Bad ground?

[electricaldoc]

I have had problems with lights dimming. I have had post on here before about it, but unfortunately still not found problem. I have had some new test, and info. So I thought I would try everyone again. I am still stumped.

1. I have tested all connections in panelboard.
2. I have checked to see if load is balanced.
3. I have had Power Company check all connections on their end.
4. I have done voltage test to see if it is ok (my multimeter does not pick up any real VD.
5. Lights will dim when load is on 15A circuit I.E.(hair dryer, sweeper)
6. I have had logging meter check for voltage spikes or dips (no major ones). Plus light do not dim unless load on.
Now with help of my new circuit analyzer, I have found out that all though my multimeter did not pick it up my circuit analyzer shows an 8.7%VD on one outlet and a 15.4% on another. Now maybe its 14AWG wire, or maybe loose connections on devices them selves. The thing is I have a very low neutral to ground resistance. This should mean I have both good grounding wire connection, and a good neutral wire connection. This would again lead me to the hot wire, but what are the odds of both lighting circuits having loose hot some where?

This got me thinking about grounding rod again, if bad ground then it would explain lightning strike I get affecting my electrical system. The circuit analyzer would only test resistance from grounded wire to grounding wire in my house; not to the ?earth ground?. So I could still have bad ground resistance and not now it. The power company says it is fine (of course). I am still convinced this is problem. So I am going to a new grounding system.

The question is if any of you see this, and find a different reason, or opinion. Then I would love the input.

 

[bphgravity]

Re: Bad ground?

The grounding electrode system plays no role in the issues your are explaining. Upgrading or installing a new system will do nothing to correct your issues. You have a classic case of voltage drop. This voltage drop is a product of heavy loads starting or switching on-and-off while the lights are on. In most cases, this issue is only a nuisance and will not cause too many problems.

 

[hurk27]

Re: Bad ground?

Dan are you around Portage,In.?
As Bryan has pointed out grounding electrods do not play any role in current returning to source and should not be, because 120volts @25 ohms would only allow 4.8 amps of current to pass. All current returning to source should be via the grounded conductor (neutral) As you said your sure test found that you have a 15% voltage drop on one of your circuits and if the lighting is also on this circuit you will see the lights dim when a appliance that uses any large amount of current it will dim the lights.
If it is excessive which 15% is high then the cause needs to be found. If it is just because the leanght of the wire is long like over 100' then there would not be any danger of fire, but if it is because of a loose connection then there is.
Older buildings usualy had home runs ran to the light then spider down to each receptacle in a room somtimes receptacles on ajoining walls would be connected to the same receptacles on the other side of that wall.
But you need to map out the electrical to see how it was ran and then test each run to see where the voltage drop changes accross each connection.
If the lights are dimming through out the house first find the common point between the lighting circuit and the receptacles if it is the main panel then this should be where to look but if it is as above you might need a larger wire size for the home run.
It doesn't take much resistance in a set of conductors to start dropping voltage.

a 14awg circuit would exceed the 3% with a 15 amp load if it was longer then 38' so you can see how quick it drops.
Now apply the same current to a 12awg wire and you can run 50' before you exceed 3%
for 10awg it would be 96'

But a voltage drop of 5% would not be to bad:
14awg=64'
12awg=102'
10awg=160'
Now if we just size the circuit for 80%(12.5amps) rating we even get a little longer.
14awg=46'@3%,76'@5%
12awg=73'@3%,121'@5%
10awg=117'@3%,193@5%

Ok my brain is warn out.

 

[hardworkingstiff]

Re: Bad ground?

Did you check for a voltage drop across the main breaker? The higher the load the better the check.

 

[maintain]

Re: Bad ground?

"Lights will dim when load is on 15A circuit I.E.(hair dryer, sweeper)" "15% Voltage Drop" "14awg"

As you may know a 15% Voltage Drop is not good...it's very bad. You are heating the 14awg wire insulation, which will become brittle and flake off. A 15 amp circuit is only allowed to be loaded 80% of its capacity which is 12 amps or 1,440VA or wattts. If you are using a 1800 watt Hair Dryer then you are over loading the circuit!

To use these higher amperage draw (over 1,440 watts) "Small"(yeah right) Appliances then you with require a circuit with minimum 12awg wire and 20amp breaker. But that may not stop your lights from dimming if the recepticals are on the same circuit. You may need to have seperate circiuts for the lighting and recepticals. We have to have seperate circuits for the recepticals in the kitchen just because of these high amperage draw appliances.

 

[electricaldoc]

Re: Bad ground?

I live in a mobile home (fire trap), but it is not very old 1998 to be exact. I have done VD test at main. Unfortunately my multimeter does not seem to pick them up, but my circuit analyzer has 120V plug and can not be plugged into panel at main. I am starting to look for loose connection in outlets now. Hopefully I will find something. If for no other reason than to make me feel safer with out having to rewire everything.

 

[ccjersey]

Re: Bad ground?

Been there done that I've seen some of the best wiring and a whole lot of the worst wiring in mobile homes I've lived in. I think if you are lucky you'll find a bunch of the quick push-in connections are not so good. Not so lucky the wire may just be too small. Really unlucky- there'll be defective wire buried in the wall.

