Concerned about voltage drop. And question might need to be, how many feet of electrical wire can I run from the transformer. I will give the details. Underground transformer is located on 42 acres in CO. Electric meter is located on a pole about 30’ from it with 200 amp service.
AIUI, I believe it is 5% that some electricians consider the maximum voltage drop you want to experience and still not cause problems for electrical devices and appliances which may not have them run properly, if at all, and if they do, could still lead to them wearing out prematurely. Have welders, plasma cutter, and air compressor that I’d like to keep for a long time and don’t want to make a mistake with the voltage.
For national code standards, does it list what gauge wire for a 200 amp box, and how many feet from meter would you estimate to still keep me under 5% voltage drop, if that is indeed the figure used? A ball park figure would be fine for now.
I want to move my cabin and building to a new location and was hoping for a better site without having to move transformer because that would be even more costly, especially since it’s on the steep side of a mountain.
Here’s some quick, back-of-the-napkin calculations. These assume distance = 30 feet, voltage = 240 V, and current = 200 A, and temperature = 25 °C:
0.40% voltage drop with 0000 gauge aluminum wire.
0.51% voltage drop with 000 gauge aluminum wire.
0.64% voltage drop with 00 gauge aluminum wire.
0.81% voltage drop with 0 gauge aluminum wire.
None-the-less, I would run the largest gauge wire the lugs will accept. At only 30 feet, it won’t be that much more expensive; almost all the cost is labor.
It may be unnecessary, but I’ll point out that if you use aluminum wire, make sure all connectors are compatible with it, as AL and CU don’t get along well.
Sorry, Crafter Man, it looks like I didn’t do a good job of explaining what I was asking, and can see now why you went that way.
Right now, electric meter is 30’ from transformer box on a utility pole. It will probably remain on utility pole at that distance if it is allowed. I have a circuit box under the elec’ meter that has the main breaker on that pole. I was wondering how many feet from that could I run, and still be alright with the voltage drop. Could I go, say, 400’ with a thick enough gauge wire? Especially if I went with copper?
400 feet isn’t that far with a thick copper wire. You’d probably be OK. It depends on what you’re running on the other end as to the exact voltage drop. If it’s a light bulb, that doesn’t draw many amps, so you can run a wire a long way. If it’s an air conditioner, then that’s pretty heavy amp load, so you’ll lose a lot due to the wire resistance.
These assume distance = 400 feet, voltage = 240 V, current = 200 A, and temperature = 25 °C:
Aluminum Wire
5.36% voltage drop with 0000 gauge aluminum wire.
6.73% voltage drop with 000 gauge aluminum wire.
8.53% voltage drop with 00 gauge aluminum wire.
10.73% voltage drop with 0 gauge aluminum wire.
Copper Wire
3.27% voltage drop with 0000 gauge copper wire.
4.12% voltage drop with 000 gauge copper wire.
5.20% voltage drop with 00 gauge copper wire.
6.55% voltage drop with 0 gauge copper wire.
FYI, 000 AWG and 0000 AWG copper wire isn’t cheap.
Thanks everybody, and especially Crafter Man both for your time and patience. This is good news, indeed! At least, with copper wire, I’ll be in good shape. Might keep my main building, maybe 100’ from electric box, but cabin around 400’. If what senoy (thx for chart) is saying, I should be even safer there, since I won’t have any HVAC, or anything drawing any major current. Probably only use about 200 KW a month with it.
Naw, used 000 and 0000 AWG copper wire is cheap around here, all you have to do is find somebody with a meth habit. Don’t know why, but they always have an abundant supply of it, and just pennies on the dollar too!
Not to mention a total pain in the ass to work with; even worse if it’s a bundled cable. There are even special tools to bend cable when it gets into the larger sizes. I remember using a mallet to beat a piece of 350 MCM into submission back in the day.
Let’s say I want to run 0000 gauge aluminum wire between my transformer and meter, but the lugs on each will only accept 000 gauge and smaller wire. I go ahead and purchase 0000 gauge wire. After stripping off the insulation on each end of the wire, can I just cut off of a few strands so that the wire can fit in each lug?
