# Lights Getting Brighter - Possible Loose Neutral?

#### BillB3857

Joined Feb 28, 2009
2,568
Since the problem is related to the sub panel, I would suspect a problem with the neutral wire between the main and sub panels. The two adjacent breakers verify that the two loads (refrigerator and lights) are indeed on opposite sides of the source. Breakers that have their handles tied together are protecting a 220V feed, such as a central air conditioner, clothes dryer or water heater, where each of the two breakers is monitoring one 120 volt side.

Imagine a 12v center tapped filament transformer feeding two 6v lamps. If both lamps are of the same wattage, the center tap would not be needed since each lamp would ,since being of the same wattage, have the same resistance and see 1/2 of the 12v. Think Ohms law and voltage divider circuit.

If, on the other hand, one lamp were twice the wattage of the other, without the center tap of the transformer being connected to the junction of the two lamps, the lower wattage lamp, having higher resistance than the other, would become very bright, even to the point of burning out. Again, think Ohms law and voltage divider circuit.

By connecting the center tap of the transformer to the junction of the two lamps, both would be lit appropriately to their own wattage since each would be receiving 6v.

#12

#### mostlydrummer

Joined Feb 8, 2016
19
Since the problem is related to the sub panel, I would suspect a problem with the neutral wire between the main and sub panels. The two adjacent breakers verify that the two loads (refrigerator and lights) are indeed on opposite sides of the source. Breakers that have their handles tied together are protecting a 220V feed, such as a central air conditioner, clothes dryer or water heater, where each of the two breakers is monitoring one 120 volt side.

Imagine a 12v center tapped filament transformer feeding two 6v lamps. If both lamps are of the same wattage, the center tap would not be needed since each lamp would ,since being of the same wattage, have the same resistance and see 1/2 of the 12v. Think Ohms law and voltage divider circuit.

If, on the other hand, one lamp were twice the wattage of the other, without the center tap of the transformer being connected to the junction of the two lamps, the lower wattage lamp, having higher resistance than the other, would become very bright, even to the point of burning out. Again, think Ohms law and voltage divider circuit.

By connecting the center tap of the transformer to the junction of the two lamps, both would be lit appropriately to their own wattage since each would be receiving 6v.
BillB, just to clarify, when I said "adjacent" I meant that one is above the other (as opposed to directly across from each other). Is that what you understood, and if not does it change your view?

#### #12

Joined Nov 30, 2010
18,224
Yes, Bill understood you. Any two adjacent spaces in a breaker box connect to the 2 sides of the 240 volts.
Now it's time to check the neutral wires to the sub-panel.

#### mostlydrummer

Joined Feb 8, 2016
19
Yes, Bill understood you. Any two adjacent spaces in a breaker box connect to the 2 sides of the 240 volts.
Now it's time to check the neutral wires to the sub-panel.
Agreed - I'm looking for a different electrician. After this discussion, I'm confident that the electrician who looked at this understood nominally the way things are supposed to be connected but didn't understand the physics well enough to troubleshoot it.

While I'm not about to go sticking a screwdriver anywhere, is there anything about the neutral connection between the two panels that would be visually obvious if it were awry?

#### #12

Joined Nov 30, 2010
18,224
Yes. Look at the cable that goes from the circuit breakers to the sub-panel. Be sure it has its wires firmly connected at both ends.

#### cmartinez

Joined Jan 17, 2007
7,911
I'm a little late for this thread, but I'm gonna stick my spoon in it anyway

Have you considered acquiring a \$10 dlls multimeter and check things out for yourself? I'm sure most of us would be more than happy to guide you through it.

#### Lestraveled

Joined May 19, 2014
1,946
How about posting some clear photos of the two panels with the covers off. If you do this I want you to be careful. Don't go probing around in the box. You want to take photos of where the white wires are clamped into a buss bar. It is a straight piece of metal with a lot of screws in it.

#### mostlydrummer

Joined Feb 8, 2016
19
How about posting some clear photos of the two panels with the covers off. If you do this I want you to be careful. Don't go probing around in the box. You want to take photos of where the white wires are clamped into a buss bar. It is a straight piece of metal with a lot of screws in it.
I was traveling again and didn't get to the photos (but great idea), but I talked to a great electrician today who asked great questions and was clearly quite knowledgeable and had a mind for troubleshooting. He's coming tomorrow morning to take a look, so I will report back. Thanks.

#### mostlydrummer

Joined Feb 8, 2016
19
Well, the electrician referenced above was unable to resolve this and didn't have a theory. I removed the covers of both service panels and it appears that all of the connections are quite tight (although I didn't try to tighten them myself). I'm going to try to upload photos.

#### mostlydrummer

Joined Feb 8, 2016
19

In L to R order above (which is not a great order, but the best I could do with posting):

1. Connection to neutral bus on sub panel.
2. Feed from main to sub panel.
3. Incoming to main panel detail.
4. Incoming to main panel.
5. Main panel neutral bus detail.
6. Main panel neutral bus.
7. Neutral feed from main panel neutral bus to sub panel.

Any additional insight is much appreciated! Thanks.

#### shortbus

Joined Sep 30, 2009
9,804
Without rereading the whole thread, where is your ground/earthing rod? Some older houses had it in the basement then the concrete floor was poured around it. That was OK for old 60A service but isn't up to code today. The earth over time drys out and doesn't conduct good enough, and isn't good enough for modern high amp service. And if the ground is connected to the water pipe, with the use of newer plastic water lines there is no real ground.

