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Re: Mcb's used as functional switches? #143744 09/02/05 06:20 PM
Joined: May 2004
Posts: 186
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aland Offline OP
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Mxslick, these sound a lot like our type D breakers the tripping charecteristic is something like 20-25 times In for instant tripping hence they withstand the initial surge of a heavy load switching on. Dont think the mechanics of the breaker are any differennt though; so ausies point about the switching endurance probably still has to be considered. Thanks to everyone for the comments. Aland

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Re: Mcb's used as functional switches? #143745 09/03/05 08:29 AM
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Posts: 2,455
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Texas_Ranger Offline
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Don't think so. There are dedicated switches that look like MCBs though.

Re: Mcb's used as functional switches? #143746 09/03/05 10:13 AM
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Posts: 186
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aland Offline OP
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Texas_Ranger, I stand corrected never seen anything like that, do they still have all the electrical and mechanical charecteristics of a normal Mcb then? Who makes them? Aland.

Re: Mcb's used as functional switches? #143747 09/04/05 10:04 AM
Joined: Sep 2005
Posts: 20
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TeesdaleSparkUK Offline
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I agree with the comments about Emergency Lighting. I have done a PIR where MCBs are used as functional switching and, although I think its not good practice, have considered that it does not contravene the Wiring Regulations.

I looked at Merlin Gerin data sheets and they say that their MCBs are good for 20000 operations on load.

PS
133-01-01 States "Good workmanhip and proper materials shall be used." So could you say using a MCB as a functional switch is not good workmanship?

[This message has been edited by TeesdaleSparkUK (edited 09-04-2005).]

[This message has been edited by TeesdaleSparkUK (edited 09-04-2005).]

[This message has been edited by TeesdaleSparkUK (edited 09-04-2005).]

Re: Mcb's used as functional switches? #143748 09/04/05 11:12 AM
Joined: May 2004
Posts: 186
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aland Offline OP
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TeesdaleSparkUK, Hi, and welcome to ECN, thanks for the info. Good points you raise, never thought of looking up the number of operations recomended by manufacturers. This seemed to be a popular practice in pubs and clubs a few years back apparently. I see the bigest problem as the fact that the E-lighting is on seperate circuit and is not going to operate unless a complete failure of the mains occures. That and many other things were the reasons for the unsatisfactory status on the P.I.R. Thanks again aland

Re: Mcb's used as functional switches? #143749 09/04/05 11:47 AM
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Posts: 54
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britspark Offline
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Trumpy,
within the building/environmental codes and the local fire officer,

emergency lighting must be fed via the local lighting circuit, not on it own MCB.

if the lighting fails within an area the emergency lighting must be available for egress from that part of the property.

scenario;
power fails to general (local) lighting in the main bar area, emergency lighting is emergised via its own back up batteries, (for Single Point Units only.
if the feeder for the emergency lighting is fed from another breaker it will still be energised and not running on its own batteries.

but thinking on this;
if the fittings are Maintained, IE, lamps lit at all material times, then that would probably be ok.

but with the cost of a Non Maintained fitting being about £14.00 and the cost of a MAintained fitting being about £21.00 most of the clients that i know would go for a Non Maintained fitting all the time, Due to them being tight.!

i personallay prefer MAintained fittings every were, due to the fact if the lamp aint lit its usualy faulty!!

Emergency lighting facts: supply on.
Non Maintained, lamp off battery charging
Maintained, lamp on battery charging

supply off
Non Maintained, lamp on
Maintained, lamp on

this is for single point units only.

Central Battery Systems are totaly different!!

Britspark

Re: Mcb's used as functional switches? #143750 09/04/05 06:25 PM
Joined: Dec 2001
Posts: 2,455
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Texas_Ranger Offline
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Quote
do they still have all the electrical and mechanical charecteristics of a normal Mcb then? Who makes them?

No, they're just ordinary switches, without any tripping mechanism, only built for DIN rail mounting.
I think most breaker manufacturers also do switches, I've found them at the ABB web site, without any specific model # though. They're listed under 'modular DIN rail components'.
I never used them personally, but I've seen some old Austrian F&G brand and I read a rather hefty discussion at a German board which concluded using MCBs as switches is _not_ up to code since the frequent operation _might_ wear it out to a point where it wouldn't trip on faults any more. From personal experience I can say nuisance tripping is much more likely.

Re: Mcb's used as functional switches? #143751 09/04/05 08:05 PM
Joined: May 2004
Posts: 186
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aland Offline OP
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Texas, if these devices do not have any charecteristics of a circuit breaker you still need a fuse or mcb in line with them. Cant quite see the advantage over a normal switch. other than they are din rail mounted. Thanks for the info though. aland

Re: Mcb's used as functional switches? #143752 09/05/05 10:23 PM
Joined: Jun 2005
Posts: 12
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Spock Offline
Member
Master switch is common in many large common areas, have seen them particularly in teaching labs and classrooms. Usually i have wired them as a switch or mushroom button feeding a contactor on the load side of the c/b.

I would suggest that use of a c/b as a switch may lead to contact welding, dependant on load or more likely internal failure causing an open circuit.

Re: Mcb's used as functional switches? #143753 09/06/05 08:28 AM
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Posts: 2,455
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Texas_Ranger Offline
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Quote
Texas, if these devices do not have any charecteristics of a circuit breaker you still need a fuse or mcb in line with them. Cant quite see the advantage over a normal switch. other than they are din rail mounted.

That's the problem! The only advantage is you can fit them inside the panel and don't need extra switches. Might be easier to handle all the wires for larger switching asse,blies in a DIN rail panel instead of usual switch boxes. Of course you need an MCB in line.
At some hotels I've seen electricians put in sigle row or even two row panels with switches next to the door in bigger rooms because it's easier to install than let's say 10 individual light switches.

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