Subpanel breaker type

[Rollie Meyers]

This thread saved me a bunch of money. I had forgotten that the largest bus bar breaker you could get was 125. I was going to run 200 down there, just in case I needed that much later. Doing some refiguring, 125 is plenty, so I'm saving almost 7,000 dollars by only needing 500-500-500-350 MCM instead of 750 MCM. The cost is almost double for 500 feet. It needs to be that large because there will be a 65 amp subpanel another 300 feet away.

I wasn't going to be able to pick up that spool of 750 with my tractor, but can easily handle the spool of 500, so it saves more than money.

65A subpanel? 65A is not a standard size fuse or circuit breaker, it jumps from 60A to 70A.

[Tom M King]

Thanks for that Rollie. 70 will be better anyway. 65 was listed on the wire sizing chart I was using. I haven't gone to order any of this stuff yet. Still working on other things, and in the meantime wire prices have come down some, so no need to get in a hurry to have supplies sitting here. I'll have an irrigation pump that draws 43 amps at the end of that total run. Design is still all in my head.

[Bill Dufour]

500 feet of wire? you will need to upsize the wire to allow for voltage drop. Before I did anything more about planning I would measure what voltage is supplied to the meter now. Measure at different times of the day.
make sure the voltage drop calculator is using single length or double length to size the wire run.
Bill D.

[Tom M King]

That's why I'll be using 500MCM, as I said, for a 125 amp service. There are plenty of size calculation converters online that give several different potential percentages of voltage drop. It will be serving a two bathroom little building 487 feet from service that will only supply this, and 300 more feet away from that a boathouse with lights, boat lift motors (not likely to ever all be working at the same time), and a 10 hp single phase water pump for the irrigation system that will only run when nothing else is running. The bathrooms will not be used much other than when the point is rented for weddings. Water is already supplied and no requirements for electricity other than a 20 gallon water heater, lights, and small mini split.

On this point.

Anyone else's calculations are welcomed. I could go up to 750 MCM, but the difference in price for that first run is $7,000 and the spool of wire is heavier than I can handle easily with my loader.

[Dwayne Watt]

Are you certain you want 500-500-500-350 cable? That is typically for 3-phase installations (3 phase conductors and a common neutral). 500-500-350 MCM is single phase tri-plex cable with two phase cables and one neutral.

[Tom M King]

It’s a feed to a sub panel.

[Tom M King]

The price of that 500' foot roll of 500 MCM quadplex just dropped $1100. I'll keep watching a while longer, and hope for another drop.

[Bill Dufour]

Keep an eye on Craigs and ebay list for cable. I doubt you will get that long a piece but anything is possible. If you got a deal. on shorter piece you could come up in the middle of the run and put a breaker panel junction box in a small summer house/
Bill D

[Rollie Meyers]

Conductors larger then 1/0 can be paralleled, they have to be the same material, insulation type, & the same length, but is a good way to make things easier to work with over wrangling larger cables.

[Tom M King]

I don't know how they come on the spool. I haven't seen any in person yet. It would suit me fine if they aren't twisted. It will be next Fall at the earliest before I get into that job.

Part of it will go through 8" PVC water pipe. Years ago, when the county was putting in a water system, the contractor stopped by my place and told me they had a bunch of leftover pieces, and some the hub end had been messed up on, and asked me if I wanted it and if I had anywhere they could put it. I didn't turn it down, and still have a big pile of it.

Part of the run goes down a hill through Pine trees and I already have the 8" pipe buried through there. I don't have enough of the pipe for the whole run, but I intend to slice it in segments, put one down to lay the wire on in the trench, and then put another piece of top of it. I have a plenty to do that with it.

The run through the trees is straight. I intend to weld a bracket to hold the spool on the tractor with the loader, and use another tractor or the truck to pull the wire through the run of 8" "conduit). Wire of course is direct bury rated.

[Rollie Meyers]

2/0 copper is 175 amp or 195 amp. you need 3/0 for 200 amps.
Bill D.
https://www.cerrowire.com/products/r...pacity-charts/

Under NO circumstances can the 90°C column be used for sizing conductors except for derating since equipment is not rated for 90°C, NM cable "Romex®" is sized from the 60°C column, & larger feeders are usually sized from the 75°C column.

[Charlie Velasquez]

Are you certain you want 500-500-500-350 cable? That is typically for 3-phase installations (3 phase conductors and a common neutral). 500-500-350 MCM is single phase tri-plex cable with two phase cables and one neutral.

Since the...uh, ... long time ago NEC revision, subpanels needed 4-wire feeders , plus,in this location you need to add ground rods . So altogether in his sub panel box he will have:
two phase conductor, a neutral, and an equipment ground conductor all originating at his main panel; plus a redundant equipment ground conductor (connected to the unbounded ground bar and the ground rods).

[Tom M King]

Still waiting on purchasing that roll of wire, but it's getting tempting not to wait any more. The price dropped today from$6675 to 4600. I'll wait a little while longer just to see.