I know that if you are using stranded conductors with more then 7 strands you must bunch tin them or use a proper compression clamp. My question is WRT the wires in the Fire Alarm devices.
Say for example a listed device such as a supervised sprinkler valve. Inside the listed device is a micro switch with stranded copper conductors. Must these also be tinned even though it is a listed device or does that just apply to the condustors that we are bringing to the device?
I know that it would make sense to tin them but if it is required then why don't the manufacturers do it?
Just wondering if i have to get the soldering iron out to tin the conductors that are part of the listed assembly. Any help appreciated.
What I usually use is the crimp on wire caps if I am bringing stranded wire to the device, this covers the rule, I believe, since all wires are covered under an appropriate crimped connector. I also find stranded wires from the factory come tinned, unless you cut the wire and loose the tinned end.
I always tin any stranded conductors and usually even go so far as to solder the stranded to the solid before putting on a wire nut. It does take a few more minutes to do, but I know the connection will not likely provide an opportunity for future corrosion and problems with intermittent troubles down the road.
One thing to watch out for when tinning stranded conductors, using them under a compression style connector can result in the failure of the connection. The soldered bundle of wire strands may fracture and break apart under compression, resulting in a loose connection.
I use the soft copper ferrules when terminating small stranded wires (16-24 AWG) in control panels for industrial applications.