The Electrical Contractor Network

ECN Electrical Forum
Discussion Forums for Electricians, Inspectors and Related Professionals

Books, Tools and Test Equipment for Electrical and Construction Trades

Register Now!

Register Now!

We want your input!


2017 NEC and Related
2017 NEC
Now Available!

Recent Posts
Speaking of Plugmold ...
by gfretwell
10/17/16 02:37 PM
Broken battery charger? Check for cobwebs!
by gfretwell
10/17/16 02:30 PM
Son of Sparky
by gfretwell
10/16/16 07:53 PM
230 or 345 kV transmission lines?
by annemarie1
10/12/16 01:23 PM
Is this a fix or just a bandaid?
by gfretwell
10/10/16 06:49 PM
New in the Gallery:
12.5A through 0.75mm˛ flex (just out of curiosity)
Shout Box

Top Posters (30 Days)
gfretwell 11
renosteinke 6
ghost307 5
HotLine1 5
Potseal 4
Who's Online
1 registered (hyetal), 285 Guests and 4 Spiders online.
Key: Admin, Global Mod, Mod
Topic Options
Rate This Topic
#193924 - 04/28/10 03:42 PM Failure rate of RCDs
C-H Offline


Registered: 09/17/02
Posts: 1508
Loc: Stockholm, Sweden
The Danish authorities have undertaken a large study of the realibility of RCDs in which hundreds of installations have been tested. From 2 to 10% of the units were found not to work as intended. Some passed the test button test, but failed to work when tested with proper equipment test. The failure rate was found to increase with age and brand name products were not immune to failure.

A comprehensive report in English is available at:

Test Equipment:

Large Selection of Test Equipment For Electrical, HVAC, Test & Measurement
Large Selection of Test Equipment For Electrical, HVAC, Test & Measurement

#193925 - 04/28/10 04:06 PM Re: Failure rate of RCDs [Re: C-H]
Wolfgang Offline

Registered: 09/25/05
Posts: 154
Loc: the very West of Germany
The main problem, I see, is not a failure rate of 10% after 10 years, because we can easily check these devices (as electricians), but what about fuses or breakers. There are so many out there, aged 30 or 40 years, but nobody can tell whether they will trip at the correct overcurrent value after such a long time.

#193936 - 04/29/10 07:05 AM Re: Failure rate of RCDs [Re: Wolfgang]
Texas_Ranger Offline

Registered: 12/17/01
Posts: 2331
Loc: Vienna, Austria
I haven't seen to many failed RCDs so far, and most failed on the safe side - tripped and couldn't be reset any more. Only one or two refused to trip, on one even the test resistor blew up spectacularly.

Same goes for MCBs, but I did encounter one very old range (Schrack HLS, manufacturing date stamp 1960) that refused to trip as a whole. There were a few dead shorts (faulty light socket) but the MCBs (10A H curve) never tripped before the 20A gL main fuse blew.

#193941 - 04/29/10 11:20 PM Re: Failure rate of RCDs [Re: Texas_Ranger]
frenchelectrican Offline


Registered: 02/06/03
Posts: 938
Loc: Wi/ Paris France { France for ...
I haven't run into too many RCD failure in France unless you got a Le Cheapie or butched work on the RCD unit.

Yeah we do test the RCD but with older units it pretty tricky to get set up to function properly.

But with nice hevey bolted fault circuit then it is good time to replace the RCD I have deal with that due once you reset it it will never function correct.

Pas de problme,il marche n'est-ce pas?"(No problem, it works doesn't it?)


ECN Electrical Forums - sponsored by Electrical Contractor Network - Electrical and Code Related Discussion for Electrical Contractors, Electricians, Inspectors, Instructors, Engineers and other related Professionals