OT-ish - NAS Safety Issue?

I recently bought an Iomega 320gB external HDD, and a Linksys NSLU2 NAS.

When reaching round the back of the HDD to switch on/off, the back of my
hand touched another device and I received an electric shock from the HDD.

I discovered that the case of the HDD was at 90 volts, but that this voltage
depended partly upon the NSLU2. Even if the psu for the HDD is switched
off, the HDD case is at 50 V AC, this being on the outer connection of the
NSLU2 power lead, and the metal on the usb plug outer, and presumably
passing to the HDD this way.

So, both device psus appear to have about 50V AC on their power lead outer.
Other psus I've checked do not. Is this a quirk, or a fault, or a safety
issue, or what. (Iomega have agreed to replace the psu, but Linksys don't
yet seem to understand the issue.)

Should I be concerned? How should I proceed, if at all.

Allan

In article <eut9u6$o8m$(E-Mail Removed)>, datemas
(E-Mail Removed) says...
> I recently bought an Iomega 320gB external HDD, and a Linksys NSLU2 NAS.
>
> When reaching round the back of the HDD to switch on/off, the back of my
> hand touched another device and I received an electric shock from the HDD.
>
> I discovered that the case of the HDD was at 90 volts, but that this voltage
> depended partly upon the NSLU2. Even if the psu for the HDD is switched
> off, the HDD case is at 50 V AC, this being on the outer connection of the
> NSLU2 power lead, and the metal on the usb plug outer, and presumably
> passing to the HDD this way.
>
> So, both device psus appear to have about 50V AC on their power lead outer.
> Other psus I've checked do not. Is this a quirk, or a fault, or a safety
> issue, or what. (Iomega have agreed to replace the psu, but Linksys don't
> yet seem to understand the issue.)

IANAE. Sounds like there's no earth connection on the Linksys PSU,
allowing it to 'float'. Does it look like there should be one? If so,
check that the mains socket and any extension leads have a good earth
connection. Try a different PSU if you have a suitable one.

> Should I be concerned? How should I proceed, if at all.
>
Don't use it in the bath. :-)

"Rob Morley" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed) t...
> In article <eut9u6$o8m$(E-Mail Removed)>, datemas
> (E-Mail Removed) says...
>> I recently bought an Iomega 320gB external HDD, and a Linksys NSLU2 NAS.
>>
>> When reaching round the back of the HDD to switch on/off, the back of my
>> hand touched another device and I received an electric shock from the
>> HDD.
>>
>> I discovered that the case of the HDD was at 90 volts, but that this
>> voltage
>> depended partly upon the NSLU2. Even if the psu for the HDD is switched
>> off, the HDD case is at 50 V AC, this being on the outer connection of
>> the
>> NSLU2 power lead, and the metal on the usb plug outer, and presumably
>> passing to the HDD this way.
>>
>> So, both device psus appear to have about 50V AC on their power lead
>> outer.
>> Other psus I've checked do not. Is this a quirk, or a fault, or a safety
>> issue, or what. (Iomega have agreed to replace the psu, but Linksys
>> don't
>> yet seem to understand the issue.)
>
> IANAE. Sounds like there's no earth connection on the Linksys PSU,
> allowing it to 'float'. Does it look like there should be one? If so,
> check that the mains socket and any extension leads have a good earth
> connection. Try a different PSU if you have a suitable one.
>
>> Should I be concerned? How should I proceed, if at all.
>>
> Don't use it in the bath. :-)

Both devices have non-metallic earth pins on their mains plug. They will
both be floating, but if there is 50V AC to earth on the metallic case of
the HDD and I am earthed, then is there not a hazard, albeit perhaps not
potentially lethal? Actually, the case may have a lacquer finish as only
the edges appear to be 'live'.

Yes, I must remember the bit about the bath!<BG>

Allan

allan wrote:
> "Rob Morley" <(E-Mail Removed)> wrote in message
> news:(E-Mail Removed) t...
>> In article <eut9u6$o8m$(E-Mail Removed)>, datemas
>> (E-Mail Removed) says...
>>> I recently bought an Iomega 320gB external HDD, and a Linksys NSLU2 NAS.
>>>
>>> When reaching round the back of the HDD to switch on/off, the back of my
>>> hand touched another device and I received an electric shock from the
>>> HDD.
....
> Both devices have non-metallic earth pins on their mains plug. They will
> both be floating, but if there is 50V AC to earth on the metallic case of
> the HDD and I am earthed, then is there not a hazard, albeit perhaps not
> potentially lethal? Actually, the case may have a lacquer finish as only
> the edges appear to be 'live'.

Since the coupling is capacitive, the impedance will be correspondingly
high at mains frequencies, so there's no real hazard for most people.
Can still give anything from a tingle to a minor jolt though.

>
> Yes, I must remember the bit about the bath!<BG>
>
> Allan
>
>

"Mike Scott" <(E-Mail Removed)> wrote in message
news:zAPQh.1736$(E-Mail Removed)...
> allan wrote:
>> "Rob Morley" <(E-Mail Removed)> wrote in message
>> news:(E-Mail Removed) t...
>>> In article <eut9u6$o8m$(E-Mail Removed)>, datemas
>>> (E-Mail Removed) says...
>>>> I recently bought an Iomega 320gB external HDD, and a Linksys NSLU2
>>>> NAS.
>>>>
>>>> When reaching round the back of the HDD to switch on/off, the back of
>>>> my
>>>> hand touched another device and I received an electric shock from the
>>>> HDD.
> ...
>> Both devices have non-metallic earth pins on their mains plug. They will
>> both be floating, but if there is 50V AC to earth on the metallic case of
>> the HDD and I am earthed, then is there not a hazard, albeit perhaps not
>> potentially lethal? Actually, the case may have a lacquer finish as only
>> the edges appear to be 'live'.
>
> Since the coupling is capacitive, the impedance will be correspondingly
> high at mains frequencies, so there's no real hazard for most people. Can
> still give anything from a tingle to a minor jolt though.
>
>>
>> Yes, I must remember the bit about the bath!<BG>
>>
>> Allan

Thanks Mike.

"Mike Scott" <(E-Mail Removed)> wrote in message
news:zAPQh.1736$(E-Mail Removed)...
> allan wrote:
>> "Rob Morley" <(E-Mail Removed)> wrote in message
>> news:(E-Mail Removed) t...
>>> In article <eut9u6$o8m$(E-Mail Removed)>, datemas
>>> (E-Mail Removed) says...
>>>> I recently bought an Iomega 320gB external HDD, and a Linksys NSLU2
>>>> NAS.
>>>>
>>>> When reaching round the back of the HDD to switch on/off, the back of
>>>> my
>>>> hand touched another device and I received an electric shock from the
>>>> HDD.
> ...
>> Both devices have non-metallic earth pins on their mains plug. They will
>> both be floating, but if there is 50V AC to earth on the metallic case of
>> the HDD and I am earthed, then is there not a hazard, albeit perhaps not
>> potentially lethal? Actually, the case may have a lacquer finish as only
>> the edges appear to be 'live'.
>
> Since the coupling is capacitive, the impedance will be correspondingly
> high at mains frequencies, so there's no real hazard for most people. Can
> still give anything from a tingle to a minor jolt though.
>
>>
>> Yes, I must remember the bit about the bath!<BG>
>>
>> Allan

Thanks Mike.