Three phase DB, water, you can geuss!

[Engineer54]

It should be pointed out that there ARE certain rules that govern the use of parallel supplies/feeds. The cables Must be of the same construction, Must be of the same CSA size, Must be substantially the same length point to point, should follow the same route in/by the same containment means.

Remember, we are not talking about a ring circuit, although a ring can be classed as a crude parallel circuit but one that serves multiple loads/points. However a true parallel circuit will supply/feed just one load point!!

 

[J25GTi]

That, would frankly defeat the point wouldn't it?? Most main switchboards, will actually be constructed to accommodate parallel feeds and in some circumstances even outgoing ways...

Not sure why you are obsessed with one leg failing, why would just one leg fail? Taking that all connections have been professionally made off, what would you say, is the chances of that ever happening??

I'm not obsessed with it. Just asking the wquestions that's all, as obviously there is something I have missed here!

 

[Engineer54]

I'm not obsessed with it. Just asking the questions that's all, as obviously there is something I have missed here!

Probably something else that's not covered in an electricians training these days... :sick: lol!!!

 

[Knobhead]

As an industrial electrician you must have come across a service head like this. A Lucy 630A unit (spreader boxes not shown).
View attachment 12183
If you can’t run parallel cables, why are there 2 cable outlets per phase.
As has been said in industry parallel cables are normal practice.

 

[J25GTi]

As an industrial electrician you must have come across a service head like this. A Lucy 630A unit (spreader boxes not shown).
View attachment 12183
If you can’t run parallel cables, why are there 2 cable outlets per phase.
As has been said in industry parallel cables are normal practice.

Yes of course I have seen these, but I've never used parrallel supplies etc. Only single cables up to 5 core 195mm. But we live and learn

 

[Knobhead]

Given the choice would you prefer to run a 185 or two 95’s. I know which my moneys on.

 

[Engineer54]

Yes of course I have seen these, but I've never used parallel supplies etc. Only single cables up to 5 core 195mm. But we live and learn

Are you convinced yet, that there is nothing wrong with a parallel circuit run?? And, ...can you now see the benefits that such circuits can bring to an installation, in both current carrying etc and cost savings in labour and cable costs??.... These can be very significant in larger projects, especially where long cable runs are involved...

 

[Brightspark2]

Good work, massive improvement there...


Once you start getting to larger CSA's, cables ran in parallel get more common for reasons already stated. Im just completing an installation in a data centre where we have run various cables in parallel, 2 x 185mm etc.

 

[Mark_Burgess]

Lets hope they have sorted the leak in the roof!!
What I would say is, it looks if the MCB they put in is the right way round, the MCB spring clip is supposed to be on the outside, well hager boards always state it.

 

[RISElectrical]

Cables ran in Parallel as stated are fine. If we worked on the principal of "when" a leg fails, a 2.5mm ring would either need to be on a 20A MCB or wired in 4mm as what your saying contradicts the design of a ring final circuit

 

[Knobhead]

We’re talking of power feeds to a MCC so possibly a 1200A feed. I don’t think it would fit in a CU.

Read through a post before commenting.

 

[RISElectrical]

We’re talking of power feeds to a MCC so possibly a 1200A feed. I don’t think it would fit in a CU.

Read through a post before commenting.

Correction, that's what you were talking about. The OP and indeed all the first page mention noting above 50A and 4mm. The attached pictures are of MCBs that 185mm wouldn't fit in to them would they?

I was merely making the point (someone else already made it earlier in the thread!!) about the principal of a ring so it relates to other areas as many people don't know about cables in parallel.

 

[J25GTi]

Lets hope they have sorted the leak in the roof!!
What I would say is, it looks if the MCB they put in is the right way round, the MCB spring clip is supposed to be on the outside, well hager boards always state it.

Yes I got a builder in to sort the leak from the roof, So we solved the problem and the cause of the problem, making for one very happy customer and then no future issues

 

[J25GTi]

Correction, that's what you were talking about. The OP and indeed all the first page mention noting above 50A and 4mm. The attached pictures are of MCBs that 185mm wouldn't fit in to them would they?

I was merely making the point (someone else already made it earlier in the thread!!) about the principal of a ring so it relates to other areas as many people don't know about cables in parallel.

This would be my college tutors fault (4 years ago now? jeez time flies)

As he always instilled the view on us that rings were inherently dangerous if you lost a leg etc then you have 2x 25a cables running on a 32a mcb etc. So this would be where i have formed this opinion from.

Obviously where practicable it would be better to use one single cable, but in alot of instances it obviously isnt practicable.

In the case of this supply i dont see why there is any reason to use parallel supplies for the length of cable it was just lazyness as they didnt happen to have any of the right size cable i imagine.

 

[Engineer54]

As he always instilled the view on us that rings were inherently dangerous if you lost a leg etc then you have 2x 25a cables running on a 32a mcb etc. So this would be where i have formed this opinion from.

Yet another collage lecturer that perpetuates his own personal views on to his students, ....inherently dangerous, what a complete plonker!! I wonder what he would of made of a 3 phase ring circuit that are commonly used in industry??

As for the parallel feed, not something i would have done myself, but never the less, fully compliant!!

 

[mark ju]

Parallel supplies are quite common as stated, but to get back to the original post, nice install, keep that up and i'd let you work with me!