Proper gauge wire + conduit for outdoor outlets?


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Old 10-25-19, 06:57 AM
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Proper gauge wire + conduit for outdoor outlets?

Greetings:
I need to have a couple of outdoor 120VAC electrical outlets some distance from my house (farthest one - 200 away). Outlets will mostly be used for low-wattage stuff like LED lighting, irrigation control, etc., but I want to have the ability to occasionally run power tools from them.
Ill have an electrician install a 20A breaker for this circuit, which of course will be GFCId, but to save money Id like to do the conduit + wire pull myself.
I have the trench dug (18 deep), and plan on using PVC conduit + two THHW conductors.
My questions:
1. What gauge wire do I need?
2. Can I just ground each outlet with a ground stake at each one, or do I need a ground wire for the entire circuit?
 
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Old 10-25-19, 07:24 AM
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I'd be using UF 12-2 with ground wire and no conduit until it was exposed above the ground.
Water tight box and 20 AMP. GFI outlet with an in use cover.
 
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Old 10-25-19, 07:43 AM
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AWG 10, and it still really only a 15A rating, with that 200' distance.
 
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Old 10-25-19, 08:11 AM
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Eight gauge wire will give you the full 20 amps at the far end with 4% voltage drop. This should be good enough for most tools although a tool or appliance that drew a momentary somewhat higher current might have difficulty starting.
 

Last edited by AllanJ; 10-25-19 at 08:33 AM.
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Old 10-25-19, 09:29 AM
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Thanks for the replies. Given that the price difference between 8 and 10 gauge for a 500’ roll is only about $60, I’ll just go with 8 and be done with it.

Thoughts on whether I can just drive ground rods at each outlet rather than having 200’ of ground wire?
 
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Old 10-25-19, 10:03 AM
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Thoughts on whether I can just drive ground rods at each outlet rather than having 200 of ground wire?

Nope, can't do that.


20 AMP. GFI outlet with an in use cover.

No need to use 20 amp GFCI receptacles, 15 amp devices are all that is required and fine.
 
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Old 10-25-19, 01:22 PM
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Thanks; just read elsewhere that code no longer allows the old way of using ground rods rather than an isolated ground wire. (Hey, it’s been 40 years since I last worked as an electrician’s helper!)

For a 20A GFCI circuit, it appears 12 AWG is all that’s needed for the ground wire. Is that correct or do I need to go up to 10 (especially given the 200’ run)?
 
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Old 10-25-19, 01:50 PM
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Before NEC2014, that answer was 8 gauge. With 2014, the new answer is 12 gauge.
 
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Old 10-25-19, 04:29 PM
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#12 will not be large enough for the ground since you upsized the hot conductors. The ground needs to increase by the same percentage.
 
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Old 10-25-19, 04:59 PM
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8awg for the grounding wire, since you upsized to 8awg for voltage drop reasons (upsizing for ampacity would not require an increase in grounding size). Also note that the grounding wire must be green (or bare), and the neutral white.
 
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Old 10-25-19, 06:00 PM
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Ground rods have nothing to do with grounding a receptacle. You can connect the hot directly to a ground rod and never trip the breaker.

upsizing the hots for any reason requires the grounding to be upsized.
 
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Old 10-25-19, 07:35 PM
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Thanks for correction. Further research shows upsizing ground is necessary when current carrying conductors are upsized for voltage drop reasons, but not for ambient heat or bundling reasons.
 
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Old 10-25-19, 08:04 PM
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The upsize needs to be done ANYTIME the ungrounded are upsized, not just for voltage drop.
 
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