I always have to replace at least one when PAT testing

I always used nyloc nuts. They just get loose in transit otherwise.

Artisan Electrics My wife often says I have an odd screw on top.....

It's common to loose a washer or a screw 😂

Bet he took twice as long as everyone else to finish his jobs though!

trickyd2013 uhm... why? You mean he took a quarter of the time, right? Apart from the safety aspect, 240V motors work better than 110V.

Jasper Janssen 240v motor running on 110v is faster?

trickyd2013: no, he put 110v c-form plugs on 240v tools

Chris Walford I think I get it. So you mean he wired the 110v leads and sockets straight into the 230v supply with no transformer, replaced the plugs on his tools for 110v ones and so ran his 240v tools at 230v on site. Very crafty. I’m surprised nobody noticed that there was no transformer. It would have been more crafty to have had a transformer case with a brick in it that was wired straight through. This shouldn’t happen on our sites because all 230v MDU are padlocked and we supply and regularly test the 110v transformers and cables.

Yes and not reuse the original clamp ,he talks a good job

Haha don't collect manky old screws very modern he will go far

The transformer is supposed to be NEAR the mains socket, preferably indoors. You should then run 110 volt extension leads out and up the scafolding. The whole point of 110 volt is to prevent running 240 volt cables across outdoor works

Steve Ashcroft yes correct

@@drivewasher what a nonsense 110 volt powertools. We dutch run 230/400 volt cables on construction sites and on scaffolding. Tools are dubble insulated every user socket is protected with 30mA rcd, sockets has a springloaded hatch/flap distributionboxes ip 66 watertight, permanent shaffonding is connected to ground with there own ground rod.

why the sand ?

@@cagmito76 stability, some use weights

@@cagmito76 protection from impacts, and I would suspect the same as fuses extinguishing any arcs or flames

I think it has been repaired before, the terminal block was the clue.

Centre earth means any fault to ground is only 55V. Floating would be ok until a 1st fault occurred, then it would be 110V to earth when a 2nd fault occurred.

@@jwflame That makes sense. Pretty interesting concept!

But the case is yellow plastic.

@@simontay4851 Oops sorry yeah but it is plastic heavy dutty hard and and sharp on the edges, where soft cable would be torn and wear out

One of these: www.toolstation.com/industrial-connectors-ip44/p35522

Covered in this video kzfaq.info/get/bejne/nLiYosmUst-lqZ8.html

The screws on this are likely knackered enough that it makes no odds!

+1, we used them on our fan heaters etc, at Rima Electric (taken over by Sunbeam Electric).

Probably only an issue when really heavy duty tools are used for extended periods of time. This particular unit seems to be for experimental and occasional use. That said, I'd feel comfier with ferrules!

Brass is lower resistance. I think the silver colour of the pins on some plugs is chrome plating.

Brass is a better choice for it's electrical properties, but other metals are cheaper and cost usually wins.

John Ward cheers John for the information

John Harwood - silver can tarnish 🙁

That’s only a good idea if your choc block is too big for your cable size. It doesn’t add any mechanical strength, except by filling up the hole a bit more.

@@JasperJanssen Whilst I appreciate your response. Singles can and will slide down the side of the thread of the screw and have floating wires in the terminal block. You're also less likely to cause crush damage to the wires with them folded - Especially when using flex. Good practice imo.

They weren't folded over originally, and it's lasted for 15+ years like that from the factory. The wires are large relative to the terminal block size.

@@mernok2001 Hahah, afraid so slip of the tongue.

Better still, crimp ferrules onto the flexible strands.

I put ferrules on all stranded cable in screw terminals now. They're so cheap, and the crimp tools aren't exactly expensive either. Crimping an end on barely takes any longer than twisting/doubling up a stranded cable. It's a habit I got from wiring narrowboats (where all of the mains cable is stranded and sockets aren't designed to accept stranded cable) which just stuck with me as a sensible idea for everything else.

No need to double up or use crimps if the screw terminal block / choc block has wire protectors (plates).

@@Mark1024MAK Admittedly less of a need but it still creates a better connection.

Robin Whitfield - the company that I’m employed by has over fifty years experience of using stranded tinned copper wire terminating in screw terminal block / choc blocks that have wire protectors. Our failure rate on these is extremely small and we have millions of terminals.

