240 or 120 Volt?

[BobRip]

Well, it seems you have had your question already answered.

Disclaimer: I am not an electrician. I just know enough to be dangerous:laughing: But I have a good understanding of electrical and residential wiring, enough to tackel anything I need, but again, I am not an electrician.


I was going to say 115V minimum, but you already got that answer.

There are a coouple of things that could be causing you issues. First (and you say you are on it) is to check what you have at the MAIN panel. It could be low from the get-go. My mains are usually 121-122V:thumbsup:

Second, you probabally have TOO long of a run with TOO small wire. 12ga is the standard for 20A circuits. BUT, when you start to go over 100ft, the voltage drops is what gets ya.

I am not sure of your lay-out, but you say this is the farthest outlet, is their a MAIN 240v panel in that building, or only a 120 line running to it? May need to upgrade and put a panel in that building. Just thinking out loud.

Well said. If there are many outlets in that circuit prior to your compressor they will add to the drop. The runs get longer and connections add losses. Can you move the compressor closer to the breaker panel?

 

[ducks13]

The actual voltage drop is not a particular concern except it will use slightly more energy since there are more losses. What is of concerning is the actual operating voltage of the equipment during starting and running and that really depends upon the equipment and what you are needing to do. My opinion would be that you don't really have a problem as long as your compressor starts okay. 109 is on the low side of what I would like for a motor to start but it would be fine for a heater or a light bulb since the low voltage would just cause low heat or light output respectively. Transformers have taps that can be changed to adjust the voltage; you might ask the electric company to increase the voltage output of their transformer so you have a higher voltage at your panel but they may not be willing to for various reasons. What is your actual voltage at the main panel? Excessive operation of a motor with low voltage may cause the motor to fail prematurely do to overloading.

 

[ducks13]

A little information on utilities.

http://www.pge.com/includes/docs/pd...ergystatus/powerquality/voltage_tolerance.pdf

 

[wrooster]

I have one better than that. My BIL who is a pretty good computer programmer and has forgotten more about electronics than I'll ever know likes to talk about "Two phase" electricity. As in "So, when you wired your air compressor did you wire it two phase." Since he's the kind that's never wrong, I make a point to not argue. I'll usually respond something like "I wired it for 240 with two hots."

A little clarification here:

Typical US 120/240Vac residential power is termed "split phase". The POCO service drop to your house from the secondary side of a center-tapped pole transformer consists of 4 wires. There are two legs (L1 and L2), which are 180 degrees out of phase with each other, and are connected to the "ends" of the transformer secondary winding. Then there is the neutral (N), sourced at the center tap of the transformer secondary winding. And finally there is ground (G).

Due to the 180 degree phase difference between L1 and L2, the following voltages result:
L1<->L2 = 240Vac
L1<->N = 120Vac
L2<->N = 120Vac

In a residential circuit breaker panel, every other breaker location is on the same leg (either L1 or L2). Ergo, a double-width breaker picks up both L1 and L2, and is thus used for a 240Vac branch circuit (and also used for an MWBC but that is another topic altogether).

The primary advantage of split phase power distribution is reduction in the amount of copper (or aluminum) needed in the service drop. For a given amount of power delivered to the residence, split phase minimizes the aggregate size of the conductors and therefore the overall amount of (expensive) conductor material required.

This is because with split phase power, the N carries only the *difference* between the L1 and L2 currents, and not the *sum* of the L1 and L2 currents. In other service drop schemes, the N would have to carry the total current sourced by L1 and L2, and the result would be that the size of the N conductor would have to be increased accordingly.

As you can see by inspection of your home's service drop, the L1, L2, and N conductors are all the same gauge. As noted above, this is the beneficial side effect of split phase power distribution. At worst case for the N conductor, L1 = I(max), L2 = 0, and therefore N = I(max). Otherwise, current in the N conductor is L1-L2, and lower. You can see by extension that when the total load on the residence is at it's maximum, the N carries no current.

It may also be useful to understand what is meant by "100A service" (or insert your residential service drop ampacity, which could be 150A, or 200A, et, in the example).

