I am installing this. After tightening the screw hardly, the big wire still falls out if I pull it a little bit with very small force. I am not sure that I am doing like others would do. Do you have any idea to tighten the wire into that hole? The wire is 105C - 600V, the circuit breaker is 63A

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  • You are putting the wire inside the clamping part ?
    – Solar Mike
    Apr 9, 2020 at 9:02
  • @SolarMike do you have picture of clamping part?
    – Dat
    Apr 9, 2020 at 9:09
  • Well, you are best placed to take a picture of the device you have... I suggest that you turn the clamping screw and watch the clamp to see how it operates.
    – Solar Mike
    Apr 9, 2020 at 9:11
  • 1
    Did you fully open the clamp by turning the screw counter clockwise until ir stopped then insert screw under the plate and tighten CW until it is properly torqued? I usually back off and re torque 3 times to allow large wires to relax and clamp better.
    – Ed Beal
    Apr 9, 2020 at 12:10
  • 1
    @ThreePhaseEel the red wire is Awg-6, the circuit breaker is A9F74463
    – Dat
    Apr 10, 2020 at 3:34

3 Answers 3


No guessing is allowed.

The breaker's labeling or specification sheet will call out a specific torque you must use. Torque it to that spec. And no other. If you lack the equipment to do so, get it.

I would say look closely inside there while you turn the screw on an empty one, so you have a clear understanding of how the mechanism works. The wire flaring out like that suggests it may be missing the mechanism.

Also, as Programmer66 suggests, make sure that particular hole isn't broken; try another hole.

  • I know that there are torque specs, and obviously it is wise to follow them. But I never met an electrician who would ever do that for a 63 A circuit breaker. Very, very few electricians (at least in Denmark) even have a torque wrench. When I was in a electrical board production facility, we never used a torque wrench for anything this size. When we worked with larger currents, starting from a few hundred amps, we would use torque wrenches. Apr 9, 2020 at 21:28
  • This is why I specified residential, commercial and even setting the transformers and meters outside of residences, I would imagine the torque would need to be set, even the main coming into the panel inside the house... but after that since I was a supervisor overseeing the construction, never witnessed a torque wrench used. That said, the specs are set for a reason, and from a legal respect for the most part, a torque wrench should be used, since a DIY'er may not know what "snug and a little more" may mean.
    – Jack
    Apr 9, 2020 at 23:53
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    "But I never met an electrician who would ever do that" @MadsSkjern ... and so it was in America until they took a test rig to trade shows and found out how really, really awful people were at this. And being an electrician didn't make you any better at it; Jane in the billing department was setting torques with equal ... skill. That started the rumbling that became a Code thing and now everybody has to own a torque screwdriver, and inspectors inspect for it. Apr 10, 2020 at 15:57

That I am aware of, it is not to be tightened gently, it needs to be tightened rather snugly, typically there is a torque rating that is given, that will be on the breaker itself, if not on the makers website.

If you are certain that the wire is stripped bare to the correct length, and inserted into the correct spot, and tightened, the wire will not easily pull out, if at all.

  • And I'll stress that to do this properly, you need a torque driver. Too little torque and the wire will pull out. Too much and you will (at best) just squish the wires or (worse) split the circuit breaker and ruin it.
    – jwh20
    Apr 9, 2020 at 15:23
  • Try inserting the wire into one of the other holes and check and see if it has the same issue. The hole you are using may be defected. Apr 9, 2020 at 16:38
  • The main clue for me was in the question the " After tightening the screw hardly, " and "(very gently)"
    – Jack
    Apr 9, 2020 at 18:16
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    Aside from the SF Bay Area: almost all of our electrical inspections include a torque test these days. This started about a year ago and has spread through adjacent jurisdictions. Most require the electrician present. I have the impression there was a high profile fire locally in the last few years that prompted a bit of CYA behavior. Apr 9, 2020 at 20:43
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    @AloysiusDefenestrate -- yeah, I suspect that the folks who are going with the program re: torque inspection are going to get pleasantly surprised by not getting callbacks 20-30 years down the line because some lug burned up XD Apr 10, 2020 at 1:58

That appears to be a rising clamp wire attachment, with these you must fully loosen the screw before inserting the wire, else you risk the wire passing below the clamp jaw and not being connected, or worse only some of the wire strands being clamped and the join overheating.

After insering the wire tighten the screw to the correct torque,

  • yes I fully loosen the screw, all the wire strands being clamped
    – Dat
    Apr 10, 2020 at 3:47
  • 1
    Please try another hole and see if it is still failing to secure the wire. Apr 10, 2020 at 4:09

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