Locating the suspected loose neutral problem

Thread Starter

chefnhouston

Joined Jan 2, 2016
9
Thanks BR-549. Using Google Maps - as best I can tell, the pole is about 80 yards from the house. This house has been on the family farm for generations and the pole/transformer/lines never checked as far as I'm aware of. I do notice more light flickering in bad weather - which we've had a lot of this year... I've chalked that up to lightning in the area etc and not caused by appliances or wiring issues. An infrared temp scanner is definitely on the shopping list.

Thanks!
 

tranzz4md

Joined Apr 10, 2015
310
These problems typically come to BAD connections, not necessarily loose ones. If you have aluminum parts or conductors,,, this chickens have come home to roost.

Moving the utility transformer closer to your house (the "load"), does nothing that replacement of the conductors from the transformer secondary to your branch circuit panelboard with larger conductors wouldn't accomplish.

Re-tightening screws is actually troublesome; if a connection is suspect, it should be cut back to "fresh" copper, and then properly tightened.
 
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#12

Joined Nov 30, 2010
18,217
Moving the utility transformer closer to your house (the "load"), does nothing that replacement of the conductors from the transformer secondary to your branch circuit panelboard
First, I wish that was a sentence. Second, moving the pole and transformer will force inspection and refurbishing of all the connections from the kilovilt line to the standpost on the house, and that is several of the parts that could be responsible for the whole house going dim because of a 10 amp heater load.
 
The Ideal Sure test http://www.idealindustries.ca/produ...cuit_analyzers/suretest_circuit_analyzers.php isn't a bad device for individual runs.

It did help me find a bad ground. It was basically a twist without a wirenut.

True, lots of stuff can go wrong. A closer transformer should help.

Newbies may not think about checking the voltage drop across things that are not supposed to have a voltage across them. Some examples:
1) The wire to the terminal
2) The voltage across the breaker under load.
3) The neutral to ground voltage.

A friend had one of the exterior splices at the house go bad.

GFCI's where no ground is used is permissible as long as the receptacle is labeled. Something like "No Earth ground". Not sure what the wording should be.
 

n1ist

Joined Mar 8, 2009
189
The issue isn't low voltage, it is high voltage. With the neutral open, you have effectively the loads on the two legs in series across 240V. Depending on the current draw, the midpoint (normally where the neutral is connected) will move. One set of loads will have low voltage across it (won't usually kill things, but some motors are sensitive to it) but the other will go above 120v and will blow things.
/mike
 

SLK001

Joined Nov 29, 2011
1,548
The issue isn't low voltage, it is high voltage. With the neutral open, you have effectively the loads on the two legs in series across 240V. Depending on the current draw, the midpoint (normally where the neutral is connected) will move. One set of loads will have low voltage across it (won't usually kill things, but some motors are sensitive to it) but the other will go above 120v and will blow things.
/mike
That's not how they are connected. There is no path from L1 to L2 as the picture shows for a 120V branch.
 

GopherT

Joined Nov 23, 2012
8,012
That's not how they are connected. There is no path from L1 to L2 as the picture shows for a 120V branch.
120v is from a hot to the center tap of a 220v transformer. So, if the connection to the center tap is broken (or high resistance, the pictures in post 28 are exactly correct (simplified). In reality, there are many appliances and lamps in parallel with the hair drier and many appliances and lamps in parallel with the TV.
 

SLK001

Joined Nov 29, 2011
1,548
120v is from a hot to the center tap of a 220v transformer. So, if the connection to the center tap is broken (or high resistance, the pictures in post 28 are exactly correct (simplified). In reality, there are many appliances and lamps in parallel with the hair drier and many appliances and lamps in parallel with the TV.
I guess that if you extend the center connection back to the neutral in the panel, then this could happen. However, both items would have to be in the "on" state for this scenario. Also, they are in series, not parallel. For this to occur, they would have to be on 120V breakers on opposite sides of the panel. This kind of situation can have fatal consequences.
 
However, both items would have to be in the "on" state for this scenario.
Well, not exactly. Look at the 120 V filter schematic here: http://www.te.com/usa-en/product-1-6609037-2.html

With a neutral open, the center point of the ground feeds the open neutral, so you can get contributions from there. They are leakage paths, but a voltmeter will see them. An open ground on an outlet strip basically made the "ground" of the bad outlet at 60 VAC because one of the other devices (a computer) had an RFI filter in it. Nevertheless, some things were not happy.
 

SLK001

Joined Nov 29, 2011
1,548
With a three prong outlet, the ground wire and the neutral are connect at the panel, so with the neutral open, there still is a connection path.

However, the picture in #28 implies only a two pronged outlet. With the neutral open (and no ground wire), the only path back to the panel is thru the two hot lines. Since the two devices are in series, to complete the circuit, both devices must be on. So, using the picture, someone wanting to watch a football game would have to yell to his wife, "Honey, can you dry your hair for the next three hours?"
 

GopherT

Joined Nov 23, 2012
8,012
With a three prong outlet, the ground wire and the neutral are connect at the panel, so with the neutral open, there still is a connection path.

However, the picture in #28 implies only a two pronged outlet. With the neutral open (and no ground wire), the only path back to the panel is thru the two hot lines. Since the two devices are in series, to complete the circuit, both devices must be on. So, using the picture, someone wanting to watch a football game would have to yell to his wife, "Honey, can you dry your hair for the next three hours?"
But a hair drier and a big screen tv no longer consume the same power as they did in the days of CRTs. Be careful which load you select as your voltage divider.
 
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