[butch 17]

I respectfully disagree, I have solved this problem more than a couple of times by rearranging CBs, I'm not saying that it is the solution in every case. Having a large load at the TOP of the panel was the potential problem as stated by me, not the BOTTOM as you just said. (Top being closer to Main Lugs, bottom further away this example) Voltage drop along the bus bars is definitely a real phenomenon

Then I will try. Couldn't hurt

[shuntripper]

Are there big breakers between the lugs and the lights? Did you look yet?

[tkrussell]

This is exactly what should be done:

i will meet a/c and electrician on Tuesday.

Between both of them, the issue should be resolved, or at least identified.

ANY panel that had a voltage drop between the top and bottom of the busbars has a mechanical issue causing the "phenomenon".

When dealing with existing panels, which is done often, and a new large load is to be added, where the breaker will sit in the panel is and should not be an issue, since most times the available space is at the bottom of the panel.

[shuntripper]

This is exactly what should be done:




Between both of them, the issue should be resolved, or at least identified.

ANY panel that had a voltage drop between the top and bottom of the busbars has a mechanical issue causing the "phenomenon".

When dealing with existing panels, which is done often, and a new large load is to be added, where the breaker will sit in the panel is and should not be an issue, since most times the available space is at the bottom of the panel.

You are entitled to your opinion. I'm not going to back away from what I know to be true.
I'm not new at this, TK, I don't mean to step on any toes

All panels are not top fed either, by any means. My point is that a motor load or other load that pulls a lot of amperage when it starts causes a voltage drop along the bar. That's why you put lighting circuits closest to the lugs. Common knowledge and practice.
I'm curious what "mechanical issue" you think a solid bar might have, OP said that everything had been checked and was tight, in good shape.

[stanfortyman]

my point is that a motor load or other load that pulls a lot of amperage when it starts causes a voltage drop along the bar. That's why you put lighting circuits closest to the lugs. Common knowledge and practice.

Nope. NOT common knowledge or common practice at all.
Sorry, but I completely disagree here.

[shuntripper]

Nope. NOT common knowledge or common practice at all.
Sorry, but I completely disagree here.

Go ahead, maybe you guys can learn something new, I've been doing this for a long time and I'm pretty sure I don't know it ALL, maybe you do?

[stanfortyman]

go ahead, maybe you guys can learn something new, I've been doing this for a long time and I'm pretty sure I don't know it ALL, maybe you do?

I'm not sure where it is I said, or even implied, that I know it all. Maybe you can point that one out to me.

While you're at it, maybe you can point to some verification to support your claim there there is significant enough voltage drop across the buss of a panel to cause voltage sag, and that the arrangement of the breakers has any significant effect in alleviating this.

[butch 17]

This is exactly what should be done:




Between both of them, the issue should be resolved, or at least identified.

ANY panel that had a voltage drop between the top and bottom of the busbars has a mechanical issue causing the "phenomenon".

When dealing with existing panels, which is done often, and a new large load is to be added, where the breaker will sit in the panel is and should not be an issue, since most times the available space is at the bottom of the panel.

House was built in 1996. The a/c unit was replaced 4 years ago. The lights dimming just started when remote control and energy system was install on the furnace . The furnace is run from a 110v outlet. The lights only dim when compressor starts. I know it pull a higher start loan than run load. But can't understand why it is pullling voltage from lighting circuit ?

[tkrussell]

Butch , Has the HVAC tech and electrician been on site yet?

I would be checking the running and starting current of the AC unit, just so I know what it is, and compare to nameplate rating.

I would be checking the Main Breaker, both, connections to the bus bar, and the contact resistance of the internal contacts.

Check the entire bus bar of the panel for any bolted connections.

Check each circuit breaker, how it connects to the busbar. What is the condition of the entire strip of both bus bars?

Check how this energy management system is connected, what does it control, and how. Possible it causes too much load to start at same time?

So many possibilities.

Can you describe the dimming? How long duration is the dimming?

[butch 17]

Butch , Has the HVAC tech and electrician been on site yet?

I would be checking the running and starting current of the AC unit, just so I know what it is, and compare to nameplate rating.

I would be checking the Main Breaker, both, connections to the bus bar, and the contact resistance of the internal contacts.

Check the entire bus bar of the panel for any bolted connections.

Check each circuit breaker, how it connects to the busbar. What is the condition of the entire strip of both bus bars?

Check how this energy management system is connected, what does it control, and how. Possible it causes too much load to start at same time?

So many possibilities.

Can you describe the dimming? How long duration is the dimming?

Hopefully the a/c teck will be tomorrow. Electrician says that all connections are tight the bus bar is in good shape the main is in good shape. Ground is connected doesen't find any reason for dimmimg ? Dimming is like a blink of the eye. Voltage drop was enough to have to re set clocks and TV and electronic stuff. What is giving me trouble is that the problem just started when the management system was put in. but the lights only dim when compressor kicks in. so it has to have something to do with the a/c or the a/c circuit?

[tkrussell]

The lights are dimming due to the voltage drop caused by the high starting current of the AC.

Should not occur. There is most likeley a loose connection, someplace, that with the high current impressed on that connection, the resistance is high enough to drop the voltage, and apparently enough to be of longer duration that must be low enough to out of tolerance that the clocks need.

Once this connection is found, you may be surprised it would to be of such small signifiance, to cause this problem.

What type of management systen was installed? It may be more than just low voltage control wiring, and may have line voltage contactors.

Odd the problem started after this got installed. May be the starting point for troubleshooting.