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?

http://www.tlc-direct.co.uk/Products/ASJ803.html
http://www.tlc-direct.co.uk/Products/ASJ804.html

Obviously 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

On Oct 11, 11:26*pm, John Sabine wrote:
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?

http://www.tlc-direct.co.uk/Products...ts/ASJ804.html

Obviously 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

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.

On 12/10/2012 08:05, harry wrote:
On Oct 11, 11:26 pm, John Sabine wrote:
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?

http://www.tlc-direct.co.uk/Products...ts/ASJ804.html

Obviously 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

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 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.

I never heard of joint boxes needing maintenance.

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.


--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

On Oct 12, 1:32*pm, John Rumm wrote:
On 12/10/2012 08:05, harry wrote:









On Oct 11, 11:26 pm, John Sabine wrote:
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?

http://www.tlc-direct.co.uk/Products...www.tlc-direct....

Obviously 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

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 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.

I never heard of joint boxes *needing maintenance.

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.

There must be millions of loose screws about then.

On 12/10/2012 13:35, harry wrote:
On Oct 12, 1:32 pm, John Rumm wrote:
On 12/10/2012 08:05, harry wrote:









On Oct 11, 11:26 pm, John Sabine wrote:
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?

http://www.tlc-direct.co.uk/Products...www.tlc-direct...

Obviously 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

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 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.

I never heard of joint boxes needing maintenance.

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.

There must be millions of loose screws about then.

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)


--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

John Sabine wrote:

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?

http://www.tlc-direct.co.uk/Products/ASJ803.html
http://www.tlc-direct.co.uk/Products/ASJ804.html

Obviously 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?


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.

--
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