MCB melted

[stillp]

Yes, that's true, but when we are doing 'mechanical' things, we usually use spanners or socket wrenches of appreciable length (many inches), hence appreciable leverage, whereas when tightening electrical terminals, the screwdriver will not usually not have a radius greater than half an inch or thereabouts.

Yes, I was just making the point that sometimes 'judgement' is not good enough.

OOI, have you tried torquing a terminal, then returning to it some time later and re-torquing it after it has settled down?

 

[JohnW2]

Yes, I was just making the point that sometimes 'judgement' is not good enough.

Sure - and, as I have acknowledged, I don't know whether what I do (and have been doing for 50+ years) is right or wrong.

OOI, have you tried torquing a terminal, then returning to it some time later and re-torquing it after it has settled down?

Oh, yes. Indeed, with some of the 'heavier' stuff (things like cylinder head nuts) it's more-or-less essential to do that.

Kind Regards, John

 

[stillp]

No, I meant an electrical terminal, with your torque screwdriver.

 

[kai]

Putting things into context, when I recently checked the connections in my five year old consumer unit, all the larger connections could be tightened one full turn, including the busbar connections. Thank god I checked the tightness of all connections in the board!

 

[JohnW2]

No, I meant an electrical terminal, with your torque screwdriver.

I realise that, and my first sentence ("Oh, Yes.") was a reply to that. The bit about cylinder head nuts was an add-on.

To expand my two-word reply, if I returned to a torqued terminal after a day or three and re-torqued it, I would usually get a fair bit more tightening - but it will still be far less tight (after that re-torquing) than I would have done manually.

Kind Regards, John

 

[JohnW2]

Putting things into context, when I recently checked the connections in my five year old consumer unit, all the larger connections could be tightened one full turn, including the busbar connections. Thank god I checked the tightness of all connections in the board!

That doesn't surprise me, and you should be even more worried about the fact that they may well have been that loose since just a few days after they were initially tightened, five years ago.

Kind Regards, John

 

[Iggifer]

My experience is very limited but I have to wonder where these enormous PFCs in domestic premises come from, even in London - not that it means much, but I don't think I have ever seen one appreciably over 1kA. A PFC of 6kA means a total loop impedance of less than 0.04Ω - which would seemingly require one to have a substation in, or close to,one's garden, connected by pretty fat cable

Recorded a Ze today of 0.03Ω with a PFC of 6.6kA. Wasn't domestic but there were plenty of 6000 breakers in the board

 

[JohnW2]

Recorded a Ze today of 0.03Ω with a PFC of 6.6kA. Wasn't domestic but there were plenty of 6000 breakers in the board

Well, yes, I did indicate that I was specifically talking about domestic premises. If one is talking about a high-capacity supply, then obviously the PFC has to be very high (since, otherwise, their supply voltage at high load would be exceeding low!). However, I confess that I had not thought about blocks of flats, which can easily have a 'commercial' (or even 'industrial'!) supply, despite the fact that the individual dwellings are modest.

Kind Regards, John

 

[stillp]

all the larger connections could be tightened one full turn

With a torque driver kai?

 

[kai]

No, just an ordinary PZ2 screwdriver

 

[Adam_151]

all the larger connections could be tightened one full turn

With a torque driver kai?

Ah, but can you 'check' the torque with a torque driver?

 

[kai]

Why is it when using a Torque driver on electrical connections, one can still tighten the connector by a quarter turn or two with a standard screwdriver??

 

[EFLImpudence]

Because as John has said - the torque setting is not as tight as he does it manually.

You could increase the torque setting until it matches your manual tightening and see what it is.
I can't; I don't have one.

I do have the 'proper' +- (or whatever they are called this week) drivers and you can do them even tighter.

 

[Nozzle]

Do you boys get your torque screwdriver calibrated regularly? No calibration, no point!

Nozzle

 

[JohnW2]

Because as John has said - the torque setting is not as tight as he does it manually. ... You could increase the torque setting until it matches your manual tightening and see what it is.
I can't; I don't have one.

I've done that experiment a good few times. It seems that my "manual torque" (as I've used for the past 40+ years) is usually 30% - 50% higher than the 'recommended' torque.

Kind Regards, John