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Thread: Any benefit to run DC on 110 vs 220?

  1. #1
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    Any benefit to run DC on 110 vs 220?

    I have the option to run either voltage on my 1.5HP DC. Will I see any benefits running one versus the other?

  2. #2
    No. There are certain situations where 220 will help with less than ideal electrical service. It won't, however, perform any differently.

  3. #3
    I prefer to wire anything I can to 220v over 110v. There's less current draw for one. Especially something like a DC since it draws a bunch when you first start it up.

  4. #4
    Technically, it will perform exactly the same on either voltage (and it's probably 120 volts and 240 volts, not 110 volts and 220 volts). However, as John points out, running it at 240 volts will cut the current in half so you can use smaller wire for the circuit feeding it. Losses in wire are I (squared) R so cutting I in half cuts the losses in the wire by 4 (given the same wire in both cases).

    And it will also cut the inrush current on startup - and the losses in the circuit during that time.

    Mike
    Go into the world and do well. But more importantly, go into the world and do good.

  5. #5
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    Quote Originally Posted by Scott Winter View Post
    I have the option to run either voltage on my 1.5HP DC. Will I see any benefits running one versus the other?
    It depends mostly on the size of the wire and the length of the run from the panel (assuming the panel has plenty of capacity.)

    A longer run with the same wire size will have higher resistance. More resistance will cause voltage drop under load. Voltage drop can affect motor performance and in extreme cases can overheat and damage the motor. (The type of motor typically found on shop machines will try to develop the rated HP by drawing more current if the voltage drops, causing more drop, causing more draw, etc…)

    However, you are unlikely to have problems in a typical shop unless the wire is undersized for the motor amperage and length. In that case, if the motor is convertible, powering with 220v instead of 110v will require 1/2 the amperage. You can use an online voltage drop calculator to compare the voltage drop with both voltages.

    I can give you two examples of where using 220v made a difference. One: In a previous house the shop power was fed underground from the house where the panel was on the far end of the house and the tiny shop (actually more of a shed) was about 40’ from the house. The total run was fairly long. I don’t remember the wire size but it must have been marginal. The biggest tool was a Craftsman radial arm saw. Using the same wire I switched the power and motor to 220v. Instantly the saw came up to speed quicker and had more power.

    Another example: many years ago my BIL had an electric water pump in a spring house a long way from his house, evidently too long from the house for the amperage and wire size. He burned up one motor after another, seemed like every six months to a year. After switching to 220v powering the same HP motor he never burned up another motor for the next 10 years he lived there.

    When I built my current shop I did the voltage drop calculation for the 250’ underground run from the main feed near the house. I believe the generally acceptable voltage drop is around 3%. I decided to go with larger copper so the worst case voltage drop would be closer to 1%, even in the unlikely case where multiple things were all pulling power at the same time. The cost of the wire was more but compared to the total cost of the shop I considered it insignificant.

    JKJ

  6. #6
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    I have seen voltage drop distance tables done two ways. The way I was taught is to take the length of the wire run and double that to look up. Some tables already have the distance doubled so they are direct reading. Make sure you understand which way the table you are looking at is designed.
    Bill D

  7. #7
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    As long as the installation is wired to code, there will be no difference in power, efficiency or performance.

  8. #8
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    Another consideration is how your poco bills you for electricity.
    The amount of energy used will be the same, so your kilowatt/hrs will not change.
    But pocos usually have ancillary fees.

    I have experienced “meter charges”, “facility charges”, “peak hour charges”, “demand charges”, and others.
    Some of those are fixed, such as the meter charge, but some are variable.
    One that was our school district nemesis is the demand charge, similar to peak hours, kinda.
    Demand was computed by taking the greatest amount of amps used during any 15 minute interval, then multiplying by our service rating.
    The meter measured each leg separately then took the highest value to compute the demand.

    When I started our district’s energy program I discovered the industrial arts welders were mostly drawing from one leg of our service. By distributing those welders evenly within the panel we saved thousands of dollars.

    Wiring at 240 will help balance the load, which can reduce lights dimming and such, and possibly save you money.
    Comments made here are my own and, according to my children, do not reflect the opinions of any other person... anywhere, anytime.

  9. #9
    For single phase induction motors, anything over about 1.5HP is probably best run on 240 volts. At least that's what I do.