This term of "100A" means you can draw 100A x 240Vac = 24,000W from the utility service drop. (Which, by the way, is a lot!)

You can split up this power however you need in terms of the voltages, but you can not exceed the maximum above, nor can you exceed 100A at 120Vac on either L1 or L2.

Example:
30A at 240Vac = 7200W
50A at 120Vac = 6000W on L1
60A at 120Vac = 7200W on L2
-------------------------------
Total 20,400W

ps:
In the example above, the N conductor is carrying 10A.

Wrooster

 

[JD 4520]

Thank you all for taking the time to address my question. All my meter tests have been down line from the main panel. The transformer is in my driveway 20 feet from my house connection / panel.

 

[hr3]

A little clarification here:

Typical US 120/240Vac residential power is termed "split phase". The POCO service drop to your house from the secondary side of a center-tapped pole transformer consists of 4 wires. There are two legs (L1 and L2), which are 180 degrees out of phase with each other, and are connected to the "ends" of the transformer secondary winding. Then there is the neutral (N), sourced at the center tap of the transformer secondary winding. And finally there is ground (G).

Due to the 180 degree phase difference between L1 and L2, the following voltages result:
L1<->L2 = 240Vac
L1<->N = 120Vac
L2<->N = 120Vac

In a residential circuit breaker panel, every other breaker location is on the same leg (either L1 or L2). Ergo, a double-width breaker picks up both L1 and L2, and is thus used for a 240Vac branch circuit (and also used for an MWBC but that is another topic altogether).

The primary advantage of split phase power distribution is reduction in the amount of copper (or aluminum) needed in the service drop. For a given amount of power delivered to the residence, split phase minimizes the aggregate size of the conductors and therefore the overall amount of (expensive) conductor material required.

This is because with split phase power, the N carries only the *difference* between the L1 and L2 currents, and not the *sum* of the L1 and L2 currents. In other service drop schemes, the N would have to carry the total current sourced by L1 and L2, and the result would be that the size of the N conductor would have to be increased accordingly.

As you can see by inspection of your home's service drop, the L1, L2, and N conductors are all the same gauge. As noted above, this is the beneficial side effect of split phase power distribution. At worst case for the N conductor, L1 = I(max), L2 = 0, and therefore N = I(max). Otherwise, current in the N conductor is L1-L2, and lower. You can see by extension that when the total load on the residence is at it's maximum, the N carries no current.

It may also be useful to understand what is meant by "100A service" (or insert your residential service drop ampacity, which could be 150A, or 200A, et, in the example).

This term of "100A" means you can draw 100A x 240Vac = 24,000W from the utility service drop. (Which, by the way, is a lot!)

You can split up this power however you need in terms of the voltages, but you can not exceed the maximum above, nor can you exceed 100A at 120Vac on either L1 or L2.

Example:
30A at 240Vac = 7200W
50A at 120Vac = 6000W on L1
60A at 120Vac = 7200W on L2
-------------------------------
Total 20,400W

ps:
In the example above, the N conductor is carrying 10A.

Wrooster

Retired engineer ???

 

[wrooster]

Retired engineer ???

Why would you lead you believe someone is retired?

wrooster

 

[Iplayfarmer]

Why would you lead you believe someone is retired?

wrooster

Who else would have the time to write such a good explanation to an amateur like me?

 

[5030]

Im considering a heater , and the choice of 240 volt or 120 volt.same wattages each one puts out/ So I wonder , is one better than the other? I can wire them either way.Would the 240 one be easier on the equipment? And I believe it would use the same amount of power?(cost)
Thanks.

Your induction electric meter measures wattage and bills accordingly. wattage is volts x amps so 240 is haf the cost of 110 in a given situation.

Better yet, get 408-440 3 phase.

 

[tallyho8]

Your induction electric meter measures wattage and bills accordingly. wattage is volts x amps so 240 is haf the cost of 110 in a given situation.

I wish this was true. If it was, everything in my home would be 220v.