From a strictly electrical POV, I don’t see the problem in doing this. But perhaps there’s something in the NEC that prohibits this?
Don’t know what the NEC says, and doubt it would hurt anything under most loads, and bet it is done all the time. I think I’d still opt to have wires uniform from one end to the other. If either end was cut down to the next size wire, seems like one spent more money on an extra size thicker wire than was necessary, and load may be only as good as to whatever was the thinnest part of the wire. Hoping somebody that actually knows what they are talking about can give you a qualified answer. I’m curious too.
This is not true. Let’s say the largest wire your lugs can accept is 000 gauge. Using 0000 gauge wire, and then cutting back a few strands so the ends will fit in the lugs, will reduce the overall wire resistance and the voltage drop will be less.
In other words, all you’re doing is lowering the resistance of the wiring, and there’s no prohibition on that - the lower the better, regardless of the amperage of the service. Heck, you’re free to run 000 silver conductors, which would drastically reduce the resistance, but you had better have deep pockets.
There is no drawback from an electrical POV; only benefit. OTOH, it might be prohibited by the NEC for some reason, hence the reason for my previous post.
In general, all mechanical connections are potential places for hot spots.
The way the connection is made, (very well, neat and tight with air circulation possible vs a near airtight small cramped box) is way more important than 10% strands removed right in the clamped collar.
Note that the voltage drop is based on the amps drawn, not by the size of the breaker. If you are only drawing 100A, the voltage drop will be significantly lower for a given voltage and wire size than 200A. Have you done a load calculation?
Good to know since I only plan on maybe 5) 20 amp circuits for cabin, and it won’t be drawing on a few circuits at any one time. I’ve been using senoy’s chart (post # 6), showing various amp loads, just to see the difference, so thanks.
Cabin got caught up in Spring fire last month, so just starting all over, and will move future cabin to a different location, where I can get more southern sun in winter months moving me even higher up on the side of the mountain.
It’s electric motors you have to worry about. Refrigerators, air conditioners, washing machines, particularly motors you run without paying any attention to if they are slow, stalled, or running hot. Lights, electronics, not a problem. With the welder, if the voltage is really so low that it doesn’t weld correctly you may be able to adjust the strike voltage as well as the current, and that would probably be a problem before you burnt out a fan – and fans don’t normally burn out anyway.
Dunno about the plasma cutter: I’ve never used one or looked inside – they weren’t around for home / shop use when I was young.
An electrician would cut off a few strands, like you suggested, without a second thought. An “official” method could be crimping large pin terminals onto the wire - the “pin” part of the terminal would likely fit in the lug.
You can run the wires as far as the moon provided you go large enough. This boils down to an Ohm’s law calculation for a rule of thumb number. Exact data takes a lot more numbers into account.
For starters you started calculating at the wrong end. What is the total expected load and duty cycle of everything that you plan on running at once. From there you get the minimum wire size to handle the amperage. Your feed breaker is sized at 125% to handle this. Now you have to use the derating factor based on the length of the wires from the supply to the load plus the return leg back to the supply. Are you going underground or overhead? In a bundle or conduit? Triplex or separated runs? All have additional derating factors due to expected heat load. Aluminum and copper have separate charts.
Nipping a few strands as noted above is a way to upsize the wiring taking into account some of these derating factors. The proper method is to run a short wire of the proper size that fits the lugs and then splice it to the larger wire for the long haul. For me every splice point is an additional failure point. The anti-oxidants are made for aluminum or copper and for both. Some is good, more is not better. Depending on your cabin siting, you may be better off putting a disconnect by the meter if one is required at all and moving the panel to the main building. I don’t know your state and local codes as to whether you need one there or not nor do I know how large a % can be fed through to a sub panel.
tl;dr: voltage drop is allotted for in the temperature, volume, and distance derating charts for aluminum and copper.
