[Question] Busbar at the top or bottom of the circuit breaker

[Isetech]

This topic has been discussed on this forum in the past.

I am busy wiring up numerous distribution boards for a few different sites. I have given the customers the option of a cheapie and slightly better option, not quite ABB, but a product which has been around for a while (Hager).

I dont like using the standard copper Europa busbar at the top of the circuit breaker, I prefer the forked busbar, the reason it fits between the screw and clears the terminals for their intended use, the wire.

The problem is most din rail mounted circuit breakers are not designed to fit the busbar at the top. So the question I ask myself, should I not be using the product as per the manufacturers standard. I understand that we generally install the line in the top and the load out the bottom, but that is just because the old Heinemann type clip tray dominated the market.

Because in most cases, Heinemann are no longer the preferred supplier of circuit breaker, should we not be moving away from an old standard and wiring panels the way the breakers are designed to be wired?

I very bring wires in from the bottom of the panels, in fact I cannot tell the last time I did. 100% of the DB's I have wired in the past 10 years have all been top in the DB.

Another issue is making the nice neat loom around the side of back of the breakers, creates heat when you strap them all together.

What do you think, should we just stick to do it the old way just because CBI created the abnormal method?

Maybe you have proof that wiring a breaker into the top as the line and (out) the bottom (load) is in fact the correct method, please feel free to share.

Personally I think it time to start doing it right. It would make wiring DB's a lot neater, save money on wire and make fault finding a lot easier. There is nothing worse than trying to fault find over populated DB with a 4 terminal earth and neutral with 16 wires connected to them Yes there I am sure there is reg which indicated that you shouldn't be putting 4 or 5 wires in one terminal, especially if it is a certain size.

[Dylboy]

I agree... Once more all DIN I see in the UK is busbar at the bottom... I have been meaning to look at manufacturing specs of say Hager to see what they say as I also want to swop it and have the busbar at the bottom.

I have seen sometimes an ELU with Line and Load markings then that is what I follow but in a din CB I can not find such markings.

Also what is a Europa busbar ?

I am nieve with busbars and don't actually know what the diffrences are. I just call it "old stuff" and then "Din" hahaha.

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[Dylboy]

There is a reg somewhere about if we swop it then markings needs to be made clear and no confusion can be had basically.

With Din CB I never see markings of LINE and LOAD. Perhaps a nice sticker telling next oke that look it's swopped and that not illegal as reg number XYZ or read manufacturing specs...

Mounting sideways in SANS is not recommend and manufacturing specs too I believe but that needs to be consulted.

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[GCE]

Yes there I am sure there is reg which indicated that you shouldn't be putting 4 or 5 wires in one terminal, especially if it is a certain size

6.1.5 A maximum of three conductors may be connected to any one terminal
provided that the terminal has the correct rating.
NOTE Each neutral conductor exceeding 4 mm2 cross-sectional area should be
terminated in separate terminals to facilitate disconnection of any one neutral conductor
without disturbing the connection of any other neutral conductor.

6.6.1.10 If a conductor of cross-sectional area exceeding 4 mm2 is used, it
shall be so installed to allow any one neutral conductor to be disconnected
without disturbing the connection of any other neutral conductor.

[GCE]

Maybe you have proof that wiring a breaker into the top as the line and (out) the bottom (load) is in fact the correct method, please feel free to share.

Regulation pasted below basically answers the question.

I know of a contractor that lost his life on a D/board with reverse feed. Was a 3 000Amp supply with busbars onto the C/breakers top and bottom.
It was assumed after the investigation that it was the reverse feed that caught him and that his meter was possibly faulty when he tested as it was alongside him.

Most of the bigger frame C/Breakers are not marked line and load


6.8.2.3 Circuit-breakers, disconnectors and switch-disconnectors shall not be
mounted upside down. Horizontal mounting is allowed unless specifically
prohibited by the manufacturer.
Any deviation from the convention of connecting line to the top and load to the
bottom of switchgear is not recommended. Reverse connection is allowed
only if
a) it is specifically allowed by the manufacturer,
b) "load" and "line" are so marked that they are clearly visible during
maintenance, and
c) any contradictory marking is not visible after installation

[Isetech]

Any deviation from the convention of connecting line to the top and load to the
bottom of switchgear is not recommended. Reverse connection is allowed
only if
a) it is specifically allowed by the manufacturer,
b) "load" and "line" are so marked that they are clearly visible during
maintenance, and
c) any contradictory marking is not visible after installation

This is my point, the Hager circuit breaker only have the option to install a fork busbar at the bottom of the breaker, which means we are doing it wrong installing the busbar at the top?

ABB on the other hand have the option to install the busbar at the top and bottom.

CBI also have the option to connect the fork busbar at the top or the bottom.

I have just gone through a pile of circuit breakers and found something interesting, has anyone noticed the small hole at the bottom of the circuit breakers, never taskne not of it before, it looked like you could fit a straight busbar in to the slot, but when you tighten its doesnt secure the busbar. Now I need to find out what it is for.

[Isetech]

I made the mistake of assuming something many years ago, it almost cost me my life. That's why they teach you to test, test again, then lock out. It sounds like the guy who opened the door of the fridge, sat on the compressor to have lunch, the temp increased, the compressor switched on, he died instantly.

I had just qualified, I was working on a site, brand new to the industry private sector, the site manager, told me the panel was isolated, I stepped up reached for the red and blue busbars at the back of the panel to pull myself up, thank goodness there was no load on the panel yet. My first wake up call.

I recall most isolators were wired line in the bottom and load out the top, most of the old Heinemann main switches in domestic DB's are still wired like that, which is why I have wired many DB's with the line in the bottom of the main switch, out the top with a busbar across the top to save wiring into the top of the main switch, out the bottom, then another wire from the bottom of the to the top of the earth leakage, what a waste of time and wire, more room for error and loose connection.

My question - Do you agree with the way DB's are wired or would you prefer it wired, mains in the bottom of the main switch, out the top across to the top of the earth leakage unit, out the bottom and across to the bottom of all the breaker, just imagine how much time and wire and money you would save.

It just makes sense rather than the old backward method used by CBI

I know of a contractor that lost his life on a D/board with reverse feed. Was a 3 000Amp supply with busbars onto the C/breakers top and bottom.
It was assumed after the investigation that it was the reverse feed that caught him and that his meter was possibly faulty when he tested as it was alongside him.

Most of the bigger frame C/Breakers are not marked line and load

[Alfred M]

You get 2 types of circuit breakers polarized and non polarized. If curcuit breaker is marked line and load by manufacturer then it is a polarized curcuit breaker and must be connected accordingly. If there is no marking line or load by manufacturer it is an non polarized curcuit breaker so load or line can be connected top or bottom so with non polarized curcuit breakers busbar can be connected at the bottom and load out at top of curcuit breaker

[Isetech]

Lets simplify the question - If you are called out to a property to carry out an electrical test report and you remove the DB cover and find that the busbar is at the bottom of the non polarised circuit breakers.

Would you pass the installation YES or NO ?

[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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[Isetech]

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]

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]

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]

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?

[Isetech]

If you use Onesto products, there is a label which clearly indicates the Line at the top and load at the bottom on the circuit breakers and there is an arrow on the KCN which faces from top to bottom.

Why can some some breakers operate in both direction and other only in one direction, IE line/load.