OT for a sec: US wiring sources of info

[Allison]

>
>Subject: Re: OT for a sec: US wiring sources of info
>   From: Alistair MacDonald <a.macdonald+classiccmp at slitesys.demon.co.uk>
>   Date: Fri, 07 Oct 2005 17:50:53 +0100
>     To: General Discussion: On-Topic and Off-Topic Posts <cctalk at classiccmp.org>
>
>Chuck Guzis wrote:
>
>> If I remember what my friend from Aylesbury told me aobut UK wiring, it 
>> isn't uncommon for a 50 amp 220 volt pair to be run to all outlets;
>
>Your friend would appear to live in a different UK to me. It is however 
>common practice for the outlets to be in a ring with a 30A fuse in the 
>fusebox.

Well UK and USA differ on wiring and voltage.  We often have large 
numbers of outlets (parallel connection) per fuse/breaker. For example
this house has 9 rooms and three breakers control the bulk of the outlets
(1957 construction).  And added outlets since then are on new breakers.
This is typical of homes more than 15-20 yers old and varies a lot.

the other is MY understanding is UK is 230V where we use 115/120.  Further
the mains are Line/Line in UK and here they are line/neutral.  The differnce 
is under nominal conditions one side of the outlet is at earth potential 
(or very close).  We add the third prong as earth or safety ground.

>> the fuse being in the plug of the appliance. He also mentioned that,
>> although in theory, each appliance is to be fused according to its
>> current use, the common practice is to install a 13 amp fuse in
>> everything as a replacement.
>
>Most people don't understand the difference and it is more annoying to 
>get the correct fuse. It isn't helped by the manufacturers supplying 
>items with the wrong fuse. Those of us who perform Portable Appliance 
>Tests on things get very annoyed at having to replace the fuses on the 
>first test. Anyone want any 13A fuses? 8-)

While a good practice the design differnce here is internal fuse 
(or on equipment) for equipment fault and circuit (breaker box) fuse
to protects building wiring from fault or overload.  fire people often 
report that electrical fires resulting from circuit overload (impropper
fusing or use of under weight extension cords.) more often than an 
appliance causing fires.  From what you say it's done the same there
only location of the equipment fuse is at the connector.  Each has 
it's merits.

I may add here we also have fixed appliences that use 230V line/line
for power too allow lower line currents that come with higher voltages.
Devices like that are electric ranges, Ovens, clothes dryers and generally
any non portable appliance that would draw 20A or more at 115/120V.
US household generally have power delivers from the pole as 230V Line/Line
aand 115/120V line/neutral.  A code specifies that neutral will be bonded 
to earth (via pipe or ground rod) at only one point.  From that point 
protective ground and neutral will be distributed to all loads either as
star or bus.  



Allison