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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:

Enter image description here

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.?

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    "An extension cable ..... would be buried 1" underground" - if an insurance inspector ever notices that you'll be dropped instantly, if a city inspector sees it they'll make you take it out of or else condemn the place. Do it right. Jul 10 at 21:32
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    @whatsisname If, rather than running out extension cables, I make necessary adjustments such that each pump plugs directly to the house outlet (e.g. split the two outlets to four immediately, plug in each pump directly) does that avoid insurance/inspector issues?
    – Village
    Jul 10 at 22:21
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    @Village if you’re still wanting to bury them: no.
    – Tim
    Jul 12 at 16:52
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    Assuming your breaker is sized properly for the wire gauge and distance then I believe the rule is 80% of breaker load 24/7 is okay. So 9.2 amps is well under 80% load for the presumed 15 amp breaker.
    – MonkeyZeus
    Jul 12 at 17:22
  • @MonkeyZeus the extension cord will carry the load (that's a simple "plug it in and see if the magic smoke comes out" test). The real issue is making this a permanent installation by burying a cord that's not rated for burial.
    – FreeMan
    Jul 14 at 12:38
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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.

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  • Jack, the point about permanent wiring is a good one. Do you know what in the rules (NEC/IRC etc...) makes it permanent vs temporary installation? Also, OP should derate for continuous load.
    – P2000
    Jul 10 at 18:23
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    @P2000The "For construction, remodeling, maintenance, repair, or demolition of buildings, structures, equipment, or similar activities, temporary installations shall be permitted for the length of time needed for these events. A period of 90 days is specified for holiday decorative lighting and similar installations. For emergencies, tests, and experiments temporary installation are permitted for the duration of each. [NEC 590.3(A), (B), and (C)" (From Electrical Contractor.) I'm thinking this would be a "similar installation".
    – JACK
    Jul 10 at 18:48
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    @P2000 As I read it, it would be allowed for 90 days like holiday seasonal lighting.
    – JACK
    Jul 11 at 11:49
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    Buried basically implies permanent. Jul 12 at 4:24
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    @LorenPechtel I think you could argue it’s fine to bury during construction, for example if you will have vehicles going over it.
    – Tim
    Jul 13 at 9:14
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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.

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    Safer in what sense? I wouldn't trade an unknown amount of electrical simplicity for the risk of soaking my basement. In regard to electricity, one may have an arc protection, ground fault protection, overcurrent protection, hire-a-sane-electrician protection... but in regard to plumbing, you are in a worse position. Detecting underground leaks is HARD (and usually late) even if the plumbing is done well. And I am sure the Code has to say something about the plumbing as well.
    – fraxinus
    Jul 11 at 19:56
  • A few thousand would be a bit highway robbery. Especially if OP digs the trench themself this should be an hour's work, so only $300 or so (which is already grossly overpriced, but hey that's electricians for you).
    – TylerH
    Jul 13 at 14:12
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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.

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  • THIS is the correct answer. OP's plan is NOT to code. Hope it doesn't catch fire - his insurance company will most likely not pay when this is discovered
    – FreeMan
    Jul 14 at 12:36

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