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m85476585

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A question for any electricians/EEs out there-- I have a small space heater, rated for 1500 watts, when I plug it in, it dims the lights more than I would expect. I think the lights are on a separate circuit, but I can't remember for sure. I measured the wall voltage, and it reads 120.0 V with the heater off and around 108 V with it running. The reading is the same on two outlets on the same circuit, one below where the heater is plugged in, and one on the other side of the room. Is a 10% drop in voltage normal for that kind of load in a new house? Does that mean roughly 135 watts (if my calculations are right) is being dissipated in the wall?

These voltage measurements were made with a standard cheap multimeter, if that makes any difference.
 
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SCE to AUX

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Licensed electrician (NJ) here.

10% voltage drop is right at the maximum allowable for a standard branch circuit. It's more than I like to ever actually see in practice. Is this circuit a really long distance from the main panel?

You say that this is a "new" house. That generally translates to "code minimum" and "cheapest installation possible". It is likely that the receptacles were installed using the "backstab" connections, rather than the more secure (but slower) screw connections. The receptacles may be "daisychained" rather than connected using proper pigtails at the boxes. The breaker panel may use an aluminum bus, rather than plated copper. And the builder might have tried to get away with 14 gauge wire, rather than 12 gauge to save a few bucks.

These are a few points to start looking at. Whether you should investigate further by yourself or call an electrician depends on your personal comfort level with electrical work.
 

jcDerRedMax

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Guy on pirate 4x4 was chasing a voltage ghost. Massive drop under certain conditions. His box looked like a 4th grader wired it. Turned out the insulation on the overhead lines had been chewed on.
 

m85476585

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The voltage drop isn't as bad in the rest of the house. On another 15A circuit I measures 10 volts, and on the 20A circuits in the kitchen, living room (??), and laundry room I measured 2-5V drop. The circuit in question is a 15A circuit that supplies outlets and lights (2 cans/bedroom, ~60 watts each) for 3 bedrooms. The bedrooms are basically right above the panel, so the run shouldn't be too long. The outlets are daisy-chained with push-in connections. I don't know how far down the "chain" the outlet I tried is. I didn't look at the wiring closely, but it was yellow (12 gauge) for one of the 20A circuits, and I assume 14 gauge for the 15A circuits.

I just plugged the heater into an outlet on the same circuit in one of the other bedrooms and measured 102V! The voltage still drops to 108V at the first outlet I tried, so there is clearly extra loss between those two outlets.
 

RimfireJim

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The voltage drop isn't as bad in the rest of the house. On another 15A circuit I measures 10 volts, and on the 20A circuits in the kitchen, living room (??), and laundry room I measured 2-5V drop. The circuit in question is a 15A circuit that supplies outlets and lights (2 cans/bedroom, ~60 watts each) for 3 bedrooms. The bedrooms are basically right above the panel, so the run shouldn't be too long. The outlets are daisy-chained with push-in connections. I don't know how far down the "chain" the outlet I tried is. I didn't look at the wiring closely, but it was yellow (12 gauge) for one of the 20A circuits, and I assume 14 gauge for the 15A circuits.

I just plugged the heater into an outlet on the same circuit in one of the other bedrooms and measured 102V! The voltage still drops to 108V at the first outlet I tried, so there is clearly extra loss between those two outlets.
Based on this data, I'd second Bob's advice to focus on the the voltage loss due to the push-in back connections. There is very little contact surface in those connections compared to what you get with a loop under a screw head. And, even if they work so-so now, they will only get worse with age, never better.
 

SCE to AUX

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I would suggest completely redoing all the receptacle and switch terminations throughout the entire house ASAP, and discontinuing the use of heavy loads like space heaters and window A/C units until you do. Those backstab connections should be outlawed as the fire hazard that they are. :mad:

If they used the .39 cent Chinese receptacles (and they probably did), consider replacing them while you are at it. Some of these ONLY accept the backstab connections, and they will HAVE to be changed to convert over to proper screw terminals.

If you REALLY want to do the job right, install pigtail leads at each box, so that the downstream loads aren't carried through the receptacles themselves. Just make sure that you have sufficient space in the boxes to accommodate the splices.
 

