troubleshooting branch circuit

[charlietuna]

This circuit arrangement does not sound right to me-dinning and kitchen mixed and then supplying the refrigerator?? If(?) you did as i said you would find the problem before you trimmed out the resepticles? Throw away any tester except the wiggy! If you do not ring out the wires between outlets--re: end to end--you don't know what else might be covered inside the wall??

 

[gar]

090113-1037 EST

rickl:

I can not understand what has been said because I don't want to sort thru the chaff.

What I conclude is:
1. You have a main panel.
2. There are many circuits in the house with no problem.
3. There is one circuit with three outlets with a problem.

Find a 3 prong outlet near the main panel on a known good circuit. Obviously this is not on the bad circuit. This test outlet gives you three test points to the inside of the main panel. One is the ground bus. Another is the neutral bus. And the last one is a hot phase.

Plug a 3 prong extension cord into this test outlet. Use an extension cord long enough to reach any of the outlets on the problem circuit.

If you already truely know the sequential order of the outlets on the problem circuit, then go to the last one, the end of the circuit. Assuming these are duplex receptacles plug your meter into one side between hot and neutral. Apply your hair dryer load. What happens? Before the load it was probably near nominal 120. After the load it drops substantially I believe.

If this is not correct, then either you are not at the end of the circuit or you have not triggered the problem.

If this is correct, then remove the meter from the outlet. Connect one meter lead to the EGC of the extension cord. The other meter lead is a probe to any other point you want to test.

All the following measurements are with your reference point being the EGC of the extension cord which also we are assuming is directly connected to the ground bus in the main panel.

At the outlet with the load check the hot voltage, neutral, and the EGC. What you see determines the next step.

Probably from here you go to each of the other outlets and check the same points.

These measurements should help pinpoint the region of the high resistance problem.

Also when composing your questions or comments preview your post before submitting the reply with the "Preview Post" button. This way you may be estimate whether what you said is what you intended to say.

.

 

[stud696981]

Just a thought, perhaps the nail from the siding hit the home run, breaking the nuetral, but making contact enough to give a reading but not enough to handle a load. (Note, I only read the first few posts.)

 

[Pullnwire]

my thought exactly

my thought exactly

I was going to say severed neutral. Could be a nail thru the wire where it runs horizontal on the wall.

Just a thought, perhaps the nail from the siding hit the home run, breaking the nuetral, but making contact enough to give a reading but not enough to handle a load. (Note, I only read the first few posts.)

 

[Cow]

Since you haven't been able to find the problem yet, how much trouble would it be to fish another wire in. Not worth wasting 2 hours looking for a nail through the sheath if you can fish one in, in half the time. Or J-box it somewhere in the attic and extend from there if you don't want to run all the way back to the panel/recep.

Wire is cheap. Labor is not.

 

[Fulthrotl]

This looks like a job for the see snake.

i got to use my sea snake today.... life was good.....
couldn't snoodle a wall, coudn't figure out why.... greenlee
flat tape wouldn't work, tape measure wouldn't work, fish
stick wouldn't work.....

poked a 1" hole above the tbar, in went the snake..... insulation
wrapped around a 1/2" conduit horizontal in the wall...
got the see snake by that, all the way to the cut in box..
tied on a string, and tuggled... the sea snake is a great thing to
have, especially if you have a 3' extension for it....

 

[Power Tech]

Funny, my father used to say it's $5 to hit it with the hammer. It's $490 to know where to hi it. Anyway did you take the breaker out and check the bussing and breaker for corrosion. Just install a new one and change the location on the buss. I have had many Zinco where the house looks like a Disco with the lights dimming and going off and on.

 

[rickl]

charlietuna:{This circuit arrangement does not sound right to me-dinning and kitchen mixed and then supplying the refrigerator?? } look at 210.52(b)1. it states that you can feed dining rm recp & refrig from the s/a branch circuit. i didn't design or wire the house, just troubleshooting a problem.
gar: why start at the last receptacle when i know the problem is at the first receptacle.
first receptacle with just the homerun hooked up to the receptacle, no load h-n 120 volts h-g 120 volts, with load ( hair dryer) h-n 50 volts h-g 120 voltd n-g 70 volts. your extension cord idea is a good one. i've used it in the past to chase out opens. but at this point i believe i have a open or loose neutral between the panel & the first receptacle. possible from a nail, & i was just hoping that someone else had run it to this problem before and offer some insight


stud6969: thats what i'm thinking,

i'm sorry for not being a very good typist, i'm also sorry if i come acrossed sounding rude i didn't mean too.

