- Reaction score
- 3,818
What mft is it?Will try, just PM me your address to mail the charred remains to........
Discuss Problematic Ze........ in the UK Electrical Forum area at ElectriciansForums.net
What mft is it?Will try, just PM me your address to mail the charred remains to........
Correctamundo - 0.38 for 100A and 0.51 for 80A (Table 41.4 BS88-3 with 5sec)0.35 is a typical value for a 100A fuse at the head. I suspect the reason they reduced the fuse to 80A is to allow for a higher Ze of 0.50 but I can't recall the exact figure.
For a bs 1361 type 2 80amp is 0.48Correctamundo - 0.38 for 100A and 0.51 for 80A (Table 41.4 BS88-3 with 5sec)
Is that bs 88-3?Correctamundo - 0.38 for 100A and 0.51 for 80A (Table 41.4 BS88-3 with 5sec)
It becomes academic if the protective device in the cut out takes longer than 5 seconds to disconnect due to a high ze/zs at the origin.All this is academic really if all circuits within the installation are 30ma RCD protected, it would have been more relevant in the past before such widespread use of RCDs was regulatory.
But if the ze is high when measured at the incoming main switch and above what is required to disconnect the fuse in 5 seconds at the cut out then that's ultimately the issue.Yes of course but any circuit fault with RCD and MCB protection will disconnect well before the main fuse gets involved.
By that reasoning what's the point of the DNO stipulating max ze figures on tn-c-s and tn-s systems.Yes but what of the thousands and thousands of TT systems with much higher Ze , they all have the same problem but much worse than your sub 1 ohm reading.
Apologies dave I don't mean to seem to be arguing, I do see what your saying though about the tt system scenario.I'm not being argumentative Ian, just wondering if your perceived issue is really worth worrying about with the Ze that you have on this particular job. I just think a note stating DNO informed on your EIC would cover you fine.
Reply to Problematic Ze........ in the UK Electrical Forum area at ElectriciansForums.net
We get it, advertisements are annoying!
Sure, ad-blocking software does a great job at blocking ads, but it also blocks useful features of our website. For the best site experience please disable your AdBlocker.