Dangerous fuseholder wiring in variac

[Circlotron]

Opened up my variac to have a look inside and I noticed that the incoming mains active wire goes to the fuesholder connection that is closest to the front panel. This means that with the fuse removed, the live part of the fuseholder can be contacted by the user. Good idea to swap the fuseholder wires.

[TimNJ]

Now that's an interesting design accident that I've never considered. I've used this style of fuseholder many times in my own projects, and never once thought about that. Though, I'd say most people will *probably* unplug the thing anyway, but who knows.

[NiHaoMike]

I wonder why those variacs have a voltmeter that is too imprecise to adjust the voltage with rather than an ammeter that would actually be useful. Better yet, nowadays they should be using digital panel meters that can at least match a cheap Harbor Freight DMM for accuracy and precision.

[Ian.M]

That looks remarkably similar to the far east 'red peril' variac user 'tkamiya' tore down here: https://www.eevblog.com/forum/beginners/shopping-for-a-variac-shopping/msg3066512/#msg3066512
and eventually decided to condemn for scrap as irremediably unsafe based on his findings here:
https://www.eevblog.com/forum/beginners/shopping-for-a-variac-shopping/msg3068574/#msg3068574 

If the wiper doesn't have a slip ring but is connected by an ordinary wire wrapped a couple of turns round the uninsulated steel shaft that flexes and rubs every time the knob is turned, yours is the same as 'tkamiya's and should probably also be condemned as eventually the insulation will rub through and the shaft go live.  If you want to keep it safely in service you'll need to add proper ground bonding straps between all its metalwork, an insulating sleeve on the shaft, and glassfibre sleeving over the wiper wire, (which for reliability should also be replaced with extra-flexible test lead wire of an appropriate CSA) to protect it from rubbing! 

[wraper]

fuseholder can be contacted by the user. Good idea to swap the fuseholder wires.

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.

[newbrain]

fuseholder can be contacted by the user. Good idea to swap the fuseholder wires.

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.

This.
At least, the way it is now, connection to live can be broken by turning off the switch (if you don't unplug it and not even bother to turn it off, you might be eligible for a Darwin Award).
In Europe, where most of the plugs are not polarized (and in some places, there's even no neutral), reversing the contacts would only make it more dangerous.

[GlennSprigg]

fuseholder can be contacted by the user. Good idea to swap the fuseholder wires.

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.

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.

[Ian.M]

I'll rewrite that for you: "ALL such legally imported factory supplied equipment plugs ARE correctly polarized" or  "ALL such factory supplied equipment plugs ARE required to be correctly polarized" . . .

As to what's actually out there in service down under, especially on 'red peril' variacs, YMMV. 

However there is clear benefit in making sure its correctly wired as the O.P. proposed, both the fuse and switch are in the Line, not the Neutral, and that the incoming power cord's plug is wired correctly.  While its on the bench, the O.P would be well advised to upgrade it by fitting a fuseholder (or a miniature panel mount circuit breaker if there's room and you can find one with the right current rating for an affordable price) for the output as well.

Over here in the EU, external mains fuseholders that can be opened without the use of tools have been banned on new equipment for many years . . . .

[wraper]

fuseholder can be contacted by the user. Good idea to swap the fuseholder wires.

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.

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.

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.

[schmitt trigger]

"Red Peril" Variacs.

That name should be trademarked. 


Similar to Superior Electric's Powerstats.

[Ian.M]

'Red Peril Variac' brand motto: "Safer than a Scariac!" 

[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]

fuseholder can be contacted by the user. Good idea to swap the fuseholder wires.

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.

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.

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]

fuseholder can be contacted by the user. Good idea to swap the fuseholder wires.

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.

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.

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.

Yes I do 
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]

fuseholder can be contacted by the user. Good idea to swap the fuseholder wires.

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.

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.

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.

Yes I do 
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! 

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.

[Greg Robinson]

Another concern, I don't see a fuse on the output?!?
Thanks to transformer action, at low voltage output the input current to an autotransformer is low, but the output current can be the input/output ratio greater. Without a fused output, the brush and winding can burn out...

[duckduck]

fuseholder can be contacted by the user. Good idea to swap the fuseholder wires.

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.

This.
At least, the way it is now, connection to live can be broken by turning off the switch (if you don't unplug it and not even bother to turn it off, you might be eligible for a Darwin Award).

That's how mine is. The fuse holder is wired in "backwards" (live end out) but to touch a live part someone would have to unscrew the fuse with the unit plugged in and turned on. I also noticed that all of the mains wiring was soldered  Add to that the perils mentioned by the guy that tore one down and I'm going to have to look at this thing closer.

Sociopaths continue to build these mains-powered fire-starters because people like me continue to buy them. Maybe it's time for me to look in the mirror.

EDIT:

When I bought my current nest I checked all of the outlets and found that 3 (of the many outlets) had a reversed line and neutral.

[Cubdriver]

'Red Peril Variac' brand motto: "Safer than a Scariac!" 

(But not much...)

-Pat

[Zero999]

fuseholder can be contacted by the user. Good idea to swap the fuseholder wires.

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.

This.
At least, the way it is now, connection to live can be broken by turning off the switch (if you don't unplug it and not even bother to turn it off, you might be eligible for a Darwin Award).

That's how mine is. The fuse holder is wired in "backwards" (live end out) but to touch a live part someone would have to unscrew the fuse with the unit plugged in and turned on. I also noticed that all of the mains wiring was soldered  Add to that the perils mentioned by the guy that tore one down and I'm going to have to look at this thing closer.

Sociopaths continue to build these mains-powered fire-starters because people like me continue to buy them. Maybe it's time for me to look in the mirror.

EDIT:

When I bought my current nest I checked all of the outlets and found that 3 (of the many outlets) had a reversed line and neutral.

Why not just return it and the same for the original poster?

These cunts shouldn't be allowed to sell defective products like these!