the doctor
Part P Doctor ™
- Joined
- Mar 1, 2008
- Messages
- 580
- Reaction score
- 1
Hi All,
Its a while since I posted so forgive me. I moved to Ireland and am busy trying to carve a living in a desolate place, as well as fixing up an old house... Anyway, I have a gem to share with you. I have picked up a little work doing condition reports for a local contractor. If you have read this on my blog already, again please forgive me|!
I wanted to stick this one on here as I almost walked past it... Its a TT supplied church hall. Notice anything?
Mmmm metal board with RCD main switch so board is an exposed conductive part and no RCD protection..... nice one! Of course it is worse than that. The loop impedance is around 40ohms so if a tail did somehow chafe through, a grand total of 6A would flow around the earth fault loop...
I= V/Z = 240/40 =6A
(teaching mode here sorry!) This will flow .... for ever!
Of course this 6A would generate near mains voltage on the board ( sorry, teaching again) .... taking the line side impedance as say 1 ohm and the earth 39ohm . The voltage on the board would be...
V=IxR = 6x 39 = 234V
Of course it gets worse again.... as the 234V would be transmitted to the earth bar bolted to the metal board and every bonding conductor and cpc in the church hall. Talk about being nearer to God...
Once more, I am sorry for not posting at all for so long.. Ireland is riddled with stuff like this, so I may stick some more on ..
Its a while since I posted so forgive me. I moved to Ireland and am busy trying to carve a living in a desolate place, as well as fixing up an old house... Anyway, I have a gem to share with you. I have picked up a little work doing condition reports for a local contractor. If you have read this on my blog already, again please forgive me|!
I wanted to stick this one on here as I almost walked past it... Its a TT supplied church hall. Notice anything?
Mmmm metal board with RCD main switch so board is an exposed conductive part and no RCD protection..... nice one! Of course it is worse than that. The loop impedance is around 40ohms so if a tail did somehow chafe through, a grand total of 6A would flow around the earth fault loop...
I= V/Z = 240/40 =6A
(teaching mode here sorry!) This will flow .... for ever!
Of course this 6A would generate near mains voltage on the board ( sorry, teaching again) .... taking the line side impedance as say 1 ohm and the earth 39ohm . The voltage on the board would be...
V=IxR = 6x 39 = 234V
Of course it gets worse again.... as the 234V would be transmitted to the earth bar bolted to the metal board and every bonding conductor and cpc in the church hall. Talk about being nearer to God...
Once more, I am sorry for not posting at all for so long.. Ireland is riddled with stuff like this, so I may stick some more on ..
