Wiring up an old Bayonet Plug

Just a bit more trivia on grounding for you all. Initially grounding was NOT done as a safety feature. It was a cost cutting measure. The first systems ran two wires to bring the high voltage power to the transformer. With the length of runs required, especially when you got out into the country, the costs of the wire became prohibitive. To cut this cost it was discovered that they could "Ground" or "Earth" one side of the transformer and use the earth itself as the return line. Allowing a single wire to be utilized instead of two.

With the two wire, or isolated system, you had to come in contact with both wires in order to get a shock (think of a car battery - you have to touch both terminals or at least something connected to both terminals to get a shock)

When they went to the single wire system it also necessitated grounding the low voltage side of the transformer as a short within the transformer could charge one side of the secondary with a lethal voltage and anyone touching that wire and the ground would get a shock. This was avoided by grounding the secondary but it now introduced the problem that anyone who was in contact with the ground and touched the ungrounded connection would now get a shock instead of this only occurring if you contacted both poles of the power. Essentially you were now constantly in contact with one pole. Grounding or earthing appliances was an attempt to solve this problem by giving the electricity an easier alternate path to take, which would also blow the fuse, in the event of a fault.

Incidentally, when power plants were first being set up 220-240 Volts was considered to be the most efficient voltage at which to run electrical systems but authorities in North America deemed the voltage to be too high for public safety so it was reduced to 110-120 here. For similar reasons Japan set their standard voltage at 100 volts.


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Post# 247479 8/24/2013 at 12:47 (3,895 days old) by beko1987 (Stokenchurch, United Kingdom)
Checkrate/Likes I want to put the old bayonet light fitting plug back on my 119. I've bought a bayonet plug especially! Any wiring gurus in the house able to help? However, when I open the old plug up I have no idea how to connect it! I think it's missing the terminal screws, but I've got lots of old 3 pin plugs so will hope that the terminal screws from that will fit. Does it matter which way round the wires go? From Hoover Junior 119 With the brass pins removed it looks like an even older style of plug, would there have been a blanking plate to cover the electrics when used like this? Struggling to think of any old sockets that looked like that! From Hoover Junior 119 Also, where would the earth wire go? No idea if it's connected at the machine or not. Would I just leave it disconnected? From Hoover Junior 119 Or would I be better just leaving the 3 pin plug on and stop all this nonsense?!

Post# 247496 , Reply# 1 8/24/2013 at 14:19 (3,895 days old) by jakesvacs ()
Checkrate/Likes You can wire it anyway as its AC, just think of it as an old American type plug which goes in the socket either way.

Post# 247497 , Reply# 2 8/24/2013 at 14:26 (3,895 days old) by beko1987 (Stokenchurch, United Kingdom)
Checkrate/Likes Wicked, cheers Jake. Any idea on the earth lead?

Post# 247499 , Reply# 3 8/24/2013 at 14:31 (3,895 days old) by jakesvacs ()
Checkrate/Likes Don't worry about the earth wire, just cut it back and it will be fine :)

Post# 247501 , Reply# 4 8/24/2013 at 14:53 (3,895 days old) by DaveTranter (Central England, U.K.)
Checkrate/Likes *Bayonet adaptor* From the photographs, it looks like you've got half of a 5amp two-pin plug to bayonet adaptor there. Is it properly insulated when assembled?? It looks to me like half of the bakelite is missing. Wires either way, it predates earthing in most domestic premises.... If your appliance SHOULD be earthed, be careful using it on a bayonet fitting as the suppressor capacitors will probably introduce leakage to the chassis. Not necessarily dangerous, but can give you an unpleasant 'tingle'..... All best Dave T

Post# 247524 , Reply# 5 8/24/2013 at 18:55 (3,894 days old) by vintagerepairer (England)
Checkrate/Likes *Earth* If provision for an earth is there, then it is essential to connect it. Back in the day, a good deal of appliances were earthed and yet either had two-pin plugs attached as standard, or else gave instructions on how to connect to a two-pin set up. However, it always begged the question as to why an earth was fitted if there were circumstances where it would be ignored. Essentially, the use of two-pin plugs should never have been utilised on such appliances, though of course the reality was such that a good deal of homes had only the overhead light as a power source, possibly a socket attached to a skirting board in one or two rooms if one was lucky. Thankfully, earthed household wiring soon became the norm and three-pin plugs took the lead, if you will please excuse the pun. To that end, anything which required an earth was soon to be described as needing such at all times, in all instructions provided. Today, even on a double-insulated (none earthed) appliance, the use of a two-pin plug today means that correct polarity of the on/off switch cannot be guaranteed, and that's at best. You have also to take into account the age of this vacuum cleaner, and the fact that many insulated parts (including the mains lead) are made of rubber. Rubber perishes, as I am sure you know, leading in this instance to a breakdown in insulation. Because of this, the earth is more important than ever. My advice would be to keep that plug for display purposes only. If you want to be as authentic as possible, fit a black 13amp plug to the lead, as use the lowest rated fuse possible for the cleaner. In this case a 3amp would be safest.

