Bonding Neutral in sub panel confirmation

[dyermullet]

Hello I apologize in advance for a simple question. Just bought a house in the process of moving all my tools are boxed up, no phone signal at the house etc. Posting this simple question to confirm that sub panel should not have neutral bonded to ground. I have had some lights flickering and the strange occurrence of when the AC comes on some of the lights in the house get brighter. This occurs on multiple circuits. I suspect that I have a loose neutral connection, I am going to buy volt meter after work (all of mine are packed away) so I can check everything out and determine if the issue is on my equipment or the power company side. That brings us to the question,

I opened the panels last night just to look at what was going on. The house has two panels (both panels in same building), the meter feeds the main panel. This main panel has three breakers in it, one is an outside light, one is an outside outlet, and the third is a large amp breaker that feeds the sub panel. The sub panel is the traditional style panel that has a main disconnect on the incoming power, every load from the house is connected to this sub panel. The sub panel has the bonding strap installed between the neutral bar the the ground. I thought sub panels need to have the neutral and ground isolated correct? Can this double bonded neutral cause the symptoms I am having?

 

[Chuckster in NJ]

Only a main panel should have the neutral and ground bonded together.
Sounds like you have an issue with a loose neutral so I suggest you call a licensed electrician who knows what to do.…….. Don’t wait on this issue because it may get worse and cause more problems.

 

[dyermullet]

I forgot about the FAQ, I just found the diagram that confirms I should not have neutral bonded.

 

[mm08822]

The sub panel neutral and ground should not be bonded. Shut off power to the sub-panel before you remove the bond.

Visually inspect all connection points and those related conductors for signs of heat caused by loose connections. Going through all connections is not a bad idea as you have zero history of this equipment. If found tight, leave it. If found loose, you may need to strip back for new conductor if heat damaged. If looks ok otherwise, just tighten.

Dimming upon start-up is common due to voltage drop caused by high inrush current. If it is 240vac ac equipment, it won't use a neutral.

The main panel should have its connections checked also. Start with the visual. Depending on your knowledge and comfort level, you may want professional help in that one. Even at the meter. Is it overhead or underground service?

Lights getting brighter during a start-up.......I need to think about that one.

Call the POCO if everything "looks" good as you found it.

 

[dyermullet]

Only a main panel should have the neutral and ground bonded together.
Sounds like you have an issue with a loose neutral so I suggest you call a licensed electrician who knows what to do.…….. Don’t wait on this issue because it may get worse and cause more problems.

Thanks for the confirmation.

 

[mm08822]

Take pics pics of panels with covers removed. Include outside meter and any other electrical service equipment.

 

[dyermullet]

The sub panel neutral and ground should not be bonded. Shut off power to the sub-panel before you remove the bond.

Visually inspect all connection points and those related conductors for signs of heat caused by loose connections. Going through all connections is not a bad idea as you have zero history of this equipment. If found tight, leave it. If found loose, you may need to strip back for new conductor if heat damaged. If looks ok otherwise, just tighten.

Dimming upon start-up is common due to voltage drop caused by high inrush current. If it is 240vac ac equipment, it won't use a neutral.

The main panel should have its connections checked also. Start with the visual. Depending on your knowledge and comfort level, you may want professional help in that one. Even at the meter. Is it overhead or underground service?

Lights getting brighter during a start-up.......I need to think about that one.

Call the POCO if everything "looks" good as you found it.

I will go through everything, last night late was the first opportunity I had to look at this.

240 AC central air. I believe I have a bad neutral due to the increase in light brightness that occurs when AC is running.

overhead service.

I have a lot of electrical experience (just not residential code experience) I will be able to safely work on the system.

 

[NostraThpmas]

Is the sub panel fed by 3 wires (Hot, Hot, Neural) or 4 wires (Hot, Hot, Neutral, Ground)?

 

[Chuckster in NJ]

Most of the time on an overhead service the utility "insul link" connections will fail at the weather head or pole and must be redone……. Typical utility issue that gets resolved with a phone call.

 

[dave*99]

Is the sub panel fed by 3 wires (Hot, Hot, Neural) or 4 wires (Hot, Hot, Neutral, Ground)?