I have the same model as this, they are very common, and it is the same inside.

Probably due to noise problems being introduced when devices where being used. Old BT Party lines used an earth but different system is used today.

Earth & neutral are separate.

So that’s why you switch inductive loads at zero crossing, it makes things harder! Yeah, sure. Somewhere you’re making an error of reasoning.

@@dkek383 I'm not able to think about this mathematically, but I've always imagined that an inductor presents a high resistance to a sudden change in voltage. The changing magnetic field seeks to generate a current which opposes the one which created that field in the first place. It's also known as Lenz's law. How can an inductor draw a surge current when suddenly presented with a voltage? That's what capacitors do. PS I'm being a bit lazy with terminology when referring to resistance/impedance/reactance.

Yes I noticed that too I'm not sure whether the earth is connected to the centre tap which it certainly should be

@@dkek383 it's supposed to be earthed to comply with regulations.

The insulation test is DC. DC does not go through a transformer. Insulation test was between the 13A pug (primary winding) and the output earth (secondary winding). If he'd tested between the output connections and output earth then the insulation would be almost zero.

john flower - on all the 110V CTE (55V - 0 - 55V) portable or fixed transformers that I have encountered, the transformer secondary mid tap is connected to earth. So a multimeter on the resistance range should show continuity between either of the 55V line output socket terminals and any earth connection (be it the output earth terminal or the mains input earth).

Weeble Wobble - no, because the DC test current should flow from the mains plug earth terminal to the transformer mid tap, through the copper winding of the secondary and to the output terminal on the 110V socket.

like getting a marsh mallow up a wild cats arse, in reverse

I have not found any official standards but two private websites who say site transformer are grounded on the secondary. His measurements do indeed indicate the the secondary is floating. Perhaps the secondary "ground" is isolated from mains ground just like on a portable generator?

The insulation test is DC. DC does not go through a transformer. Insulation test was between the 13A pug (primary winding) and the output earth (secondary winding). If he'd tested between the output connections and output earth then the insulation would be almost zero.

The last test was between supply earth and secondary tap so open ins res is right. I would have tested output voltage thou..

Hauptwerk Hardware - on all the 110V CTE (55V - 0 - 55V) portable or fixed transformers that I have encountered, the transformer secondary mid tap is connected to earth. So a multimeter on the resistance range should show continuity between either of the 55V line output socket terminals and any earth connection (be it the output earth terminal or the mains input earth).

Weeble Wobble - no, because the DC test current should flow from the mains plug earth terminal to the transformer mid tap, through the copper winding of the secondary and to the output terminal on the 110V socket.

Because the test is DC and it can't pass through the primary coil - which it would need to to in order to get from the plug to the 110v outlet

Fick dich - no, because the DC test current should flow from the mains plug earth terminal to the transformer mid tap, through the copper winding of the secondary and to the output terminal on the 110V socket. On all the 110V CTE (55V - 0 - 55V) portable or fixed transformers that I have encountered, the transformer secondary mid tap is connected to earth. So a multimeter on the resistance range should show continuity between either of the 55V line output socket terminals and any earth connection (be it the output earth terminal or the mains input earth).

If this was for site use I'm sure he'd have done just that ;)

If you knew how a cable gland works, you wouldn't ask. When used the "normal way" there is a round gripping clamp that squeezes into the outer sheath. That thing is right at the end of the domed clamp nut, and it is quite sharp. So, flexing of the cable is pushing it against that sharp edge inside the end of the gland. By reversing the gland, there ends up being a rounded edge plus the sharp thing is nowhere near the flexing point. Bottom line = the protection is BETTER with the gland reversed.

Yes, although it won't convert frequency so is of no use if something requires 60Hz.

Yes, and it's a requirement on most construction sites, at least for external work. It's especially important in damp climates when builders are often working in wet, muddy conditions.

Ireland uses these as well as the UK, not sure about anywhere else.

I also thought it was a very clever solution! Never seen anything like it here in Australia, but all our stuff uses RCDs and generally is much drier than the UK. Never thought that one if the reasons why it would be in use is because of the damp climate, but makes sense now.

