220 vs. 110 feed to barn

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  #1  
Old 02-05-16, 07:43 AM
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220 vs. 110 feed to barn

Good chilly morning to all,

Is the voltage drop caused by length or distance the same with a 220 feed vs. a 110?

Thanks in advance, new to forum.

DW
 
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  #2  
Old 02-05-16, 08:26 AM
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Welcome to the best DIY forum on the Internet!

First of all, you are at least fifty years out of date using "110 and 220". The common residential voltages are 120 and 240. This is true even though far too many manufacturers and retailers use the old numbers.

Voltage drop is a result of the size of the wire (gauge size) the length of the wire, the voltage used and the amperage of the load. Generally speaking, as the voltage is increased the voltage drop will decrease BUT this only happens under specific conditions. Example, If you have a 250 foot run from the source to the load and you use #12 copper wire with a load of a 120 volt 10 ampere electric motor the voltage drop from source to load will be 9.6 volts (8%) leaving a voltage at the motor when running under normal load(10 amperes) of 110.4 volts. Now if you change the source voltage to 240 AND re-connect the motor to use 240 volts the voltage drop will still be 9.6 volts but now it is only a 4% drop from the original voltage leaving the motor with 230.4 volts. Although there are no regulations on maximum voltage drop it is generally preferred to limit a branch circuit 3% or less and an overall drop (from the service) of 6% or less for best performance. From this you can see that the higher voltage is better in this example.

However, most of the consumer appliances in the US work on only 120 volts. Also, we have in the US a "split voltage" system in most residences. Instead of having two wires with a single voltage we use three wires with two voltages. Another example: Running power to an outbuilding 250 feet (wire length) from the service (main) circuit breaker panel. You run three wires and then have a choice at the outbuilding of using 240 volts OR 120 volts. You connect that 10 ampere electric motor for 240 volt usage and it is the same as the second example and you will get a voltage drop on that motor circuit of 4%. But say for whatever reason that motor must be connected for 120 volts then you will get the 8% voltage drop of the first example. Moving forward, let now connect 10 amperes of lighting at 120 volts to the second 120 volt circuit (more on this second circuit idea later) and now we have what is called a "balanced load" on the three-wire 240/120 volt circuit. This then gives a total voltage drop of...4% rather than the 8% of using only a 120 volt circuit.

Now you ask, "Where the heck did this "second" 120 volt circuit come from?" The "three-wire/dual voltage" circuit goes all the way back to Edison and his direct current (DC) electrical system. Edison discovered he could use TWO 120 volt (actually 110 volt but ignore that historical discrepancy for now) generators wired in series (+ pole of one generator connected to the - pole of the second generator) with one wire connected to -, a second wire connected to + and a third wire connected to the junction of +and - to allow for a 120 volt circuit between the - (only) wire and the +/- wire OR a second 120 volt circuit from the + (only) and the +/- wire OR a 240 volt circuit by using only the +and - wires and ignoring the +/- wire.

What is interesting about this "Edison three-wire circuit" is that when the load is balanced between the + and - wires there is NO current flow on the +/- wire. We now call these wires the 'hot" wires for either the + or - wire and the combination +/- wire is called the "neutral" (Lots more theory but I need to wrap it up as my fingers are about to break.)

The bottom line is that higher voltages offer less voltage drop but only when the higher voltage can actually be utilized by the load. You can run a three-wire circuit (240/120 volts) but ONLY if you are able to distribute the load across the higher voltage can you actually reduce the voltage drop.

Read this through a few times and then come back for clarification.
 
  #3  
Old 02-05-16, 08:40 AM
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I was looking for a 'yes' or 'no' answer.

But with my limited intellectual abilities, I see your point about the balanced load. Considering I won't ever need 220v, and this feed is mostly for 200 watts of LED lighting and an occasional radio, charger or leaf blower, I am going to say it's not worth it to run a 220 sub panel.

Thanks so much for your very detailed answer.

DW
 
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Old 02-05-16, 09:44 AM
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Your leaf blower will be the largest of your listed loads. Look at the nameplate for the amperage listing or, if no amperage listing, then the wattage which you will divide by the voltage (120) to get amperage.

