Scout, describe your situation. How long is your power line? Does it feed a few or many?
Everything sags. It's all about the money, which is never infinite. 5% sag (often figured as 2% in nearest transformer + 3% in feeder) is a good commercial choice. 240V at 100A, 5% sag, is 0.12 Ohms total source resistance.
My 240V 100A line has 0.4 Ohms impedance at least! However my shack is back in the woods and 500 feet of line is private (me), not company capitalized. I know the difference and do not care to spend $5k+ to hang bigger wires or a private transformer (and attendant tree-fires). The lights dim a bit when the well-pump starts, I can live with that.
OTOH there are places where four or more houses are set cheek to cheek with a central transformer, under 50 feet of feeder to each, and that wire company supplied (a bit generous). Such place may have <0.5r feed resistance. Maybe much less: main breakers may be rated to break 40KA in a dead-short.
Anyway: at 5% tolerable sag, a 12V drop at maximum load (not just a toaster or fire or iron) is entirely expected. This measured at/near the Service Entrance (what you call CU?). If the heavy load is at the opposite corner of the house, another 3% of drop in internal wiring is reasonable.
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Set up is Cable into property overhead (10m from street supply) into an outside cabin, directly under the overhead cable pole. This goes to a meter. After the meter there is a split and a feed that goes to a garden shed/workshop and the other goes into a SWA cable to the house, about 15m long. I think this is 94A cable.
In the house the SWA feeds a splitter to 2 domestic consumer units as per the photo and then another 94A cable also takes the feed to a 3rd consumer unit. This feeds just 8 spurs to individual plugs with 30A cable for the HiFi. The consumer unit is on the wall behind the music room with the 8 plugs.
In the house the SWA feeds a splitter to 2 domestic consumer units as per the photo and then another 94A cable also takes the feed to a 3rd consumer unit. This feeds just 8 spurs to individual plugs with 30A cable for the HiFi. The consumer unit is on the wall behind the music room with the 8 plugs.
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We have 3 phase supplies to our homes in Sweden, and it sure is nice being able to ring fence circuits. I won't have to worry about the life support machine failing because a bulb blows downstairs ;-)
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Thanks a lot for this - need to do some more reading as when I run the simulation I don't match the starting values, I added a diode too as this seemed to be missing, but may not be essential for the circuit to work/simulate.
Yep the diode is to protect the cathode follower before the heater warms up. It seems private emails don't allow attachments.
The UK mains supply is about 230 volts AC (it used to be stated as 240V on appliances - and in physics questions), but in 2009 was brought down by 10V to allow compatibility in the intended voltage of appliances made for both the UK and European market.
The UK mains supply is about 230 volts AC (it used to be stated as 240V on appliances - and in physics questions), but in 2009 was brought down by 10V to allow compatibility in the intended voltage of appliances made for both the UK and European market.
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