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Topic Title: correct torque settings for breakers and main switches
Topic Summary: a bit of help please
Created On: 12 April 2015 05:15 PM
Status: Read Only
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 17 April 2015 09:18 AM
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Zoomup

Posts: 3284
Joined: 20 February 2014

"How about experience, feel and common sense.

oh and decent materials to work with."


Gary

Hear , hear. I agree totally. I think that at least two screws should be available to hold meter tails into a terminal. That is what we used to have in the old Wylex boards. The first screw acted as a good mechanical grip and electrical grip, the second or inner screw was a belt and braces good electrical grip. Two screws minimum is what I would require, not the weak modern flimsy carp inferior "cage" type excuses for a terminal.

Bye,

Z.
 17 April 2015 09:25 AM
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Zoomup

Posts: 3284
Joined: 20 February 2014

Originally posted by: davezawadi

Well J the problem is not simple but one which trained and experienced electricians have managed very well for a long time. The thing is whether the wire is firmly held and doesn't move in the terminal when you move the rest of the wire. 3Nm might do this on some days, but a few experiments with a bit of 25mm tails cable and a main switch will convince you that it is completely inadequate. This is completely untested politics being used to divert attention from an underlying serious problem.



If I can over tighten a screw terminal in say a main switch or a M.C.B. by hand, using just a screwdriver, then the terminal is weak inferior rubbish and is not fit for purpose. If I can really graunch down the screw to a proper tightness so that I can ensure good mechanical grip and electrical continuity that will withstand later movement without loosening off, then that is good in my opinion.

Z.
 17 April 2015 02:11 PM
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WiredScience

Posts: 318
Joined: 25 January 2012

I personally think you are more likely to break the plastic casing of the MCB / RCD / RCBO / switch than damage the copper conductors with cage clamps.

Does anyone know if the torque screw-driver instructions say tighten until it clicks then walk away, or do they assume that the operator knows that a quick waggle will free the cable from its not very secure cage?
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