Neutrals from same circuit connected together…is this ok?

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I have both electric gates and outside LED lights powered from the house electrical supply via a single armoured multi core cable.

Each of the three circuits (2 lighting & 1 gate) is powered by a separate a RCD in the house (although the lighting circuits are connected together here (at the start of the armoured cable in the house) so in essence act as one.

However both RCDs trip when either the gate or the lighting circuit is turned on, when the other is already on (powered by the other RCD).

However if both circuits are powered from the same RCD no problems occur.

My thought is, due to the lack of available wires in the multi core cable, both the earth and more importantly neutral cables are common to all the circuits in question. I'm thinking this may be the reason why both RCDs trip when each circuit is powered through separately as there is an uneven load between the lives and neutral cables? It also explains why a single RCD does not trip with only one...

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I am replacing the wall outlet that my refrigerator uses, and I noticed something odd. I recently purchased my house, which is 35 years old. The outlet has a built-in surge protector, so it has dedicated line and load terminals.

This outlet appeared to have a dedicated circuit. When I switch off breaker #3 in the breaker panel, the refrigerator turns off, but all other outlets in the house remain on. A circuit tester also shows the outlet is off. However, I still received a shock when I touched one of the neutral (white) wires. When I shut off breaker #10, then the wire is dead. Breaker #10 also shuts off some other outlets in the kitchen.

There are two sets of wires in that outlet box. One set (set #1) is a white and a black wire. The other set (set #2) is a white, black, and red wire. The two black wires are capped together. The two white wires are connected to the outlet, and so is the red wire.

I believe that set #2 is the line, and set #1 is the load...

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If you are not sure what an earth leakage fault is or how the residual current devices detect it such as an ELCB, RCCB, RCBO or RCD then please look at this post where I explain what these terms are and what it all actually means. In this post I will look at an obscure fault, which can be perplexing and describe what it is and what can cause it.

Please note that this article is my opinion and cannot be considered advice. For any issues regarding any electrical fault or installation, seek the advice and knowledge of a qualified electrician fully conversant with the laws and regulations of your country or region. Where the applicable regulation specifies a specific installation or action, this must be followed to comply with your regulations.


Index.


What exactly is an, "Earth" in a domestic situation?
What is an equipotentially bonded area or zone?
Do RCDs have significant limitations?
Aren't earth leakage faults simple to...
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HOME SitemapResidential Electrical Troubleshooting Stories

October 23, 2006

A busy day. First and easiest, Mrs. Shaw. All she had done was unscrew an indoor flood from a recessed can. And I saw that the bulb was now hanging by some wires. Usually that means the glass broke loose from its metal threads and I need to use my needlenose (spread outward) to remove the metal end from the socket. But this was different. Never seen a bulb DESIGNED to unthread from its metal end. This was a compact fluorescent flood and it got ruined by this unscrewing. I replaced it.

Next a sad story. This guy's mobilehome had oodles of electronic stuff. Most of it got fried back in June, he said. So the power company thought they found a bad neutral in the transformer and replaced it. Now his next set of stuff fried, some in spite of good surge protectors. Sustained higher voltage isn't a surge. It's a melted icecap, not a little thing like a tsunami. Lights were getting bright,...

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If it's only an occasional need then it's not that hard to synchronise two generators, although with small 2kw units it gets trickier because their speed varies so quickly and they quite often hunt around their target frequency. Often they hunt worse off-load so you may have to apply a bit of load to each to get this to work.

Traditional method:
Connect neutral from both together, connect line together via a switch. Connect an ordinary tungsten light bulb across the switch and with the switch open start both generators. If their speed is sufficiently similar then the bulb should pulse slowly, if there's a rapid flicker you'll have to tweak the speed of one generator until you get a slow pulsing. At the point of minimum brightness close the switch. It's not all that difficult but there's a risk of damage if you get it wrong, although TBH with small generators you'll probably just open the breakers or collapse the excitation.

Alternate method (for horribly out-of...

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8.4.2 - Ring final circuit continuity

The ring final circuit, feeding 13 A sockets, is extremely widely used, both in domestic and in commercial or industrial situations. It is very important that each of the three rings associated with each circuit (phase, neutral and protective conductors) should be continuous and not broken. If this happens, current will not be properly shared by the circuit conductors. {Fig 8.4} shows how this will happen. {Fig 8.4(a)} shows a ring circuit feeding ten socket outlets, each of which is assumed to supply a load taking a current of 3 A. In simple terms, current is then shared between the conductors, so that each could have a minimum current carrying capacity of 15 A. {Fig 8.4(b)} shows the same ring circuit with the same loads, but broken between the ninth and tenth sockets. It can be seen that ...

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Electric Outlets Don't Work

I have two outlets on one wall that don't work. I have replaced both outlets so have concluded that isn't the problem. There is power in the black wire so I assume the problem is continuity in the white wire. Other Outlets and lights on the circuit work. Any suggestions on the cause and solution would be greatly appreciated.

You checked the black wire and it was energized. Since the white seems to be the problem, then I assume you tested black to ground to determine there was juice there. But when you test black to white, you get nothing.

Thus, the white has an open some where. Do you know where the feed to the outlets comes from? Is there an outlet that feeds them, or perhaps fed from a light fixture in the floor below?

Not knowing what floor these are on, and if you have access to the ceiling below, I am not sure where to tell you to look. But you need to find where they are being fed from. Then you check to see if the...

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From Wikipedia, the free encyclopedia

A shared neutral is a connection in which a plurality of circuits use the same neutral connection. This is also known as a common neutral, and the circuits and neutral together are sometimes referred to as an Edison circuit.

In split phase house wiring, for example, a duplex receptacle in a kitchen is typically connected with a cable that has three conductors, in addition to ground. The three conductors are usually colored red, black, and white. The white serves as a common neutral, while the red and black each feed, separately, the top and bottom hot sides of the receptacle. Typically such receptacles are supplied from a ganged breaker, i.e. a breaker in which the handles are tied together for a common trip, so that if one kitchen appliance malfunctions and pops the breaker, the other side of the duplex receptacle will be shut off as well. This is called a multiwire circuit.

In a three-phase circuit, a...

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The answer to that question depends on exactly

where in the building's wiring

is being asked about.

The only place the neutral and ground (or "earth") wires in a building should ever be tied (or "connected") together is at the incoming service main breaker panel "upstream" of all the fuses and/or circuit breakers which are there to protect the hot (or "live") wires for the various circuits installed in the building.

In the absence of an earth wire (= ground wire in US/Canadian English), if the appliance suffered some damage that caused a short circuit between the high voltage "hot" lead and the case of the appliance, the damage would make the case live and it would cause an electrical shock to anyone who touched it.

If the case is earthed by using a ground wire (= earth wire in British English), if that same damage occurred the hot lead would immediately be shorted to ground and in theory cause the fuse to blow or circuit breaker to open, thus...

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all of the grounds must be connected unless it is an isolated ground.

as to the size;

there needs to be one ground heading home that is as large as required for the highest ampacity circuit in the group. You need no other ground technically. 250.122C

310.4 concerns parallel conductors for the same circuit. Not applicable here. Rarely have I seen the section used in resi wiring.

250.122F not applicable because it addresses situations in 310.4, which is not applicable.

250.148 says they must be connected together except for the isolated ground situation I mentioned previously. If metal boxes are used, tey must also be connected to the metal box.

btw; the reason an iso ground is not required to be interconnected at any point past the main service is; noise can be found on many EGCs due to non linear loads and this can affect the operation of a sensitive piece of electronics. The conection at the main will not cause those currents to be...

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