Quicky - 2382 question - Electricians Forum | Electrical Forum | An electrical forum for electricians in the UK

**LukeScotty** · 22-07-2008

where would i find this in the red book?

The correction factor for cables installed in free air with 70oC thermosetting insulation and an ambient temperature of 50oC is?

any help would be much appreciated,

regards

ccrowe · 22-07-2008

Table 4B1 on page 267.

**LukeScotty** · 22-07-2008

this is wat is confusing me, it says 70oC thermosetting insulation. the tables has "70oC thermoplastic" and "90oC thermosetting" so which one do i look under?

heres another one, too

The correction factor for cables installed in free air with 90oC thermosetting insulation and an ambient temperature of 40oC is

A: 0.76
B: 0.69
c: 0.96
D: 0.86

mjvor · 25-07-2008

The new table 4B1 is more limited than the old one.

I think the first questioin may have been a typing error - not unusual for C&G).

Your second question doesn't have the right answer - should be 0.91 - again another C&G error, but I think you copied it incorrectly as only one of the 4 answers (0.76) is a possible answer. They will only list 4 figures which you could get from the table.

However, you can get 90deg thermoplastic and 60deg thermosetting which the table doesn't address.

You need to just go on the temperature rating of the cable, not what it's made of.

The rating factor will allow enough current to heat the cable up to its maximum temp.

So if you have a 90deg thermoplastic in an ambient of 70deg then the rating will be 0.58 which will get it to 90deg

P296 gives ratings and factors for 60deg and 90deg flexible cords whether thermoplastic or thermosetting

Mike