@@Berkeloid0 RCDs are used in the UK too, but as with any device, they aren't 100% reliable and in a wet environment they are going to be prone to nuisance trips. Also, some of the types of devices used in construction sites can trip RCDs on start-up unless they have characteristics which allow for it (and those characteristics are not the best for protecting people). The 55+0+55 system is inherently safer. For the same reason telephone systems which (usually) have a nominally 50V DC supply superimposed to provide low power and diagnostics was limited to 50V for safety reasons. Fortunately, the availability of Li-Ion powered kit has replaced a lot of the need for mains-powered portable kit in construction sites. There are now very capable SDS drills, circular saws, jigsaws etc.

t0nito - the same 110V yellow socket outlets are found in some industrial buildings, fed via fixed 230/240V to 55 - 0 - 55 transformers so that 110V power tools can be used.

NO. A 110volt tool connected to a United Kingdom 230volt 3 pin socket will blow the 13amp fuse. This is because a 110volt tool has a lower resistance than a 230volt tool and as a consequence will pass too much current. Should some idiot replace the 13amp fuse in the 3 pin plug then the tool will burn out.

Not really, as you are going from a flexible cable to a solid core. Should have a fixed terminal on the case so any flexing of the input wire does not stress the solid wire and fatigue it. The solid wire is the transformer primary, and if you break it off at the most common point, the place where it goes into the potting, you now have a very heavy paperweight. Ferrules on the CPC however are fine, they are both flexible cables. John should have taken some sandpaper to the top epoxy to clean a spot, then used solvent to degrease the spot before putting on a cable tie base and 3M VHB foam to hold the base, then a cable tie to hold the floating connector block to the top there. Less stress on the solid wires. The original gland is easy to take apart, just push the wedge back out the back, or use the cable stub to pull it out, and then reuse it again. Those glands are quite strong, you can easily hang the transformer on it with no problems, the cable will break before the gland lets go. Cable is a silicone rubber cable, rated for use in Arctic conditions, and also rated for use in water, so it is waterproof and still flexible at -55C, and can be used up to 130C. You normally find it used on pond pumps, and I have made quite a few extension cords out of them when the pump fails, or if, as I was doing, I only needed a 50cm tail on the cable, and the pumps come standard with 10m.

BS 7671 Regulation 526.9.1 In order to avoid inappropriate separation or spreading of individual wires of multiwire, fine wire or very fine wire conductors, suitable terminals shall be used or the conductor ends shall be suitably treated.

@@garymckeown4278 common c2 on my eicrs where people shorten rcbo neutrals and just twist. No amount of tightening will guarantee a solid connection.

thomas bourne yep and on my last NICEIC assessment this was mentioned by the assessor.

@@garymckeown4278 as an apprentice I was taught to twist and double but that was through lack of knowledge and the fact it takes longer but once you know it's wrong why would anyone continue to do it. It doesn't make you popular when you fail entire marinas where the pontoons are all wired in h07-rnf without a single boot lace ferrule in sight when the client has only recently rewired it.

In theory yes - the earth connection to the secondary needs to be accessible so that it can be removed. Voltage output is still 110V however, so not really of much use.

you could make a pretty good step down transformer for travel purposes. if you're visiting the UK/Europe from the states. But due to the high in duction of first plugging in the transformer of that size, it be more practical in theory.

Thanks @@jwflame

Jonathan Furtado - eh? It is a step down transformer! You can connect most electrical items from the U.S.A. (or any other country that uses 110V/115V/120V) to these transformers. The only limitations are the rated power of the item has to be no greater than the rating of transformer (keeping in mind that these transformers are often tool rated, the continuous rating is lower) and any device that needs the supply to actually be 60Hz (clock/timer) will run slow.

JW referring to your reply, if you were really desperate, or bored, you could get a second tranny and fix 110V O/P of first tranny to 110V O/P of second tranny which will act as a step up giving you 230V. I can't think why on earth you would want to do such a thing in real life but it's possible

It’s failed due to repeated stress at a particular point. Not at all due to age. And it shouldn’t have a power switch.

@@JasperJanssen I recognized the cracking on the jacket. The rubber, or whatever it's made of, has deteriorated and had begun to crack. It was just accelerated at the joint because of stress. In less than 5 years you'll see a repeat failure and the rest of the cord will show its true condition. Having a nice emergency off switch can't be a bad thing.

You would need a power switch to have the same IP rating as the transformer pot and then there something else to get broken during use. ,

It may be the RCD - some can be tripped by sudden large surges, or the large voltage spike when it is turned off.

