Ashley-Hager junction boxes

[John Sabine]

Out of interest, is there any substantive difference between the Ashley-Hager J803 and J804 boxes to justify the different ratings, or is it likely to be down to something like heat dissipation?

the 803 comes with 3 connectors and is rated at 32A while the 804 has 4 connectors and a 20A rating: the boxes and terminals look identical. Would removing a terminal block from an 804 essentially turn it into an 803? If the rating is down to heat dissipation, would removing the 4th block be necessary for 32A use, or would it be OK just to not use it?

-- John

[harry]

The rating is normally down to the size of the terminals and how big a cable you can get into them. There should be no heat from a joint box. If there were, you have a loose connection and every possibility of a fire.

I never heard of joint boxes needing maintenance.

[A.Lee]

I read last week that it is something to do with the combined current passing through that gives the rating availble for maintenance free operation.

Wago have a .pdf about this subject on their site. If it is not maintenance free, then the current rating is higher iirc.

[John Rumm]

>>> Obviously the 803 comes with 3 connectors and is rated at 32A while

I think that statement is misleading. While it is true that there should be no *additional* heat from the joints in the box, you can't ignore combined thermal effects on the box from the normal conductor temperatures. At full cable load that could well be 70 degrees.

Hence more conductors may necessitate a reduction in the overall capacity of the box due to the effects of conductor grouping.

On circuits that are regularly (but not continuously) loaded to their full capacity, they will experience significant thermal swings, and hence expansion an contraction cycles. With time this will result in loss of clamping pressure from screw terminals.

[harry]

There must be millions of loose screws about then.

[John Rumm]

Almost certainly... not usually enough to cause problems on most circuits, but they do on a few. (they are just as likely to be in an accessory or the CU itself as in a JB)