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Roger Hayter[_2_] Roger Hayter[_2_] is offline
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Default Economy 7 supply wiring question

Mike Humphrey wrote:

Roger Hayter wrote:
I have an economy seven supply. Two 25mm wires go from the main fuse
block to the meter (presumably live and neutral) and then to a switch
and then to two Henley blocks. From one of these a 25mm wire goes to a
radio controlled switch, and out of this time switch another 25mm wire
goes to a third Henley block. The house supply runs from the first two
blocks, and a separate wire from the third block presumably supplies
live to the night time only supply.

However, there are two 10mm wires from the main fuse block to the radio
switch, and one 6mm wire joins the radio switch to the meter.


OK, so it sounds to me like the 25mm wires carry the power. The 10mm
ones power the timeswitch, and the 6mm one signals the meter to change
rate. If you can find a model number of the timeswitch you may be able
to Google somthing that will confirm it.

The supply that powers the timeswitch should be isolated from the
switched terminals. If power flowed between them it would be dangerous
for a number of reasons - as you say, the switch would not reliably cut
power, but also with the switch open the electric heaters would run
through a 10mm tail protected only by a 100A fuse. So I think you can be
fairly confident that the switch does in fact cut all output power -
only the timeswitch and meter stay live.


Thanks for confirming my thinking, I am much happier for a second
opinion.




The consumer units should also have shrouds on the incoming terminals,
so as long as the main switch in the CU is also off the CU won't become
live even if power was supplied unexpectedly. If I was working on the
input side of the CU, I'd be tempted to remove the main fuse anyway
(though strictly this is illegal).


It looks as though the whole CU will need replacing, the one with the
single, uncovered, MCB in the picture



It's something to be careful of in multi-rate installations that there's
often not a single switch to cut all power to the building. My house
used to have THTC, which meant there were *four* main switches
(general supply, 24 hour heating, water heating, timed heating). Unless
all four were off, something was still powered or could become powered
under timeswitch control.

Mike

That's complicated, did you have four separate incoming cables and main
fuses, or was it all done after the meter?

--

Roger Hayter