Single Phase, Dual Voltage Electric Motor

Thread Starter


Joined Dec 7, 2016
A question if you please? I recently purchased a Marathon 1 phase, dual voltage, 2 hp motor. I have a 15 amp breaker, will have a 30 amp installed soon. I wired it in low voltage according to the manufacturer plate. Does that mean the motor is running at 1 hp, and will not run at full capacity until the power to the shop is stepped-up?

Thanks for any input you can offer, I really appreciate it.
Last edited:


Joined Aug 21, 2008
The motor takes far less than it rated hp because it is doing very little work beyond overcoming bearing friction. So, no it will not generate the full horsepower until you take that much power via the shaft.


Joined Jul 18, 2013
I take your question to mean is it now rated at 1hp because it is ran on the low voltage setting, if so the answer is no, it is 2hp rated regardless of the voltage supply used, when connected appropriately.


Joined Dec 29, 2008
An interesting fact concerning these motors is that the current demand in starting the motor is typically several times the current magnitude when the motor has reached the so-called steady state. I owned an air compressor that was rated at 15 amps, but actually measured 70 amps for several seconds at start-up. ... A situation which often opened the 15 amp breaker switch for that circuit.
... However, If your application does not require a load on starting, it will likely have a lower start current requirement. A 30 amp breaker would be sufficient to cover the initial current requirement.
... Just to mention, if the supply voltage to the motor were doubled, then the current demand would be halved.


Joined Jul 18, 2013
This is often due to the motor starting on full load at switch on, with loads such as compressors it is usual to start unloaded, if the load remains for several seconds that usually indicates a off-load means of starting is needed.
Several seconds may exceed the time delay operation the breaker.