#### mostlydrummer

Joined Feb 8, 2016
19
Not sure where the grounding rod is, but as shown in the photos above there is a ground connection to the pipe through which the main service comes into the main panel (this pipe goes through the basement wall to outside). You can also see a separate ground wire going into its own pipe at the lower right of the main panel. This pipe exits the panel and turns down into the concrete floor of the basement near the foundation wall. I can't see where it goes from there, but the house is only 12-13 years old, so I would be surprised if it has "old house" issues.

#### #12

Joined Nov 30, 2010
18,224
The Earth ground at the house is merely redundant. The "real" neutral is the wire from the transformer on the pole to the neutral bar in the circuit breaker box. THAT is the wire which is responsible for carrying significant current.

When the Neutral wire in my house went bad, I found 3 amps to 10 amps grounding through my water pipes. That is not what is supposed to be happening. The water pipes are merely a redundant safety factor not intended to carry any significant current. That is not where you will find your problem.

#### mostlydrummer

Joined Feb 8, 2016
19
I have some new facts that seem very strange to me.

As noted, in my basement, any time the compressor on a small refrigerator cycles on, the thirteen overheard can lights controlled by one dimmer in the same room flash brighter for about a second and then dim to their normal level. The fridge and the can lights are on separate circuits, and the breaker for one circuit is above the breaker for the other on the service panel.

Tonight, I was trying to gather more facts by trying to determine whether the two other dimmers in the same switch plate as the "main" dimmer for the thirteen can lights, each of which controls another pair of lights, are on the same circuit as the main dimmer (they are), whether the GFI outlet in the same switch plate is on the same circuit as the outlet for the fridge, which is on the same wall (it is), and finally, whether the fridge compressor causes the same brief brightening in either or both of the pairs of lights controlled by the other two dimmers. I turned off the main dimmer and the thirteen lights, turned on the other two dimmers, and opened the fridge door, but I couldn't get the compressor to kick on. At a variety of settings and forced spreads between ambient and set temperature and with the door open and closed, the compressor never audibly ran or kicked on or made the telltale "sighing" sound that it normally makes a few seconds after it kicks on but after the lights have brightened and dimmed again. It did, however, generally stay cool and at or close to the set temperature unless I left the door open for a long time. After a couple of hours, I finally gave up, turned the thirteen overhead lights back on, and shut the fridge door. Within 15-20 seconds, the compressor kicked in, the thirteen overhead lights brightened and quickly dimmed, and the fridge made the usual, very audible "sighing" sound. So the thirteen overhead can lights seem to brighten and then quickly dim when the fridge compressor cycles on, but the fridge compressor only cycles on (audibly, at least, because it still seems to cool, and with the odd "sighing" sound afterward) when the dimmer with the thirteen can lights is turned on. In other words, the fridge behaves differently (although it cools perfectly all the time) when the thirteen lights are on than when they are not. This make no sense to me.

Any takers? Thank you.

#### Lestraveled

Joined May 19, 2014
1,946
OK, try this. See what happens when you set the dimmer of the thirteen lights to maximum.

#### wayneh

Joined Sep 9, 2010
17,201
Something is askew for sure but the only thing I want to comment on is that dimmers can behave very oddly, sometimes changing brightness quite a bit for no apparent reason. It's usually related to turning something else on or off but is not predictable. That alone wouldn't be a problem to chase down.

Dimmers also make a butt load of RF noise at any setting other than full on.

#### mostlydrummer

Joined Feb 8, 2016
19
Lestraveled, the dimmer for the thirteen cans is almost always set at maximum and definitely was tonight any time it was on (or off - it's a Lutron dimmer with an on-off rocker on the bottom and a larger, vertical slide above it for the dimmer).

#### cmartinez

Joined Jan 17, 2007
7,911
Lestraveled, the dimmer for the thirteen cans is almost always set at maximum and definitely was tonight any time it was on (or off - it's a Lutron dimmer with an on-off rocker on the bottom and a larger, vertical slide above it for the dimmer).
Can you bypass the dimmer? Turn the lights on and see how it affects the fridge...

#### mostlydrummer

Joined Feb 8, 2016
19
Can you bypass the dimmer? Turn the lights on and see how it affects the fridge...
I haven't tried that, although it's probably a good next step. I'm not really an electricity guy so I would probably call an electrician for that. I can say that the same thing (lights brightening) happened with a previous dimmer as well, so the issue would seem not to be with the dimmer itself.

#### DGElder

Joined Apr 3, 2016
351
"After a couple of hours, I finally gave up, turned the thirteen overhead lights back on, and shut the fridge door. Within 15-20 seconds, the compressor kicked in,"

The compressor may be designed to only come on when the door is closed.

Are the lights LEDs? Can you put a multimeter on the circuit with min max voltage capture to see if the line voltage is dipping or rising?

I could imagine that a voltage drop or phase change on the line when the inductive load of the compressor kicks in causing the dimmer to briefly increase the duty cycle of the lights - making them brighter. I don't know how your dimmer works, but that sounds like an innocuous problem compared to a loose neutral connection. If you have to, take the dimmer out and put a regular switch in there and see what happens.

"...the same thing (lights brightening) happened with a previous dimmer as well, so the issue would seem not to be with the dimmer itself"

It still could be the dimmer design, not a fault in the dimmer.

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