Red, blue and black cable

[mil5om]

Is blue neutral or earth when there is a black cable (which is the old neutral) - old system? Other one is red, no green / yellow

 

[westward10]

I think you need to elaborate as you aren't making much sense. The conductors you describe can serve any purpose providing they are correctly identified.

 

[buzzlightyear]

 

[freddo]

Red Blue and Black are old DC supply colours. What is the cable used for? As above any colour could be used for any purpose.

 

[littlespark]

In some older buildings where there was 3 phase supplies serving single phase loads, and the installation was singles in conduit…. The phase colours were used.

So normally where you would see red, black and g/y, you could have yellow, black, g/y or blue, black, g/y

If metal conduit, there may be no green/yellow…


What is the situation you have found?



BTW, @buzzlightyear why is your diagram showing the cores in the wrong order? Old 3 core and earth is red, yellow, blue…. And your new cables on the right are similarly mixed up…. Should be brown, black, grey.

I’m not 100% certain the cpcs are in the right place either.

 

[buzzlightyear]

BTW, @buzzlightyear why is your diagram showing the cores in the wrong order? Old 3 core and earth is red, yellow, blue…. And your new cables on the right are similarly mixed up…. Should be brown, black, grey.

6 Changes to cable core colour identification​

Table 7B – Cable to BS 6004 (flat cable with bare cpc)​

Cable type	Old core colours	New core colours
Single-core + bare cpc	Red or black	Brown or blue
Two-core + bare cpc	Red, black	Brown, blue
Alt. Two-core + bare cpc	Red, red	Brown, brown
Three-core + bare cpc	Red, yellow, blue	Brown, black, grey

 

[LewisM]

In some older buildings where there was 3 phase supplies serving single phase loads, and the installation was singles in conduit…. The phase colours were used.

So normally where you would see red, black and g/y, you could have yellow, black, g/y or blue, black, g/y

If metal conduit, there may be no green/yellow…


What is the situation you have found?



BTW, @buzzlightyear why is your diagram showing the cores in the wrong order? Old 3 core and earth is red, yellow, blue…. And your new cables on the right are similarly mixed up…. Should be brown, black, grey.

I’m not 100% certain the cpcs are in the right place either.

Some of the vauxhall factory in Luton is wired like this the live is the colour of what phase it goes to in the DB