THIS IS IMPORTANT - The OP should not un-bond the sub panel ground and neutral unless he confirms the 4 wire feed.

 

[WildBill]

They might be treating the first panel as just an emergency disconnect, in which case they could just have three wires going to the sub panel.

 

[wyliesdiesels]

Hello I apologize in advance for a simple question. Just bought a house in the process of moving all my tools are boxed up, no phone signal at the house etc. Posting this simple question to confirm that sub panel should not have neutral bonded to ground.

If the subpanel is in the same structure as the main or feeding panel, then it should NOT have a bonded neutral. If in a detached structure it could have a bonded neutral with some exceptions prior to 2008 code cycle

I have had some lights flickering and the strange occurrence of when the AC comes on some of the lights in the house get brighter. This occurs on multiple circuits. I suspect that I have a loose neutral connection,

a bonded neutral and a loose or failing neutral would NOT cause the lights to get brighter when a 240v AC load turns on. An AC compressor running on 240v does not use a neutral so it has no bearing and because the in-rush current is high, the lights should actually be dimming in some cases due to voltage sag.

If the lights are getting brighter youve got other problems than a loose neutral.

I am going to buy volt meter after work (all of mine are packed away) so I can check everything out and determine if the issue is on my equipment or the power company side. That brings us to the question,

there is only one way lights can get brighter when a large load starts up and that is a VR on the PoCo side switching to a higher tap because of the load. nothing in your house can make the voltage increase when an AC compressor starts. that defies basic electrical101.

I opened the panels last night just to look at what was going on. The house has two panels (both panels in same building), the meter feeds the main panel. This main panel has three breakers in it, one is an outside light, one is an outside outlet, and the third is a large amp breaker that feeds the sub panel. The sub panel is the traditional style panel that has a main disconnect on the incoming power, every load from the house is connected to this sub panel. The sub panel has the bonding strap installed between the neutral bar the the ground.

It should not be bonded. Is the feeder 3-wire or 4-wire?

I thought sub panels need to have the neutral and ground isolated correct? Can this double bonded neutral cause the symptoms I am having?

nope not at all because the load (Ac compressor) is 240v. a 240v load does not connect to neutral and has no bearing on line to neutral loads.

 

[wyliesdiesels]

They might be treating the first panel as just an emergency disconnect, in which case they could just have three wires going to the sub panel.

Since there are 3 branch breakers in the "main panel" it would not be an emergency disco...

 

[mm08822]

They might be treating the first panel as just an emergency disconnect, in which case they could just have three wires going to the sub panel.

First point of overcurrent protection is considered the main panel.

The grounding electrodes should also connect in this panel.

 

[wyliesdiesels]

Only a main panel should have the neutral and ground bonded together.
Sounds like you have an issue with a loose neutral so I suggest you call a licensed electrician who knows what to do.…….. Don’t wait on this issue because it may get worse and cause more problems.

a loose neutral would not cause lights to get brighter when a 240v load starts up...

 

[wyliesdiesels]

The sub panel neutral and ground should not be bonded. Shut off power to the sub-panel before you remove the bond.

need to confirm number of conductors in feeder first. if 3-wire, feeder will need to be updated to 4-wire. also need to move grounds/EGCs over to ground bar as well. ground bar(s) may need to be added

would be really helpful if OP posted pics of everything otherwise we are just guessing

 

[Innovate1]

Have had bad connection on the neutral at the weatherhead on a previous house. When load was placed on one phase the voltage on the other phase 120V loads would go up and lights would brighten. That issue shouldn't do much if only a 240V load but with AC you have both - the outdoor unit is 240 but the inside unit is typically 120V so loading one line only and relying on current back through the neutral. If you check the voltages from each hot to neutral at the panel as larger loads are turned on and off you will probably see the voltages changing. I would look for steady state changes rather than when the motors start and there are large, short current spikes. I would check in first panel and if there the problem could be in the overhead splices. If you don't see any big changes there then go to the second panel. A call to the utility should get them out to check and fix if it's the weatherhead splices. They can also turn off the power so you can check the main connections.