RimfireJim

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If you REALLY want to do the job right, install pigtail leads at each box, so that the downstream loads aren't carried through the receptacles themselves. Just make sure that you have sufficient space in the boxes to accommodate the splices.
I have a hard time seeing how a wire nut splice is better than using the buss bar on the side of the receptacle. The buss bar itself doesn't seem like it would be a factor. One connection instead of two? (Fewer connections is always better.)
 

SCE to AUX

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One connection instead of two? (Fewer connections is always better.)
That's essentially it for standard branch circuits. Fewer connections to loosen up can only help reliability. And a loose connection at the receptacle will only effect THAT receptacle, not the rest of the circuit downstream.

Once you get into multiwire branch circuits (where circuits fed from 2 different phase legs share a single neutral conductor--a common cost-cutting measure in residential work), such pigtail connections are REQUIRED by the NEC. The logic here is that replacing a receptacle on one side of the circuit could cause an open neutral on the other side of the circuit, which might still be live! Such circuits are also supposed to be fed from 2 pole circuit breakers, but this is widely ignored by inspectors.
 
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stickershock23

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I would suggest completely redoing all the receptacle and switch terminations throughout the entire house ASAP, and discontinuing the use of heavy loads like space heaters and window A/C units until you do. Those backstab connections should be outlawed as the fire hazard that they are. :mad:

If they used the .39 cent Chinese receptacles (and they probably did), consider replacing them while you are at it. Some of these ONLY accept the backstab connections, and they will HAVE to be changed to convert over to proper screw terminals.

If you REALLY want to do the job right, install pigtail leads at each box, so that the downstream loads aren't carried through the receptacles themselves. Just make sure that you have sufficient space in the boxes to accommodate the splices.
I agree 100% with everything he has said (12 years as an electrician myself CA)

Track houses are notorious for quick and cheap. if you want to be safe make the upgrade. its well worth it.

When outlets are backstabbed, there is a little tiny copper jumper between the top half and bottom half of the outlet, that takes full load of everything past it on the circuit (any load you are using) and in this case that seems to be lights too. that is a very weak point on those cheap ".39 outlets" this is were your fire will start. it won't be today but a few years down the road...

Their is only one other thing he did not ask. when you lights go dim on that half of the house, is there anywhere else that seems to go brighter? if so you may have a problem with a loose or bad neutral. this is an even worse fire hazard. if you do seem to get surges up elsewhere call an electrician ASAP.

Good luck, and remember if you try to do it yourself. TURN THE POWER OFF. and all will go well LOL

How do I know this? Hell I have absorbed so much electricity when I go swimming I line up north and south...
 

stickershock23

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That's essentially it for standard branch circuits. Fewer connections to loosen up can only help reliability. And a loose connection at the receptacle will only effect THAT receptacle, not the rest of the circuit downstream.

Once you get into multiwire branch circuits (where circuits fed from 2 different phase legs share a single neutral conductor--a common cost-cutting measure in residential work), such pigtail connections are REQUIRED by the NEC. The logic here is that replacing a receptacle on one side of the circuit could cause an open neutral on the other side of the circuit, which might still be live! Such circuits are also supposed to be fed from 2 pole circuit breakers, but this is widely ignored by inspectors.
Yep almost all electricians make that short cut (pun intended) and I don't know an inspector that will call you on it. Although I had one in cali that wants a two pole when you have a Disposal and dishwasher circuit under a cupboard sharing a neutral..

Just be lucky we don't need to explain a stinger leg.. SUX.. (really common in old so cal industrial areas)
 

SCE to AUX

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Running the numbers on this situation reveals that you might have an inherent problem using this heater on this circuit, even when the backstab connections are repaired.

A 1500W resistive load (heater) running on 120V will draw 12.5A.

You also said that you have 3 bedrooms worth of lights (6 recessed cans @ 60W each) on this same circuit. For a total of 360W, or 3A additional load.

The total load on this 15A branch circuit is now 15.5A, assuming a constant 120V. It seems to be only the fact that the voltage is sagging to 108 (causing the current to drop proportionately) that is keeping the 15A circuit breaker from tripping out on an overload. Either that, or the breaker itself is defective.

According to the NEC, branch circuits aren't supposed to be loaded beyond 80% of capacity for any appreciable length of time. Your 1500W heater by itself will load a 15A branch circuit in excess of 80%.