    Mike
    Go into the world and do well. But more importantly, go into the world and do good.

  10. #10
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    Quote Originally Posted by Mike Henderson View Post
    For single phase induction motors, anything over about 1.5HP is probably best run on 240 volts. At least that's what I do.

    Mike
    I agree with this strategy. It means less wire cost and concern with voltage drop. I do the same.

  11. #11
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    To answer the question in the heading: No.

    In theory they will perform the same. In practice 240V will usually work better and the only reason to use 120V is you have no choice. (Like in my garage which seems to have a single 15A circuit, 'cuz the only thing you'll ever need is a garage door opener, right? )

  12. #12
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    The answer to this is somewhat similar to the variance of responses in this thread.

    It comes down to what you have available. If you have the higher voltage available (or installable) it becomes preferred because of voltage drops, smaller breaker ratings, line sizes and current induced heating. If you only have the lower voltage available then you can almost completely compensate for the voltage drops and current induced heating with larger lines and larger breakers. There always is some benefit from running at the higher voltage due to reduced current and heating effects in the motor itself. But with larger wiring, breakers, connections, etc. performance is essentially the same.
    However, the lower voltage has costed more in cabling, interconnects and requires more current draw resulting in a larger breaker and more load on the phase it is on. Another item is motors can have high inrush currents and the higher voltage helps with this as well.

    There are impedance effects that higher currents (lower voltages) do produce a less desirable response from. For shop equipment it is almost always the case that ultimately the higher voltage will be somewhat advantageous in terms of performance. You will notice better transient responses using the lower current (such as startup, loading, etc.). But in the application of woodworking equipment it certainly isn't a show stopper to use the lower voltages.

    If I only needed it for a single 1.5 hp or so piece of equipment, I may choose to stick to the lower voltage. But in a shop you quickly build up multiple machines that it starts making more sense to run the higher voltage lines which are smaller and don't draw as much current.

  13. #13
    Just a correction to Eric's comment about an advantage to running a motor at a higher voltage giving a reduced current and heating effect.

    The way dual voltage motors are wired is that they have two sets of coils. When the motor is wired for low voltage (120 volts) the coils are in parallel. When the motor is wired for high voltage, the coils are in series.

    When the coils are in parallel (low voltage), the current is double the current when in series (high voltage) but only half of the current goes through each coil and the voltage drop across each coil is 120 volts.

    When the coils are in series (high voltage) the motor only requires half the current as when wired for low voltage and that current goes through both coils (in series). The voltage drop across each coil is 120 volts, half the high voltage of 240 volts.

    In either case, the voltage and current in the coils are identical and the heating effects are the same. There's no free lunch.

    Mike
    Go into the world and do well. But more importantly, go into the world and do good.

  14. #14
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    120 does have one advantage. It can be switched with a single pole switch on the only hot leg. A 240 circuit needs a two pole switch, to be safe, one pole for each of the two hot legs. So a 240 volt switch is harder to find, costs more, and requires a trivial increase in wiring time at the switch box.
    Note that any proper motor contactor can be used for 120 or 240 and the control voltage can be 24, 120 or 240 depending on the coil. The coil can be replaced with a different voltage one if needed.

    Bill D
    Last edited by Bill Dufour; 06-17-2022 at 10:49 AM.

  15. #15
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    Quote Originally Posted by Bill Dufour View Post
    120 does have one advantage. It can be switched with a single pole switch on the only hot leg. A 240 circuit needs a two pole switch, to be safe, one pole for each of the two hot legs. So a 240 volt switch is harder to find, costs more, and requires a trivial increase in wiring time at the switch box.
    Note that any proper motor contactor can be used for 120 or 240 and the control voltage can be 24, 120 or 240 depending on the coil. The coil can be replaced with a different voltage one if needed.

    Bill D
    Well, harder to find in that you may have to reach up to the next shelf to get the 2 pole switch and just a few bucks more for a 2 pole commercial spec grade switch. Any contactor you find in a shop machine, unless it's very old, is highly unlikely to have a replaceable coil. The contactor will most likely be an IEC rated one and they in the smaller sizes have no serviceable parts. Some of the old iron with have a NEMA rated contactor, which are much larger and can be completely disassembled and serviced.

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