Quite common for the inrush current to trip domestic RCD's especially the higher current 3kW versions

@@jwflame I will get that checked again, the wiring in the garage where I use the transformer was only installed two months ago, and last night the transformer tripped the 32 amp ring main breaker instead of the earth leakage. I think that they might have used the wrong grade of breakers despite being told that I was going to be running welders and other equipment in there I have a 32 amp socket on a seperate breaker for the welder they installed so they obvious ly understood what was required.

It could also be that you have a fault between ground an neutral on *another* circuit. That will cause RCD to trip when starting any heavy load.

@@mernok2001 say you have two fuses connected to an RCD. There is a small leakage or short between ground and live on fuse 1. You connect a big load on fuse 2, a small portion of the current going back through neutral on fuse 2 will go out through neutral on fuse 1 and from there to ground. Thereby tripping the RCD.

after a bit of searching answered my own question The system has its origins in the 1949 Annual Report of HM Chief Inspector of Factories, which recommended the system for use on building and construction sites and other applications involving large-scale use of portable electric tools. The system was described in the British Standard Code of Practice, CP 1017:1969, Distribution of Electricity on Construction and Building Sites (superseded by BS 7375:1991, now BS 7375:2010). Equipment was specified in BS 4363:1969 Specification for Distribution Assemblies for Electricity Supplies for Construction and Building Sites (now BS 4363:1998+A1:2013, also BS EN 61439-4:2013). referenced from IET autum 2016

Roly M Early ones had Reyrolle BS 196:1961 5 and/or 15 A outlets which were also yellow, but the casing was metal rather than plastic and I think painted with Hammerite; certainly the whole thing wasn’t yellow. I’m surprised how small the actual transformer is for 3 kVA, but I suppose that’s only a tool rating. What is the rating for continuous loads such as site lighting?

@@srfurley ive still got one of those early metal ones. Only a single outlet though and its taller, but still wotks.

It's AC.

@@jwflame Thank you very much for your swift reply! Kind regards, George

Actually almost the worst you can do, as then there is no remnant field from the previous half cycle to provide back EMF. With these a much better protection is an appropriately sized NTC inrush limiting resistor, and for larger loads you then also have a relay and time delay ( around 5 mains cycles) after power on that then shorts out the resistor. That provides enough impedance to reduce the start up surge, and still allows protection devices like fuses to act in case of a shorted output properly. I have a 2kVA variac that I did that to to reduce the inrush surge to a low enough level that it would not trip the 30A breaker it was attached to, and also not trip RCD breakers.

Actually zero crossing gives the wort case surge with a transformer. The reason is that when a transformer is running open circuit, being an inductor, the current lags behind the voltage by 90°. So normally when the voltage is crossing zero, the current is at its maximum reverse polarity and over the next half cycle of voltage it goes though zero and then to its maximum positive value. If the current starts at zero then over the first half cycle it will rise to twice its normal value. That would not be too bad except for the fact that transformers usually run with their core close to magnetic saturation for efficiency reasons. That means the core saturates during start-up. The inductance disappears and then the only thing limiting the current is the DC resistance of the primary, so the current can be enormous. Counter intuitively, the best time to turn a transformer on is when the mains is at its peak voltage.

It's CK, not sure of the model number. www.ck-tools.com/products/ck_tools/pliers_cutters/ratchet_crimping_pliers/

Cooling, Many of the users of these transformers would have them supplying 110v volts for a large amount of time during the work day. The sand would reduce the chances of the transformer overheating but it also would make it heavy, maybe they deliberatley removed the sand to make it lighter.

Why not transformer oil. That would be a better coolant than sand.

@@simontay4851It's done for stability, to stop it being knocked over, nothing to do with cooling

What's unusual is that the fix has not been a complete disaster waiting to happen and burn the house down :-)

@@benbaselet2026 Yeah, someone must have known what he's doing._

It's his real name, Jay DubbleVue

He says his initals J.W., even though that has more syllables than his full name :)

@@Petertronic Missed that. thanks

Those wires are enamelled copper, not bare.

