Voltage Drop for 750 feet advice needed

[EddieWalker]

If I'm starting out at 240 volts, what do I want to be at the end of the run? Is 220 good enough? That puts me somewhere around 8 percent loss as my goal and if it's six percent, then I'm going to be at 225 volts.

Eddie

 

[EddieWalker]

Playing around on that website, it looks like I can go with even smaller wire if I run three hot wires and even smaller if I run four hot wires. Is there a cost savings with the smaller wires or am I running into issues by going with more then two hot wires?

Eddie

 

[EddieWalker]

Do I have to run a ground wire? Why can't I run two hot wires and a neutral? then ground at the panel?

Eddie

 

[CobyRupert]

I'm not familiar with this and will look into it. Would you connect both hot wires to the same 200 amp breaker or would one go to one breaker and the other to another 200 amp breaker? It would go to the same 200A breaker, otherwise you could draw 400amps (all things being equal) before the breaker(s) popped

Thank you,
Eddie

If I'm starting out at 240 volts, what do I want to be at the end of the run? Is 220 good enough? That puts me somewhere around 8 percent loss as my goal and if it's six percent, then I'm going to be at 225 volts. Depends, what your equipment is rated for. If 220V you're good. The National Electric Code (NEC, NFPA 70) that is adopted by most municipalities has no rules on what the maximum voltage drop can be. They are concerned with safety and not setting fires and are not concerned that your lights flicker every time the A/C starts or your motors prematurely burn out because of low voltage. They do suggest that voltage drop on feeders be limited to 3%, branch circuits limited to 2% and/or a total of 5%. 3% on a 240V feeder such as yours would result in 232.8V.
And I can't stress this enough Don't base your voltage drop on 200 amps just because you have a 200 amp breaker! That's nuts. That's not how it is done! Base it on the real expected load (see my previous reply), even look into your crystal ball and add in future loads, but I can guarantee it won't be 200 amps else you've got other problems. By code (NEC), a 200 amp breaker shouldn't be continuously loaded to more than 80% of its rating (160 amps).


Eddie

Playing around on that website, it looks like I can go with even smaller wire if I run three hot wires and even smaller if I run four hot wires. Is there a cost savings with the smaller wires or am I running into issues by going with more then two hot wires?
There is a cost savings, to a point. Things you should know when running parallel sets:
1) Terminations: You've got to terminate those multiple wires somehow into the breaker lug at each end. When you've "upped" the number of cable or their size for voltage drop you're now trying to, for example, put a 400 amp cable in a 200amp lug, or 2-200amp cables into 1 lug. This may require an additional "power terminal block" (and enclosure) to at each end to land the multiple or oversized cables. Then you'd have just a short 200 amp (normal sized) jumper cable from the power block to the panel breaker at each end.
2) If you put each parallel set of cables in it's own conduit no problem, but when you add "more than 3 current carrying conductors" to a single conduit, the cables ampacity has to be derated (by Code). More than 3 current carrying conductors = 80%, more than 6 = 70%, more than 9=50%, etc... - However this is ok if you, for example, upsized your 200 amp circuit to 400 amps of cable to compensate for voltage drop and but then had to derate the cable by 50% back to 200A (understand? -The 200 amp breaker is still protecting the (derated) 200Amps of cable.)
3) If your installing parallel cables in parallel conduit runs for a 200amp feeder, by code each conduit run requires a full sized ground conductor (i.e. sized for a 200 amp circuit: #6 Cu or #4 Al). If your installing individual wires that's no problem, but if your installing cables in parallel conduits , and their individual amapacty is less than 200 amps, they won't be manufactured with a ground conductor suitable for a 200 amp circuit (i.e. (#6 Cu or #4 Al gnd).
Eddie

Do I have to run a ground wire? Why can't I run two hot wires and a neutral? then ground at the panel? Depends if your municipality has adapted the 2014 NEC or is operating under previous revisions. Prior to 2014 you wouldn't want to, but technically you could exclude a ground wire and ground at the new panel if there were no continuous metallic paths between the building (i.e. conduit, water piping, phone, cable, cloth's lines, etc..) This was a little known exception to the rule that one is required, and requires a good crystal ball as to what future metallic paths may exist. It is not recommended. Short answer is yes you need to run the ground wire so that fault current can easily find it's way back to the transformer! (i.e. it's source! Many people don't understand it doesn't "return" to the "ground", the "ground" only anchors all things connected to a safe (zero) voltage). An easy path back to the transformer ensures fault currents are large enough to trip the breaker instead of relying on the actual ground (earth) to get there. Relying on the earth may limit the amps during a fault to a level not sufficient to trip the breaker.


