I’ve got a screw loose

[michael howarth 1Participant @michaelhowarth1]

In the workshop I have a wander lead plugged in to a 13amp socket, which I use for a fan heater etc as and when required. The 13 amp plug has been in situ probably untouched for years. When I switched the heater on the other day there was no power. I suspected a blown fuse and undid the plug whereupon the brass screw from the neutral terminal fell out. How on earth did that happen?…….not just loose but totally unscrewed.

Mick

[michael howarth 1Participant @michaelhowarth1]

[HopperParticipant @hopper]

Possibly vibration from the machinery in your workshop over the years?

[not done it yetParticipant @notdoneityet]

Stranded wire, never completely tight, temperature and vibration. Tin your wires and tighten securely.

[Billy BeanParticipant @billybean67480]

I found this more than once during my life as a sparky.

From memory it was only where customers had fitted plugs themselves.

I can only suggest that the screw was perhaps not fully tightened initially and over a period of time movement / vibration has caused it to loosen.

BB

[Mick HenshallParticipant @mickhenshall99321]

Changes in temperature of plug ? Warm in use cooler when turned off can cause loosening of fixings

Mick

[Clive HartlandParticipant @clivehartland94829]

While in the Army I had control of the 27.5 Kva Gen. I distributed the power with cabling which had waterproof connectors, occasionally there was a hiccup and like Mick found that the clamping screws in the plugs and sockets had come loose. Tighten them up and all OK.

I came to the conclusion that the frequency of the power at 50 Cycles was the culprit, maybe also that the cables were manhandled and maybe stretched the connection even though they were clamped. I shellaked the screws and had no more problems.

Clive

[pgk pgkParticipant @pgkpgk17461]

Have gremlins become extinct?

[roy entwistleParticipant @royentwistle24699]

pgk pgk No they're hibernating in my shed

Roy

[Russell EberhardtParticipant @russelleberhardt48058]

Posted by not done it yet on 28/01/2018 08:53:15:

Stranded wire, never completely tight, temperature and vibration. Tin your wires and tighten securely.

Not considered to be good practice. Two reasons:

1. Solder is softer than copper so it tends to creep more, reducing the contact pressure.

2. It creates a stress point between the soldered and bare part of the wire and tends to fracture there.

Russell

[KWILParticipant @kwil]

+1 for NOT tinning. There are some crimp on ferrules whch hold the strands together which make a better contact (compression point) for the screws.

[Brian WoodParticipant @brianwood45127]

I have had a number of occasions when power has 'failed' on plug in items and always from the same cause with a loose wire in the neutral pin.

The curious thing is that it has ALWAYS been the neutral affected.

Regards Brian

[Billy BeanParticipant @billybean67480]

Soldering wires – bad advice – and in this situation is not recommended – bare twisted wires give a greater area of contact as they spread on compression.

This was the first job for new apprentices in my business and the proceedure was:-

Strip off insulation – cut wires at twice pin diameter – twist and fold back at mid point and insert and tighten screw.

This way you have a stronger joint, greater contact area and most importantly the insulation is tight to the pin so no wire/ loose strands evident.

The worse offence with plugs with customers was incorrect fuses for the appliance.

I would like a pound for every time I removed a 13a fuse from a bedside light and fitted a two amp one.

BB

[Mick HenshallParticipant @mickhenshall99321]

I have understood that 250 watts would be covered by a 1amp fuse, so if item was rated 750 watts a 3 amp fuse would cover it, in practice I would fit the next higher fuse ie. a 5 amp fuse, am I incorrect in thinking this ?

Mick

[Ady1Participant @ady1]

poltergeists

They put the oven door down for me to walk in to at mid shin height the other night

I NEVER leave the oven door open like that

[Billy BeanParticipant @billybean67480]

Posted by Mick Henshall on 28/01/2018 12:27:05:

I have understood that 250 watts would be covered by a 1amp fuse, so if item was rated 750 watts a 3 amp fuse would cover it, in practice I would fit the next higher fuse ie. a 5 amp fuse, am I incorrect in thinking this ?

Mick

Mick you are spot on – good to see.

General rule of thumb for ease of calculation is 250 watts per ampere.

As you say a 5 amp would be my choice as this would allow for any surge .

BB

[Martin 100Participant @martin100]

Fuses might indeed protect the appliance but their primary purpose in plugs in the UK is to protect the cable.

The cable should be sized to the needs of the appliance but there is no technical reason why a cable rated at 13A, fitted with a 13A fuse in the plug could not supply an appliance that had a maximum consumption of 0.1A

Oh and tinning conductors for fitting in screw terminals is a really bad thing to do..

Edited By Martin 100 on 28/01/2018 13:09:33

[not done it yetParticipant @notdoneityet]

Actually, the fuse is there to protect the lead, not the appliance. That is why there are only standard value fuses fitted to plugs. The fuse will not stop the appliance being live if there is no earth. Agreed, fitting proper loop connectors is better than tinning.

I still covet the old MK plug tops which had screw on terminals where the wire could be wrapped completely around the terminal post.

[VicParticipant @vic]

I used to install a variety of equipment at one of my former jobs and nearly all the equipment had tinned wires straight out of the factory and I don’t recall ever having problems with a bad connection. Nearly everything comes with a moulded plug these days but when they don’t they normally have a brass crimp.

[Mick HenshallParticipant @mickhenshall99321]

One would presume that any bought product would be supplied with the correct size cable fitted,at least the wattage  is a number that most people can understand and calculate the appropriate fuse for it or at least attempt to fit a fuse, cable size probably doesn't mean much to the average Joe, 

Mick

 

[Mick HenshallParticipant @mickhenshall99321]

The A's are appearing again,sorry

Mick

[VicParticipant @vic]

The biggest “electrical” problem we used to get at work was computers “not working”. The problem was in fact the guy who did the PAT testing. He insisted on fitting 3 amp fuses in the monitor plug tops. It was my job to “fix” the problem by replacing the blown 3 amp fuse with a 5 amp one!

[not done it yetParticipant @notdoneityet]

And neither will a 3 amp fuse run up a fast start one horsepower motor, particularly if under load!

[Mike PooleParticipant @mikepoole82104]

Before it was a requirement to have a plug fitted to all new equipment many "helpful" suppliers stripped and tinned the cable, I always cut the tinned ends off to get back to bare copper. With a heavy continuous load like a heater I have often found the screws will loosen over time, I think many 13A plug tops are a bit marginal at full load and will run a bit warm, this if not noticed will destroy the plug top and the socket. I think it is worth doing an annual patrol of all plugs in socket in the house and checking fuse size and screw tightness. It is worth noting that the correct way to check a screw terminal is to loosen first which proves the screw is not seized and then tighten correctly, just giving the screw a bit more each time it is checked is to invite failure of cable or screw. Unbelievably there is someone in my house who does know better who has been known to fit the wrong fuse and forget to fit the correct one asap

Mike

[Author]

Posts