Rules and Guidelines
Want to participate in the discussions? Please read our Community Rules and Guidelines. Need some help? Visit Support and Answers.

  • Replies 13 replies
  • Subscribers 36 subscribers
  • Views 2490 views
  • Users 0 members are here
Options
You may also be interested in

Overload protection - Regulation 433.1.201and BS 88 fuses

Geoff Lyons

Regulation 433.1.201 indicates that a BS 88-2 or BS 88-3 fuse, with a rated current (In) not exceeding the current carrying capacity of the circuit conductors, will comply with condition (iii) of Regulation 433.1.1. [i.e. the current (I2) causing effective operation of the protective device does not exceed 1.45 times the current carrying capacity of the circuit conductors].

However, the product standard for those fuses (BS EN 60269-1:2007+A2:2014), along with Table 4.1 of the Electrical Installation Design Guide, gives If (I2) as 1.6 In, which clearly exceeds the 1.45 of Regulation 433.1.1. Furthermore, the conventional fusing time for fuses rated in excess of 63 A is greater than 2 hours, as opposed to 1 hour for a BS EN 60898 circuit breaker, which would surely increase the likelihood of a cable overheating under overload conditions.

Does anyone have an insight into this apparent inconsistency, or am I misunderstanding something?

Geoff

  • in reply to gkenyon

    Thanks for persevering with that Graham; I hadn’t spotted the “Conventional cable overload protection test” requirement in the standard, though I now see it goes all the way back to 1988.

    It certainly explains the statement in Regulation 433.3.201 though, as you point out, and as stated in that regulation, only for general-purpose type (gG) fuses. On that point, am I correct in interpreting “a general-purpose type (gG) fuse to BS 88-2, a fuse to BS 88-3, ….”, as a gG fuse to BS 88-2, a gG fuse to BS 88-3, …?

    Geoff

  • in reply to Geoff Lyons
    Geoff Lyons said:
    On that point, am I correct in interpreting “a general-purpose type (gG) fuse to BS 88-2, a fuse to BS 88-3, ….”, as a gG fuse to BS 88-2, a gG fuse to BS 88-3, …?

    I cannot provide an "official interpretation" only an opinion.

    BS EN IEC 60269-3, and its predecessor BS HD 60269-3:2010+A2:2022, BS 88-3:2010+A2:2022 only cover gG fuses ... so the inference is that all BS 88-3 and IEC 60269-3 fuses are gG fuse links.

    Therefore, there is no problem saying 'gG fuse to BS 88-3', but there is no need to say so, just "BS 88-3" or "BS EN IEC 60269-3" infers the same thing.

  • in reply to gkenyon

    Good point!

Community Rules & Guidelines