Question for the electrical types

[Phoenix too]

When it comes to electricity I know enough to be dangerous.
,
If the neutral is lost at a transformer, what happens downstream? Within a house, if the neutral is lost on a circuit, the circuit is dead. A friend had a fire where he worked, it was electrical, lights were flickering, but besides going out, they were also getting brighter. They were told it was caused by the loss of the neutral side of the circuit.

Thank you!

 

[jpickar]

Yup that sounds like a possibility.

 

[Rick Courtright]

Hi,

P2, I don't understand the why of it, but a similar thing happened at a friend's house. Several houses on his block were flickering on and off, bright and dim, just as you describe at your friend's work, though there was no fire. Edison Co. crew came out and replaced a transformer. One of them told him something went south in the neutral leg of the old transformer. It sounds like your friend got the same explanation.

Rick C

 

[wheelgun1958]

Without a neutral (ground) there is no current path. If there is a bad or loose neutral at the transformer, current will find a new source if possible.

 

[powder smoke]

Yes the neutral is ground current must make a complete circuit . Flickering lights bright to dim usually mean
a loose connection arcing can occur which produces heat then fire.
The ground wire is redundant just a back up. Mostly to protect user of appliances or tools.
GFI monitors return power, makes sure the same amount of current return as sent.
When power returned is less than was sent it may be going thru a user, or ground instead of neutral.
When less is returned it breaks the circuit. Simplified version.

The most dangerous thing one must remember when doing their own electrical work
other than turning power off is connections.Loose connections probably burned more Homes
than anything else. CRIMP conectors are better than Wire Nuts TIGHTEN them GOOD if you use them
and take your linesman pliers and twist them wires together tight before putting on the wire nut.
Twist in the correct direction so it is not opposite of the nut. Be Safe. ps

 

[jgt]

The neutral is the most misunderstood part of an electrical system. Many do not know the difference between a ground and a neutral. The neutral is a current carrying conductor. It is different from the ground. The ground is there to carry stray current to ground for safety from electrocution. In a Y system, which most modern systems are today the neutral is grounded but is still a current carrying conductor. When circuit loads are not equal or "balanced" with the load they are connected to, the neutral carries that unbalanced portion of the load back to the source. In a system with two hots and a neutral. If one hot has a 10 amp load and the other hot has a 15 amp load the neutral carries a five amp load back to the source. If the neutral connection is lost the whole load is "backfed" back to the source on the other hot wire. We are talking 25 amps at 220 volts instead of two circuits of 110 volt with an unbalanced load. The lights get real bright but soon burn out. One of the characteristics of loss of the neutral in a system is to turn off the 220 circuits, where there can be no "feedback" occurring on the other hot wire. When you check the 110 volt circuits they will all be dead. Turn on one 220 volt circuit such as the water heater and the 110 volt circuits will all read 220 volts. The flickering is a sign of a loose connection or could be intermittent connection as the connection is burning loose. Loose connections generate a lot of heat.

 

[Fire Chief]

The loss of the neutral between the main panel and the transformer will very likely result in 220v-240v on all cicuits in the building with resulting damage to any equipment not rated for 240 vac.

 

[Phoenix too]

Thank you, gents. I knew phase to neutral (110) and phase to phase (220), but I didn't know that loss of the neutral could send phase-to-phase voltage thru the 110 system.

 

[K1500]

Aren't neutral (white) and safety grounding (bare copper) joined at the box? If so, it would seem to me that a loss of neutral upstream of the house (say at service drop or in transformer) would cause the power to return to the box and to earth through the safety ground rod. What am I missing?

 

[Fire Chief]

AC current will always try to return to it's source IE: the transformer and not the ground. The most efficient way
( least resistance ) is the other leg or hot. This is how your other 240 loads operate. They only need a neutral
if they need 120v for lights, clocks or other electronics.

 

[K1500]

The OP is talking about lights in Massachusetts, which should be 120.

 

[Fire Chief]

Without a neutral all the circuits will be 240v.

 

[K1500]

Do they become 240 because the neutral wire is carrying the 120 from the other leg? That is, suppose my lights are on one leg and my fridge is on another. If the ground is lost, the neutral of the fridge (which is now carrying electricity) flows not to ground but to the neutral of my lights, turning it into a 240 circut?

