Joining large cables

[Theo]

I have a couple of 10mm2 twin and earth cables I want to join together
non-permanently[*]. I want this to be able to take a continuous 40A load
without getting hot.

I'm not a fan of screw junction boxes because of the issue of screw
tightness causing a hot connection (especially if they don't specify a
tightening torque). I was wondering if there's a good screwless connector
out there for bigger cables?

The usual Wago 221/222 connectors don't go up to 10mm2. I found their
Topjob S series which sit on a DIN rail, but that's a PITA to have a DIN
rail enclosure and all the additional bits just to extend a cable.

Are there any better screwless junction box systems that will cope with
10mm2 cable and 40A load?

Thanks
Theo


[*] for a temporary initial installation, one will be a 2.5mm2 cable, later
to be replaced by 10mm2 after further works are done. The 2.5mm2 won't be
carrying the full 40A obviously.

[David]

Post by Theo
I have a couple of 10mm2 twin and earth cables I want to join together
non-permanently[*]. I want this to be able to take a continuous 40A load
without getting hot.
I'm not a fan of screw junction boxes because of the issue of screw
tightness causing a hot connection (especially if they don't specify a
tightening torque). I was wondering if there's a good screwless connector
out there for bigger cables?
The usual Wago 221/222 connectors don't go up to 10mm2. I found their
Topjob S series which sit on a DIN rail, but that's a PITA to have a DIN
rail enclosure and all the additional bits just to extend a cable.
Are there any better screwless junction box systems that will cope with
10mm2 cable and 40A load?
Thanks
Theo
[*] for a temporary initial installation, one will be a 2.5mm2 cable, later
to be replaced by 10mm2 after further works are done. The 2.5mm2 won't be
carrying the full 40A obviously.

https://www.swaonline.co.uk/cable-management-jointing/mechanical-connectors/line-taps

[Andy Burns]

Post by David

Post by Theo
Are there any better screwless junction box systems that will cope with
10mm2 cable and 40A load?

https://www.swaonline.co.uk/cable-management-jointing/mechanical-connectors/line-taps

Do they come with "uninsulated live conductors - do not touch" stickers?

[David]

Post by Andy Burns

Post by David

Post by Theo
Are there any better screwless junction box systems that will cope with
10mm2 cable and 40A load?

https://www.swaonline.co.uk/cable-management-jointing/mechanical-connectors/line-taps

Do they come with "uninsulated live conductors - do not touch" stickers?

Insulation? Who wants Insulation? Insulation is for sissies.

[Andrew]

Post by Andy Burns

Post by David

Post by Theo
Are there any better screwless junction box systems that will cope with
10mm2 cable and 40A load?

https://www.swaonline.co.uk/cable-management-jointing/mechanical-connectors/line-taps

Do they come with "uninsulated live conductors - do not touch" stickers?

This German company may have a solution

IDC connectors for flat 16mm cable !!. Wow.

[Fredxx]

Post by Theo
I have a couple of 10mm2 twin and earth cables I want to join together
non-permanently[*]. I want this to be able to take a continuous 40A load
without getting hot.
I'm not a fan of screw junction boxes because of the issue of screw
tightness causing a hot connection (especially if they don't specify a
tightening torque). I was wondering if there's a good screwless connector
out there for bigger cables?
The usual Wago 221/222 connectors don't go up to 10mm2. I found their
Topjob S series which sit on a DIN rail, but that's a PITA to have a DIN
rail enclosure and all the additional bits just to extend a cable.
Are there any better screwless junction box systems that will cope with
10mm2 cable and 40A load?
Thanks
Theo

If temporary then screw terminals should be fine:

https://shop4electrical.co.uk/junction-boxes/7904-scolmore-wa220-white-3-terminal-heavy-duty-junction-box-60a

Post by Theo
[*] for a temporary initial installation, one will be a 2.5mm2 cable, later
to be replaced by 10mm2 after further works are done. The 2.5mm2 won't be
carrying the full 40A obviously.

Do you plan on some form of protection for the 2.5mm cable? Wouldn't a
fused/MCB enclosure be the appropriate way forward, temporary or otherwise.

[Theo]

Post by Fredxx
https://shop4electrical.co.uk/junction-boxes/7904-scolmore-wa220-white-3-terminal-heavy-duty-junction-box-60a

The connection will be there permanently, but the two cables that will be
connected will change. (one is 10mm2 T&E, the other will later be exterior
grade hi-tuff 10mm2, but will be 2.5mm2 T&E to begin with). Since the above
has no indication of tightening torque, I don't want to risk it overheating
or loosening under consistent high currents, which is why I'd prefer a
screwless connection. It's the best example I managed to find thus far, and
if screw terminals are good enough for a Henley block then not completely
ruling them out.

