Weird open neutral voltages

[Paul McKeown]

Am working on a renovation of a crappy 3-story walkup, aluminum wired.
Supposed to be just replacing all the lights, switches and receptacles with pretty stuff as the owners want to sell the suites as condos. Running into a lot of loose wire nuts and very strange voltage readings. Common problem is open neutral in ceiling box ahead of or downstream of the octagon box I?m at. When I check the light, it doesn?t work and when I check the voltage, line to neutral, it?ll be something weird like 84 volts (120 line to gnd). Any ideas what might be happening to cause the odd voltages. Problem always resolves when I find the loose neutral.
Sorry if I sound dim....I normally work in a heavy industrial environment and haven't run into anything like this before.

 

[George Stolz]

Do a search for the phrase, "open neutral." You should find good responses as to the theory behind it.

In a nutshell, the voltage to neutral is determined by the resistance of the loads, when the neutral is opened. The circuit is actually a series 240V circuit (as opposed to two parallel 120V circuits.)

Welcome to the forum.

 

[Paul McKeown]

Thank you George,
Did as you suggested, lotsa hits. I’ll start reading.
BTW, there are no loads on the circuits as the suites have been gutted.

 

[quogueelectric]

aluminum wiring

aluminum wiring

I have nothing nice to say about aluminum wiring and the liability vs profitability is soooooooooooooo negative that I just want to walk away unless it is a special customer. First word of advice is to try to replace with cu as much as possible and lighten as many loads asap with that cu.

 

[Minuteman]

Check the service neutral. Chances are, it has overheated or is undersized.

 

[boater bill]

The aluminum branch conductors are a real problem. That may be why you are finding all of the dropped/broken neutrals. It is my understanding that even the wire nuts to be used on AL wiring must be rated for AL wiring, or else they will fail like you are seeing.

Where are these condo's so I can get the word out to stay away. Unless you replace with CU wire.

BTW welcome to the forum.

 

[Paul McKeown]

The aluminum branch conductors are a real problem. That may be why you are finding all of the dropped/broken neutrals. It is my understanding that even the wire nuts to be used on AL wiring must be rated for AL wiring, or else they will fail like you are seeing.

Where are these condo's so I can get the word out to stay away. Unless you replace with CU wire.

BTW welcome to the forum.

They're in Edmonton, Alberta and the owners won't consider cu. I'm replacing all the wire nuts I run into with marrette #63's & 65's suitable for cu and al, using an antioxidant paste for the al to cu lighting pigtails, and insisted that the owners ditch the standard switches and receptacles in favour of Leviton CO/ALR ones.
Have tightened all the panel terminations (suite and main dist in bsmt), still can't figure out the weird voltage's. Could it be an exposed neutral somewhere in the cct touching a box? Whoever removed the devices was pretty rough and damaged the insulation in a lot of places that I've found.

 

[dalesql]

get out of this job while you can.

get out of this job while you can.

Walk away from that job as fast as you can. I don't know how the licensing and liability laws in Canada work, but doing that sort of thing here in the US puts you squarely in the targets of a lawsuit, and depending on how the laws for licensing work in your state, puts your license at risk.

Go hire a lawyer right now who is familiar with construction liability law in your jurisdiction and get their advice on the advisability of continuing with the job. Also the best method of extricating yourself from the job without causing further harm to you or your reputation.

You have found substantive risks for fire, equipment damage, and life safety of any occupants of the apartments/condos. Knowingly doing a substandard repair job is a bad thing, morally, ethically and legally. Having the owner sign a statement of responsibility for the bad repair job will not look good in the eyes of the jury deliberating damage awards.

 

[SeanKelly]

We would get wierd readings on aluminum conductors all the time at my last shop. Most of the time we would find an open neutral but on more than one occasion we found the conductor damaged inside the insulation. Don't know why this occurs bit I would imagine when they were pulling it in they put to much tension on the bushings with the wire and affected the integrity. That's just a guess as to the why but I have defintely seen the conductors damaged in the jacket

 

[LarryFine]

Yep. Aluminum NM was alsmost as fragile as UTP cable is.

