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Thread: Wago 221

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    Wago 221

    So much for my new favourite connector... got a call from a mate to say the connector i gave him almost caught on fire.

    I went and collected the faulty unit ot return to the supplier to investigate ...why it burnt.

    So a few question to him...

    what did you connect ...he had it connected to a feed from solar panels drawing around 25 amps... i noticed none of the others where not burnt .

    My thought ...he didnt push the wire all the way into the connector ...something i drum into to staff and everyone who i give these connectors.

    or ... it could have got bumped and come the clip down lever lifted... a big problem with these connectors when pushing the wires in a junction or the likes... this is why the maintenance free box designed for these connectors is the best solution.

    or ... the 25 amp DC load switching load requires a DC rated connector... but not convinced because the connector should not be opening and closing ...once locked into place the wires are secure.
    Comments are based on opinion...not always facts....that's why people use an alias.

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    Quote Originally Posted by ians View Post
    So much for my new favourite connector... got a call from a mate to say the connector i gave him almost caught on fire.

    I went and collected the faulty unit ot return to the supplier to investigate ...why it burnt.

    So a few question to him...

    what did you connect ...he had it connected to a feed from solar panels drawing around 25 amps... i noticed none of the others where not burnt .

    My thought ...he didnt push the wire all the way into the connector ...something i drum into to staff and everyone who i give these connectors.

    or ... it could have got bumped and come the clip down lever lifted... a big problem with these connectors when pushing the wires in a junction or the likes... this is why the maintenance free box designed for these connectors is the best solution.

    or ... the 25 amp DC load switching load requires a DC rated connector... but not convinced because the connector should not be opening and closing ...once locked into place the wires are secure.
    The problem is that the maintenance free connection box is not yet available in South Africa. In fact I have found out that it is only available in the UK.

    Sent from my SM-A705FN using Tapatalk
    To make a mistake is human, to learn from that mistake is knowledge and knowledge is strength.

  3. #3
    Diamond Member Justloadit's Avatar
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    I am always skeptical on a spring loaded connector for high current, and bringing DC int the mix even more so.
    Current carrying capacity of the wire requires all strands to be mechanically connected to ensure that that there is no chance of a hot joint occurring due to the reduction in the resistance of the wire and the connection joint. Spring loaded connectors will not achieve this.
    Using ohms law, will clarify what I am referring to. A typical relay new contact will have a closed resistance of approximately 10 milliohms. Does not sound like much, but if we push 25 amps through the contact, then P = I^2 x R
    25 x 25 x.01 gives us 6.25Watts of heat generated across the contact. Does not sound like much, but let this continue for hours, and it is amazing damage this amount of heat causes. A few switching operations under high load, and with inductive loads, the contacts get pitted and covered with a little carbon, increasing the closed contact resistance. This will increase the heat generated by the contacts.

    Now lets assume that the wire only has half the strands making mechanical connection, which an I am making an assumption here that the contact resistance is 20 milliohms because of the poor mechanical connection, from our calculation above, it now becomes 12.5 Watts of heat generated, but this heat now gets into the contact material and copper wire, and over time, the copper wire loses its annealed property, noticed by the colour change, and becomes oxidized and becomes more pliable, and now the resistance of the connection increases, and so more heat is generated, and we get what is called thermal runaway causing the plastic to catch fire.

    Bring in DC to the mix, and any minor arcing that occurs exacerbates the issue due to the DC creating an arc.

    So the fact that using an Ohm meter shows zero resistance across a contact does not mean you have a sound joint. After all the Ohm meter only uses 3V and a couple of milliamps to do the resistance measurement. The only way to do a proper measurement is with a very sensitive Wheatstone bridge.
    Victor - Knowledge is a blessing or a curse, your current circumstances make you decide!
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