Dwayne,

I'm not trying to start a "my electricity system is better than yours" match, honest!  :-)

On Mon, 08 Aug 2005 12:38:35 -0600, Dwayne Reid wrote:

> At 07:32 AM 8/8/2005, Howard Winter wrote:
> >  Did you know they habitually join wires by twist-and-cap?  I thought it 
> > was a bodge
> >until I saw the stuff they sell at Home Depot - it seems to be the 
> >accepted practice!  :-#
> 
> Those "twist and cap" connectors (Marrettes or Murrettes - depending on age 
> of the box) are some of the most reliable connectors I've ever used.  The 
> wires are twisted into a helical spring within the cap which maintains 
> tension for decades.

I have a feeling that when they were allowed here (*many* years ago) that the caps didn't have metal in them, 
they were just ceramic.  This may explain why we don't have them any more, but you do!
 
> On the other hand, I no longer use (or allow the use of) the 
> copper-plated-steel "Stak-on" crimp connectors designed for splicing house 
> wiring.  

I don't actually know what these are - "Stak-on" isn't a name we have here.

>I have had to replace far to many of them that went resistive 
> after 10 or 15 years.  These were installed with the proper tooling and 
> duly inspected and passed - and some of them have failed.  The copper 
> conductors appear to deform (cold-flow) over long periods of time and 
> become loose.

The things I'm talking about shouldn't if crimped properly - they should form a gas-tight (cold weld) join 
that can't flow, since it is effectively a single piece of metal.
 
> But I have *never* seen a properly-installed Murrette connection 
> fail.  Properly-installed means that the wires are twisted uniformly after 
> removing the cap to inspect the connection.  And I always inspect every 
> splice that is done by a homeowner or do-it-yourself person who has asked 
> me for help.  It is distressing how often I find connectors that just 
> aren't tight enough.

What is the correct process?  Do you have to clean the wires before twisting?  Do you twist the wires together 
"naked" then screw the cap on, or do you use the cap to act as a "handle" to twist the wires?  I wouldn't have 
thought it was safe to remove and replace the cap after the joint is made, since undoing it would tend to 
loosen off the twist, wouldn't it?
 
> As an interesting aside, Marr also still sells one of their earliest 
> products: the Marr connector.  This is a brass sleeve that clamps the 
> conductors with a large diameter set-screw through the side of the 
> sleeve.  A plastic cap then screws onto the sleeve for insulation.

I don't remember ever seeing anything like that, except for use in high-powered car audio systems where a low 
resistance power supply is needed.  And they tend to be gold plated!  :-)

> The interesting thing about those Marr connectors is how I once saw them 
> used: aboard ships.  The electrician inserted the wires as usual (tighten 
> the set-screw until you hear it squeak), then got out a tiny flame torch 
> and proceeded to fill the whole brass sleeve with solder.  He told me that 
> was the secret to making connections that would not fail in a salt-mist 
> environment.
> 
> I believe him!

I'm fairly sure that soldering isn't allowed on mains connections here, at least I've never seen them.  I can 
see it being useful in a belt-and-braces situation as above, where the physical strain is taken by the metal, 
and the solder is then just protecting it, but solder-only joints would be a problem as it's difficult to 
detect dry joints, and cold-flow in solder is much more likely than in copper.

Cheers,


Howard Winter
St.Albans, England


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