General > General Technical Chat
Dangerous fuseholder wiring in variac
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Ian.M:
'Red Peril Variac' brand motto: "Safer than a Scariac!"  >:D
Benta:
I'd argue that not the wiring is bad, but that the fuse holder design is bad. Exposed metal has no place in mains circuits, there are better types on the market.

Whether you get the whack directly from L or through the primary doesn't make a big difference.

tooki:

--- Quote from: GlennSprigg on July 15, 2020, 12:22:39 pm ---
--- Quote from: wraper on July 15, 2020, 02:03:53 am ---
--- Quote from: Circlotron on July 14, 2020, 11:21:57 pm ---fuseholder can be contacted by the user. Good idea to swap the fuseholder wires.

--- End quote ---
That's basically how most of similar fuse holders are made. Swapping wires won't help much since it still will be connected through transformer anyway. You may argue that Australian mains plugs are polarized but I would not count on that.

--- End quote ---
I understand what you are saying, but in Australia, (and unlike say a homemade extension cord that
may be wired wrongly), ALL such factory supplied equipment plugs ARE correctly polarized. And unlike
the U.S. plugs, always have an Earth, (unless the device is double-insulated), which ensures the correct
orientation of the pins. Our power-outlets are also 99% switched, isolating the L.H. active (hot) pin.
We generally don't switch an 'outlet' in the ceiling for say an exhaust fan.

--- End quote ---
FYI, in USA, polarized 2-pin plugs are very common, ensuring correct orientation even without an earth pin. Double-insulated devices don’t need them, but they’re very common all the same.
GlennSprigg:

--- Quote from: wraper on July 15, 2020, 01:49:44 pm ---
--- Quote from: GlennSprigg on July 15, 2020, 12:22:39 pm ---
--- Quote from: wraper on July 15, 2020, 02:03:53 am ---
--- Quote from: Circlotron on July 14, 2020, 11:21:57 pm ---fuseholder can be contacted by the user. Good idea to swap the fuseholder wires.

--- End quote ---
That's basically how most of similar fuse holders are made. Swapping wires won't help much since it still will be connected through transformer anyway. You may argue that Australian mains plugs are polarized but I would not count on that.

--- End quote ---
I understand what you are saying, but in Australia, (and unlike say a homemade extension cord that
may be wired wrongly), ALL such factory supplied equipment plugs ARE correctly polarized. And unlike
the U.S. plugs, always have an Earth, (unless the device is double-insulated), which ensures the correct
orientation of the pins. Our power-outlets are also 99% switched, isolating the L.H. active (hot) pin.
We generally don't switch an 'outlet' in the ceiling for say an exhaust fan.

--- End quote ---
No you don't. First of all, you may have incorrect mains or extension cord wiring with L/N swapped. That is not something rare. Secondly, if neutral wire breaks somewhere, then you will have line potential on neutral wire through other equipment passing current from line to neutral.

--- End quote ---

Yes I do  :D
However, did you see my statement that...
(and unlike say a homemade extension cord that may be wired wrongly)...
And to 'tooki', yes I'm aware that a lot of U.S. plugs are now 'polarized' by way of a slightly larger
pin as one of the pair, but a large amount of older plugs do not, and generally an Earth pin was rare!
Back to the O.P. though, it's plain to see that the 'exposed' portion of the Fuse-Holder could obviously
could pose a problem, even if the 'supply' was done correctly. It was a very valid point!  :-+
Zero999:

--- Quote from: GlennSprigg on July 17, 2020, 12:48:56 pm ---
--- Quote from: wraper on July 15, 2020, 01:49:44 pm ---
--- Quote from: GlennSprigg on July 15, 2020, 12:22:39 pm ---
--- Quote from: wraper on July 15, 2020, 02:03:53 am ---
--- Quote from: Circlotron on July 14, 2020, 11:21:57 pm ---fuseholder can be contacted by the user. Good idea to swap the fuseholder wires.

--- End quote ---
That's basically how most of similar fuse holders are made. Swapping wires won't help much since it still will be connected through transformer anyway. You may argue that Australian mains plugs are polarized but I would not count on that.

--- End quote ---
I understand what you are saying, but in Australia, (and unlike say a homemade extension cord that
may be wired wrongly), ALL such factory supplied equipment plugs ARE correctly polarized. And unlike
the U.S. plugs, always have an Earth, (unless the device is double-insulated), which ensures the correct
orientation of the pins. Our power-outlets are also 99% switched, isolating the L.H. active (hot) pin.
We generally don't switch an 'outlet' in the ceiling for say an exhaust fan.

--- End quote ---
No you don't. First of all, you may have incorrect mains or extension cord wiring with L/N swapped. That is not something rare. Secondly, if neutral wire breaks somewhere, then you will have line potential on neutral wire through other equipment passing current from line to neutral.

--- End quote ---

Yes I do  :D
However, did you see my statement that...
(and unlike say a homemade extension cord that may be wired wrongly)...
And to 'tooki', yes I'm aware that a lot of U.S. plugs are now 'polarized' by way of a slightly larger
pin as one of the pair, but a large amount of older plugs do not, and generally an Earth pin was rare!
Back to the O.P. though, it's plain to see that the 'exposed' portion of the Fuse-Holder could obviously
could pose a problem, even if the 'supply' was done correctly. It was a very valid point!  :-+

--- End quote ---
I don't think I've ever encountered an extension lead with the live and neutral swapped. Have you seen an extension lead with a neutral and earth swapped? That would work, if it had a polarised plug and was used in a circuit with no RCD present, but it doesn't mean it's safe.

If the device is designed to be used in an area with polarised sockets, then it's perfectly acceptable for it to be designed with that in mind. Of course it needs to be made safe in the event the neutral or even earth conductor is broken, but that's a different matter.
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