Yup, enamelled wire. But I'd still have been tempted to add some sleeving :-) Also I'd have used a 3-way choc block, LEN, so any future flex cable change didn't need a re-crimp; and glued or bolted it down, to avoid any wiggling of the transformer wires... :-)

Yep I know but enamelled can crack and ware off when things are touching and not fastened down. Put it like this, I would not risk holding an enamelled wire that was live if it had been able to move around freely. Not even sure I would want to anyway. In the transformer the windings you essentially have double the insulation between the windings and they are fixed and still. No cracking, flaking in the enamel should occur when totally still. But the wires are out in the open and can flex/move a bit, all bets are off (in my opinion).

Because then it would just be an isolation transformer, this is a site transformer - in which the whole point is to give it a centre tap. Though you can omit the extra earth connection yourself on some of these transformers if you so desire

Because then a short between primary and secondary in the transformer would not blow a fuse and would make the secondary side live at up to 1.5 times mains voltage relative to Earth.

@@petehiggins33 That's not true, omitting the centre tap doesn't make much difference it just makes the output 0v - 110v rather than 55v - 0v - 55v. The primary and secondary core cannot short together because they are only connected via a magnetic coupling not an electrical one - even so the power is supposed to flux between the primary and secondary coils to make it work anyhow

Ben Vahanian - because the whole point is to keep the voltage of any accidentally exposed conductor as low as possible. In a damp or wet construction site environment, it may be troublesome to maintain the system to be earth free. And the system would have to undergo regular testing to find out or confirm if it is earth free. By earth free, I mean all the 110V supply equipment, all the extension leads, all the tools etc. would have to have absolutely no insulation faults. It all would have to be tested with a insulation tester. This is not very practical. Why? Well if any of the conductors suffered an insulation fault (say a cable snagged on a piece of metal that was lying on the ground), your isolated earth free 110V system would now be an earthed 110V system. If a second fault was to occur, say a worker damaged the flex going to a power tool they were using, but did not notice. And then later on accidentally made contact with the conductor. If this was the now ‘hot’ conductor, they would complete the 110V circuit to earth/ground and could receive an 110V electric shock which could electrocute them. Even if no second fault occurred, it would fail the next insulation test. Bringing the job to a halt. Hence the solution is to centre tap the secondary winding of the transformer. Now by having an intentional proper earth, if either of the hot lines becomes earthy due to an insulation fault and a high fault current flows, the overload device will trip. Even if no significant fault current flows, if a worker accidentally makes contact with either one of the conductors, the maximum voltage that they would experience would be 55V. It is unlikely that this voltage will cause them injury. Hence this is the safest system.

www.toolstation.com/industrial-connectors-ip44/p35522

Known as CEE form colour coded yellow for 110 blue for 240 and red for 415

@@jwflame Oh, nice. Those appear to be very well designed.

Those are known by several common names, the correct designation is IEC 60309, it is now an international standard for "industrial connectors". They are strongly color coded for voltage and have the earth/ground pin in a different "Clock position" based on that voltage color correlation. The ones in the video are IEC 60309 4h 16/20a. Common colors are Yellow for 100 ~130 VAC, Blue for 200 ~ 250 VAC, Red for 400 ~ 480 VAC (230/400 Three phase being most common for red), There are several less common colors but one in particular that may be of interest to you is Orange, Orange is only found in areas that use split single phase that wish to distribute to the end point at 120/240... that would be North America. Orange came about as part of series 2 certification for IEC 60309 plug and socket type pin & sleeve devices for use in North America. You can get these in North America but their use has primarily been industrial, but are gaining traction as replacements where proprietary pin & sleeve designs were already popular. Most smaller North American domestic sockets (NEMA) are just that, for domestic use, but in general are absolute garbage in the shop, do they work yes... are they going to survive being stepped on... well once or twice. A 60309 takes allot of abuse, I actually use these on all my portable power tools, and since I attempt to only buy 50/60hz small tools, I can use them anywhere in the world with a proper local adapter and/or transformer. Wikipedia has a nice table of voltages and configurations which offers a basic introduction to the system. en.wikipedia.org/wiki/IEC_60309 Edit: P.S. In North America they seem to be ridiculously expensive, but can be had cheaply if you keep a watch, I have boxes upon boxes of them I've picked up for reasonable prices, so I always have them at hand when I want one.. they really are superb.