Use this calculator Voltage Drop Calculator to determine the voltage drop with any given size of wire. Where it says to enter 1/2 the total circuit length just enter the distance from the main panel to receptacle in the barn that you will be using. (Total circuit length is out and back). The most likely candidates for wire size will be #12 and #10, only using the #10 (larger than #12) if you have excess voltage drop with the #12. Try to keep the voltage drop below 6%
 
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Old 02-05-16, 09:52 AM
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Are you sure future use won't require more power in the barn? If you run 240 now you'll have more options later.
 
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Old 02-05-16, 09:52 AM
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Is the voltage drop caused by length or distance
Distance + Amps + Voltage + Wire size + Copper or aluminum.
I won't ever need 220v
Hopefully not because your house has 240/120 volts.
 
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Old 02-06-16, 07:19 AM
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Would someone with a lot of patience for a guy like me with limited resources, explain why the attached scheme is dangerous.

Simply just so I know.

"Tell me and I forget. Teach me and I remember. Involve me and I learn." Ben Franklin

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  #8  
Old 02-06-16, 07:40 AM
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Because there is no grounding path back to the source. The ground (earth) is not a reliable grounding path. There should be 4 wires from the main panel (hot, hot, neutral, ground)
 
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Old 02-06-16, 08:13 AM
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Futureproofing is a gamble whether or not you flip a coin (you may) to make your final decision.

This is an example if the following syndrome:

"You can choose among economy, standard, or deluxe. If you choose economy and wnat to upgrade to standard (or deluxe), you must start over from square one, namely all the cost and effort you put in so far cannot be salvaged. Similarly, if you choose standard and want to go deluxe later, all the cost and effort you put in so far cannot be salvaged and applied towards the upgrade."

You may have only one feeder (either 120 volt only or 120/240 volt) running between any two buildings.

Looks to me that a 120 volt line (probably 10 gauge to combat voltage drop, but still 20 amps) will serve you fine. But if, two years from now, you want to partition off a space and add an air conditioner, you will have to abandon the old feed and bury a new feed. (Well, you could use the old feed as a switch loop for remote controlled lighting and fed by the barn power.)

Shoot for at most 3%, not 6%, voltage drop from the panel to the barn. The 6% refers to the total run from the utility pole to the leaf blower and you don't yet know the voltage drop from the utility pole to the panel with a good amount of power usage in the house (washing machine, hair dryer, etc.) at the same time you are using the leaf blower out near the barn..
 
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Old 02-06-16, 08:24 AM
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I am not trying to be a douche here, but if ground (earth) is not a reliable ground, then why is it required.

Like I said, I just want to learn.
 
  #11  
Old 02-06-16, 09:03 AM
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The resistance of earth is too high to trip a breaker. The ground rod is for high voltage event like lightning strikes. You could connect a hot directly to a ground rod and the breaker will not trip. The neutral and ground bond ensures a low impedance path to allow the breaker to trip.
 

Last edited by Tolyn Ironhand; 02-06-16 at 11:26 AM. Reason: added "rod"
  #12  
Old 02-06-16, 10:51 AM
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There are two types of grounding:

There is the GEC (Grounding Electrode Conductor). That is to bleed off atmospheric electric charges to lessen the chances of a lightning strike.

There is the EGC (Equipment Grounding Conductor). That is a low resistance path from the panel to the metal shell or chassis of a device or appliance. Should it become energized this path will trip a breaker.

There is also bonding you may wish to research.
 
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Old 02-07-16, 08:47 AM
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Start with the neutral bus bar (terminal strip) in the panel where the first master switch or breaker for the building is. That is the official electrical system ground.

The service neutral from the meter and utility pole should be attached there. This is also connected to the ground wires on the utility poles.

Grounding electrode conductors are the fat ground wires from the neutral or ground bus bar (only of the panel with the first master disconnect) to ground rods and/or the cold water pipe close to where that exits the house underground.

Ground wires connected to gas pipes or between other parts of water pipes are called bonding jumpers regardless of fatness.

Equipment grounding conductors are the ground wires in branch circuit cables or conduits, sometimes the metal conduit itself, and also the ground wire in the power cord going to the appliance or light or other equipment. EGCs and neutrals are not connected to each other except indirectly via one interconnection (bonding), for example a metal strip between the neutral bus bar and the ground bus bar, at the panel where the first master switch is.
 

Last edited by AllanJ; 02-07-16 at 09:02 AM.
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