DNO Cables

[Monkeyblaine]

Someone on here said once that there is no way that the DNO allow 100A supply per house, which obviously makes sense. So why do a lot of house have 100A main heads. Surely that means that the cables can take 100A or more otherwise cable would get hot before fuse went? Surely house have the ability to take 100A just the DNO knows that most houses won't. Also am I right in thinking when you turn an electric 10kw shower on and the lights in your house dim is that due to a VD On the main incomer. Say for example the lights were working at 238v, shower comes on, incomer drops to 230v? EXAMPLE of course.

 

[iamelectric]

its supplied by a 25mm so could take 100amp but they use diversity not everyone is going to use 100amp and not all at the same time

 

[Monkeyblaine]

Understood and am I right with the shower question. So what we see when then the lights dim is a VD on the incoming supply but still probably above 230v what we see before the shower comes on is the lights working at a slightly higher voltage.

 

[iamelectric]

not sure about that one , when i use my shower the lights dont dim!!

 

[Darkwood]

When a large load is demanded on a supply their is obviously a surge in current to said load when its switched on which for a fraction of a second during the surge can create a volts drop on the local supply system, this can be seen by standard incandescent lamps dimming, once the supply has 'caught up' with the extra demand (the best way i can put it) all is back to normal. This is more noticeable if the DNO system feeding your area is 'weak', heavily loaded or supplying industry that users heavy start up demanding equipment like inductive loads of motors etc..... where this is likely the companies usually have restrictions on how often they create this transient in the supply, abuse of this restriction can lead to fines or request that said company pay for their own independent transformer off the 11kv network.