In short, this heater really needs a 20A branch circuit in order to meet code requirements.
 

RimfireJim

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Once you get into multiwire branch circuits (where circuits fed from 2 different phase legs share a single neutral conductor--a common cost-cutting measure in residential work), such pigtail connections are REQUIRED by the NEC.
I have such a circuit in my house, one side for the dishwasher and the other side for the microwave oven. Each side has only one receptacle, though the microwave outlet neutral is "downstream" of the dishwasher. So it sounds like the neutral connection at the dishwasher should be done with a pigtail, but what about the other connections? Doesn't seem to be any point in using a pigtail when there is only one connection (a single receptacle) being made.

By the words "cost-cutting" you imply substandard, but as an engineer, I view the shared neutral approach as an efficient use of materials with no compromise to safety,providing the installation is done to code.

Such circuits are also supposed to be fed from 2 pole circuit breakers, but this is widely ignored by inspectors.
That's pretty incredible. As you know, the only reason the shared neutral approach is allowed is that, with the "hot" legs on different phases, the neutral will carry no more, and usually less, current than that in either of the hot legs. With them on the same phase, it could be forced to carry the sum of the hot leg currents rather than the difference. For an inspector to ignore it is unconscionable. I'm sure I'd be appalled by the other things that get ignored or overlooked.
 

SCE to AUX

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Doesn't seem to be any point in using a pigtail when there is only one connection (a single receptacle) being made.
2 devices on a single yoke, fed by a dedicated multiwire circuit, would be an obvious exception to the pigtailing requirement.


By the words "cost-cutting" you imply substandard, but as an engineer, I view the shared neutral approach as an efficient use of materials with no compromise to safety,providing the installation is done to code.
Provided that the installation is also MAINTAINED in a code-compliant condition, I would tend to agree. Once Harry Homeowner starts playing around, all kinds of problems can result.


That's pretty incredible. As you know, the only reason the shared neutral approach is allowed is that, with the "hot" legs on different phases, the neutral will carry no more, and usually less, current than that in either of the hot legs. With them on the same phase, it could be forced to carry the sum of the hot leg currents rather than the difference. For an inspector to ignore it is unconscionable. I'm sure I'd be appalled by the other things that get ignored or overlooked.
Every inspector I've seen will at least look to see that the red and black conductors from each cable are landed on adjacent breakers (and therefore opposite phases). Enforcing the use of 2 pole breakers (or 2 singles with an approved handle tie arrangement) is where a lot of them fail.

And again, if a well-meaning DIYer gets into the panel and starts switching stuff around, you can easily end up with overloaded neutrals. I wish I had a dollar for every one of those I've come across when doing a panel upgrade. Same with 14 gauge wires on 20 (or even 30) amp breakers.

Once you get into commercial wiring and 3-phase power, the shared neutral concept starts to become a generally bad idea. An ever-growing percentage of electrical demand consists of so-called "non-linear" loads (switching power supplies, electronic lighting ballasts, etc.), where individual phase currents may not cancel (and may actually become ADDITIVE under some conditions) in the neutral.
 

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Not an electrician but required to be knowledgeable on residential and industrial power distribution...

1.) I'm surprised that you'd find a 14/2 15 amp circuit in new construction. With few exceptions I thought NEC required a minimum of 2 independent 12/2 20 amp wall circuits, and a separate 12/2 fixed lighting circuit per room, not counting the kitchen which requires a lot more separate circuits.

2.) While it makes logical sense to run a 12/3 120/240 VAC circuit to a split tang duplex outlet to get (2) 20 amp 120 VAC circuits sharing a common neutral, I thought it was only allowed by NEC for a dual dishwasher/disposal hookup.

3.) Considering the contemporary need for many electrical outlets (in place of extension cords, it would sense, and be environmentally and economically advantageous (25% cost reduction), to use 12/3 wiring in a triple box or larger wall power units with (1) 4-wire 240 VAC outlet, and at least (2) duplex outlets with separate 120 VAC 20 amp circuits. This would permit more appliance flexibility, and eliminate the need for extension cords.

