Attn Cary/ SBerry!!!!

[calweld]

I have a friend, with a 5 HP submersible pump. Single phase 230. Overheating a 40 amp circuit breaker. Put an ampmeter on it, 25 amps one leg 27 amps the other leg. Circuit breaker itself was too hot to touch, wires weren't hot. We replaced the breaker, all seems fine now, not overheating, amp readings are 25 amps both sides.

Question: What amp readings should I be getting with a properly operating 5 HP submersible? I checked mine, but I have a three phase turbine, not the same thing.

Thanks,

Joe

[Blacksmith]

Considering that one hp = 746 watts, along with losses for motor efficiency and lagging power factor (amps that go to forming the motor's magnetic field but do not do any "real" work), 25 amps sounds reasonable. However, with a single phase, what goes in one leg should come out the other. Barring any measurement error, you should see the same current in each leg. Did you check the ground wire? It should read near zero. I'm wondering if there is some insulation breakdown and leakage current into the ground wire or the well/ground.

[calweld]

Considering that one hp = 746 watts, along with losses for motor efficiency and lagging power factor (amps that go to forming the motor's magnetic field but do not do any "real" work), 25 amps sounds reasonable. However, with a single phase, what goes in one leg should come out the other. Barring any measurement error, you should see the same current in each leg. Did you check the ground wire? It should read near zero. I'm wondering if there is some insulation breakdown and leakage current into the ground wire or the well/ground.

Once we replaced the breaker, both legs are essentially equal.

[Blacksmith]

Then likely the breaker was bad. They do fail/wear out. I didn't carefully read the original post. But I stand by ~25 amps being correct for 5 hp single phase.

[calweld]

Thanks. Checked the motor plate on a 5hp commercial compressor (NOT homeowner type), amps were listed as 22. I figured we were in the ballpark. My own pump (three phase) pulls about 15 amps.

[Blacksmith]

Three phase power watts (hp) is volts x amps x 1.73 (square root of 3), so if the single phase 5 hp is drawing 25 per line, 15 per line on 3 phase is in the ballpark.

[calweld]

I ran into an old friend/ retired electrician who used to own the most professional electrical/pump shop around, he told me 25 amps for a single phase 5 hp pump is well within tolerances. Thanks for your input, Blacksmith, you were correct.

[Blacksmith]

You're more than welcome. I dabble in this stuff at work. New diesel gensets arriving.