 

[charlietuna]

I never said anything about code--just assuming how the average house is wired ! Normally two circuits to feed kitchen appliance receptacles--good chance refrig is on a separate circuit----dinning room might be another circuit! You are looking for something you can't see and seem to be stuck on "A NAIL" which might be??? But a bad splice in a box you have not looked into is more likely--and this box may not necessarily be in line with these outlets you have opened. The fact that dinning-kitchen and refer is on this circuit raises a red flag to me---like someone has re-directed the normal house layout..................

 

[S'mise]

Ok, I give. What's a see snake? Got a link?

 

[rickl]

charlietuna: i think its a poor design also, its a small dining area ( just the one receptacle) the frig & counter recp are 2' apart. all 3 are within 15' wall space. & theres nothing else in the area. i checked all other receptacle & switch box in the general area & on the opposite wall with breaker off & they all have power except for the 3 i mentioned
power tech: i did that, i know the breaker is good because i have 120volts from hot to ground under load.

 

[gar]

090114-0922 EST

rickl:

Is the following correct?
1. The problem exists at the outlet closest to the main panel.
2. The problem is on the neutral wire. This was verified by the voltage out of the main panel breaker at the breaker being 120 and also at the hot terminal of the outlet. These measurements being made to ground with and without the hair dryer load.
3. The neutral voltage at the outlet is near zero relative to ground with no load, and rises to about 70 V with the hair dryer load.

Assuming the above is correct, then under load check the voltage from ground in the main panel to a point on the neutral wire directly and close to where it is clamped in the main panel neutral bus. The point here is to contact the neutral wire and not make contact with the bus.

If this voltage is near zero, then there is a high resistance in the neutral wire path from the neutral bus to the neutral termination at the said first outlet.

Further assuming there is high resistance in the neutral wire, then disconnect the neutral at the first outlet. Now use a DVOM or Simpson and measure the resistance from the neutral bus to the disconnected end of the said neutral wire. All these meters probably use less than 6 V in the ohmmeter circuit. I have no idea what you will read. It might be very high, moderate, or even less than 1 ohm.

If we assume your hair dryer is 16 ohms, then from your voltage readings the resistance in the neutral is 16*70/50 = 22 ohms. This apparent resistance might not be the same at other current levels.

I do not believe that you have indicated whether this is an intermittent problem. Meaning that sometimes you get this result with said load and sometimes not.

I have measured a hair dryer that is rated 1200 W. Results: Fluke 27 reads 18.8 ohms. Current voltage measurement, 120 V @ 7.5 A, is 16 ohms. So the wattage rating is not very correct. Actual power is 7.5*120 = 900 watts.

If you get a resistance reading in the range of 25 ohms that would be a good correlation with your voltage measurements under load. You either find the cause or replace the wire. If you are driven to find the cause of the problem then proceed in that direction, otherwise just replace the wire.

.

 

[rickl]

gar
1 yes
2 yes
3 yes
intermittent problem, no last time i was there it was not intermittent, but 2 weeks ago it was
i'm scheluded to go back tomorrow i'll try you ideas
thanks

 

[gar]

090114-2209 EST

rickl:

Intermittent. Look for a screw problem at the neutral bus in the main panel since you have, I believe, replaced the receptacle.

.

 

[SiddMartin]

just a thought, run a temp wire from panel to outlet (pull outlet outside box, run RX along the floor or whatever) and connect everything as it was. Then check your readings.

 

[rickl]

update

update

i go back today, go up in the attic, remove all the insulation along the crack where the problem circuit runs. there are 4 cables running in the crack with no staples, so i turn the main off & go back. I start trying to pull the cable out of the crack, none of them will move, everyone of those cables had 6 to 10 nails in them, a couple of the nails went through 2 cables. so i ended up putting 2 j boxes in the attic & ran 4 new cables from jbox to jbox. its amazing they just started having problems ( the siding was put on in july),& no breakers were tripping ( siemens panel with siemens breakers) also the problem circuit had the neutral broken by a nail in 2 spots
thanks for all your input