Eddie

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[C4Ranch]

If you don't run a ground, there is a possibility strange things could begin happening....
Strange shocks when touching stuff..... Even heard of a dog being shocked drinking outta his water bowl...

 

[EddieWalker]

I think I understand amps better then I do volts. I don't think I'll have any problems with amps because my main use will be the AC, then it's mostly just lights and a few things that get plugged into outlets. The building will have natural gas for heat, so that takes care of the heating the building, stove and the water heater.

This just might be doable. Thank you,

Eddie

 

[buickanddeere]

When the breaker trips, all live lines are to be shut off. Can't do that when the breaker is not tied together. Some confusion here .it's a breaker that is single ,double or three pole. Each pole is not an individual breaker . Something like somebody tells me they have four scv'so on their tractor when there is actually "two pair" when there is four hose connections.

 

[buickanddeere]

Do I have to run a ground wire? Why can't I run two hot wires and a neutral? then ground at the panel?

Eddie

Because code states the grounds have to be tied together. We electrical engineers, trades people, techs, utility workers and code inspectors have tried here several times . To explain to Bubba why but 99% of lay people can't or won't grasp the concept. They either don't have the theory or they are blinded by not wanting to spend the bucks.
Your situation requires the utility to run power over to your new building. It will be cheaper and work better . If you let professions do the planning and the work . All you have to do is write a cheque. Nobody gets hurt. You don't get charged and sued. You and loved ones don't get maimed or killed.

 

[CobyRupert]

I think I understand amps better then I do volts. I don't think I'll have any problems with amps because my main use will be the AC, then it's mostly just lights and a few things that get plugged into outlets. The building will have natural gas for heat, so that takes care of the heating the building, stove and the water heater.

This just might be doable. Thank you,

Eddie

A quick guide to understanding electrical power: Power (the ability to do work, create heat) is measured in Watts (1 Watt = 1 Volt x 1 Amp). A good analogy of electricity's ability to do work (say at a motor) is to compare it to water in a pipe's ability to turn a pump you're using as a motor. The outlet of the water wheel is to ground (no pressure/voltage).

The power is a multiple of both the pressure drop across (voltage) and the current (amps). Again, 1 Watt=1 volt x 1 amp. Water-wise we would think of this as the product of the pressure (PSI) x current (gpm).
Repeat: Think of amps as current (it is). Think of voltage as pressure (it's only the "potential" to do work, stored energy. Actual work will only be done when there's flowing current (amps).

Now, regarding pressure drop in a conductor:
So imagine your water pump motor is connected to a 700' pipe that has 60 PSI at it's source. When there's no current flowing (a closed pipe, valve at turbine is shut off) you have 60 psi everywhere in that pipe. (i.e. with no amps flowing you have 240V everywhere). However when there's current flowing it causes a pressure drop IN that 700' of pipe drop due to the friction ("resistance") that the pipe has. So maybe if you're drawing 1 gpm you have 55 psi at your pump, if your drawing 2 gpm you have 50psi, etc.... The pressure drop in the pipe (voltage drop) is directly proportional to the current flowing through it and the resistance of that pipe size.
This is why you hear calls to: 1) boost (transform-er) the pressure at the source end and then reduce (transform) it, or 2) Put in bigger or multiple pipes.

Let me stress again: What is your current? I know it's not 200 amps. Get a realistic idea of what your actual load (amps) will be. (What size A/C, how many lights?) As a safety factor, add in what you think may be realistic future loads. Base you voltage drop calculations on these amps! Not on the 200 amp rating of the feeder's circuit breaker.

 

[GPintheMitten]

You really need to put a better plan together on the final load. If you need help determining load, you need to sit down with an electrician. But a electrician can't do that unless you can state what you are going to do with these structures, not in general terms ... A wedding venue... but specifically. You need to determine the size of A/C based on volume and insulation etc. Then determine other loads. Then ask an electrical planner to design a solution.

You probably need a building plan too.