How can I know if one extension cable and outlet can handle so much electricity use?

Question

I intend to run an extension cable from an outdoor outlet to power four pond pumps. Currently I have a mess of different wires running across the yard from three places.

The cable runs from the outlet, would be buried 1" underground, run to a 2 ft stake, where it is attached to a power strip, that the pond pumps plug into, something like this:

Each pond pump is rated the following:

• Current: 2.30 A
• Maximum power: 276 W
• Voltage: 120 V
• Frequency: 60 Hz
• Variable Frequency

Given it will need to power four of these, running 24/7, how do I know when I purchase the cable and power strip, that they, plus my outdoor outlet, that it is capable of running these, without risk of fire, blowing breakers, etc.?

Answer 1

The four pumps will require 9.2 amps. Your outdoor outlet has a breaker that's either 15 or a 20 amps so if nothing else is on the circuit, you'll be OK. If you have other stuff plugged into that circuit, you'll have to add up the amps so see if they exceed the 15 or 20 amp breaker.

Now the bad news. The cable and power strips are not allowed to be permanently installed like this or temporarily buried. You would need cable rated for direct burial and it would need to be 18" deep or wire in conduit to a location where you'd need weather proof outlets. The outlets would need to be GFCI protected. This is only a brief summary of what you'd need to do.

Answer 2

A Professional is Relatively Cheap

You’re going to spend thousands of dollars on electricity over the life of this pond:

(4 pumps)(0.276 kW/pump)(0.1319 USD/kW/hr)(8766 hr/yr)(10 yr) ≈ $13,000

If you can afford the electric bill, then you can afford to pay a few thousand dollars to a contractor for a building permit, a deeper trench, and a new branch circuit.

Plumbing is a Safer Alternative

The other answer explains why shallow-burying an extension cord is a bad idea. If you still don’t want to run a power line the Right Way, but are still vexed by the safety and permitting implications, you could instead run water lines. This improves safety in the sense of reduced fire and electrocution hazard. (If your property is damaged by water outdoors, then you have a drainage problem, which is beyond the scope of this answer.)

The pumps could be located near the existing receptacle, and no cord would be buried. Each pump would send water through a separate hose back to wherever in the pond it should go.

The pond-to-pump flow may be more problematic if these are typical submersible pumps. You’d need to create a sump near the receptacle at the same elevation as the pond, connected by a hose big enough for the water to flow by gravity.

The question doesn’t have details of the length, flow rate, or elevation, so no further plumbing advice can be given.

Answer 3

The cable runs from the outlet, would be buried 1" underground,

Circuits that are GFCI protected at the source, as you intend, require at least 12" of cover, not 1". Unless they are in RMC or IMC conduit and not under a driveway, then 6".

Also, the cable must be of a type fit for direct burial, such as UF-B. It cannot be cordage regardless of the cordage's rating.

The descent to burial depth must be protected by a conduit or other damage shield.

It will need to come up a pole set in the ground such as a 4x4, but you'll already have that. The receptacle can then be installed there.