[mythtv-users] Power Line Network Connections and Myth ?

Simon Hobson linux at thehobsons.co.uk
Thu Sep 30 06:55:46 UTC 2010


Craig Huff wrote:

>One might think that those on the left were on one half of the split 
>220 service (220 is the nominal service voltage, some power 
>companies may only supply 200V and others may supply 240V or more) 
>and those on the right were on the other half of the split 220 
>service.  One would be wrong!  If you look closely, you most likely 
>will find one or more double-wide circuit breakers that support 
>things like a 220V electric dryer, 220V oven, etc.  The breakers 
>from top to bottom on one side of the panel alternate between one 
>side of the split 220 service and the other.  Thus the odd ones 
>counting from one end are on one side of the split 220 service and 
>the even ones are on the other.

That is no surprise - it's how 3 phase boards are generally arranged. 
Down each side, the circuits go L1, L2, L3, L1, L2, L3, ... Single 
phase circuits use one position and their loads get spread across the 
phases, 3 phase circuits are taken off one set of L1, L2, and L3.

Having a 2 pole breaker like you have for 220V loads also means that 
if it trips, both sides of the supply are switched off - with 2 
separate breakers/fuses, you could trip/blow one and leave the supply 
inoperative but still live. Worse still, if the fault were a short to 
earth on one side of the supply, the equipment might still be working 
(sort of, on 110V) using one half of the supply and earth !

>OTOH, both outlets are on the second floor and the circuit breaker 
>box is in the basement, so the distance between the outlets may be 
>20 feet "as the crow flies", but it's about 80 feet following the 
>power lines down and back up.
>
>So... After all that, the net result was nowhere near 200Mbps, or 
>100Mbps, but rather around 14Mbps.  Casual testing post-install 
>indicates it may be "good enough" for my SD use, but it is still a 
>far cry from the performance over a CAT-5 drop.

And do radios still work - in your house, or elsewhere in the 
neighbourhood ? It's interesting to see that figure - just shows how 
"optimistic" the headline speed of the units is :-/


-- 
Simon Hobson

Visit http://www.magpiesnestpublishing.co.uk/ for books by acclaimed
author Gladys Hobson. Novels - poetry - short stories - ideal as
Christmas stocking fillers. Some available as e-books.


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