Post by Fredxx

Post by Theo
[*] for a temporary initial installation, one will be a 2.5mm2 cable, later
to be replaced by 10mm2 after further works are done. The 2.5mm2 won't be
carrying the full 40A obviously.

Do you plan on some form of protection for the 2.5mm cable? Wouldn't a
fused/MCB enclosure be the appropriate way forward, temporary or otherwise.

What do you mean protection, mechanical or circuit protection? There are
MCBs at both ends of this cable run so there's sufficient existing circuit
protection. I don't really want a third MCB box. I could put a short
length of DIN rail in a plastic box with a bunch of Topjob connectors, but I
was hoping there was something neater.

Theo

[Fredxx]

Post by Theo

Post by Fredxx
https://shop4electrical.co.uk/junction-boxes/7904-scolmore-wa220-white-3-terminal-heavy-duty-junction-box-60a

The connection will be there permanently, but the two cables that will be
connected will change. (one is 10mm2 T&E, the other will later be exterior
grade hi-tuff 10mm2, but will be 2.5mm2 T&E to begin with). Since the above
has no indication of tightening torque, I don't want to risk it overheating
or loosening under consistent high currents, which is why I'd prefer a
screwless connection. It's the best example I managed to find thus far, and
if screw terminals are good enough for a Henley block then not completely
ruling them out.

What you should use is down to access. If accessible after then screw
terminal JBs are ok, otherwise it's crimp or solder for that size of cable.

Post by Theo

Post by Fredxx

Post by Theo
[*] for a temporary initial installation, one will be a 2.5mm2 cable, later
to be replaced by 10mm2 after further works are done. The 2.5mm2 won't be
carrying the full 40A obviously.

Do you plan on some form of protection for the 2.5mm cable? Wouldn't a
fused/MCB enclosure be the appropriate way forward, temporary or otherwise.

What do you mean protection, mechanical or circuit protection? There are
MCBs at both ends of this cable run so there's sufficient existing circuit
protection. I don't really want a third MCB box. I could put a short
length of DIN rail in a plastic box with a bunch of Topjob connectors, but I
was hoping there was something neater.

I meant what current protection will you have for the 2.5mm cable.

[Smolley]

Post by Theo

Post by Fredxx
https://shop4electrical.co.uk/junction-boxes/7904-scolmore-wa220-white-3-terminal-heavy-duty-junction-

box-60a

Post by Theo
The connection will be there permanently, but the two cables that will
be connected will change. (one is 10mm2 T&E, the other will later be
exterior grade hi-tuff 10mm2, but will be 2.5mm2 T&E to begin with).
Since the above has no indication of tightening torque, I don't want to
risk it overheating or loosening under consistent high currents, which
is why I'd prefer a screwless connection. It's the best example I
managed to find thus far, and if screw terminals are good enough for a
Henley block then not completely ruling them out.

Post by Fredxx

Post by Theo
[*] for a temporary initial installation, one will be a 2.5mm2 cable,
later to be replaced by 10mm2 after further works are done. The
2.5mm2 won't be carrying the full 40A obviously.

Do you plan on some form of protection for the 2.5mm cable? Wouldn't a
fused/MCB enclosure be the appropriate way forward, temporary or otherwise.

What do you mean protection, mechanical or circuit protection? There
are MCBs at both ends of this cable run so there's sufficient existing
circuit protection. I don't really want a third MCB box. I could put a
short length of DIN rail in a plastic box with a bunch of Topjob
connectors, but I was hoping there was something neater.
Theo

https://nexusmodels.co.uk/products/deans-40a-high-current-male-connector-with-wire-shield-by-amass

[Theo]

Post by Smolley
https://nexusmodels.co.uk/products/deans-40a-high-current-male-connector-with-wire-shield-by-amass

That doesn't appear to be 250V AC rated?

There are lots of high current DC connectors out there, but they're not
designed for mains voltage. Not sure what BS7671 would think about them.

Also, I want something that isn't 'a bodge' when an electrician looks at it
- using connections from R/C models would likely fall into that category.

Theo

[Andy Burns]

Post by Theo
I have a couple of 10mm2 twin and earth cables I want to join together
non-permanently[*]. I want this to be able to take a continuous 40A load
without getting hot.
I'm not a fan of screw junction boxes because of the issue of screw
tightness causing a hot connection (especially if they don't specify a
tightening torque). I was wondering if there's a good screwless connector
out there for bigger cables?

