Re: x10 over three phase

[chris@xxxxxxx (Chris Davenport)]

Phil Lenfestey <phil@xxxxxxx> said:
>
>Main fuse (circuit breaker actually):  63A
>
>Loads:
>24 sockets (12 doubles) which presumably have to be rated at 13A each.
>9 lights
>One single oven cooker, which according to the instructions can be
wired
>to a 13A plug.
>Gas Boiler rated at 3A
>
>Now, clearly I don't understand how they work out what total load my
>board should take, because 24 sockets at 13A comes to 312 Amps already,
>which is mad.
>
>My shower wants to draw 45 Amps.
>

Ring mains are normally limited to 30A by a circuit breaker in the
"consumer unit" which is the box full of circuit breakers on the
house
side of the main 63A circuit breaker.  Even though you have 24 sockets
each individually rated at 13A you would not be able to put a load of
more than 30A on each ring-main without tripping the circuit breaker.
Not many domestic appliances require the full 13A anyway so this is
rarely a restriction.  And your 24 sockets are probably split up into
several ring-mains each with its own 30A circuit breaker.  I think its
normal to have at least a separate ring-main for upstairs and downstairs.
A kitchen or utility room may have its own ring-main, at least in
newer houses because of the higher concentration of energy-hungry
equipment.  Lights will be on separate circuits again, generally with
15A circuit breakers.

Single, high demand items such as cookers and showers will be on
separate circuits with their own circuit breakers.  I must say that
45A for a shower is A LOT!!  If you don't like paying your electricity
bill I suggest you take your showers really quick :-).  But that's
probably only a peak requirement such as when the unit is starting up.
I think it'll need a particularly heavy cable running from the consumer
unit to the shower.  I think there is also an IEE regulation that says
you have to have a cut-out switch in an adjacent room.  You could
be in for a lot of wall chasing :-(.

Hope this helps.

Chris.

--
Chris Davenport
chris@xxxxxxx

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