Choosing a CU for TT systems?

Andy Dingley · 2010-11-04T16:19:54+00:00

I ended up buying a Wylex NH series. Cheap, big (15 ways), fairly wellmade. Comes with a 100A switch and two 83A 30mA RCDs for split-loading per 17th Ed.Cost another 30 quid to fit a double-pole 100mA RCD instead of thesupplied main switch (They offered 16th Ed RCD incomers, but not yet a17th Ed triple-split for TT use). The two workshop feeds need to avoidthe 30mA RCDs, and as it's a TT (overhead) supply I can't simply runthem from the main switch, no matter what their cable (inside theworkshops are their own CUs). No RCBOs planned as yet.I'm plannning to run the kitchen cooker / oven circuit from the 100mAside too. I can protect the cable so as to not need a 30mA RCD fromthat aspect.One thing I'm not certain about is discrimination between the incomerRCD and the 30mAs, in terms of their times (When it's wired up thoughI can time them, with my new Shiny 8-) ) I've been "assured" thatit's OK, but...So, does this fly?

Nov 04, 2010 20 Replies

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John Rumm 15 years ago

The phrase "how stupid do you think I am?" springs to mind... but I guess I can predict the answer!

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Choosing a CU for TT systems?

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