What about an 831-1103 together with an 831-1203 ?

<https://www.wago.com/gb/pluggable-connectors/1-conductor-male-connector/p/831-1103>
<https://www.wago.com/gb/pluggable-connectors/1-conductor-male-connector/p/831-1203>

[Theo]

Post by Andy Burns

Post by Theo
I have a couple of 10mm2 twin and earth cables I want to join together
non-permanently[*]. I want this to be able to take a continuous 40A load
without getting hot.
I'm not a fan of screw junction boxes because of the issue of screw
tightness causing a hot connection (especially if they don't specify a
tightening torque). I was wondering if there's a good screwless connector
out there for bigger cables?

What about an 831-1103 together with an 831-1203 ?
<https://www.wago.com/gb/pluggable-connectors/1-conductor-male-connector/p/831-1103>
<https://www.wago.com/gb/pluggable-connectors/1-conductor-male-connector/p/831-1203>

Interesting, I'd not come across those. The ratings are a bit marginal:

Ratings per IEC/EN 60664-1
Rated current 41 A

Approvals per UL 1059
Rated current 37 A

Approvals per CSA
Rated current 35 A

Not sure what the difference in standards is, but presumably they are being
pushed very hard at 40A and there are different ideas of how much 'too hard'
is?

Theo

[Andy Burns]

Post by Theo
Ratings per IEC/EN 60664-1
Rated current 41 A

If I'm reading the derating curve correctly, that's at 70°C be

[Theo]

Post by Theo
Ratings per IEC/EN 60664-1
Rated current 41 A

If I'm reading the derating curve correctly, that's at 70°C better if
cooler?

Not sure I can see that - the datasheet seems to be about how they are
tested rather than the actual specifications. The derating curve doesn't
seem to go above 30A.

However, it looks like the MCS Maxi 16 series is suitable for 10mm2 (and
16mm2) and rated current is more like 60-70A, so at 40A it's going to get
less hot. Doesn't look like there's a Wagobox style enclosure for them, but
maybe that doesn't matter (the cable might be thick enough to support the
connectors if suitably clipped)

Also it looks like the 2010 series Topjobs are reasonably priced at CPC:
https://cpc.farnell.com/wago/2010-1204/terminal-block-2-conductor-through/dp/CN24284
https://cpc.farnell.com/wago/2010-1292/endintermediate-plate/dp/CN24378
and could maybe throw a bit of DIN rail in a double surface box of sufficient
depth:
https://cpc.farnell.com/europa-components/stbdr0-5m/din-rail-slttd-top-hat-35x7-5mm/dp/MC02357

Theo

[Andy Burns]

Post by Theo

If I'm reading the derating curve correctly, that's [41A] at 70°C better if
cooler?

Not sure I can see that

This was the graph I was looking at

<Loading Image...

But there is a similar graph that is "ruled off" above 41A, not sure why
they'd show both curves.

Post by Theo
However, it looks like the MCS Maxi 16 series is suitable for 10mm2 (and
16mm2)

Their full catalogue never feels very di

[John Rumm]

Post by Theo
I have a couple of 10mm2 twin and earth cables I want to join together
non-permanently[*]. I want this to be able to take a continuous 40A load
without getting hot.
I'm not a fan of screw junction boxes because of the issue of screw
tightness causing a hot connection (especially if they don't specify a
tightening torque). I was wondering if there's a good screwless connector
out there for bigger cables?
The usual Wago 221/222 connectors don't go up to 10mm2. I found their
Topjob S series which sit on a DIN rail, but that's a PITA to have a DIN
rail enclosure and all the additional bits just to extend a cable.
Are there any better screwless junction box systems that will cope with
10mm2 cable and 40A load?

Think about how that termination will be made to the MCB in the CU.
There is no reason why a screwed connection can't be made properly as a
long term solution.

Part of the issue is heat - less constant heat, and more heat cycling.

A cable that frequently cycles between close to its maximum operating
load and significantly lower load, will be subject to more expansion and
contraction stress that can work screw connections loose. In cases like
that, going for a larger CSA cable can make sense to reduce the thermal
cycling.

For your temporary smaller cable install, a conventional high current JB
would be fine (high current, for the terminal capacity more than anything).

e.g.

https://www.tlc-direct.co.uk/Products/AAJB60.html

For the permanent solution then a crimped connection would be a reliable
long term screwless solution.