Post# 249199 , Reply# 6 9/5/2013 at 15:25 (3,882 days old) by Vodhin ()
Checkrate/Likes There is a Load side and a Nutural side to the wiring. The load side is the lead that the switch is wired to. If I remember correctly, early home wiring in the USA had fuses on both Load and Nutural sides in the main pannel. When Grounding (Earth) outlets were introduced it became allowable to fuse only the Load side as long as all the outlets were polarized. A polarized plug ensures that the fuse or circuit breaker is in line with the switch in the appliance and cannot be bypassed by putting the load on the Nutural. I think I remember this correctly: the standard power model uses a high voltage feed from the power plant (top most wire on a utility pole) to a transformer that steps it down to household voltage (next wire down if the home feed isn't direct from the transformer). Most urban or suburban areas have 3 phases (sometimes 2) and rural areas have a single phase: you can countn the number of wires on the top of the pole. They all carry the same load but provide extra amperage room and the lines can be merged to create higher voltage where neeeded. The stepped-down juice is then sent to the house to run your stuff and then back to the pole to a nutural wire the is then connected to ground (usually at any guy-wire used to keep the poles straight). This means that the electricity uses the ground itself to complete the circuit between the power plant and the home. The nutural at this point has voltage but nearly no amperage and thus no decernable shock can be obtained. A grounding/earthing pin prevents an alternate path through the machine and user should the load get shorted out before its amperage (electrical force) is used to do whatever labor (wattage) the machine does. All it does is create a second route back to the power plant by channeling the juice through the wire to a pipe or grounding rod instead of your body. So when wiring any old plug there is only one correct way to do it: make sure the wires don't short out inside because it doesn't matter with today's modern home wiring which way the plug fits in the wall. You'll get zapped no matter what if the machine shorts out. ;)

Post# 249200 , Reply# 7 9/5/2013 at 15:28 (3,882 days old) by beko1987 (Stokenchurch, United Kingdom)
Checkrate/Likes Great info, thanks! Will keep the plug for display only! The MK one on it is of a good ago, and I imagine put on by Hoover, as I have lots of other Hoovers with the mk plug.

Post# 249220 , Reply# 8 9/5/2013 at 22:14 (3,882 days old) by Collector2 (Moose Jaw, Sk)
Checkrate/Likes Just a bit more trivia on grounding for you all. Initially grounding was NOT done as a safety feature. It was a cost cutting measure. The first systems ran two wires to bring the high voltage power to the transformer. With the length of runs required, especially when you got out into the country, the costs of the wire became prohibitive. To cut this cost it was discovered that they could "Ground" or "Earth" one side of the transformer and use the earth itself as the return line. Allowing a single wire to be utilized instead of two. With the two wire, or isolated system, you had to come in contact with both wires in order to get a shock (think of a car battery - you have to touch both terminals or at least something connected to both terminals to get a shock) When they went to the single wire system it also necessitated grounding the low voltage side of the transformer as a short within the transformer could charge one side of the secondary with a lethal voltage and anyone touching that wire and the ground would get a shock. This was avoided by grounding the secondary but it now introduced the problem that anyone who was in contact with the ground and touched the ungrounded connection would now get a shock instead of this only occurring if you contacted both poles of the power. Essentially you were now constantly in contact with one pole. Grounding or earthing appliances was an attempt to solve this problem by giving the electricity an easier alternate path to take, which would also blow the fuse, in the event of a fault. Incidentally, when power plants were first being set up 220-240 Volts was considered to be the most efficient voltage at which to run electrical systems but authorities in North America deemed the voltage to be too high for public safety so it was reduced to 110-120 here. For similar reasons Japan set their standard voltage at 100 volts.

Post# 249223 , Reply# 9 9/5/2013 at 22:19 (3,882 days old) by suckolux (Yuba City, CA)
Checkrate/Likes VERY interesting.