I'm in the process of obtaining quotes for a dedicated power supply . I asked the electricians for a separate Isolation Fuse BEFORE the existing circuit breaker box, minimum 30 amp, preferably 45 amp, as a bit of research on the forum suggested that this was the key requirement (along with 10mm2 cable which isn't a problem).
The quote has come back with "connect the new radial circuit (I asked for a spur) to a new 2-way consumer unit located within the external meter box, and connection of the main consumer unit to the spare way in the new 2-way consumer unit". On querying this the answer was "that's the only way the regs allow it to be done.
I'm not an electrician but it looks to me as though that defeats the object as there will not be complete isolation from the existing mains, in which case why bother? Also I'm not sure if it really matters/is possible to instal a spur not a radial circuit.
Equally I did wonder if it might be better to simply buy a couple of power lines and connect them to my Wireworld distribution box/NAP 200 - although this will be quite a bit more expensive (maybe a step for later after the dedicated supply is installed?).
Before I take it up again with the electrician, I wondered if anyone has any experience on these two issues and can suggest what I should be saying! (rather than going to another electrician, as this one did seem quite keen on hifi and understood what I was trying to do).
Thanks in advance and a merry christmas to all.
Posted on: 23 December 2015 by hungryhalibut
You need to split the meter tails using a Henley block, so that the two consumer units are totally separate. This is mine, which meets current regulations. It's a bit of a gloomy picture, but you will see what it should look like. Show your electrician!
Posted on: 23 December 2015 by naim_nymph
I'm in the process of obtaining quotes for a dedicated power supply . I asked the electricians for a separate Isolation Fuse BEFORE the existing circuit breaker box, minimum 30 amp, preferably 45 amp, as a bit of research on the forum suggested that this was the key requirement (along with 10mm2 cable which isn't a problem).
John,
What you asked for isn't possible because you can't have a 30A or 45A separate fuse box before the main household CU, which typically may have a 100A main fuse.
You have two options, one is to have a smaller and separate fuse box spur off the the meter tails using a Henley Block. This avoids the main household CU, and is a good idea if your meter and CU are fairly close to each over [under stair cupboard perhaps] however this method is sometimes impractical or not possible due to house lay out or positioning of where the meter is in relation to where you need the dedicated little fuse box to go. It maybe very expensive to have it done this way, plus many qualified electricians will have reservations about installing long meter tails...
The other option is far easier, to use the main household CU by having the dedication audio fuse on the non protected side of the RCD trips. This means the power goes from the meter tails straight into the household CU via it's 100A fuse and first port of call will be the 'audio fuse' [of your rating choice 40A or 32A]. If your present household CU does not facilitate this plan it's a good idea to take the opportunity to upgrade it to the latest regs type [17th Edition i think], which will get you what you want along with a new CU which will make the whole household safer in the process.
Debs
Posted on: 23 December 2015 by Mr Happy
The reason your electrician wants to install a 2 way consumer unit before the main unit is that strictly speaking the regs require the installation to have a single point of isolation. It can be done like this as one fuse will feed the hifi and the other will feed the main consumer unit via a much larger fuse (60A possibly) as would be used on a sub main, but this, although complying with the regs is actually more likely to cause problems than having two points of isolation.
Your electrician is correct in calling the circuit you want a radial circuit. A spur is often what it is incorrectly refered to on hifi forums, but it is infact a radial circuit.
The safest and best way to do the install is as mentioned above. Split the meter tails before the main consumer unit and install a service connector (henley block). This will allow a second consumer unit to be installed safely for the hifi.
Posted on: 24 December 2015 by Willy
A better lit photograph.
The tails from the power company fuse and meter (outside back wall of kitchen) come down between the two consumer units. There they are split via the henley blocks to feed the two consumers units. The dedicated hi-fi consumer unit has two radials to opposite corners of my listening room giving me some layout flexibility should I ever wish to rearrange my room.
The tails from the meter are actually about 6 metres, not ideal from the power company perspective but they accepted it as the best compromise.
Regards,
Willy.
