Settable C/Breaker

[GCE]

Hi

We are having a look at a COC inspection on a commercial building - There is a 400 Amp settable CB with a length of 185 sqmm cable feeding out.
The breaker can be set down to 350 Amp and the cable will be protected. SANS10142-1 table 6.4 pg 99
To me it is all legal and can be signed off
The argument in the workshop is that it is incorrect and that the cable should be sized to the maximum rating of the C/breaker .The setting down will be used purely to control the loading of the center.

Interested to hear what the feeling is on the forum.

[ians]

I would agree that the cable should be sized to the max rating...however...certain application due to design...fault levels or future upgrades could require a bigger breaker.

This could help solve the problem

https://www.schneider-electric.ca/en/faqs/FA103647/

[AndyD]

If the circuit breaker is not in the customers DB (accessible by a skilled person only) I'd say it was compliant if set correctly. If it's in the DB and accessible to the customer then, as per Ians link I'd say it was compliant if the adjustment panel on the breaker is sealed and required a tool to open and adjust. We usually use the old style wire and lead crimp tags because we have a tool that imprints an specific ID symbol into the tag but I guess even a cable strap would suffice.

[RegElec]

It will be interesting to see all the responses. I have had this in the past and am uncomfortable with a C/B which has been adjusted to accommodate the cable size. I have in the past come across instances where overloads have been turned up beyond the motor rating by 'electricians' to prevent the overload from operating instead of finding out the reason for the trip and it would be safe to say that there is no reason why this wouldn't occur with a C/B either.

[AndyD]

I think you can't stop stupidity or malice by legislation. A qualified sparky has got a duty of care not to exceed cable or motor current limits, if he ignores that duty of care he needs to be held accountable.

[ians]

It will be interesting to see all the responses. I have had this in the past and am uncomfortable with a C/B which has been adjusted to accommodate the cable size. I have in the past come across instances where overloads have been turned up beyond the motor rating by 'electricians' to prevent the overload from operating instead of finding out the reason for the trip and it would be safe to say that there is no reason why this wouldn't occur with a C/B either.

People disconnect the earth wire to prevent the e/l unit from tripping...people replace 20 amp breaker with 30 amp breakers because the 20 amp trips when they plug in a kettle...toaster and iron...or back in the day when big bang aircons started...they would trip breakers... so instead of installing a 20 amp D cure or curve 1 breaker...they didnt know any better ...so a 30 or 35 would do the trick...but that is not what i have seen burn houses down.

the last granny flat i visited after it almost burnt to the ground...the fire started at a connector block below the aircon ...used to extend the cable to reach a plug 5 metres away...lucky for the person sleeping in the room...the unit exploded which blew it across the room...waking the lady up...which saved her life.

i find when you get to the bigger stuff like adjustable breakers...the level of competency of the electricians working in that area is higher...we have a respect for the stuff because if you work in that kind of environment...good chance you have already seen the result of dumb actions...if you are still alive.

make no mistake there are way too many unskilled and inexperienced people working out there...we just have to do our best to stay on the straight and narrow.

[Darking]

If a fuse blows, fit a bigger one? Wondering how many fires resulted.

[GCE]

Hi

Still busy contemplating the dynamics around settable circuit breakers and found this under fundamentals 5.4.3 - Thought the "likely to be subjected to" kind of throws a curved ball when we basically expect everybody after us to be careless .
Was extremely happy to find 6.7.2.4 which gives us some protection if we do as Andy and Ians suggested further up


[B]5.4.3 Current[/B]
The equipment shall be suitable for operation at the maximum steady
(r.m.s.) current to which it is likely to be subjected. It shall also be able to
carry the current that is likely to flow under abnormal conditions and for the
period that the current is likely to flow.
NOTE The period that an abnormal current will flow is equal to the operating time of
any protective device

[B]6.7.2.4 [/B]Protective devices that have adjustable overload settings shall only
be used if the means of adjustment is not accessible without the use of a
tool and the adjustment can only be made by means of a tool.

[ians]

I think you can't stop stupidity or malice by legislation. A qualified sparky has got a duty of care not to exceed cable or motor current limits, if he ignores that duty of care he needs to be held accountable.

which country do you live in?

[ians]

Hi

Still busy contemplating the dynamics around settable circuit breakers and found this under fundamentals 5.4.3 - Thought the "likely to be subjected to" kind of throws a curved ball when we basically expect everybody after us to be careless .
Was extremely happy to find 6.7.2.4 which gives us some protection if we do as Andy and Ians suggested further up


[B]5.4.3 Current[/B]
The equipment shall be suitable for operation at the maximum steady
(r.m.s.) current to which it is likely to be subjected. It shall also be able to
carry the current that is likely to flow under abnormal conditions and for the
period that the current is likely to flow.
NOTE The period that an abnormal current will flow is equal to the operating time of
any protective device

[B]6.7.2.4 [/B]Protective devices that have adjustable overload settings shall only
be used if the means of adjustment is not accessible without the use of a
tool and the adjustment can only be made by means of a tool.

thank goodness we live in an era where technology has progressed so far that it is possible to to take pics and time stamp them with a hand held device which you carry in your pocket on a daily basis...set the device...take a pic... record it on a COC and walk away.