Loose Neutral of a Plug & Socket Lead to Smoke & Melting

Get a new extension strip. Discard and replace any faulty wiring and plugs.

The likely culprit is the female socket part in the extension strip. It may have lost its springiness, or have been lightweight in the first place. Also check the male plug on the UPS cord. Some prong designs are thinner/thicker than others.

When the neutral becomes open, the connected unit will get high voltage due to the other phases. The other phases will have their load which will allow series connection of two or more units across two/three phases, as there no ground/neutral potential.

Gajanan Phadte

This sounds more like single phase, but the OP has not stated single or 3 phase yet......

To the OP, if 1 phase, are you using 3 pin plugs that look similar to this:-

If yes, you need to fuse the plug correctly for the load expected, not just leave the original 13 amp (brown) fuse in.

There are also a lot of dangerous copies from China around that do not meet the specs of BS 1363......you have been warned!

You need to buy high quality components that work as they should, loose connections of badly designed and made parts can cause fires. You almost found that out the hard way. You have been lucky once.....

Please supply FULL details of your system, with pictures if needed........voltages etc..

A simple check of a finger placed on any plugs in use to see if it is warmer than the area where it is being used will tell you immediately that something is wrong.....or not!

This was a "wake-up" call, do not forget that!!!

This is something that needs to be spread far and wide as a rule of thumb:

ANY ELECTRICAL CONNECTION THAT FEELS 'LOOSE' OR 'WOBBLY' IS A 'FAULTY' CONNECTION!

If a plug feels loose in a socket, try a different socket until the plug feels secure. It should take some effort to insert or remove the plug, and when inserted, the plug should feel 'rock solid' against the wall or power strip.

Also, as a general rule: DO NOT USE 'POWER STRIPS' THAT LACK THEIR OWN CIRCUIT BREAKERS/SURGE PROTECTION! Those power strips make it too easy to overload the wiring at a single outlet, and if the wiring is not up to regulations (or the area has lax electrical codes) you can cause a fire inside the walls.

Lots of good advise, but to address an un-answered part of the question, I offer the following:

At first, I wasn't sure if the extension strip was plugged into the UPS output or the UPS was plugged into the extension strip. I believe it is the former from the available clues. In any case, the fault is an intermittant connection on the neutral (not the earth/ground) side of the AC circuit. when connection is made, current is limited by the load except for some transient in-rush current which should be brief and should not trip a breaker or fuse rated for the load. When the connection is open, there will be no current and the fose or breaker will not trip. In between, there will be sparks which will generate considerable heat locally, i.e. at the intermittant contact location. The transient current will be absorbed by the UPS on one end and the load on the other end and consequently, there should be little effect noticeable (other than the sparks) until the heat opens the gap so much that the intermittant becomes an open circuit. Oh, yes, there is also smoke.

Where I used to work, we liked to refer to the neutral as a "return" so that we didn't forget that it is an active and necessary part of the circuit.

These sockets and plugs that are made here are a big joke. However the polycarbonate ones that are expensive are good. The socket contact is made from a machined brass(tube) and the pin that is a round rod is expected to make a contact and is supposed to conduct 5/15Amps contineously. The socket contact which is made from brittle brass is having a cut lengthwise and the manufacturers think this is a spring arrangement. What a money minting engineering.

Some sockets are made from plates shaped for the purpose. I don't find words to describe the engineering disaster these are.

I have a multipin adaptor that has the earth contact not screwed to the pin. The hole is there for the purpose but the moulding design defect makes it impossible to put the screw on this contact. This is made by reputed brand here.

And by the way, you want to make your 3 pin plug to 2 pin, just unscrew the rod by turning it by hand. No need to open the plug. You can do it for any of the three pins. Remove the neutral pin(We have unipolar supply) and ...MY GOD.

Gajanan Phadte

You wrote:-

And by the way, you want to make your 3 pin plug to 2 pin, just unscrew the rod by turning it by hand. No need to open the plug. You can do it for any of the three pins. Remove the neutral pin(We have unipolar supply) and ...MY GOD.

As you do not specify which 3 pin plug type you are talking about, I can only say its not true with respect to BS1363 for example. This is a plug type prevalent in many 230VAC 50Hz countries, though it was originally designed at the end of WW2 in the UK. See a recent post of mine in this blog for an identification picture of one.

Firstly, to remove the earth pin on BS1363 plugs, it is either impossible without cutting the moulding apart (making it useless/totally dangerous), or you have to take the plug apart first to do that on oldr versions.

Furthermore, due to the way the Phase and neutral are shuttered on all BS1363 Sockets, (to stop tiny fingers pushing stuff in) and the shutter is only activated/removed when the earth pin is inserted, therefore the plug without an earth pin is now completely useless.....

If you meant another type of 3 pin plug, please quote carefully its type number and/or a picture to stop any misunderstandings of your own making..........

IN THE FUTURE, BE ACCURATE AND COMPLETE IN YOUR COMMENTS, its the only way to stop a critic up front!!! We will ALWAYS correct errors for the majority here....

Have a great day!!

To answer the original question, "how can i stop this from happening"... you could hard wire the connections (make sure power is off before doing the connections). being a low powered device you may be able to "borrow" a light switch from the neighbours and wrap everything in insulating tape.

looking at the picture of the plug, i have seen similar where the pin gets squashed together resulting in loose connections so you could spread them apart.

and yet i must repeat the advice of others - get someone qualified and competent

thought of that but it would be a huge mess to connect 6 plugs hardwired...

so i got my own made extension box using ABB brand Switch and sockets, which are sturdy and tight and used quality wire for that extension box.