Author Topic: Extension cord gauge  (Read 651 times)

sumpnz

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Extension cord gauge
« on: March 03, 2021, 10:33:14 PM »
Need to power 5x 250W heat lamps, not quite 300’ from an outlet.  Is 10ga good enough for that?

Before anyone asks, there are waterproof covers I will use to protect the connections from cord to cord, since 3x 100’ is easy to find but a single 300’ cord is not easy to get.

Jim147

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Re: Extension cord gauge
« Reply #1 on: March 03, 2021, 10:55:23 PM »
Voltage? Amps? Need one more to do the the math.
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Brad Johnson

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Re: Extension cord gauge
« Reply #2 on: March 03, 2021, 11:00:28 PM »
Short version: No. There's a reason the longest commonly available 15A-rated cords top out at 100'.

Longer version: Thats a lot of constant draw even for short runs. 300 feet? Nope. 300 feet composed of 3x 100' extension cords? Not only no but Hell No. Do it right by tapping a new breaker, running a dedicated leg, and putting in an outlet gang at point of use. UF cable can be placed above ground and weather-tight gang boxes are relatively inexpensive. If it's going to see abrasion, encase in exterior-rated conduit.

Three 15A cords, at least ones I'd trust ratings on, will total the better part of $300. I bet it wouldn't be much more than that for supplies to do it right. At the very least make whatever you do a single run with heavy duty weather-rated connectors and a quad or 3x2 box at POU.

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« Last Edit: March 03, 2021, 11:19:12 PM by Brad Johnson »
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zxcvbob

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Re: Extension cord gauge
« Reply #3 on: March 03, 2021, 11:04:38 PM »
Voltage? Amps? Need one more to do the the math.

I assume it's 115 volts and about 11 amps.  (I haven't seen many 230V heat lamps)  And heat lamps don't really care about voltage drop so 12 gauge should be fine.  (I have not actually calculated the voltage drop, just dismissed it) 

But if you have a 230V outlet available it gets interesting; you could do an Edison circuit and reduce the current about 40% -- but it would require 4 wires to do it safely.

ETA: the weakest link here is the plugs and sockets at the ends of the cords.  Those should be rated for at least 15A but you have to reduce that by... 20% I think? for a constant load.  So 12 amps, and you're right up there.  It would be a lot better if you could do a single cable run to avoid all those connectors.
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sumpnz

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Re: Extension cord gauge
« Reply #4 on: March 04, 2021, 12:14:07 AM »
Yes, standard 115V.  So should be 10.8A.  Probably a 20A circuit, might be 30A.  Have to look.

And yes, I looked for a single 300’ cord.  Not available.  Just to moot the waterproof covers I’d have preferred that.

I should only need all 5 heat lamps for a week.  After that can cut it back to 4 and then 3 lamps as the birds feather out and get more robust.

zxcvbob

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Re: Extension cord gauge
« Reply #5 on: March 04, 2021, 12:27:41 AM »
Can you get a 250' roll of 12 gauge UF cable and put a plug and socket on the ends and make a stiff hard-to-manage cord out of it?  Then add a 50' flexible cord to the end.  You can repurpose the UF after you're done with it.  Or just roll it up for next year.  UF is expensive, but is still probably cheaper than extension cords, and it's a lot tougher (almost armored)  And you'll have less connections.

Use really good connectors so they don't overheat.
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Nick1911

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Re: Extension cord gauge
« Reply #6 on: March 04, 2021, 01:32:51 AM »
Zxcvbob nailed it with the Edison circuit.  That's what I would do.  300 foot of cheap 14awg wire would net a voltage drop of 3.5% using this configuration.   I'd also be unconcerned about a fourth ground wire - these should be two prong appliances that don't need a ground.

That said, I did bury a 12awg 240v run out to my coop.  It is nice to have permanent power accessable.

charby

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Re: Extension cord gauge
« Reply #7 on: March 04, 2021, 08:25:31 AM »
I about crapped a brick when I bought a 100' 12 gauge extension cord. I'd be scared what a 10 gauge x3 is going to cost.
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dogmush

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Re: Extension cord gauge
« Reply #8 on: March 04, 2021, 08:58:52 AM »
You can easily find 200ft extension cords, which would at least cut one of the connections out, but the 100' 10 ga cords are like $150ish.  That's a lot of scratch.

If your stores have it for you, I'd use 300ft of submersible 10/2 well pump wire.  That stuff is usually sold by the foot, comes in 500ft rolls, and is by definition waterproof.  Then you'd have no splices or connectors at all.

https://www.homedepot.com/p/Southwire-500-ft-10-2-Solid-CU-W-G-Submersible-Well-Pump-Wire-55173702/202316446

Brad Johnson

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Re: Extension cord gauge
« Reply #9 on: March 04, 2021, 09:19:39 AM »
You can easily find 200ft extension cords, which would at least cut one of the connections out, but the 100' 10 ga cords are like $150ish.  That's a lot of scratch.

If your stores have it for you, I'd use 300ft of submersible 10/2 well pump wire.  That stuff is usually sold by the foot, comes in 500ft rolls, and is by definition waterproof.  Then you'd have no splices or connectors at all.


Waterproof, yes. UV-protected, no.

Brad
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"And he thought cops wouldn't chase... a STOLEN DONUT TRUCK???? That would be like Willie Nelson ignoring a pickup full of weed."
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dogmush

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Re: Extension cord gauge
« Reply #10 on: March 04, 2021, 09:35:45 AM »
It's a short term use for a couple weeks until they get feathers, no?  UV shouldn't kill it in a couple weeks.

If we are talking a more long term need, then he needs to be renting a trencher, adding a circuit breaker, burying some UF-B and putting a GFCI on a pole out by the coop.  That wire is cheaper, actually, but there is obviously more work installing it.

zxcvbob

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Re: Extension cord gauge
« Reply #11 on: March 04, 2021, 10:04:19 AM »
UF cable is cheaper than submersible well cable, and it's UV stabilized.  I do like the idea of no splices.

If you have 240V available, use 6 lamps instead of 5 to get your 1250W -- 4 x 250W and 2 x 125W.  That way the load is balanced.  You could even get by without a neutral wire.

I just thought of something, how about ordering a 300' length of SJOOW cable and make your own long cord?  It's about 75¢ a foot.
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