IET logo
 
IET
Decrease font size
Increase font size
Topic Title: RCBO reliability vs separate RCD MCB
Topic Summary: RCBO vs RCD+MCB
Created On: 19 January 2013 06:53 PM
Status: Post and Reply
Linear : Threading : Single : Branch
Search Topic Search Topic
Topic Tools Topic Tools
View similar topics View similar topics
View topic in raw text format. Print this topic.
 19 January 2013 06:53 PM
User is offline View Users Profile Print this message


Avatar for M.Joshi.
M.Joshi

Posts: 212
Joined: 10 January 2003

It would be interesting to know the long-term reliability of RCBOs compared with a separate RCD and MCB?

From recent experience, have you found that you are going back to replace more faulty RCBOs than RCDs/MCBs?

It just seems that combining the function of both into a narrow single DIN slot where a RCD+MCB would take up 3 DIN slots may lead to a higher failure rate?

Are there any particular brands of RCBOs which you have found more reliable?

-------------------------
M.I.E.T - Forfeited this due to The I.E.T's ridiculous membership rules!
 19 January 2013 07:01 PM
User is offline View Users Profile Print this message


Avatar for sparkiemike.
sparkiemike

Posts: 1552
Joined: 24 January 2008

I have had failures on MK and Wylex RCBOs so have moved over to Hager, time will tell.
 20 January 2013 06:40 AM
User is offline View Users Profile Print this message



normcall

Posts: 8164
Joined: 15 January 2005

You are not actually comparing like with like, are you?
RCBO are generally a single pole overload device combined with a single pole earth fault device.
The separate option is still a single pole overload with a double pole out of balance device.

Faulty RCD is generally an easy on site test. A faulty mcb is a much more difficult test on site apart from go/no go.

Me? I'm still the separate protection camp leader.

-------------------------
Norman
 20 January 2013 11:43 AM
User is online View Users Profile Print this message


Avatar for ebee.
ebee

Posts: 5781
Joined: 02 December 2004

We`d never know if an MCB had failed to operate within the correct time would we?
If it failed open circuit we should know.
If it failed closed circuit we might not know.

If we accept a RCD failure rate is 7% (which includes those that do not trip at all plus those that do trip outside the permitted times) and we pluck a figure of 7% again for MCBs in our ignorance then the chances of either or both failing within one RCBO might be about 13.5%.

I`ve never heard of any great amount of testing of in service MCBs or fuses.
If there was it might well frighten us when we see the results.

-------------------------
Regards,
Ebee (M I S P N)

Knotted cables cause Lumpy Lektrik
 20 January 2013 12:06 PM
User is offline View Users Profile Print this message



Jaymack

Posts: 4755
Joined: 07 April 2004

Originally posted by: sparkiemike
I have had failures on MK and Wylex RCBOs so have moved over to Hager, time will tell.

It will indeed, but a survey would assist from forum contributors.

I had a Hager RCCB failure on Monday, an 80A, 30mA unit costing over £60 with V.A.T.

A 12 way DB with 2 RCDs in B and Q cost £65!

Regards

Changed RCBO for RCCB! Doh!

Edited: 20 January 2013 at 12:26 PM by Jaymack
 20 January 2013 08:47 PM
User is offline View Users Profile Print this message



jcm256

Posts: 1925
Joined: 01 April 2006

Please note Mr .Joshi that the correct name for a RCD should be RCCB (residual current operated circuit breaker) as this is the name for a device without integral overload protection. This has no reflection on your good self or any one else, the guidance note 3 or indeed the BS7671 does not set a good example of the correct expression for this device.

For comparison, last week looking at electrical installations, on very large of semi luxury blocks of flats (In Spain, how it was done) The consumer units for a two or three bedroom and two bathroom flat consists of two Flush mounted Seavi consumer units at head height one above the other. The main consumer unit has a 25 amp (C25) MCB double pole main switch feeding a 40amp 30Ma RCCB, mounted side by side on the DIN rail. All the circuits from the consumer units are protected with C rated double pole MCBs C16 for sockets, air conditioning, cooker, water heater etc,C10 for lighting etc. no electric showers, as loading must be under 25amps. CHNT MCBs is the make they use on this development anyhow. There will come a day when Electricity in the UK will be rationed likewise , otherwise like above we will pay a bigger charge if you want more.
 20 January 2013 09:06 PM
User is offline View Users Profile Print this message



peteTLM

Posts: 3217
Joined: 31 March 2005

Originally posted by: jcm256

Please note Mr .Joshi that the correct name for a RCD should be RCCB (residual current operated circuit breaker) as this is the name for a device without integral overload protection. This has no reflection on your good self or any one else, the guidance note 3 or indeed the BS7671 does not set a good example of the correct expression for this device.
.


so everyone in the world is wrong apart from you and crabtree then?/

-------------------------
----------------------------------------
Lack of planning on your part doesn't make it an emergency on mine....

Every man has to know his limitations- Dirty Harry
 20 January 2013 09:10 PM
User is offline View Users Profile Print this message


Avatar for M.Joshi.
M.Joshi

Posts: 212
Joined: 10 January 2003

jcm256 - thanks for pointing that out!

I did realise after posting the original post that I should have used the correct terminology but just used the common term of RCD in haste!

I knew somebody would correct it Cheers!

-------------------------
M.I.E.T - Forfeited this due to The I.E.T's ridiculous membership rules!
 21 January 2013 06:56 PM
User is offline View Users Profile Print this message


Avatar for OMS.
OMS

Posts: 19861
Joined: 23 March 2004

Nope - not locked JCM

-------------------------
Failure is always an option
 21 January 2013 07:12 PM
User is offline View Users Profile Print this message


Avatar for OMS.
OMS

Posts: 19861
Joined: 23 March 2004

Originally posted by: jcm256

Thanks,

still will not let me post. (What does the question ? mean on this thread)

Will try again tormorrow

Thanks again


Other than this one ?

OMS

-------------------------
Failure is always an option
 21 January 2013 07:18 PM
User is offline View Users Profile Print this message


Avatar for Rulland.
Rulland

Posts: 481
Joined: 11 April 2008

Lol@Oms

-------------------------
Those who make no mistakes do very little work!!......
 21 January 2013 08:20 PM
User is offline View Users Profile Print this message



jcm256

Posts: 1925
Joined: 01 April 2006

Other than this one ?

Strange, wont even let me preview the message (other than this one) must have wrote something controversial.
Well forget it good night.
 21 January 2013 08:51 PM
User is offline View Users Profile Print this message



AJJewsbury

Posts: 11699
Joined: 13 August 2003

Strange, wont even let me preview the message

What's the symptom? (error message? just keeps you waiting forever?)

From one location I use, the local firewall objects to any reply I post with a colon, bracket (i.e. smile) and exclamation mark in close association - apparently it's mistaken for an injection attack.

- Andy.
 21 January 2013 11:27 PM
User is offline View Users Profile Print this message


Avatar for M.Joshi.
M.Joshi

Posts: 212
Joined: 10 January 2003

Originally posted by: jcm256
(What does the question ? mean on this thread)


I just chose the question icon for the new thread instead of the default page icon to indicate the post is a question!

-------------------------
M.I.E.T - Forfeited this due to The I.E.T's ridiculous membership rules!
Statistics

See Also:



FuseTalk Standard Edition v3.2 - © 1999-2014 FuseTalk Inc. All rights reserved.