Inverter size to run a 1/3 HP sump pump?

[Ignoramus1648]

I am considering various backup options for my currently single sump
pump. One option is to use my old 1/3 HP sump pump (which I replaced
with a Zoeller M137 1/2 HP pump) and an inverter to run it, using a
12v relay to turn the inverter on.

My thinking is that a 1/3 HP rated pump probably uses about 4A of 120v
current. That translates to about 50A of 12v current (given the losses
etc).

i

 

[Eric]

I am considering various backup options for my currently single sump
pump. One option is to use my old 1/3 HP sump pump (which I replaced
with a Zoeller M137 1/2 HP pump) and an inverter to run it, using a
12v relay to turn the inverter on.

My thinking is that a 1/3 HP rated pump probably uses about 4A of 120v
current. That translates to about 50A of 12v current (given the losses
etc).

i

probably uses? Read the nameplate, its on there. Then you also need to allow
for starting surge which can be as high as 6 times full load, again see the
nameplate and look up "motor class".
Eric

 

[George Ghio]

probably uses? Read the nameplate, its on there. Then you also need to allow
for starting surge which can be as high as 6 times full load, again see the
nameplate and look up "motor class".
Eric

Better make that 10 times. Pumps start under load.