From: David Van Horn <david.vanhorn@backcountryaccess.com>
To: Microcontroller discussion list - Public. <piclist@mit.edu>
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Date: Tue, 26 Jan 2021 11:07:23 -0800
Subject: RE: [EE] Connecting european device to US main.
Thread-Topic: [EE] Connecting european device to US main.
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Yup, only fuse hot!

--
David VanHorn
Lead Hardware Engineer

Backcountry Access, Inc.
2820 Wilderness Pl, Unit H
Boulder, CO =A080301 USA
phone:=A0303-417-1345 =A0x110
email:=A0david.vanhorn@backcountryaccess.com=A0

-----Original Message-----
From: piclist-bounces@mit.edu <piclist-bounces@mit.edu> On Behalf Of Harold=
 Hallikainen
Sent: Tuesday, January 26, 2021 11:59 AM
To: Microcontroller discussion list - Public. <piclist@mit.edu>
Subject: Re: [EE] Connecting european device to US main.

*WARNING*: This email originated from outside of the company. Lookout for f=
ake addresses and websites. Do not click on any links or open attachments u=
nless you can recognize and verify the sender and know that the content is =
safe.


I agree that the breaker panel would take down both phases. I was commentin=
g (perhaps unclearly!) on the circuit protection within the device. I have =
only seen fuses on the hot lead and not the neutral (in fact, a fuse on the=
 neutral MAY be disallowed since it might blow first with an overload leavi=
ng high voltage in the device).

Harold



> Hi Harold,
>
> If you look at a residential North American breaker panel, you'll see=20
> lots of single circuit breakers for 120V circuits, and some wide 240V=20
> breakers that grab both busbars. The 240V breakers disconnect both=20
> phases even if only one phase causes the trip. It's a code requirement.
>
> Drawing a 240V load from two opposite-phased 120V breakers is not=20
> allowed because of the safety concerns, even if it does work.
>
> On the other hand, running two 120V branches from a 240V breaker seems=20
> safe. I don't know if it's allowed by code, probably not, it could=20
> make diagnosing trips more difficult.
>
> Friendly regards, Bob
>
> ________________________________________
> From: piclist-bounces@mit.edu <piclist-bounces@mit.edu> on behalf of=20
> Harold Hallikainen
> Sent: Tuesday, January 26, 2021 9:59 AM
> To: Microcontroller discussion list - Public.
> Subject: Re: [EE] Connecting european device to US main.
>
> I agree that phase to phase will give 240 V (unless you're on a 3=20
> phase wye, in which case it will be 208 V). Most electronic devices=20
> now have "universal" power supplies that work from something like 100 V t=
o 260 V.
>
> One thought on doing a phase to phase connection is the loss of=20
> overcurrent protection. I think pretty much everything only fuses the=20
> hot side of the power line. That guarantees no high voltage in a=20
> device that blows a fuse (blowing a fuse in the neutral would remove=20
> an overcurrent load but leave line voltage in the device). But, if=20
> operating phase to phase, what about a "neutral" to ground short?=20
> There would be no overcurrent protection at the device (just the branch c=
ircuit protection).
>
> I have thought of powering audio equipment that has a universal power=20
> supply from 240 V phase to phase to provide it with "balanced power"=20
> that results in a cancellation of ground leakage current due to the=20
> EMI filter Y capacitors. But, I am concerned about a lack of=20
> protection  on one side of the line.
>
> Harold
>
> --
> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive=20
> View/change your membership options at=20
> http://mailman.mit.edu/mailman/listinfo/piclist
>


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