max amp of cable

[ritchiehulse]

could someone please help me quick its fairly easy,

left my regs book at work and cant seem to find the tables online, recieved a snag sheet from a test saying a tp breaker needs down rating from 100a to 80a

they are 25mm type of wiring b, ref method b

i thought of the top of my head they would carry over 100a or is this due to how they are wired?

 

[Flanders]

Singles pvc in trunking 90 amps single phase or 80 amps 3 phase

 

[ritchiehulse]

wow didnt know that, well it is 3 phase, the breaker is obsolete so i would imagine i would have to upgrade the tails.

the section board is next to the distribution board with a 100a 3 phase breaker in the section board. straight out of the section board in metallic trunkng so i would need to run say 32mm tails/swa instead?

 

[davesparks]

What rating factors are applicable? Without this info the tabulated ccc is not much use.

 

[Simonslimline]

wow didnt know that, well it is 3 phase, the breaker is obsolete so i would imagine i would have to upgrade the tails.

the section board is next to the distribution board with a 100a 3 phase breaker in the section board. straight out of the section board in metallic trunkng so i would need to run say 32mm tails/swa instead?

Let us know if you find any.

 

[davesparks]

i would need to run say 32mm tails/swa instead?

How can we tell you that without knowing any of the necessary information?
What's the ambient temperature, grouping factor, etc etc? What about VD and EFLI?
Being so close to a section board does any consideration need to be made for the level of fault current present?

 

[ritchiehulse]

Let us know if you find any.

lol my bad 35mm

 

[ritchiehulse]

How can we tell you that without knowing any of the necessary information?
What's the ambient temperature, grouping factor, etc etc? What about VD and EFLI?
Being so close to a section board does any consideration need to be made for the level of fault current present?

normal room temp, box trunking is 400mm with the sole purpose of providing the tails from the section board to the distribuition board. Very small run i would say 3 meters tops, no worry of fcp

 

[Flanders]

wow didnt know that, well it is 3 phase, the breaker is obsolete so i would imagine i would have to upgrade the tails.

the section board is next to the distribution board with a 100a 3 phase breaker in the section board. straight out of the section board in metallic trunkng so i would need to run say 32mm tails/swa instead?

do you know what type of cable it is , is it denfently pvc as 90 degree cable will take 100 amps , and good look finding 32mm cable the next size up will be 35mm also you need to do the full cable calcs to check what you are installing will do the job

 

[davesparks]

normal room temp, box trunking is 400mm with the sole purpose of providing the tails from the section board to the distribuition board. Very small run i would say 3 meters tops, no worry of fcp

Do you have a figure for normal room temp? The tables on the regs only use figures, not arbitrary values.
400mm? Is that 400x400 or ???
What do you mean by no worry of fcp?
What is at the load end of this cable?

 

[davesparks]

do you know what type of cable it is , is it denfently pvc as 90 degree cable will take 100 amps , and good look finding 32mm cable the next size up will be 35mm also you need to do the full cable calcs to check what you are installing will do the job

But you can only use 90degree ratings of the terminations and connected equipment are all rated to operate at 90 degrees.

 

[ritchiehulse]

the cables where 25mm single insulated single cables. The db there feeding will only be pulling max 50a

 

[ritchiehulse]

so dave if you where to test a installation that has all the perimeters i have described would you say the breaker needs down rating to a 80a?

 

[Flanders]

normal room temp, box trunking is 400mm with the sole purpose of providing the tails from the section board to the distribuition board. Very small run i would say 3 meters tops, no worry of fcp

not sure if you could class this as singles ran in trunking due to the short distance and space in the trunking its almost in free air , was this given a code 2 or 3 observation

 

[ritchiehulse]

code 2 but they want all c1 and c2 correcting

 

[ritchiehulse]

i understand you might class it as in free air but i am just going off the test sheets, its not a problem if the tails are not covered by a 100a breaker as i will simply change them for 35mm tails i just wasnt sure hence asking in here for advise

 

[Flanders]

Well if it is given a code 2 it will need to be rectified and as you say upgrade the cable or prove that the cable that is currently installed in suitable and safe to leave in service a d then no action will be required

 

[ritchiehulse]

not sure if you could class this as singles ran in trunking due to the short distance and space in the trunking its almost in free air , was this given a code 2 or 3 observation

i understand you might class it as in free air but i am just going off the test sheets, its not a problem if the tails are not covered by a 100a breaker as i will simply change them for 35mm tails i just wasnt sure hence asking in here for advise

 

[Flanders]

Ok no problem , well brian cox is on in a bit so loging off now

 

[davesparks]

not sure if you could class this as singles ran in trunking due to the short distance and space in the trunking its almost in free air , was this given a code 2 or 3 observation

They are singles, they are inside trunking, it's not exactly hard to work out what the installation method is!