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Electrical

R

rlp in Co.

Well-known Member
I had 2 neutral wires come loose in a
breaker box and it put 240 volts on my
furnace and a light circuit! The house had
been completely rewired a couple of years
before I bought it. The electrician had run
out of neutral screws and put 2 neutral
wires under one neutral screw, one from each
side of the 240 posts! This burned out a
couple of bulbs and luckily the ceiling fans
were off, but the furnace's 24 volt
transformer in the furnace, burned up and
who knows what else, because I haven't had
time to check yet! I wish I knew what
company wired it! I think they should be
responsible for my furnace!
 
Do you think the neutral wires came in contact with a breaker or the breaker bar. The wires coming loose wouldn't itself cause any problems with the exception of cutting the power off. You may be able to add an additional neutral bar but I've seen two wires under one screw often. The main thing is you get the screw good and tight.

You should be able to get a make and model of the transformer and replace it. If you have an electrical supply in your area take the old transformer in and see if they can fix you up.
 
I think they should be responsible for my furnace!

24vac transformers can easily go out caused by a power surge from the power company too.

Good luck collecting.

Good luck proving whose fault it is.

You may want to install a surge suppressor on your furnace.

I have surge suppressors on my dishwasher, garage door openers, TV, shop radio, range, all my cordless chargers, microwave after neighbor's tree fell on powerline, pulled the neutral wire loose and fried many things.

Do you think the power company paid for all my damages? Yea right, Think again.
Duke will sell you insurance to cover power surges.

Chances are, your damages are too small to even think of turning a claim to your insurance co. I would not turn in a small claim.
 
I am probably asking a dumb question, but if a neutral fell off, how does it put 220 into the line? It would just be breaking the circut of 110 volts.
 
(quoted from post at 15:41:50 12/13/22)

''The wires coming loose wouldn't itself cause any problems with the exception of cutting the power off.''

If the two circuits are fed by opposite buss bars in the panel and the white/neutral wires became detached from the neutral buss but remained in contact with each other AND the loads are different, voltage will FALL in the more heavily-loaded circuit and RISE in the circuit with a lighter load.
Click to expand...
 
If all that got fried was a 24v transformer you were dang lucky! $20 at any hvac supply house. Probably that cheap on Amazon too.
 
I hope it didn't damage the fan or the circuit board or the draft fan! I can't get up there today because there is a blizzard going on. I got stranded a few years ago and had to sleep in my car all nite till the road grader came by and opened the road! One guy died in that blizzard in his car. Lucky I had enough gas to last all nite long!
 
If the neutral wire became energized by touching something it shouldn't then you could have 240v. I believe if you reconnect the neutral wires where they belong you would only get 120V.
 
You said a light circuit and the furnace were tied together under the same neutral screw. It didn't take but a flash to get the bulbs and transform. Hopefully that's all you find wrong.

I was called to a similar problem in a old farm shop. The120 volt diesel pump would not run.
I didn't have a meter so just to see if we hD power in the shop I plugged in a skill saw and pull the trigger. The saw and diesel pump would run as long as I held the trigger. That saw was really zinging along on 240 volts. The problem was fuse box never had a ground rod driven and the neutral back to the house main panel was lose from corrosion.
 
This should help you understand. With something on circuit plugged in and on,disconnect neutral from a receptical and hold bare wire in one hand then touch screw on receptical where wire came from. You will feel current going through your body. On a nearby receptical that is fed from other bar at breaker box,disconnect neutral from that receptical and hold it in one hand and netural from first receptical in other hand. That's twice as much voltage flowing through your body. WHITE WIRES MATTER
 
Ha! White wires matter! Especially if they lose contact with the neutral bar, but stay touching together! I still say that an electrician should have known better than to do that!
 
Yes,an electricianshouldknow better but in fairness to the electrician,he shouldhave been taught better. The system and regulations for licensing electricians could alow an occasional individual being licensed without fully understanding this or another detail then going on to train others as they earn their license. Not condoning the pratice but since we know double lugging is occasionally done,not twisting wires togeather before inserting beneath screw would be safer and likly prevented the damage op suffered. That is to say wires likly wouldn't stay in contact after both are free of screw and not twisted.
 
I am confused as to why there are different opinions about what the problem was here. There is only one possibility, correct? If there are so many opinions about what went wrong, That also means there are numerous opinions as to how to do something right. Starting to see how the actual work can be incorrect. Yep. Hire a contractor and you are getting opinions too. Guaranteed. Buyer beware.
 
