looking for quick reply: 3 hp air compressor 220v to 110v

[taiden]

I'm about to go buy an older (silver) craftsman air compressor from a guy on craigslist. it's a 3 hp and he says that the manual states it can be run on 220v or 110v but that it's currently setup for 220v.

Does this seem reasonable to run a 3 hp compressor on 110v?

I'm leaving to go look at it in an hour so any info is helpful

 

[Jason641]

3 HP on 110V would be pulling right at 20 amps, it may be possible but pushing it for sure.

 

[GeorgiaHybrid]

Is this compressor from the days of old when the HP rating was based on the startup amps instead of the running amps? If it is, the motor is more than likely a 1 1/4 or 1 1/2 HP motor.

 

[Stuart in MN]

Assuming it's a true 3hp motor it will have a full load current of around 34 amps at 120vac. You could run it on 120vac, but not with a regular old 15 or 20 amp wall receptacle - it will require a dedicated circuit.

 

[Torque1st]

Assuming it's a true 3hp motor it will have a full load current of around 34 amps at 120vac. You could run it on 120vac, but not with a regular old 15 or 20 amp wall receptacle - it will require a dedicated circuit.

+1

Single Phase Alternating Current Motors Full Load Current in Amperes:
-----------------------------
HP_____ 115V_____ 230V
-----------------------------
1_____ 16_____ 8
1.5_____ 20_____ 10
2_____ 24_____ 12
3_____ 34_____ 17
5_____ 56_____ 28
7.5_____ 80_____ 40
10_____ 100_____ 50

Most motors will be slightly under these values.

 

[Norcal]

Any single phase motor over 1.5 HP does not perform well on 15 & 20 ampere 120 volt circuits as the circut breaker will trip under a load (a 1 1/2 HP is iffy).
& 30 A or larger 120 volt circuits are not common, wiring them for 240V is the best way IMO. This only applies to "real" motors not those rated by the Sears method....

 

[Torque1st]

The "Sears method" seems to apply to most consumer power tools etc. "2 or 3HP" shop vacs and circular saws that run on 120 from a wall outlet... With a 16AWG cord... -Yeah right.

The motors won't say NEMA on them anywhere.

 

[Duane]

You can only get a maximum of 1.7 hp from a 110volt 20 amp circuit period.
All these models claiming 3 horse on 110 are full of bs. It is not electrically possible to get more that 1.7 on 110.
Anything will some real power will be a dedicated 240 volt model.

Duane

 

[hidollartoys]

You can only get a maximum of 1.7 hp from a 110volt 20 amp circuit period.
All these models claiming 3 horse on 110 are full of bs. It is not electrically possible to get more that 1.7 on 110.
Anything will some real power will be a dedicated 240 volt model.

Duane

Not sure how you arrived at this conclusion. 1 hp is equal to 746 watts. A 120v/20 amp circuit is capable of providing 2400 watts which equals 3.2 hp. This is assuming 100% efficiency and disregarding the 125% continious duty issues.

 

[Torque1st]

Not sure how you arrived at this conclusion. 1 hp is equal to 746 watts. A 120v/20 amp circuit is capable of providing 2400 watts which equals 3.2 hp. This is assuming 100% efficiency and disregarding the 125% continious duty issues.

Sorry, that type of calculation is not applicable to small motors because their efficiency is so low. A 1HP motor is about all that is practical on a 120V 20A circuit. Even then, a hard start 3/4HP application can trip a standard 20A breaker occasionally on startup.

 

[comedyman809]

Not sure how you arrived at this conclusion. 1 hp is equal to 746 watts. A 120v/20 amp circuit is capable of providing 2400 watts which equals 3.2 hp. This is assuming 100% efficiency and disregarding the 125% continious duty issues.

even if you use a 20 amp breaker on a 2400 watt system, your pushing it.


there needs to be an 80 percent rule applied here

16 is 80% of 20, so if the breaker is rated for 20, then you need a smaller wattage device.

so if the motor is a legit 3hp motor, then the wattage shall be 2238 and then the amperage will be 18.65 continuous amps.

you will need a 30 amp breaker that is in good shape so the start up current does not trip the breaker. remember 30 amp breaker should have number 10 wire on it as long as you are under 50 feet to be safe.

if you set it up, put an amp meter and see what the start up current is, and then see what the continuous current is so you know for a fact what you have.

remember also, 30 amp breaker needs a 30a recepticle.dont start half assing your electrical in home, nec code is part of the nfpa(national fire protection association) and its there to keep you and your family alive.

 

[comedyman809]

ive just seen a lot of half *** work in peoples homes and in commercial buildings.

like a 100 amp box ran on 8 awg wire to another breaker box without running a neutral and using the conduit as ground and neutral.

the thinner the wire is, when load is applied, the hotter it gets....hence fire.