90 c thermosetting swa table 4e 4a. note 2

[nick611]

what does this note mean? my design consultant is using this table for my sub mains. connected to standard 3 phase mccb and 3 phase dist boards. can these operate at + 90 c. ? example 63a 3 phase sub main, 10mm thermosetting swa. should he be using 70 c table ?

 

[telectrix]

if the isolators etc. are only rated to 70deg. then you should be basing your calcs. on that, irrespective of the cable rating.

 

[nick611]

yes that's what I thought but the designers are using the 90 c all the time. are,nt the supposed to be clever *******.s ?

 

[telectrix]

calvin klein's a designer, but i'd not trust him to fit a plug.

 

[Engineer54]

what does this note mean? my design consultant is using this table for my sub mains. connected to standard 3 phase mccb and 3 phase dist boards. can these operate at + 90 c. ? example 63a 3 phase sub main, 10mm thermosetting swa. should he be using 70 c table ?

Will any of these SWA cables actually be operating at 90c?? (i doubt it very much unless your installing these cable in a furnace works ...lol!!) Depending on knowing the max demand, installation method etc, on this sub-main, i wouldn't have any problems at all having a 63A breaker sitting on a 90c 10mm SWA cable.

Think all SWA cables are now with 90c XLPE insulation. If these design consultants have designed the whole installation, they will have taken all the factors into consideration. and seeing as they know how, and the basis on which the installation has been designed, i'd leave it to them, to have the last word on specifying complying cable sizes....

 

[nick611]

Will any of these SWA cables actually be operating at 90c?? (i doubt it very much unless your installing these cable in a furnace works ...lol!!) Depending on knowing the max demand, installation method etc, on this sub-main, i wouldn't have any problems at all having a 63A breaker sitting on a 90c 10mm SWA cable.

Think all SWA cables are now with 90c XLPE insulation. If these design consultants have designed the whole installation, they will have taken all the factors into consideration. and seeing as they know how, and the basis on which the installation has been designed, i'd leave it to them, to have the last word on specifying complying cable sizes....

I don't expect the cable will operate at 90 c, but that's not what note 2 say,s. it say,s that if the equipment or accessories connected to the cable cannot operate over 70 c then that table must be used. no mention of cable temp.

 

[Engineer54]

I don't expect the cable will operate at 90 c, but that's not what note 2 say,s. it say,s that if the equipment or accessories connected to the cable cannot operate over 70 c then that table must be used. no mention of cable temp.

And why the Design Engineer(s) probably ignored what it says in BS7671!! lol!! If you check the manufactures cable data, (which the Engineer undoubtedly did) you'll probably find that the current ratings of 90C cables working to 70c, are higher than those given in BS7671. I rarely if ever, use the current carrying tables in BS7671 or it's guides....