200 amp 700 feet

[kwired]

I am curious if we could expand on a couple of concepts -

1. "Installing oversize conductors to only the loads that cause flicker without increasing the service conductors will only make the problem worse." How so?
2. "... over sizing the branch circuit conductors to the HVAC would would allow more current on inrush and would flicker the lights more." The total impedance of the load is fixed while the voltage at the load is effectively higher, I don't see how load current goes up here relative to the smaller conductor.

"Since voltage drop is tied to the load you end up with over voltage during light loaded events if you boost your voltage for your full load, plus you still have the cost of all the associated gear to set a transformer. A size or two bigger wire is cheaper."

No perfect solution here and I didn't run the expense numbers, the boost concept is just a theoretical solution. You would certainly want to size the "boost" to only compensate for the voltage drop, not overcompensate. If you upsize the wire one or two sizes you still have voltage drop, just at a lower level. If you boost the voltage at the house, you might be able to restore full system voltage at the house (depending on a lot of variables, of course). I would clarify that a potential boost system be designed for no-load voltage at the house. It is quite correct to state that an overvoltage situation would be created if you design the system based on full load current.

1, I don't totally agree the problem will be worse, but if you have to much drop across a long run of conductor or too much impedance in the source (POCO transformer is marginally sized), or worse yet both, increasing your branch circuit size may not really gain anything for you.

2, some of the same applies here, if there is already significant voltage drop before we even get to branch circuit level, increasing branch circuit conductors may not really gain much.

There is both good and bad things happening at same time. Any reduction in impedance will allow more current to flow to the motor that is trying to start and help it start faster, but if the service or feeder is where the majority of voltage drop exists, it still draws voltage down on everything. This is exactly why with larger motors and industrial applications we sometimes must use reduced voltage starting methods, soft starters, etc. The motor being started can withstand this low voltage condition during starting, it is the problems it may create for other items sharing the same supply that is an issue, even if it is nothing more than the annoyance of dimming of lights to a occupant.

I once had a customer with a shop building that had sufficient sized service lateral conductors, but they connected to some overhead conductors that happened to span a couple additional poles before hitting the source. Maybe an additional 250-300 feet of overhead conductor. Transformer was right in front of this shop but across the street, our service was at the left rear of the building as you faced it. This shop was fine most of the time but every time their air compressor started it dimmed the lights pretty bad. I was able to talk the POCO in this case to put a transformer on the pole where the lateral conductors ended and now we can't even tell when the air compressor is starting if looking at the lights.

 

[ActionDave]

If you upsize the wire one or two sizes you still have voltage drop, just at a lower level.

If you do anything you have voltage drop at some level all we are worried about is not having too much, and to be honest too much is quite a lot before there gets to be a problem.

Think about how many things can run at 90V at your house forever and not care, almost all electronics have switch mode power supplies so they don't care, lights don't care, the fridge, toaster, and most any appliance don't care.

I do not mean to imply that voltage drop is never a problem, or that circuits should be undersized on purpose, but so often it is discussed when standard sizing of electrical circuits are perfectly adequate.

If you boost the voltage at the house, you might be able to restore full system voltage at the house (depending on a lot of variables, of course). I would clarify that a potential boost system be designed for no-load voltage at the house...

At no load you are going to have whatever your boosted voltage is. Turn the pressure regulator up on your plumbing up to 200lbs and that is what you have at the faucet before you open it. Whatever the pressure drops to depends of if you are feeding your house with a one inch line or a quarter inch line.

Well then I'll run a two inch line and be sure that I don't have any problems. That's fine but you are going to end up spending extra money that is not buying you anything other than the right to beat your chest at a cocktail party and brag about the size of your water line compared to everyone else.

 

[iwire]

I am curious if we could expand on a couple of concepts -

"Installing oversize conductors to only the loads that cause flicker without increasing the service conductors will only make the problem worse."

How so?

The branch circuits conductors to the loads add impedance to the total circuit, this impedance limits the possible inrush current flow from the service conductors to the load.

If you reduce the branch circuit impedance by increasing the size of just the branch circuit conductors, the service conductors will be subject to higher inrush than they were before and this will cause greater voltage drop at the service panel.

I don't see how load current goes up here relative to the smaller conductor.

Less voltage drop on the branch circuit conductor will result in higher current being drawn by the load and therefore at the service panel as well.

No perfect solution here and I didn't run the expense numbers, the boost concept is just a theoretical solution. You would certainly want to size the "boost" to only compensate for the voltage drop, not overcompensate.

The problem with this idea is that you still get varying voltage as the load changes.

Instead of a range from say 110-115 you move it up to 120-125 either way you have a five volt swing depending on load.