Forgive me but I dont understand how it happened. You have the neutral wire from a 120 circuit and a 240 circuit under one screw on the bar. They come loose and back out of the bar but remain touching each other. 240 is transferred to the 120 circuit. Why doesnt the 240 go to the 120 circuit when they are securely fastened together in the bus bar? Why isnt all the circuits on the bus bar 240? I dont understand the electricity flow path I guess but would like to understand.
 
In my years of practicing power distribution a LOOSE/OPEN NEUTRAL (in 120/20 Volt Single Phase Three Wire services) was one of the most damaging problems. An appliances sensitive low voltage control circuitry, circuit boards and transformers can be damaged if such happens. How it works is if there are two 120 VAC loads basically in series across 240 volts ABSENT THE NEUTRAL voltage could be much higher on one leg (depends on resistances) resulting in severe over voltage damage !!!!

Being an attorney also I think negligence may be actionable against the installer but the economics may not be there grrrrrrrrr

John T Lecanto Florida Moose Club parking lot
 
Uncle Tom, you ask: I am probably asking a dumb question, but if a neutral fell off, how does it put 220 into the line? It would just be breaking the circut of 110 volts.

Thats NOT a dumb question. Many non electricians or non engineers have asked the same. If there are basically two 120 Volt loads in series across 240 volts with no Neutral to tie each to only 120 Volts, depending on each resistance, voltage could be much different on each load !!!!!!!!!!!!

John T Retired Power Distribution Engineer
 
What he actually had was two separate 120
volts circuits one from each 120 volt buss
and when the neutrals came lose but
remained touching allowed both circuits to
have a combine voltage of 240 volts.
 
(quoted from post at 05:51:23 12/14/22) What he actually had was two separate 120
volts circuits one from each 120 volt buss
and when the neutrals came lose but
remained touching allowed both circuits to
have a combine voltage of 240 volts.
Click to expand...

Thank you for the explanation. It was not clear from the original post and when people responded scratching their heads as to how it could happen, they got told to draw a picture.

What I don't understand is how they could have come loose. This house is stationary right? Once the screw is smoked down it should stay smoked down, and the wire is solid copper so once it's bent into place it should stay there.

I keep trying to draw a picture but every time it ends up being a picture of a fire-breathing dinosaur.

- BarnyardENGINEER, not BarnyardElectrician

This post was edited by BarnyardEngineering on 12/14/2022 at 05:19 am.
 
I think the resistance makes sense. When attached to the bus bar it is the path of least resistance so the flow goes that direction. Correct?
 
You ask What I don't understand is how they could have come loose. This house is stationary right? Once
the screw is smoked down it should stay smoked down, and the wire is solid copper so once it's bent into
place it should stay there.

In my many years in power distribution I saw it happen more than once !!!!!!!! Temperature changes,
vibration (albeit it small), perhaps NOT properly torqued in the first place, expansion and contraction
can all contribute to screws coming loose grrrrrrrrrrrrrrr As part of some routine annual maintenance in
some instances I instructed my electricians to check all panel connections and exercise each circuit
breaker. If two 120 VAC loads are in series across L1 and L2 240 Volts but theres no attached Neutral the
voltage across each appliance will be proportional to its resistance which can result in severe imbalance,
excess high voltage and damage !!!!!!!!

Best wishes hope this helps Merry CHRISTmas

John T Long retired and rusty EE but believe this still true
 
For those who need a picture & couldn't draw one.
uL5H53C.jpg
 
Actually, current flows IN ANY AND ALL AVAILABLE PATHS its just I = V/R that determines how much in each.

John T
 
The key is the two circuits always had a combined voltage of 240 volts, they are feed from different legs. Loss of the neutral reference at the neutral bar results in the circuits sharing the 240 volts based on circuit resistance. Now if the circuits were on the same leg, loss of the neutral connection would just result in a dead circuit. I would carefully inspect the system to ensure that loss of the connection didn't occur somewhere else in the neutral connections. Remember the same guy probably did all the work.

As to your furnace, I have discovered that most if not all solid-state devices are protected by a solid-state switch installed between the neutral and the hot wire. This switch when exposed to high voltage closes parentally and coupled with a fuse system in the circuit disables the device to prevent overheating. Sometimes you can locate this switch and replace it and the fuse system.
 
In office partitions the vacuum cleaner knocks the cable and loses neutral two hots meet due to backfeed in something like the copier light bulb feeding any equipment with 208/220 volts causing dismay.
 
This seriously not that big of a deal. As someone else mentioned the 24V transformer is dirt cheap and you do not even have to pay attention to the mounting lugs - just drill a hole near where the old one was (so the wires will reach) and screw it down, attach the wires, and go have some fun.
 
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