In a recent thread about the Ashley J803 (3 'terminal') JB, I wrote:
The question is, of course, fairly moot becuse I don't think one can get 3C+E with a greater CSA than 1.5mm² - so one would never want a rating >20A when using 3C+E. However, I can think of a few (albeit unusual) situations in which one might want a '4-terminal' JB for T+E - in which cases, Hager's argument would obviously become 'inapplicable'.
Kind Regards, John
This prompted me to ask Hager/Ashley Tech Support why the J804 was only rated at 20A, whilst the J803 is rated at 32A, given that the terminals looked identical. The (very prompt) reply I got was:There is a corresponding one [J804] with 4 sets of terminals, designed primarily for lighting circuits (lower current rating, if I recall, although I don't understand why - terminals look identical!).
Any thoughts/comments? Does this sound like a credible explanation for the difference between a 32A and 20A rating? I have to admit that it's roughly right in relation to the ratio between 8 (4*2) and 12 (4*3) current-carrying conductors, but would one really expect a significant temperature rise within the enclosure, given that there would only be a couple of inches of each conductor within the enclosure? Another consideration (which they clearly are not taking into account) is that, in practice (although I would admit not guaranteed), it's in the nature of most uses of '4-core' (3C+E) cables that only two of the conductors will be current-carrying at any point in time.Although the terminals are the same, with 4 core cabling within them,this affects the heat rise & temperature rating of the joint box enclosure.
The question is, of course, fairly moot becuse I don't think one can get 3C+E with a greater CSA than 1.5mm² - so one would never want a rating >20A when using 3C+E. However, I can think of a few (albeit unusual) situations in which one might want a '4-terminal' JB for T+E - in which cases, Hager's argument would obviously become 'inapplicable'.
Kind Regards, John