

[Rampage]

Yes, it's for a D&V course.
I know very little about parallel conductors, only what I've read in about 10 minutes tonight. I though it might be something interesting to learn.

If anyone has a good link to anythng written about parallel conductors could you post it please!

 

[Rampage]

You mention 2 cables with an mcb for each one... so to isolate the circuit you need to switch off BOTH mcbs? Never heard anything like it!

Reg (BGB) 434.4 Fault current protection of conductors in parallel
If operation of a single device may not be effective then one or more of the following measures shall be taken:
ii) For two conductors in parallel, a fault current protective device shall be provided at the supply end of each parallel conductor.

Is that refuring to something other than MCB's? Or have I interpreted it wrong?

 

[tigerpaul]

Reg (BGB) 434.4 Fault current protection of conductors in parallel
If operation of a single device may not be effective then one or more of the following measures shall be taken:
ii) For two conductors in parallel, a fault current protective device shall be provided at the supply end of each parallel conductor.

Is that refuring to something other than MCB's? Or have I interpreted it wrong?

Imagine a ring circuit with only one point. Now that should resemble your parallel fed circuit.

There is only one overcurrent device protecting both cables isnt there.

Otherwise you could switch off one mcb, take the cable out and it would be live still as it's being fed from the other end!