Late 50s(?) domestic electrical distribution boards - Page 4 - UK Vintage Radio Repair and Restoration Discussion Forum

Ed_Dinning · 7th Apr 2015, 9:31 pm

Hi Most meters measure the current in the phase (live) conductor and the neutral is simply a link and low current connection to the voltage coil.
Done this way it will discourage anyone trying to shunt or bypass the current coil and reduce the electricity bill and they could get a severe shock.

Ed

hannahs radios · 8th Apr 2015, 12:17 am

Yes that's what I was trying to get across in my earlier post I don't think its a common arrangement just something the pocos do to save on a bit of wire

teetoon · 8th Apr 2015, 12:33 am

Re post 60,
Hi John, that Wylex probably dates from the late 60's and is not an RCD but an Earth Leakage Trip. It's also rated at 100ma so not up to modern regs.

David.

thermionic · 8th Apr 2015, 6:46 am

That is certainly an RCD. These Wylex RCDs first appeared in the mid 1970's and we're very good quality. This style was available into the 1990s.

You are correct identifying that its rated tripping current is 100mA, so in this situation where it is probably protecting 13 amp socket outlets, would not comply.

SimonT

teetoon · 8th Apr 2015, 7:35 pm

Oops. I missed the Current Operated bit there. I won't make the excuse that it was late, more a case of failing eyesight

.

David.

McMurdo · 9th Apr 2015, 12:12 am

100mA would be fitted to guard against a poor earth loop resistance or fire, a bit like a voltage operated ELCB. 30mA of course is the maximum for personal shock protection but wouldn't have been mandatory when that Wylex was installed.
When installing 3 phase with earth rod in the early 90's I used a T300mA RCD as the mains incomer and then local 30mA RCDs for all final circuits.

mole42uk · 9th Apr 2015, 9:10 am

That isn't an RCD - It's an ELCD (Earth Leakage) which is not current under the 17th Ed!

ELCD's this old are usually useless for their specified purpose as well, just try testing the trip time on one!!

G6Tanuki · 9th Apr 2015, 9:42 am

ELCDs often also fail to trip if there's a fortuitous additional low-resistance path from the earth of the domestic wiring to another well-earthed conductor. A good example being when you have an immersion-heater which someone has wired up using a 13-amp plug plugged into an ELCB-protected ring-main socket, as I discovered some years back.

ELCBs also don't play well with amateur radio RF earth connections.

McMurdo · 9th Apr 2015, 7:42 pm

I think RCD and current-operated earth leakage circuit breaker are names for the same thing

7th Apr 2015, 9:31 pm	#61
Ed_Dinning Dekatron Join Date: Jan 2004 Location: Newcastle upon Tyne, Tyne & Wear, UK. Posts: 8,194	Re: Late 50s(?) domestic electrical distribution boards Hi Most meters measure the current in the phase (live) conductor and the neutral is simply a link and low current connection to the voltage coil. Done this way it will discourage anyone trying to shunt or bypass the current coil and reduce the electricity bill and they could get a severe shock. Ed

8th Apr 2015, 12:17 am	#62
hannahs radios Hexode Join Date: Jan 2012 Location: Weymouth, Dorset, UK. Posts: 422	Re: Late 50s(?) domestic electrical distribution boards Yes that's what I was trying to get across in my earlier post I don't think its a common arrangement just something the pocos do to save on a bit of wire

8th Apr 2015, 12:33 am	#63
teetoon Heptode Join Date: Dec 2010 Location: Barnstaple, N.Devon, UK. Posts: 557	Re: Late 50s(?) domestic electrical distribution boards Re post 60, Hi John, that Wylex probably dates from the late 60's and is not an RCD but an Earth Leakage Trip. It's also rated at 100ma so not up to modern regs. David.

8th Apr 2015, 6:46 am	#64
thermionic Heptode Join Date: Apr 2003 Location: Cornwall, UK. Posts: 988	Re: Late 50s(?) domestic electrical distribution boards That is certainly an RCD. These Wylex RCDs first appeared in the mid 1970's and we're very good quality. This style was available into the 1990s. You are correct identifying that its rated tripping current is 100mA, so in this situation where it is probably protecting 13 amp socket outlets, would not comply. SimonT __________________ The honesty of imperfection..........

8th Apr 2015, 7:35 pm	#65
teetoon Heptode Join Date: Dec 2010 Location: Barnstaple, N.Devon, UK. Posts: 557	Re: Late 50s(?) domestic electrical distribution boards Oops. I missed the Current Operated bit there. I won't make the excuse that it was late, more a case of failing eyesight. David.

9th Apr 2015, 12:12 am	#66
McMurdo Dekatron Join Date: Jun 2009 Location: Staffordshire Moorlands, UK. Posts: 5,269	Re: Late 50s(?) domestic electrical distribution boards 100mA would be fitted to guard against a poor earth loop resistance or fire, a bit like a voltage operated ELCB. 30mA of course is the maximum for personal shock protection but wouldn't have been mandatory when that Wylex was installed. When installing 3 phase with earth rod in the early 90's I used a T300mA RCD as the mains incomer and then local 30mA RCDs for all final circuits. __________________ Kevin

9th Apr 2015, 9:10 am	#67
mole42uk Nonode Join Date: Aug 2010 Location: Resolven, Wales; and Bristol, England Posts: 2,608	Re: Late 50s(?) domestic electrical distribution boards That isn't an RCD - It's an ELCD (Earth Leakage) which is not current under the 17th Ed! ELCD's this old are usually useless for their specified purpose as well, just try testing the trip time on one!! __________________ Richard Index: recursive loop: see recursive loop Last edited by mole42uk; 9th Apr 2015 at 9:11 am. Reason: spelling

9th Apr 2015, 9:42 am	#68
G6Tanuki Dekatron Join Date: Apr 2012 Location: Wiltshire, UK. Posts: 13,995	Re: Late 50s(?) domestic electrical distribution boards ELCDs often also fail to trip if there's a fortuitous additional low-resistance path from the earth of the domestic wiring to another well-earthed conductor. A good example being when you have an immersion-heater which someone has wired up using a 13-amp plug plugged into an ELCB-protected ring-main socket, as I discovered some years back. ELCBs also don't play well with amateur radio RF earth connections.

9th Apr 2015, 7:42 pm	#69
McMurdo Dekatron Join Date: Jun 2009 Location: Staffordshire Moorlands, UK. Posts: 5,269	Re: Late 50s(?) domestic electrical distribution boards I think RCD and current-operated earth leakage circuit breaker are names for the same thing __________________ Kevin