 

[snowman2]

On a three wire circuite which is 2 hots and a neutral. If the neutral breaks one of the hot wire will suffer a under voltage condition something cosiderably less than 120v and the other hot will in overvoltage anywhere from 120to almost the combined voltage but usualy less than 240v. This can play havoc on electronics and kitchen appliances.
cheers Harv

 

[gramps]

Wow guys, I was an electricians helper at age ten, an Amatuer Radio Operator since 1971, and NEVER heard of a "neutral". I was taught they are either "hot" or a ground. I agree that a short can and does lead to heat and fire.
gramps

 

[wheelgun1958]

Wow guys, I was an electricians helper at age ten, an Amatuer Radio Operator since 1971, and NEVER heard of a "neutral". I was taught they are either "hot" or a ground. I agree that a short can and does lead to heat and fire.
gramps

Works that way on Boeing, etc. I've never worked facilities maintenance.

 

[Rick Courtright]

Wow guys, I was an electricians helper at age ten, an Amatuer Radio Operator since 1971, and NEVER heard of a "neutral". I was taught they are either "hot" or a ground. I agree that a short can and does lead to heat and fire.

Hi,

Gramps, in my very short stint working with a couple of electricians, I was taught "hot and ground" is DC language, "hot, neutral and ground" is used for AC. I can wire 110 stuff all day cuz it's basically like DC wiring, and understand the "mechanics" of wiring simple 220 circuits, but the entire theory of AC and being able to 'splain it is something I never could quite grasp. Except it made a pretty display on the oscilloscope when my father used to build Heathkit stuff... now that seemed pretty cool to a seven year old!

Rick C

 

[longspurr]

A transformer converts one AC voltage to a different voltage (step down transformer) or is the same voltage on both sides of the transformer (isolation transformer).
The secondary side of the transformer (home side) can be only 3 wires, 2 hot wires and 1 neutral wire. It does not have to have any connection to EARTH to work properly. We connect the neutral wire to a grounding conductor at the transformer for the reasons below.

As others have said, you can have a faulty connection of the neutral wire at the transformer resulting in almost double the normal voltage in the house. A coworker had exactly that happen. He was suddenly in the market for new appliances because the ones in his house were damaged by the high voltage.

http://en.wikipedia.org/wiki/Transformer

A grounding electrode conductor (GEC) connects one leg of an electrical system to one or more earth electrodes. This is called "system grounding" and most systems are required to be grounded. The U.S. NEC list systems that are required to be grounded. The grounding electrode conductor connects the leg of the electrical system that is the "neutral wire" to the grounding electrode(s).[5]

According to the NEC, the purpose of earthing an electrical system is to limit the voltage to earth imposed by lightning events and contact with higher voltage lines, and also to stabilize the voltage to earth during normal operation. In the past, water supply pipes were often used as grounding electrodes, but this was banned where plastic pipes are popular. T

http://en.wikipedia.org/wiki/Ground_%28electricity%29

 

[blume357]

I have to disagree.... I don't see how the lack of the neutral will result in 220-240.. on the 120 side.. but then I'm by no means and expert..... Keep in mind if you lose the neutral at the transformer you will technically still have a circuit via the grounding of the system. I know this because I once went to work (sweep all the chimneys) in an empty house.... got all my equipment in and turned on my vac and then realized I needed one more tool. went out to the van to get it and when I came back in vac was not running and there was no electricity (actually 120... still had 240) to the house... bottom line was that the neutral (bare / center wire from the transformer) had come loose and been loose for a while and the house was completing its 120 circuit via the ground and my vac had pulled enough amps to burn that connection in two.

Now with all that said, maybe the newer house wiring with an Isolated Neutral might be different. I'll have to think about it sometime.

 

[jpickar]

I have to disagree.... I don't see how the lack of the neutral will result in 220-240.. on the 120 side.. but then I'm by no means and expert..... Keep in mind if you lose the neutral at the transformer you will technically still have a circuit via the grounding of the system. I know this because I once went to work (sweep all the chimneys) in an empty house.... got all my equipment in and turned on my vac and then realized I needed one more tool. went out to the van to get it and when I came back in vac was not running and there was no electricity (actually 120... still had 240) to the house... bottom line was that the neutral (bare / center wire from the transformer) had come loose and been loose for a while and the house was completing its 120 circuit via the ground and my vac had pulled enough amps to burn that connection in two.

Now with all that said, maybe the newer house wiring with an Isolated Neutral might be different. I'll have to think about it sometime.

Just remember you said you are no expert!
Electricity does weird things. And what you experianced is the exception, not the rule. But I understand what you are saying.

John

 

[jgt]

Well, I can tell you without a doubt you WILL have 220 volts running through your 110 circuits if you loose the neutral, this is "Ned in the first reader" stuff.