It has, that's what building sites are. 😉

It's a weird British thing, for safety purposes. These are used on construction sites, where there's a lot of potential to contact live wires while grounded. They have special tools as well, designed to work on 110v 50hz current (here in the US, it's 60hz, so our tools would theoretically work fine on one of these transformers, just slower.) The transformer is connected similar to our 240v appliances- the outside transformer in the US supplies 240v, with a center tapped neutral that is referenced to ground. In this case, it's a center tapped 110v transformer, with the center tap referenced to ground. That way, if a worker comes in contact with a live wire, it's at most 55v to ground, which is much less likely to cause injury or death. As for the different plugs, there's lots of different standards. Something similar to ours are used in China, but on 240v.

puckcat22679 - most electric drills used in most tools are actually DC motors fed via rectifier diodes. So these would not care if the supply was 50Hz or 60Hz. Secondly, not all AC motors care much about the mains frequency, as long as it is in the correct range. So again there would be no significant speed difference. The connectors are actually an international standard, look up IEC 60309

And the peak to peak voltage of a 240V AC RMS supply to ground is 340V. Which would you prefer?

It's really not that bad. Consruction sites have 110V power from dedicated transformers, such as www.blakley.co.uk/products/transformers/site-transformers-4kva-to-20kva/site-power-transformers/tap320s12 all of which have circuit breakers on the outputs to disconnect if short circuits or overloads occur. All tools and lighting on construction sites are 110V, and if people want to use those tools elsewhere they have a small transformer such as the one in this video. No one buys 2 sets of tools. They don't have those dreadful flimsy US plugs either. RCDs and 230V can in theory be used, but they never are. 110V with 55V to ground is reliable and safe. RCDs need to be tested often and would be quickly damaged/destroyed on a typical construction site, which in the UK will frequently be soaking wet.

Voltage here is about 250V. You are right in that the actual voltage hasn't changed in most places, but the declared voltage is 230V, and 230 is what's used for calculations, even though the actual voltage isn't usually 230V in reality.

Do you know what they *actually* changed the nominal voltage to? Here in Australia, a couple of years ago the area I live went from 240V +/- 6% to 230V +10%/-6%, which means the maximum allowed mains voltage dropped from 254.4V down to 253V. So in other words, the nominal voltage went to 230V but they didn't have to change any taps on the transformers... Although in our case they actually had a sensible reason for making this change. It seems there were so many grid-tied solar systems being installed that it was pushing the voltage too close to the limit, so by lowering the nominal voltage to 230V it means they can slowly go around changing the taps in areas that feed in a lot of solar power, and they don't have to worry about the voltage dropping below the spec on cloudy days when nobody is feeding in.

Well, when I do my calculations I use the voltage at the job n use that instead of the stated voltage thats in the regs.

@@Berkeloid0 Same here, 230V with allowed range 216 - 253.

@@jwflame madness ain't it 🤦🏻‍♂️

The copper wires are the ends of the transformer windings so they are already insulated

Yee, exactly. And he should have done.

It’s just a wedge grip, push the wedge out and reuse it.

Wow. It wasn't exactly a difficult or time consuming job though, was it? It's not like it took him several extra hours of unnecessary work. If he prefers the new one that's up to him.

Simon Tay weapon

He had a whole unsused pack of nuts and bolts. Why keep the old ones. Also reuse old spade connectors? Just NO

Solder wires to the stub on the spade connector? Please don't. The price of a spade connector is not worth the time or effort of bodging it back on, not to mention that it looks incredibly unprofessional. Have some pride in your work, and people will respect you for it. Doing poor work in order to save a few pennies does NOT look good!

This one is a portable transformer designed to be located indoors, and 110V items attached to it for use outside. Larger building sites would have a much bigger transformer with multiple outlets, located in a single location away from where the tools and other items are being used. The point is to keep the 240V away from the work area, otherwise there isn't any point in using 110V tools. Using a portable transformer with a 240V extension lead and standing next to the transformer outside with a tool connected on a short lead is totally the wrong way to use it.

UK = United Kingdom / made in the United Kingdom

ssshhhhhhh.

55-0-55, 55 volts to earth, 110 volts between the two conductors.

ed riley throbber

Most houses today in the US have two 110 volt wires and one neutral wire running into the house from the local distribution system. These wires can run underground or above ground. If there are two 110 volt wires running to the house, then the house has 220 volt service and appliances, such as dryers and air conditioners.

Back under your bridge Troll.