# Is have larger wire size can make circuit braker trip more fast ?

#### meowsoft

Joined Feb 27, 2021
607
Is have larger wire size can make circuit braker trip more fast ?
Example : use 35a wire for 16a load

#### ElectricSpidey

Joined Dec 2, 2017
2,636
It could if the branch circuit conductor was underrated in the first place.

#### ronsimpson

Joined Oct 7, 2019
2,796
Under a short condition, a larger wire will have less resistance and conduct more current, so probably the breaker will trip faster.

Another way to think about it. (not a short condition)
1)10A breaker. 10.1A load, 16A wire, voltage loss because of the wire is 10 volts, the breaker pops in 5 minutes.
2)10A breaker, 35A wire so the loss in the wire will be less so lets say there is 5 volts loss in the wire, so the voltage on the load is higher by 5 volts than in example (1), so the load is 10.6A. Now the breaker will pop in 2 minutes.
3) 10000A wire, wire loss is almost nothing, voltage on the load is higher, current is 11.1A and the breaker pops in 30 seconds.

#### GetDeviceInfo

Joined Jun 7, 2009
2,180
Generally, your wire and O/C are sized together. Increasing your wire size will not alter the characteristics of the breaker. It may however influence other components of the circuit. Some code calculations are based on wire size, and changing it in one section may dictate that it must be changed in others, as well as ratings for devices. Feeders are an example. There are many types of breakers with varying characteristics, depending on the load requirements and required protection schemes.
Regardless, you should be able to view the data from your specific breaker and make a logical deduction about what you ask.

#### meowsoft

Joined Feb 27, 2021
607
Under a short condition, a larger wire will have less resistance and conduct more current, so probably the breaker will trip faster.

Another way to think about it. (not a short condition)
1)10A breaker. 10.1A load, 16A wire, voltage loss because of the wire is 10 volts, the breaker pops in 5 minutes.
2)10A breaker, 35A wire so the loss in the wire will be less so lets say there is 5 volts loss in the wire, so the voltage on the load is higher by 5 volts than in example (1), so the load is 10.6A. Now the breaker will pop in 2 minutes.
3) 10000A wire, wire loss is almost nothing, voltage on the load is higher, current is 11.1A and the breaker pops in 30 seconds.
What's if we use NH fuse ? It is more instantly cut the circuit ?

#### meowsoft

Joined Feb 27, 2021
607
Under a short condition, a larger wire will have less resistance and conduct more current, so probably the breaker will trip faster.

Another way to think about it. (not a short condition)
1)10A breaker. 10.1A load, 16A wire, voltage loss because of the wire is 10 volts, the breaker pops in 5 minutes.
2)10A breaker, 35A wire so the loss in the wire will be less so lets say there is 5 volts loss in the wire, so the voltage on the load is higher by 5 volts than in example (1), so the load is 10.6A. Now the breaker will pop in 2 minutes.
3) 10000A wire, wire loss is almost nothing, voltage on the load is higher, current is 11.1A and the breaker pops in 30 seconds.
I think circuit breaker specifically MCB is not really safe...

#### MisterBill2

Joined Jan 23, 2018
16,582
A proper circuit breaker has a defined overload versus time characteristic and so the wire size, as long as it is at least adequate, will not have an effect worth considering. So using 20 amp wire on a circuit with a 15 amp breaker provides no benefit, except if there is a need to change to a 20 amp breaker in the future.
Of course, this is assuming that copper wire is used.
With aluminum wire there may be some benefit in using 30 amp wire for a 10 amp circuit, if the proper connection arrangements are used. That mmay tend to reduce the wire heating somewhat.

#### GetDeviceInfo

Joined Jun 7, 2009
2,180
I think circuit breaker specifically MCB is not really safe...
Safe for what, human interaction or circuit protection.

#### Papabravo

Joined Feb 24, 2006
20,607
Only if the breaker was intelligent enough to know what size wire you had. It only uses what's inside to make it's determination

#### shortbus

Joined Sep 30, 2009
10,038
I'm wondering what the TS implant is telling him?

Joined Jul 18, 2013
28,050
@meowsoft If you need fast release, use a fast sweep through fusing, the fastest is rectifier or semi-conductor type fusing.

#### meowsoft

Joined Feb 27, 2021
607
A proper circuit breaker has a defined overload versus time characteristic and so the wire size, as long as it is at least adequate, will not have an effect worth considering. So using 20 amp wire on a circuit with a 15 amp breaker provides no benefit, except if there is a need to change to a 20 amp breaker in the future.
Of course, this is assuming that copper wire is used.
With aluminum wire there may be some benefit in using 30 amp wire for a 10 amp circuit, if the proper connection arrangements are used. That mmay tend to reduce the wire heating somewhat.
It is copper not aluminium, aluminium is so bad, also difficult to find in my local area, minimum size is 10mm², and it's very large for office use, imagine you have 3x10mm² aluminium XLPE insulated wire under the table, also aluminium outlets it's hard to find

#### meowsoft

Joined Feb 27, 2021
607
Only if the breaker was intelligent enough to know what size wire you had. It only uses what's inside to make it's determination
Yes... it's good idea to install CT sensor with micro-controller and detect when something is shorted then trip a contactor coil / mccb with shunt trip ?

#### meowsoft

Joined Feb 27, 2021
607
Safe for what, human interaction or circuit protection.
Circuit protection, not human interraction, for example it outlet contact made from thin copper is burnt, or shorted that MCB can't cut power so instantly

#### meowsoft

Joined Feb 27, 2021
607
A proper circuit breaker has a defined overload versus time characteristic and so the wire size, as long as it is at least adequate, will not have an effect worth considering. So using 20 amp wire on a circuit with a 15 amp breaker provides no benefit, except if there is a need to change to a 20 amp breaker in the future.
Of course, this is assuming that copper wire is used.
With aluminum wire there may be some benefit in using 30 amp wire for a 10 amp circuit, if the proper connection arrangements are used. That mmay tend to reduce the wire heating somewhat.
No... I just wan to make installation with can properly used even degraded by age, so... I calculate maximum use of wire is about ~30%, if 10 years later capacity is degraded 15% that wire still only use ~38% capacity, it's very safe

#### MisterBill2

Joined Jan 23, 2018
16,582
My point in mentioning aluminum wire is that it has a number of different additional challenges. I do not ever recommend aluminum wire, nor components, for interior power wiring.

#### meowsoft

Joined Feb 27, 2021
607
My point in mentioning aluminum wire is that it has a number of different additional challenges. I do not ever recommend aluminum wire, nor components, for interior power wiring.
Ok... it is good idea for use aluminum wire for outdoor purpose ?, wind turbine ? generator set ?

#### MisterBill2

Joined Jan 23, 2018
16,582
Ok... it is good idea for use aluminum wire for outdoor purpose ?, wind turbine ? generator set ?
OUr utility companies use aluminum wire for distribution. It reaches as far as my house, where it transitions to the copper wire that I provided. I do not choose to use aluminum wire at all, anywhere. It is much more effort to make a good connection with it and so I do not recommend it anywhere.
IN another part of the world aluminum wire is used in new construction because the theft of copper wire is such a problem. I do not know how they avoid the well known problems that may result. Someplace here is the thread about that issue.