I might be able to shed some light on some of it. The temperature rise is probably specified as being measured by the change in resistance method. The change of resistance method will average the internal temperatures and allows for a 5C hot spot. Hence, A 75 C rise, taken by the change of resistance method, equates to a hot spot temperature of 105 C. (75 +25 ambient + 5 hot spot + 105). The same applies for the E and B classes. I can't account for the wider class F and H apparent discrepancies, I assume it goes along the same lines of reasoning.
The above may be completely off base, since I do not have a copy of either standard, but may be helpfull. Gabriel Roy Hughes Network Systems MD Of course the above are my opinions only, not corporate. -------------------- snip ----------------- Raymond Li wrote: I have read through two international standards relative to the captioned subject. There are some differences even though they both are called the same classes. EN 60 355-1 IEC 85 Class Temp rise Actual temp A 75 degC 105 degC E 90 degC 120 degC B 95 degC 130 degC F 115 degC 155 degC H 140 degC 180 degC Since the readily available enamelled copper wires are largely quoted American specifications as below, I am seeking some advice how to tie the American approved/classified wires into European requirements. UL 506 Class Temp rise 105 70 degC 130 95 degC 155 115 degC 180 135 degC 200 150 degC 220 165 degC Appreciating any expert advice. Thanks and regards, Raymond