 

[wyliesdiesels]

240 AC central air. I believe I have a bad neutral due to the increase in light brightness that occurs when AC is running.

a loose neutral WOULD NOT cause lights to get brighter when a 240v load turns on. a 240v load doesnt even use a neutral so the 2 are unrelated.

 

[wyliesdiesels]

Have had bad connection on the neutral at the weatherhead on a previous house. When load was placed on one phase the voltage on the other phase 120V loads would go up and lights would brighten. That issue shouldn't do much if only a 240V load but with AC you have both - the outdoor unit is 240 but the inside unit is typically 120V so loading one line only and relying on current back through the neutral. If you check the voltages from each hot to neutral at the panel as larger loads are turned on and off you will probably see the voltages changing. I would look for steady state changes rather than when the motors start and there are large, short current spikes. I would check in first panel and if there the problem could be in the overhead splices. If you don't see any big changes there then go to the second panel. A call to the utility should get them out to check and fix if it's the weatherhead splices. They can also turn off the power so you can check the main connections.

He said its while the AC is running. an air handler doesnt take much power to run the blower motor. all of a few amps. and its happening on multiple circuits so that rules out branch circuits. garbage disposals and dishwashers take more power than an air handler so if it was a loose neutral, the issue would be even more noticeable when either of those are running but OP only mentioned AC

 

[Innovate1]

a loose neutral WOULD NOT cause lights to get brighter when a 240v load turns on. a 240v load doesnt even use a neutral so the 2 are unrelated.

AC runs internal air handler which is often 120V. That could cause lights on other phase to get brighter. I don't see any other way for some circuits increase in voltage other than a bad neutral connection somewhere.

 

[Innovate1]

He said its while the AC is running. an air handler doesnt take much power to run the blower motor. all of a few amps. and its happening on multiple circuits so that rules out branch circuits. garbage disposals and dishwashers take more power than an air handler so if it was a loose neutral, the issue would be even more noticeable when either of those are running but OP only mentioned AC

Blower motors are typically 1/3 - 1 Hp in traditional HVAC residential setups. The larger ones are up to about 12A. If the loose neutral is at the weatherhead it would affect every circuit.

 

[Innovate1]

To the original question - the double bonded neutral isn't correct but isn't going to cause the increased brightness. That is something else.

 

[wyliesdiesels]

Blower motors are typically 1/3 - 1 Hp in traditional HVAC residential setups. The larger ones are up to about 12A. If the loose neutral is at the weatherhead it would affect every circuit.

Op said multiple circuits are affected but not all. and only the HVAC is causing this. not any other large 120v load (which he may or may not have) such as disposal, dishwasher, washing machine, dryer, etc. so how could only the HVAC showing a loose neutral issue and not other appliances?

 

[Chuckster in NJ]

a loose neutral would not cause lights to get brighter when a 240v load starts up...

That is true, however "IF" the furnace blower is 120 volts and it starts the same time as the condenser some lights may get brighter.……… A loose neutral will cause all sorts of wacky things.

BTW! Without seeing and testing the ENTIRE system nobody can troubleshoot this issue over the internet.

 

[mm08822]

He said its while the AC is running. an air handler doesnt take much power to run the blower motor. all of a few amps. and its happening on multiple circuits so that rules out branch circuits. garbage disposals and dishwashers take more power than an air handler so if it was a loose neutral, the issue would be even more noticeable when either of those are running but OP only mentioned AC

AC runs internal air handler which is often 120V. That could cause lights on other phase to get brighter. I don't see any other way for some circuits increase in voltage other than a bad neutral connection somewhere.

The blower motor turning on at the same as the 240vac ac unit could (and most likely would) alter the neutral voltage on any 120v circuit that has loads turned on.

Some branch circuits would go higher and some lower......constantly changing based on the connected energized 120v loads.

The blower motor being 120 is the key not the 240v ac.

OP, so check hot-neutral voltages from the sub panel back to the line side of main cb with and w/o ac/blower running.

 

[dyermullet]

Thanks everyone for the replies.

