Buildings catch fire due to electrical problems fairly often (I wouldn't
be surprised if it wasn't the most common cause of fires now-a-days).
Sometimes it's due to improper wiring ("oversized" breakers, etc),
sometimes it's due to degradation of the wiring over time (the old
frayed extension cord phemonemon).
Which isn't to say the OP might be at risk of fire - but in looking
at the worst case problem he could see, certainly fire would be
that, particularly if his shop is in an elderly building.
There isn't any decision to make if you have a 5HP motor. That
probably draws something on the order of 18 amps on 220V. In order to
run it on 110V (even if the motor is convertible) you will need to run
it on a 40 amp circut breaker and #8 wire. Hardly a fun wiring job. On
220V, all you need is a 20 amp breaker and #12 wire.
By the way, it's neither efficiency or power as far as 110V vs 220V is
concerned. The only difference to the motor is if the feed is a long
distance. The voltage drop will be less at 220V by a factor of four.
Otherwise, the watts is the same for either voltage.
Master Woodbutcher and seasoned termite
Shamelessly whoring my website since 1999
The quick simple answer is that with 220 volt you can normally run a TRUE 3
hp motor. With 110 volt you are limited to motors with make believe hp
ratings over 1.5 hp. If you think you will ever have a typical cabinet saw,
you will need 220 volts.
The analogy about efficient breathing is really not valid for electric power
usage. In fact trying to explain electric power in terms of any fluid is not
really a valid analogy.
The two biggest practical advantages of 220v are:
1. you can run larger motors (already mentioned) over typical sized wiring.
2. You can carry more load for a given size wire. I had a 1.75 HP tablesaw
on a #12 circuit. By converting to 220v, I could add a 2 HP dust collector
on the same circuit.
As an example, a 20 amp circuit at 220 will have twice as much power as a 20
amp circuit at 110. Power is current x voltage.
For motors around 2 hp or larger, you most likely will not have a choice.
You will have to run them at 220. If I were wiring from scratch, I would
put everything at 220, but since you would have to rewire, probably just put
the larger motors on 220. It's up to you
Sometimes, I think the efficiency issue is exaggerated.
Frank - EE
All those answers and so little information.
240v is always preferred because you get one quarter the voltage drop for
the same wire size. That only makes a difference when running if you have a
very long cable, but is pretty dramatic when turning the machinery on.
Also, you get twice the power capacity for an almost identical installation
Supposedly motors last longer because they don't have to fight the voltage
The only downside to 240v is having to change stuff over, and that outlets
can cost a bit more.
Yes, but you are not putting twice the voltage on a single wire, you are
putting 110V on each of two wires but with half the current in each.
In other words, a 10A 220V cable will have two hot wires, each of 10A 110V.
The equivalent in 110V would be 110V @ 20A on a single hot wire.
That is where you are wrong. The current of 10A flows from one pole of the
breaker, back to the other pole and vs versa. The total current in the
conductor is 10A. The same motor on 110V would draw 20A from hot to
neutral. Therefore, for the same conductor size the voltage drop is
directly proportional to the current. Twice the current, twice the voltage
Assume that the resistance of the wire is .1 ohms. The voltage drop for the
220 v motor is 10 * .1= 1 volt. For the 110 v motor it is 20 * .1 = 2
The power supplied is the same in both cases. P=V x I, 220 x 10 = 110 x 20
On the other hand, the power dissipated (P=I^2 x R) is higher by a factor of
4 for twice the current thru the same conductor.
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