 

[hardworkingstiff]

While I don't agree that you need to walk away from this job (somebody has to do it), I do agree you need to dot the I's and cross the T's with some well worded written documention. This has the potential to be a nightmare and you should be well compensated for your efforts.

 

[Paul McKeown]

I'm done. they never called me back after I hunted down a bunch loose neutrals in ceiling boxes one day, before installing lights (#63 or 65 wirenut with No-ox Al to Cu pigtail). Once they found out how expensive CO/ALR stuff is, and I refused to install the cu only approved units they'd already bought, they lost interest in me and probably got some daft twit who'd do the job the way it had always been done---treat the Al conducters as it they were copper.

 

[Jack Maynard]

Re: strange voltages on AL wire w/ open neutrals....
As George Stolz said, with an open neutral what you are looking at is the divided voltage of a 240v series circuit rather than two 120v circuits in paralllel.

You mention that all loads are removed as the building is gutted. Maybe not. Remember that those squirrely AL connections have undoubtably become resistive and are themselves the loads now unequally dividing your 240 circuit.

An appprentice at the shop where I work recently removed a 2-pole breaker feeding a multiwire branch circuit (two 20A circuits sharing a neutral) and in his wisdom not only did it hot, but removed the neutral wire first. The resulting errrant voltages smoked a couple lightbulbs as well as an electronically controlled doggy door. The poor boy sure knows how to land new nicknames.

 

[iwire]

You mention that all loads are removed as the building is gutted. Maybe not. Remember that those squirrely AL connections have undoubtably become resistive and are themselves the loads now unequally dividing your 240 circuit.

There would have to be 'real' loads still connected for this to happen.

 

[LarryFine]

An appprentice at the shop where I work recently removed a 2-pole breaker feeding a multiwire branch circuit (two 20A circuits sharing a neutral) and in his wisdom not only did it hot, but removed the neutral wire first.

There's a man who should have his Kleins suspended for a while.

 

[tallguy]

An appprentice at the shop where I work recently removed a 2-pole breaker feeding a multiwire branch circuit (two 20A circuits sharing a neutral) and in his wisdom not only did it hot, but removed the neutral wire first. The resulting errrant voltages smoked a couple lightbulbs as well as an electronically controlled doggy door. The poor boy sure knows how to land new nicknames.

If you're going to do it hot, at least remove the CB from the bus first... then the order doesn't much matter.

 

[Jack Maynard]

There would have to be 'real' loads still connected for this to happen.

After some thought I would agree, iwire.

I've been drawiing the circuit in my head trying to find a way that resistive splices in either of the legs or neutral could show voltage division with no "real" load--that is, a load between neutral and either hot---and I cant get there from here.

For a second I was thinking that the meter used to measure could "complete" the circuit and show division between the resistive elements, but as our modern meters can be modeled as infinite resistance when used as voltmeters, no current would flow and therefore no voltage would be dropped across the resistances.

So I stand corrected, but enjoy the discussion.

As for suspending the apprrentice's Kliens for a while-- the boss who had to pay for the dogggy door was more apt to suspend him by his Kleins...Calvin Kleins.

Jack Maynard
Journneyman Electrician
Ex Electronics Engineer (couldn't stand the fluorescent lighting)

 

[ratsso]

Always rule out the utility companies supply to the house if you really get stumped. It does happen. Loose connects at transformer and lines.

 

[quogueelectric]

Loose utility neutral

Loose utility neutral

I somehow found myself on an extention ladder at home wed nite checking the point of attatchment at midnite. 830 pm power surges went down and tightened all panel connections. all is fine until 10 30 pm broke out the volt tester and 141v on light surges told me all I needed to know. Call lipa took them 12 hrs to respond then 12 hrs to appologize no damage done tho all is well again after they rewired the whole block. Like I need this excitement in my life.

 

[haskindm]

Paul,
Just to CYA, I would send a registered letter to the building owner informing them of the problems that you found and your recommendations for the best way to remedy the situation. That way, when the building burns down or someone gets hurt they cannot claim that you did sub-standard work that contributed to the problem. Lawyers love to add anyone that ever worked in the building to the lawsuit in the hopes that someone (or someone's insurance company) will go ahead and pay in order to avoid a lawsuit. Sometimes it amounts to legalized extortion.