As said in first post, just moved don't know where any of my possessions are, including phone chargers (no pictures last night). Don't have phone signal at home and no internet service. Just jumped on computer here while at work. Will take some pictures but won't be able to post for a few days.

House was built in 1994, electrical would have been to the code at that time. No updates to electrical since that time. To clarify service is above ground to the utility pole, then runs underground to the meter. So I don't have a weather head at the house.

Like Innovate1 said I believe blower on the evaporator is 120, which I am educated guess why I am seeing the lights get brighter, when the AC startup. Other appliances like the fridge could be doing the same thing I haven't spent enough time in the house yet to corrolate.

Wyllesdiesels - I understand the 240 load doesn't use the neutral.

Had no volt meter or patience (or phone battery for pictures) last night, that why I made a post this morning to ensure I remembered the code correctly.

I saw four wires into the subpanel last night, will investigate and identify everything first before removing bonding strap.

Going to test for changes in potential tonight with different loads on and off. Hopefully I can identify a loose neutral on my side so it can be a quick fix and not have to wait for the power company to come out.

edit- corrected to saw 4 wires in sub panel.

 

[WildBill]

Since there are 3 branch breakers in the "main panel" it would not be an emergency disco...

In theory and per code, but I've seen it done many times around here with the same setup.

 

[dyermullet]

In theory and per code, but I've seen it done many times around here with the same setup.

Down here the main panel breaker serves as the emergency disconnect.

 

[mm08822]

Thanks everyone for the replies.

As said in first post, just moved don't know where any of my possessions are, including phone chargers (no pictures last night). Don't have phone signal at home and no internet service. Just jumped on computer here while at work. Will take some pictures but won't be able to post for a few days.

House was built in 1994, electrical would have been to the code at that time. No updates to electrical since that time. To clarify service is above ground to the utility pole, then runs underground to the meter. So I don't have a weather head at the house.

Like Innovate1 said I believe blower on the evaporator is 120, which I am educated guess why I am seeing the lights get brighter, when the AC startup. Other appliances like the fridge could be doing the same thing I haven't spent enough time in the house yet to corrolate.

Wyllesdiesels - I understand the 240 load doesn't use the neutral.

Had no volt meter or patience (or phone battery for pictures) last night, that why I made a post this morning to ensure I remembered the code correctly.

I saw four wires into the subpanel last night, will investigate and identify everything first before removing bonding strap.

Going to test for changes in potential tonight with different loads on and off. Hopefully I can identify a loose neutral on my side so it can be a quick fix and not have to wait for the power company to come out.

If the sub panel is fed by metallic conduit, then that should be acting as the ground.

If it is only cable, then it is wired wrong and needs a 4th conductor.

 

[dyermullet]

I corrected my post, it has 4 wires.

 

[mm08822]

Here the main panel breaker serves as the emergency disconnect.

If it is located on the exterior of the building then it is considered the emergency disconnect for current code.

 

[wyliesdiesels]

In theory and per code, but I've seen it done many times around here with the same setup.

an emergency disco (ones required by latest code) was not required by code in 1994 so it is moot

 

[Innovate1]

Thanks everyone for the replies.

As said in first post, just moved don't know where any of my possessions are, including phone chargers (no pictures last night). Don't have phone signal at home and no internet service. Just jumped on computer here while at work. Will take some pictures but won't be able to post for a few days.

House was built in 1994, electrical would have been to the code at that time. No updates to electrical since that time. To clarify service is above ground to the utility pole, then runs underground to the meter. So I don't have a weather head at the house.

Like Innovate1 said I believe blower on the evaporator is 120, which I am educated guess why I am seeing the lights get brighter, when the AC startup. Other appliances like the fridge could be doing the same thing I haven't spent enough time in the house yet to corrolate.

For testing you could switch on the indoor blower with the fan on switch on the thermostat rather than running the whole AC system. Probably the easiest thing to turn on and off and run at full, steady load. A plug in heater or blow dryer could be useful for testing too. I would be a careful about running things until you resolve the issue especially not plugging in things like TV and electronic stuff. When it happened to me I didn't end up having anything damaged by overvoltage but it could happen.

