Busbar at the top or bottom of the circuit breaker

**Isetech** · 05-Jun-22, 07:30 AM

After watching a few circuit breaker videos, something I noticed about the construction of the breaker, which could be the deciding factor, but then how would a non polarised breaker work ?

A circuit breaker has a short circuit and and overload protection and a few other things to consider, but we not going down that road. Keeping it in simple terms, the overload protection is achieved using a a strip which bends according to temperature and overload protection is achieved by using a coil and sleeve.

The way I would see how they might select line and load would be by the side the protective devices are installed: ie if the coil and strip is is connected to the bottom terminal then that terminal would be the load, if connected to the top, that terminal would be load.

Then we have the arc shutter, this could be what determines the line and load?

I find that in SA we just do as we are told, people make rules and everyone follows blindly. As pointed out in anther thread, one person can influence an entire industry (geyser connected to than ELU) , not that the info could be incorrect, just the fact that there are not enough people with the knowledge to dispute the recommendation. Like the ZA plug rule, how on earth did that regulation even get past the suggestion box? A quick trip to the local appliance store would have cleared up that silly reg. The only time you will see me installing more than 2 ZA sockets in a room, would be at tables in a restaurant. For that application I give it the thumbs up, why because 90 % of the people who go to the Mugg and Bean for example between 08:00 and 14.00 might plug in a laptop or phone, so a standard socket for the laptop and a ZA plug for the phone good idea, and that is it. My kitchen has 14 socket outlets of which 2 are ZA. I will be replacing another socket with one of those 6 x 2 pin in my charge cupboard because I dont need a standard socket in the cupboard, for charging devices only.

**Dylboy** · 03-Jun-22, 07:36 AM

I would, I would try Google for specs of the CB to see if any markings in manual as well.

Also would put a sticker stating line at bottom.

NB is to make sure ELU is wired correct as they are often line top and load bottom but other than that I think all fine.

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**Isetech** · 03-Jun-22, 07:52 AM

Originally Posted by Dylboy

I would, I would try Google for specs of the CB to see if any markings in manual as well.

Also would put a sticker stating line at bottom.

NB is to make sure ELU is wired correct as they are often line top and load bottom but other than that I think all fine.

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So we have a YES

Your comment about the ELU is interesting, if using a Hybrid inverter, and the power is feeding back in to the non essential DB which is fed via an ELU, would the ELU function correctly ?

**Dylboy** · 03-Jun-22, 07:56 AM

Ahhh interesting on the hybrid backfeeding.... It would not go through the ELU as would go straight to busbar... How ever the ELU does trip when i test but I need to draw this out now hahaha.

But good point on the now reverse fed now too ok markings...

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**Derlyn** · 03-Jun-22, 08:44 AM

The current is changing direction through all the breakers and the earth leakage 50 times a second irrespective of whether the supply is in the top or in the bottom.

Makes no difference.

Remember we talking AC. ( alternating current )

**Isetech** · 03-Jun-22, 10:40 AM

Originally Posted by Derlyn

The current is changing direction through all the breakers and the earth leakage 50 times a second irrespective of whether the supply is in the top or in the bottom.

Makes no difference.

Remember we talking AC. ( alternating current )

I am trying to understand why we waste time going in the top and out the bottom of devices which create more resistance (longer wires) waste time and wire.

So even if you still the busbar on the top of the circuit breaker, you could wire in the top of the mains isolator (which by the way was always installed in the bottom out the top) out the bottom a bridge from the bottom of the isolator to the bottom of the ELU, out the top and connect the busbar directly to the top of the ELU?

**Justloadit** · 03-Jun-22, 12:22 PM

Originally Posted by Derlyn

The current is changing direction through all the breakers and the earth leakage 50 times a second irrespective of whether the supply is in the top or in the bottom.

Makes no difference.

Remember we talking AC. ( alternating current )

True, however the mechanical construction of the circuit breaker will dominate the manner in which it is to be connected, such as which terminal with in the breaker will always have power, and how the arc is dispersed?
lets take a relay, do you connect live to the moving terminal and load to the stationary terminal?
or do you connect the live to the stationary terminal and the load to the moving terminal?

**Derlyn** · 04-Jun-22, 08:29 PM

Originally Posted by Justloadit

True, however the mechanical construction of the circuit breaker will dominate the manner in which it is to be connected, such as which terminal with in the breaker will always have power, and how the arc is dispersed?
lets take a relay, do you connect live to the moving terminal and load to the stationary terminal?
or do you connect the live to the stationary terminal and the load to the moving terminal?

Just checked all the relays I have in the workshop.
The moving terminals have no connections to the outside.
Much like a contactor, the moving connections either make or break the 2 stationary terminals.
It does not matter which stationary contact is used for line or load.

**Dylboy** · 04-Jun-22, 10:13 AM

Very interesting and good reminder that it osolates and not flows as we always think flow like DC.

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**Isetech** · 05-Jun-22, 07:44 AM

This video tells it as it is for most of us tradesmen, there are a few exceptions, but I think most of us would agree, when we were stuck in an airconditioned room with some person rattling on about some crap out of a book, scribbling stuff of a whiteboard, most of us, were still trying to recover from the night out. there was a lot nodding

I learnt most of what I know today from on site experience and night school many years after I qualified. I got 14 % for N4 mathematics, once I settled done with a family, I went back to classes and got 89 %, it wasnt that I was stupid, I just had no interest in maths and classroom studies.

This video by the way is a really bad explanation of line and load, I just thought his comment at the beginning was appropriate for us tradesmen. Please feel free to add a video with a decent explanation of why a circuit breaker/device has line and load.

https://www.youtube.com/watch?v=N3vu...nel=HVACSchool