Note that a fairly serious crimp tool will be needed:

https://www.tlc-direct.co.uk/Products/SWRP625.html
--
Cheers,

John.

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[Theo]

Post by John Rumm
Think about how that termination will be made to the MCB in the CU.
There is no reason why a screwed connection can't be made properly as a
long term solution.

Agreed, but MCBs have specific instructions about how to terminate them -
there's a specific tightening torque to give a connection at the rated
current. Random screw junction boxes don't seem to have that, which means
you're at the mercy of doing it 'good enough' by feel. A lot of the time CU
loads are intermittent, so you can get away with a substandard termination,
but if the load exists for hours then that's the time you have to do it
right otherwise you get overheating.

Post by John Rumm
Part of the issue is heat - less constant heat, and more heat cycling.
A cable that frequently cycles between close to its maximum operating
load and significantly lower load, will be subject to more expansion and
contraction stress that can work screw connections loose. In cases like
that, going for a larger CSA cable can make sense to reduce the thermal
cycling.

Indeed, which is why we're at 10mm2 rather than 6mm2. More copper, big
chunky JB, less heat (and less energy wasted in the connection). But only
if the terminals are bearing down on the wire correctly and correctly
torqued.

Post by John Rumm
For your temporary smaller cable install, a conventional high current JB
would be fine (high current, for the terminal capacity more than anything).
e.g.
https://www.tlc-direct.co.uk/Products/AAJB60.html

I was planning to keep the JB in place and just swap out the wiring, ie not
have a temporary JB, just a temporary cable in it. But that's not set in
stone.

Post by John Rumm
For the permanent solution then a crimped connection would be a reliable
long term screwless solution.
https://www.tlc-direct.co.uk/Products/SWRP625.html

Thanks, I'd not considered crimping. It gets used a lot in DC
installations, but the usual stud terminations (car batteries and similar)
aren't rated for 250V AC. Might need to see if I can find some properly
shrouded AC crimp connections.

Theo

[John Rumm]

Post by Theo

Post by John Rumm
Think about how that termination will be made to the MCB in the CU.
There is no reason why a screwed connection can't be made properly as a
long term solution.

Agreed, but MCBs have specific instructions about how to terminate them -
there's a specific tightening torque to give a connection at the rated
current. Random screw junction boxes don't seem to have that, which means
you're at the mercy of doing it 'good enough' by feel. A lot of the time CU
loads are intermittent, so you can get away with a substandard termination,
but if the load exists for hours then that's the time you have to do it
right otherwise you get overheating.

Intermittent loads can be harder to deal with than constant ones due to
the thermal cycling. An "always" on load will tend to run at a fairly
constant temperature.

Post by Theo

Post by John Rumm
Part of the issue is heat - less constant heat, and more heat cycling.
A cable that frequently cycles between close to its maximum operating
load and significantly lower load, will be subject to more expansion and
contraction stress that can work screw connections loose. In cases like
that, going for a larger CSA cable can make sense to reduce the thermal
cycling.

Indeed, which is why we're at 10mm2 rather than 6mm2. More copper, big
chunky JB, less heat (and less energy wasted in the connection). But only
if the terminals are bearing down on the wire correctly and correctly
torqued.

Post by John Rumm
For your temporary smaller cable install, a conventional high current JB
would be fine (high current, for the terminal capacity more than anything).
e.g.
https://www.tlc-direct.co.uk/Products/AAJB60.html

I was planning to keep the JB in place and just swap out the wiring, ie not
have a temporary JB, just a temporary cable in it. But that's not set in
stone.

In which case go for a suitable enclosure and using crimps for both
installs - just leave enough spare wire to allow you to cut off the
first set and remake the connection later.

Post by Theo

Post by John Rumm
For the permanent solution then a crimped connection would be a reliable
long term screwless solution.
https://www.tlc-direct.co.uk/Products/SWRP625.html

Thanks, I'd not considered crimping. It gets used a lot in DC
installations, but the usual stud terminations (car batteries and similar)
aren't rated for 250V AC. Might need to see if I can find some properly
shrouded AC crimp connections.

Crimping is used widely in AC installs as well for permanent maintenance
free joints (and before the advent of "modern" sprung terminal
connectors, was one of the few practical approved methods of maintenance
free jointing).

You can get insulated crimps, or you can use separate insulation (e.g.
heatshrink) on "bare" crimps. You will still need some for of enclosure
or second level of insulation though. (the second level could be an
overall jacket of heatshrink)

Post by Theo
Theo

--
Cheers,

John.

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| Internode Ltd - http://www.internode.co.uk |
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