 

[BillK]

If it was me I would call the POCO and have them come out and check the feed. Tell them you just moved in and the lights are flickering. I bet they will come out and take a look. At least that will rule out that part of the system.

 

[Innovate1]

If it was me I would call the POCO and have them come out and check the feed. Tell them you just moved in and the lights are flickering. I bet they will come out and take a look. At least that will rule out that part of the system.

Me too. They said they don't want to wait for the power company to come out but they would likely have been there already. Or maybe it's that they aren't living there yet so might not be there when the POCO came by.

 

[dyermullet]

Turned off most loads in the house voltage was balanced h to n to h. Turn on hair dryer. One phase to N drops to 117vac. Other phase went up to 131vac hot to n. Measured at main breaker and sub panel had same voltages. Will contact power company tomorrow morning.

Left the hair dryer out the window plugged into an extension cord incase they want to test and no one here.

Wiring between the main panel and sub panel is not correct. Will post details later for advice on how to correct.

Thanks again for all the help and giving me refresher to on how to approach this.

 

[BurtEggley]

Me too. They said they don't want to wait for the power company to come out but they would likely have been there already. Or maybe it's that they aren't living there yet so might not be there when the POCO came by.

Definately this is how it should be handled right away. If it is overhead let them confirm that no squirrel, rat or corrosion is causing issues. Eliminate them as the cause.

The science of it may be that a connection common to both the AC and Lights (plural) is loose, has resistance, and /or corrosion in it. When the AC turns on there is a large flow of power for a split second. That can overcome a bit of the corrosion as it arcs, and the connection is better for just a little. The real issue is that if that bad connection is in a wall, then the heat could start a fire. Call the POCO.

 

[dyermullet]

Just got off phone with the power company rep, have a work order in for the issue.

To all the recommendations above of "just call the power company", I understand your point. Remember, I just acquired ownership of the property, I wanted to confirm the problem wasn't on my end so I didn't get hit with a $150 charge.

This property has two meters and I have already had the lineman out about the second meter (turn out PO had requested power turned off after the closing date, jerks).

Also, their was some PO ******** that I wanted to deal with before the lineman had to come out for this, including extension cord being wired into the main panel (i turned off this breaker immediately when I took ownership), and an non interlocked breaker for running a generator to power the house (including permanent marker written all over). Last night I just went ahead and pulled all three of the branch breakers out of the main panel since they were all wired wrong.

Last night I found I had some of the details wrong on what I posted above, I was going off of memory from inspection 6 weeks ago the property has 2 meters and three panels and the details got fuzzy. I believe what I called the main panel started life as a disconnect, and the subpanel with the bonded neutral was actually the main panel (this is also where the driven ground is connected). At some point the PO added the three branch circuits into the disconnect panel at that point in my mind it technically became the main panel and the old main became a sub. I pulled all the branch circuits out of the disconnect panel. The current state is the disconnect panel has a 200 amp breaker from the meter feed, at the bottom of its bus has lugs where the power then leaves that panel and lands on the breaker in the main panel.

I will post an update with a resolution of the neutral when I have the details. Because I started this post with some incorrect details, I will create a new one later. I have some questions on best way to accomplish some changes, want to update to the modern dual ground rods, maybe replace this disconnect panel, add a proper generator plug in, etc.

Thanks again to everyone for their help.

 

[Innovate1]

Did you have a home inspection? They are usually big on writing up electrical things - if so I'm surprised they didn't flag the extension cord connection. In my experience they are sometimes overly aggressive flagging things that are allowed like double taps on breakers that may be rated for such or splices in the breaker panel. I have mixed feelings about the need for inspections - in my case I am pretty familiar with construction but having an inspector flag something carries more weight when negotiating to get things fixed. And they might catch something I overlooked. Sounds like you are on your way to getting it cleaned up and not too difficult to resolve things.

 

[mm08822]

Still seems like your disconnect panel would have (should have) become the main panel.

Now with 2 meters in the story, the plot thickens.

NEED PICS WITH COVERS OFF! (otherwise word salad continues to get tossed.)

Calling the POCO after you confirmed the bad neutral was upstream of your equipment was correct. (And now you know how to verify their fix.)