But Hey, you are still alive, so you can do something about it! How unlucky can that be!

Jim

[ July 05, 2005, 11:17 PM: Message edited by: ccjersey ]

 

[hurk27]

Re: Bad ground?

electricaldoc

If you have a double wide the first place I would check is the marriage wall connections They problem have three or four 4 squares under the middle of both halves and this is where they tie the home run back to the panel. The moisture under a trailer can corrode connections in no time. If you find it use NoLox in the wirenuts when you put them back.

 

[rick hart]

Re: Bad ground?

Check voltage across the main breaker- line A to load A. You aren't looking for much here- a couple of volts indicates a real problem. If there is any voltage present, you have high contact resistance on your main which will cause this sort of dimming. Make sure you are making good, solid contact with the test leads and you have a good meter. After that check from line to the load side of the branch breakers, looking for a VD there. Since the VD is different between circuits, it sounds like a bad connection somewhere.
Now to the hunch-Are the lights that show a problem controlled by an electronic dimmer? Even when full bright, these things still put a slight notch in the waveform which makes any voltage drop more noticeable. Dimmed slightly the VD is more pronounced.

 

[electricaldoc]

Re: Bad ground?

I have a good multimeter a?Fluke 189 logging meter.? I thought I had a good connection, but I can always try again. It is a single wide so no connection underneath. I also noticed service wires coming in are aluminum which doesn?t make me very happy either. I guess its time to take measurements on every circuit and find the trouble. So I can start the repair process.

[ July 06, 2005, 01:10 PM: Message edited by: electricaldoc ]

 

[rick hart]

Re: Bad ground?

That Fluke oughta do it.
Realize that what I am recommend you do is check voltage in series along the current path as the current flows to the load. I did not notice that in your previous post. You are looking for any measurable voltage through the breaker's contacts, not to ground, neutral or the other phase. Good luck.

 

[stud696981]

Re: Bad ground?

Hurk27 is correct about this problem on double wide mobile homes. I have seen this on more then one occassion and they were also fairly new well constructed homes. It may be simply easier to pull a new circuit then actually access these connections.

 

[harley]

Re: Bad ground?

Please check all connections @ recept and SW's. All connections @ recept need to be on screws not the back stabs check any wire nut connection make sure wires are twisted. When I see voltage drops always back stabs are the cause on 15 amp circuit. Accuracy of some measuring equipment can be questioned.

 

[George Stolz]

Re: Bad ground?

Maintain, welcome to the forum!

Originally posted by maintain:
A 15 amp circuit is only allowed to be loaded 80% of its capacity which is 12 amps or 1,440VA or wattts.

Can you be more specific? This statement is not entirely correct.

210.23(A)(1) states that any one cord-and-plug-connected appliance cannot exceed 80% of the rating of the circuit. In general, circuits can be loaded to their max OCPD rating, so long as it's not for more than three hours.

Given your hair-dryer analogy, I'm sure that's probably what you meant anyway.

Anyway, welcome!

 

[hurk27]

Re: Bad ground?

As you may know a 15% Voltage Drop is not good...it's very bad. You are heating the 14awg wire insulation, which will become brittle and flake off. A 15 amp circuit is only allowed to be loaded 80% of its capacity which is 12 amps or 1,440VA or Watts. If you are using a 1800 watt Hair Dryer then you are over loading the circuit!

This is not quite true as if the wire is sized for the current of the load then it will not heatup because of a voltage drop. Only more current will do this, does a wire with voltage drop waste energy as in heat? yes it does but this is because the heat generated is over the total length of wire. A current reading taken at any point along the length of wire will not be over the rating that the wire can safely handle. Also resistance is current limiting so the longer the run the wire will have less current on it.

 

[maintain]

Re: Bad ground?

Originally posted by hurk27:

As you may know a 15% Voltage Drop is not good...it's very bad. You are heating the 14awg wire insulation, which will become brittle and flake off. A 15 amp circuit is only allowed to be loaded 80% of its capacity which is 12 amps or 1,440VA or Watts. If you are using a 1800 watt Hair Dryer then you are over loading the circuit!

This is not quite true as if the wire is sized for the current of the load then it will not heatup because of a voltage drop. Only more current will do this, does a wire with voltage drop waste energy as in heat? yes it does but this is because the heat generated is over the total length of wire. A current reading taken at any point along the length of wire will not be over the rating that the wire can safely handle. Also resistance is current limiting so the longer the run the wire will have less current on it.

Resistors converter current to heat. So what resistor is getting heated? The wire. But the insulation of any 14 awg wire (THHN included)is rated at 15amps. The Inverse Time Delay Curcuit Breaker will take time to trip on heat. Also when a motor runs on voltages lower than rating (as is the condition when higher VD is present) the motor current is larger than the nameplate rating. So for a short period the curcuit may have higher current than the OCP rating. That is why overloads are required on motor curcuits. In a house with cord-and-plug loads on 15amp curcuit and 14 awg wire is used VD is important is the voltage from the Power Utility is 120V or a fraction lower (in Rural Electric land 125V at Service not uncommon if customer is closer to the transformer). Any current above 15amps is heating insulation, which degrades insulation faster, which may cause fire if conductor is in contact with conbustible material (wood framing).