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All-In [48847]
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Electrical bros - this is a test. This is only a test.
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May 15, 2024, 2:46 PM
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Replacing quad bypass bros electric water heater. Running on double pole 30 amp circuit breaker (number 4 and 6 shown). Need to extend wire as new heater is taller and will now be on a stand. What is the proper gauge wire?
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All-In [48847]
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At least tag the man
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May 15, 2024, 2:47 PM
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flow0440 soccerkrzy® and whoever else wants to answer
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All-In [32099]
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#10 AWG solid***
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May 15, 2024, 4:16 PM
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Oculus Spirit [82170]
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Yup, what Flow said. If you're more than 150' from the panelboard
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May 15, 2024, 8:11 PM
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I'd consider #8s
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Oculus Spirit [87357]
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Sounds like you just need a good pair of
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May 15, 2024, 2:58 PM
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wire stretchers.
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All-In [48847]
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Geez
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May 15, 2024, 3:00 PM
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why didn't I think of that?
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All-In [44853]
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I've got a laundry hamper in my garage full of the exact gauge you need.***
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May 15, 2024, 3:02 PM
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CU Medallion [59142]
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10***
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May 15, 2024, 3:18 PM
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CU Medallion [59142]
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Assuming 30 amp is the proper size breaker (almost all home hot water heaters
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May 15, 2024, 4:30 PM
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require a 2-pole 30 amp breaker) #10 is the correct wire size. Anything smaller and there is the potential for the wire overheating and nuisance tripping over time, while anything bigger than #10 is unnecessary.
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Oculus Spirit [82170]
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Anything smaller will burn the wire and NOT trip the breaker and is
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May 15, 2024, 8:11 PM
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against code and dangerous, so yup, #10. #8 potentially if it's significantly far away from the panel to account for voltage drop.
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CU Medallion [59142]
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It could, but not necessarily. A 12 gauge wire won't immediately blaze up if
May 15, 2024, 8:26 PM
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it sees 30 amps. It will get warm first, which should bend the bimetallic strip in the breaker, causing it to trip. That repeated heating/expansion and cooling/contracting of the wire can loosen the connection at the terminals where the wire connects to the breaker or heater, not to mention ruin the insulation, creating a potential fire hazzard. The smaller gauge wire you use, the greater that risk becomes, and of course, if you used a small enough gauge, it would get red hot and glow like a heating element and could indeed burn up.
Agree about voltage drop.
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Oculus Spirit [82170]
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You're arguing with a licensed electrical engineer...
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May 15, 2024, 9:10 PM
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#12 NM-B is rated for 20A. #14 NM-B (most common in residential) is rated for 15A.
If you put a sustained 24A on that wire, which would never trip the breaker, it would eventually indeed melt the insulation and cause a fire. Sure, it might not happen for a very very long time, but it would.
The wire getting hotter doesn't trip the breaker, the current running through the bimetallic strip is what will trip the thermal part of the thermalmag breaker. And on a 30A breaker, it will run 24A indefinitely, it will trip on extended periods of greater than 24A.
This is all hypothetical because it's against code to put a #12 wire on a 30A breaker...
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CU Medallion [59142]
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Interesting. I always assumed the actual heat from an overheated wire would
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May 16, 2024, 12:15 AM
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cause the bimetallic mechanism of the breaker to heat up and trip just like an overload. I know ambient heat, like on extremely hot days, can contribute to breakers tripping. But, I see what you are saying; the bimetallic strip is designed to bend or flex due to heat caused specifically by an overload, not heat created in other ways (which may or may not happen). In this case, it is not designed to trip due to a connected wire that heats up; the bimetallic strip is not designed to detect that. Thanks for clearing that up.
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Oculus Spirit [98479]
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All I know is when I was a kid our neighbor's house burned down
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May 16, 2024, 8:24 AM
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Now our neighbor was a contractor and architect. He actually built his own house, and my parents' house next door too. Same electrician/electrical company in 1978? wired both houses. His house burned one night, to the ground. Complete loss. horrible fire. It started in the middle of the lower part of the house, worst possible place. We slept through it. They were at Disney World on vacation at the time, otherwise someone could have died.
They had engineers come out and inspect the damage to locate the cause/source, and my dad got to talk to them. The source of the fire was in the crawlspace underneath the floor in the middle of the house. A wire was tacked to a floor joist and that wire had a short due to the connector where it was tacked to the joist, which heated up and eventually, over years, started a fire. Neighbors never had issues with that circuit breaker either. Never tripped. And it never tripped when the fire started.
We had our wiring inspected after this fire and they found two tacks that were shorting that caused burn marks on our floor joists. We had all the tacking replaced, but we never could tear out all the walls to replace the tacking in the wall studs. Just the attic, crawlspace, and everywhere they could access.
But this seems to lend credence to heat not tripping the fuse. It has to be a major voltage change.
Side note.....My parents built a pool in 1985 (same house). In doing that they had to reroute the main electrical line from the SCE&G pole in the backyard, to the house. They ran it along the base of a retaining wall they built for the pool. From 1985 to 1998 they went through 5 AC compressors on their HVAC (all covered by warranties). The HVAC company finally sent an engineer or someone who took measurements and learned we did not have consistent voltage in the lines to the HVAC, and the voltage fluctuations were killing the HVAC compressors, AND this was for the entire house as well, explaining three deaded computers, and a TV as well. So SCE&G came out, and dug up and replaced the entire line from the pole to the house, and found two places where the line sheathing was torn, moisture had entered, and there was a big calcified white chunk of crud on the wire at both places.
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All-In [47179]
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I can guarantee you those new arc fault and gfci breakers will trip
May 16, 2024, 9:11 AM
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mine trip if I drop something heavy on the floor.
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CU Medallion [59142]
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Yep. Didn't have those in 1978.***
May 16, 2024, 10:01 AM
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CU Medallion [59142]
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Yep - and I apologize for derailing this conversation with bad information.
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May 16, 2024, 10:38 AM
[ in reply to All I know is when I was a kid our neighbor's house burned down ] |
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The bottom line is, as others have pointed out, just follow the NEC and use #10 on a 30 amp circuit (unless you have to upsize due to voltage drop on a long run).
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CU Medallion [59142]
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Oculus Spirit [98479]
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110%er [7143]
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#10***
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May 15, 2024, 3:24 PM
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All-In [48337]
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7.
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May 15, 2024, 3:29 PM
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Isn't that the Jounge go to answer?
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CU Medallion [67358]
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Residential, I'd use a #10***
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May 15, 2024, 3:35 PM
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All-In [47179]
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6. and leave a good 100 feet rolled up in case you ever want to move it***
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May 15, 2024, 4:00 PM
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Replies: 22
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