DC Circuit Breakers maximum load possible

Thread Starter

LHBTC

Joined Feb 11, 2015
13
Good Day Everyone.

What is the maximum current that a circuit breaker could carry? What I understood from my readings is that every CB has its own percentage of the labelled rating. i.e. if the breaker rating is 32Amps, the maximum load to be attached to it must not exceed 25.6Amps if percentage is 80%, 32Amps if the percentage is 100% and 38.4Amps if the percentage is 120%.

I am not an Electrical Engineer so please clarify if what I got is correct, what the official term for that percentage and how to find it?

The attached picture is one of my important breakers that I want to find that for.
 

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tranzz4md

Joined Apr 10, 2015
310
Not a good pic.

The manufacturer publishes the information you're seeking. It may well be available online. The load it will carry without tripping is time dependant.

You will need to know the exact part or catalog number of the breaker you are dealing with to find the correct information.

Please be careful.
 
I'm not going to be much help either, but I might be some help. There has to be some hidden numbers on the side of the whatever to help.

I can tell you where the 80% might come from. The NEC (National Electric Code) in the US is the bible, but not the full word. The AHJ or (Authority Having Jurisdiction) can place extra limitations on how stuff is wired.
This is 240 AC and it could be a panel or whatever. Test monthly may be a residual current type of breaker. (GFCI or RCB) depending on where in the world you are.

A few comments:
There are time/trip curves for breakers. They usually can support 100% of the rated load forever without tripping. So, a 30 A breaker will pass 30 amps forever, but might only pass 40 A for 0.1 seconds and a 100 A for 0.01 s.

When wiring "stuff" like homes usuallly numbers like 3%, 80% and the notion of "continuous" show up if we ignore motors. "continuous" might be an electric oven in a restaurant, but not a home. Once you get through the "continuous" definition we would like no more than a 3% drop in voltage when the voltage reaches the load. That puts a boundry on the thickness of the wire and so does the breaker value. So, a circuit is never loaded more than 80% of capacity of the "continuous" loads.

A bathroom might have a outlet for a hair dryer which is high wattage intermittent load. but it may have otjer requirements like GFCI protected, 20A 120 V should exist in the bathroom.

Don't add up the breaker totals to get capacity of the panel.

Temperature, number of current carrying wires in a raceway can also de-rate the allowances,

So, for a typical house in the US, the standard 120 V receptacle can be 15 A or 20 A and it;s wired with NM-B cable. The outer jacket color is, I believe, yellow for 12 Awg,

But if you want a 20 A circuit in a detached barn 300 feet away using UF cable, you get new rules to follow.

You can read the NEC code online for free, but no copying or printing.
 

be80be

Joined Jul 5, 2008
2,058
80% is a rule of thumb type of thing.
But some breakers are way better then the rest you have to look up the datasheet on them.
 

Thread Starter

LHBTC

Joined Feb 11, 2015
13
Thanks dears for the valuable answers.

two information pieces may slipped my mind when I wrote this thread:

1- This is for a DC servers.
2- I don't have anything other than the information written in the breaker, so how can I get its datasheet (and specifically the time/trip curves as @KeepItSimpleStupid mentioned).
 

Reloadron

Joined Jan 15, 2015
6,225
This is your circuit breaker. I suggest you contact the manufacturer for a complete data sheet or with any product specific questions you may have. The link only makes mention of:
Product Description
1 Technical data

·Rated Current(In) 6,10,16,20,25,32,40A
·Rated Voltage(Un) 230VAC/240VAC
·Breaking capacity 6kA
·Rated Tripping Current 30mA,100mA,300mA
·Type AC,A
·Characteristic B,C
·Number of Poles 1P+N
·Type of Terminal Lug type
·Termianl Capacity cable up to 25mm2
·Width 18mm/module
·Standards IEC61009,EN 61009
·Certification CB,SEMKO

There is a contact us link at the bottom of the page, you may want to use that with any questions on your specific circuit breaker.

Ron
 

tranzz4md

Joined Apr 10, 2015
310
Well, you've been quite lucky so far, you've gotten these responses, particularly from Reloadron, as he did your small task for you.

If you still cannot understand how to obtain the data, how did you ever get online and find this website, and post your question? How would you know how to look at the data? What are you calling "D.C. Servers"? Your questions appear to be insincere, and you won't understand accurate or even generalized answers (like these you've been given)?

Undoubtedly some others will give their answers to my questions, but these questions are for YOU, LJBTC to answer!
 

mcgyvr

Joined Oct 15, 2009
5,394
The breakers shown are not suitable for DC and are intended/rated for AC use only..
So the answer is 0 Amps or 0% as that breaker cannot be used at all and as such shall not carry any DC current..
 

Thread Starter

LHBTC

Joined Feb 11, 2015
13
The breakers shown are not suitable for DC and are intended/rated for AC use only..
So the answer is 0 Amps or 0% as that breaker cannot be used at all and as such shall not carry any DC current..
There is a misunderstanding propably because of me.

I meant Data Center by DC, not DC power.
 

Thread Starter

LHBTC

Joined Feb 11, 2015
13
This is your circuit breaker. I suggest you contact the manufacturer for a complete data sheet or with any product specific questions you may have. The link only makes mention of:
Product Description
1 Technical data

·Rated Current(In) 6,10,16,20,25,32,40A
·Rated Voltage(Un) 230VAC/240VAC
·Breaking capacity 6kA
·Rated Tripping Current 30mA,100mA,300mA
·Type AC,A
·Characteristic B,C
·Number of Poles 1P+N
·Type of Terminal Lug type
·Termianl Capacity cable up to 25mm2
·Width 18mm/module
·Standards IEC61009,EN 61009
·Certification CB,SEMKO

There is a contact us link at the bottom of the page, you may want to use that with any questions on your specific circuit breaker.

Ron
I have tried to contact them but with no answer from them.
 

Reloadron

Joined Jan 15, 2015
6,225
I have tried to contact them but with no answer from them.
Then I would suggest multiple email attempts. The only data to be had is what I , you and everyone else can see online. They make it pretty clear:
"We appreciate your visit to our website. We are interested in knowing your opinion and we’ll be glad to answer any questions you might have. Please do not hesitate to contact us with any of our offices".

While many China based companies are good to deal with I avoid them all for the most part for the very reasons you are experiencing. When designing systems I wanted to use parts with a high availability and needed data sheets for all the sub assemblies I used. When they fail to respond to inquiries you, the end user, is pretty much left out in the cold.

Ron
 

JohnInTX

Joined Jun 26, 2012
4,602
Here's what I see from the picture. It is manufactured by TECS (not Air-Safe). It is rated at 32A 240VAC with a 'C' class Trip Characteristic curve. It will break a 6000 amp overload. It also incorporates Residual Current Detection (ground fault detection) set at 300ma, a standard value for industrial installations. Here is a short form catalog showing what the C curve looks like and it explains a bit about the 300ma RCD. The C curve is shown on pp4. and shows that some de-rating is necessary as the breaker will eventually pop at 100% of rated current. That is typical of a thermal/magnetic breaker.

Wikipedia has some general info:
https://en.wikipedia.org/wiki/Circuit_breaker#Standard_current_ratings

The Schneider Electric document has detailed information about trip characteristics, derating etc. ABB has good info about the RCD detection. There is lots of other info if you google 'C' curve circuit breakers etc.

Good luck!
 

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