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Old 04-13-2019, 07:15 PM   #1
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Default Over Tightening

Over tightened lugs in residential panels can bite through a couple strands of 4/O stranded aluminum conductor. Although obviously not ideal, does anyone see this causing major problems if it’s just one or two strands? Re terminate?
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Old 04-13-2019, 07:18 PM   #2
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Please fill out your profile. If on a smart phone select pc view & turn phone sideways.
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Old 04-13-2019, 07:25 PM   #3
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Use the recommended torque and see what happens ya we are suppose to torque to the manufactures specs I go by feel lol I know if i over torque the hex screw will want to strip.
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Old 04-13-2019, 07:30 PM   #4
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When I torque terminations, I tighten it to specs, wiggle the wire, which will loosen it, and torque again. I usually do it several times, till it stops getting loose. The first time I torqued something, I just went till it clicked and the inspector made me tighten them more because they were loose.

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Old 04-13-2019, 08:26 PM   #5
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Since the first electric lines were connected to a house electrical connection in the range of 99.9% have been over tightened.
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Old 04-13-2019, 11:54 PM   #6
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Given the torque specs I've seen, I'm pretty sure that some stuff would burn up if they were followed........
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Old 04-14-2019, 12:01 AM   #7
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The question is more about the fact that the over tightened lug cut through a couple strands of the 4/O aluminum service conductor. Wondering how likely it is that this would cause a safety issue.
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Old 04-14-2019, 03:41 AM   #8
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If youíre cutting through strands, itís a safety issue.
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Old 04-14-2019, 05:46 AM   #9
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TTR in BC makes us use 250 mcm Al for 200 amp services
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Old 04-14-2019, 06:18 AM   #10
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Quote:
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The question is more about the fact that the over tightened lug cut through a couple strands of the 4/O aluminum service conductor. Wondering how likely it is that this would cause a safety issue.
It is probably less likely to be a safety problem then a loose connection would be.

The only safety concern I can see with over tightening is that alll the components of the lug/termination points are potentially stressed beyond their tinsel strength and could conceivably fail with vibration and/or excessive ambient temperatures.

I think you'll have a hard time finding specific data on overnighting of electrical connections, but it's probably out there.
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Old 04-14-2019, 07:12 AM   #11
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I have never seen over tightening cut thru strands of the wire.
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Old 04-14-2019, 07:13 AM   #12
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It's more likely that the installer used a razor knife/utility knife to strip the conductor, nicking it, and that caused the strand to break.
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Old 04-14-2019, 12:27 PM   #13
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I’ve seen this when guys do a “clean and torque “ on existing equipment. Some customers shut down and do one every five years. I’ve worked with guys feel they need to actually tighten every lug and many don’t use a torque wrench which causes the wires to get over torqued.
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Old 04-14-2019, 01:01 PM   #14
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Quote:
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TTR in BC makes us use 250 mcm Al for 200 amp services


Table 39 allows 4/0 for 200 amp residential services...


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Old 04-16-2019, 01:00 AM   #15
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I'd say it's best to re-terminate. I don't like seeing cut or damaged conductors. Yes, aluminum is easy to squash in a terminal but I don't like seeing the conductors cut into. - I'd say it decreases the conductor's surface area thereby decreasing the overall ability to carry it's rated current without overheating. - I typically like to ere on the side of caution.
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Old 04-16-2019, 05:39 AM   #16
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Quote:
Originally Posted by Sam22 View Post
Over tightened lugs in residential panels can bite through a couple strands of 4/O stranded aluminum conductor. Although obviously not ideal, does anyone see this causing major problems if itís just one or two strands? Re terminate?


Nope, itís the same as throwing a chair off the titanic.


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Old 04-16-2019, 06:19 AM   #17
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I've torqued feeders to manufacturer engineering spec and then gave them a wee tug and out they came.


Somebody sitting in a comfy chair in an engineer's office needs to put down his pencil and actually get out to the field and try his chit out sometime.

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Old 04-16-2019, 09:00 AM   #18
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I had a buddy help me on a panel change, yes he's a j-man, and he used his little Makita impact on the breakers. Now those were over torqued.


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Old 04-16-2019, 05:08 PM   #19
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Quote:
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I had a buddy help me on a panel change, yes he's a j-man, and he used his little Makita impact on the breakers. Now those were over torqued.


Tim.
Meh. I use the M12 on all the branch breakers, neutrals and grounds and the 18 on the feeders. I'll let you know when and if I get a call back or a fire results
To the OP
Residential services never see close to their FLA and the rare occasion that they do, it it's only for a split second. You could probably shave half of the strands off of your feeders and nothing bad would ever happen. I don't suggest this, just saying.
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