Torque Talk

[slartybartfast]

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Happens at moderate temperatures, especially when stranded cables have been tinned with solder. That is why they shouldn't be tinned.

Doesn't necessarily need such high temperatures for it occur.

Ferrules on stranded cables will be mandated in regs before long for sure !

 

[DPG]

Ferrules on stranded cables will be mandated in regs before long for sure !

I think they are mentioned in the regs for fine stranded wires aren't they?

 

[pc1966]

I think they are mentioned in the regs for fine stranded wires aren't they?

Not exactly, but 526.9.1 says the ends have to be "suitably treated" and ferrules are one way to do that. The other common way is the ultrasonic weld you see on some RCBO neutral tails that are fine-stranded.

Also that section (526.9.2/3) say no to tinning conductors for screw terminals, etc.

Soldering is great though if it is actually the means of connection!

 

[pc1966]

hmmm....if temperatures are getting high enough to that then cable is likely undersized

It is more the cycling of hot/cold you get with time-varying loads or, to a lesser degree, just from day/night temperature changes, etc.

 

[Rockingit]

Not exactly, but 526.9.1 says the ends have to be "suitably treated" and ferrules are one way to do that. The other common way is the ultrasonic weld you see on some RCBO neutral tails that are fine-stranded.

Also that section (526.9.2/3) say no to tinning conductors for screw terminals, etc.

Soldering is great though if it is actually the means of connection!

Indeed, but who in their right mind gets out the soldering iron station when it takes 2s to put a ferrule on?!

 

[Lucien Nunes]

In the days before ferrules were widely known outside the panel-building industry, it was quite a popular albeit misguided pastime. For example, we saw a number of small theatre lighting installations with a plug patch at the dimmers, where the flexible patch cords were tinned before connecting to the conduit cables via normal terminal block. Someone obviously tinned their way along the line of them making each and every connection a loose one.

 

[pc1966]

As above, was quite common and obviously enough for it to be added to the regs as a no-no.

Ferrules are quite a neat way of helping fine stranded wire, and occasionally I have put them on coarse stranded if it is a big screw terminal instead of cage-clamp, etc, as I have seen wires removed and looking worryingly tin and flat as a result.

 

[Other_Tucker]

I'm all for the correct tightness in theory, it winds me up when colleagues use impact drivers to tighten (permanently weld) screw connections in CU's. I'd bet the correct, recommended torque, is less than normal wrist driver tightness.

If it becomes mandatory bureaucracy, how long until you need a calibration certificate for your torque screwdriver.

 

[Rockingit]

As above, was quite common and obviously enough for it to be added to the regs as a no-no.

Ferrules are quite a neat way of helping fine stranded wire, and occasionally I have put them on coarse stranded if it is a big screw terminal instead of cage-clamp, etc, as I have seen wires removed and looking worryingly tin and flat as a result.

You only have to fix one and then take it out again to see where the screw clamped down and all the strands it missed!

 

[DPG]

I'm all for the correct tightness in theory, it winds me up when colleagues use impact drivers to tighten (permanently weld) screw connections in CU's. I'd bet the correct, recommended torque, is less than normal wrist driver tightness.

If it becomes mandatory bureaucracy, how long until you need a calibration certificate for your torque screwdriver.

You should have it calibrated regularly already.