My last 'non Amd 3' CU Install.

Dave OCD · Dec 21, 2015

Put this in today, I hope it doesn't burst into flames.:tongue3: Didn't have the time to faff about and get the cabling 'perfect' as I had so much to do today but I think it's ok. With the BG boards I generally 're number' the earth bar as to me it's illogical having the CPCs running in the opposite order of the neutrals,I'll miss the insulated CUs. Sorry about the
poor photo.

[ElectriciansForums.net] My last 'non Amd 3' CU Install.

davesparks · Dec 28, 2015

HandySparks said:
I think that the points of the teeth on the brass nut will be somewhat flattened and biting tightly into the steel of the enclosure. I recon the joint will be as good as the usual banjo, which will only be making metal-to-metal contact in places if looked at at a microscopic level anyway.

The banjo would be making full contact with the gland and have a flylead attached for the earth.

The piranha nut instructions state that the grub screw should be fitted and a flying earth lead should be fitted

davesparks · Dec 28, 2015

This from the earthingnuts website

Midwest · Dec 28, 2015

You lot should be going to bed at a respectable time!

happysteve · Dec 28, 2015

The last few posts, between Handy- and davesparks, have been very good: reasoned, polite debate, with historical insights and reference to good quality sources (eg manufacturers instructions). You are both a credit to the trade.

HandySparks · Dec 28, 2015

davesparks said:
This from the earthingnuts website...

I see that they don't regard the teeth as guaranteeing a good connection to the enclosure every time due to varying paint thicknesses, etc. It's a fair point, although in my defence, I measured the resistance and was happy with the result. Had I thought about it at the time, I might have added a little protective grease to reduce the chances of future corrosion affecting the conductivity of the joint.

Edit: Actually, I bought a small tube of Contralube 770 at Elex a year ago. Looks like it might have been just the stuff for protecting the joint where the paint has been scraped off:
Contralube | Contralube 770

Problem is, it's been sitting on my desk rather than in the van.

Dave OCD · Dec 28, 2015

I think for the minimal additional effort and cost I'd always fit an additional appropriately sized earth lead between gland and earth terminal/bolt within the metal enclosure, it would just give me additional peace of mind.
One of the best products I know of for corrosion protection is ACF50, excellent stuff - although in my case 99% of its usage is on my motorbikes.

davesparks · Dec 28, 2015

HandySparks said:
I see that they don't regard the teeth as guaranteeing a good connection to the enclosure every time due to varying paint thicknesses, etc. It's a fair point, although in my defence, I measured the resistance and was happy with the result. Had I thought about it at the time, I might have added a little protective grease to reduce the chances of future corrosion affecting the conductivity of the joint.

Edit: Actually, I bought a small tube of Contralube 770 at Elex a year ago. Looks like it might have been just the stuff for protecting the joint where the paint has been scraped off:
Contralube | Contralube 770

Problem is, it's been sitting on my desk rather than in the van.

I have before used the nut the other way round when terminating into unpainted enclosures such as galv trunking and relied on that as an earth connection. Thinking about the example you posted I wouldn't be so concerned as the connection to the armour is there as a bond so theoretically is not required to stand up to fault currents. In the example I posted the armour is the cpc so I am far more concerned about it.

A resistance test is fine but doesn't give a clear picture of what will happen when serious current flows. If I get a chance I'll see about setting up some tests with a decent current source.

Contralube is terribly good, but Vaseline is just as good. A dab of Vaseline on any high current connection can reduce contact resistance and therefore temperature quite a bit. I think it was Tony who posted some actual figures for a busbar connection he improved with a bit of Vaseline

davesparks · Dec 28, 2015

Midwest said:
You lot should be going to bed at a respectable time!

If I could actually sleep I would.

My body clock is screwed, I seem to sleep every other night at the moment, if I sleep at all.

Midwest · Dec 28, 2015

Sorry to hear that davesparks, my remark was a flippant reply and wasn't meant as derogatory. Perhaps a break from forums might help?

Gardner · Dec 28, 2015

HandySparks said:
I'm happy to rely on the teeth biting into the metal enclosure and don't even think that the locking screw is required in this situation if done up nice and snug. This is provided that the cable is properly cleated to eliminate movement and that it's a dry environment, so corrosion at the interface is unlikely.

Here's one I did last week. Continuity between gland and earth bar was confirmed (and actually there's a separate cpc in the cable anyway).

View attachment 31052

Should raise a couple of other issues, but I don't care!

My personal opinion, the only way to earth anything is via full conductor. Ive never felt right with the armor of SWA doing it.

davesparks · Dec 29, 2015

Gardner said:
My personal opinion, the only way to earth anything is via full conductor. Ive never felt right with the armor of SWA doing it.

What do you mean by full conductor? If the calculations work out ok then there is no reason not to use the armour in the way it was designed to be used.
Do you also not use steel conduit as an earth?

davesparks · Dec 29, 2015

Midwest said:
Sorry to hear that davesparks, my remark was a flippant reply and wasn't meant as derogatory. Perhaps a break from forums might help?

It was taken in the spirit intended and certainly wasn't taken as derogatory, I've always been pretty much nocturnal

A break from working weird and varied hours would help possibly.

Gardner · Dec 29, 2015

davesparks said:
What do you mean by full conductor? If the calculations work out ok then there is no reason not to use the armour in the way it was designed to be used.
Do you also not use steel conduit as an earth?

I dislike using the armor as earth, I do not agree with the way its terminated. Id rather the armor be twisted together and terminated under a screw.

As for steal conduit it depends. Sometimes I will pull a separate earth.

davesparks · Dec 29, 2015

Gardner said:
I dislike using the armor as earth, I do not agree with the way its terminated. Id rather the armor be twisted together and terminated under a screw.

As for steal conduit it depends. Sometimes I will pull a separate earth.

An armoured gland properly fitted gives a secure connection to every strand of the armour with equal pressure, whereas twisting it together into a screw terminal doesn't give the same equal pressure on every strand.

I don't see what the problem is with using a specially designed and thoroughly tested method of termination?

How do you decide when to pull an early wire into conduit and when not to?

Gardner · Dec 29, 2015

davesparks said:
An armoured gland properly fitted gives a secure connection to every strand of the armour with equal pressure, whereas twisting it together into a screw terminal doesn't give the same equal pressure on every strand.

Why do you believe it to be so? Im not saying your wrong, but when done right a screw termination would not be an issue imo.

I don't see what the problem is with using a specially designed and thoroughly tested method of termination?

How do you decide when to pull an early wire into conduit and when not to?

Generally if I feel the conduit could become disconnected inadvertently. But I side toward you on this one.