4.) I use a variation of the above in my labs. On the back of my instrument racks I have (2) wall raceways mounted vertically each fed by a 5-wire 12/4 20 amp 208 VAC 3 phase 25' long power cords with a total power capability of 25 KW per instrument rack. With this setup I have (3) sets of (2) duplex 120 VAC outlets, (3) separate 208 VAC outlets and (1) 208 VAC 3-phase outlet so I can power any laboratory instrument provided any single leg does not exceed 20 amps, with a power draw up to 12.5 KW (208 VAC, 20 amps. 3 phase), whichever comes first, and bbest of all I can position the racks anywhere in the lab without rewiring the room.

Bob
 

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While I am not a licensed electrician I used to work for an electrician. SCE to AUX speaks the gospel here.

If I were you I would discontinue the use of the electric space heater until a dedicated properly wired outlet is available right where you want to use the space heater. If we were discussing what I would do in my own house I would wire a dedicated circuit with 10 gauge wire (overkill I know but still cheaper than a fire). I also only use armor clad (still referred to as "BX" in some circles) when I do any wiring in my house. I was a firefighter for 15 years and I've seen a lot of dead-shorted wires glowing red hot with all of the insulation melted off when a breaker failed to do its job, or the homeowner who knows everything had put a penny behind the screw-in fuse that kept blowing. "Lincoln-Fuse, one amp!" I have even seen cartridge fuses replaced by short lengths of copper tubing. "What do you mean you shouldn't have a 7hp air compressor, a plasma cutter and a space heater all on the same circuit?" See picture below. This is the house in question.

I have my own experience with using a 1500 watt heater on a sub-par circuit. I added outlets in my parents' garage when I was young and penny wise pound foolish. The only smart thing I did was use BX cable sleeved in EMT for the horizontal runs surface mounted on a concrete block wall. The breaker tripped one day and wouldn't reset. I unplugged the heater and still the breaker would not reset. I opened the outlet box to find that the $0.39 outlet was mostly melted. The insulation on the conductors was charred about six inches into the armor. Up until this point the only thing that would happen is that other lights in the house would dim slightly wne this heater was turned on. This happened a few years after the initial installation so I knew how to fix the problem. I removed all of the 14ga. cable and replaced it with 12 ga. I also junked the heater.

I am now in the market for a house and one of the first things I evaluate on the first visit to a prospective home for my family is the electrical system. I have so far rejected about 50 houses over the past year and a half based solely on the abundance of non-metallic (AKA "Romex") 14 ga. cables at the breaker panel.

IMGP2532.jpg
 

stickershock23

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I am just curious why so many are against 14/2 romex. If used correctly (thats the hard part) it is just fine. 14/2 romex is perfect to run lighting circuits in a home. as long as you keep track of the maximum wattage that could be used on that branch, and keep it to 80% of 15 amps.

Of course the only Outlet I would wire in 14 gauge would be a dedicated circuit for say a garage door opener, refrig, microwave or disposal. the other thing that I see wired in 14 a lot in newer tract homes are Half hot switched outlets in rooms that do not have light fixtures in the ceiling. but then again those outlets are almost never daisy chained together.
 

bobkrech

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...According to the NEC, branch circuits aren't supposed to be loaded beyond 80% of capacity for any appreciable length of time. Your 1500W heater by itself will load a 15A branch circuit in excess of 80%.

In short, this heater really needs a 20A branch circuit in order to meet code requirements.
Bob

AFAIK the continuous ampacity for 14/2 or 14/2 is 15 amps by NEC and 20 amps for 12/2 or 12/3 and this is already conservative as they are each rated at least 5 amps higher or more by the allowable temperature rise of the insulation specifications, so I can't fathom the rationale your 80% comment for branch circuits. (Not that any NFPA code has to make sense.)

Is the the 80% of capacity actually code, or does it apply only to the most common type, and cheap, type of circuit breakers?

Most commonly available circuit breakers are rated to carry no more than 80% of their nominal rating continuously (3 hours or more) (NEC Art. 100). 100%-rated circuit breakers are manufactured for and may carry 100% of their nominal rating continuously.

http://en.wikipedia.org/wiki/National_Electrical_Code

If so, then it's really a matter of getting the right breakers in the first place.

Bob
 

SCE to AUX

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14 AWG romex represents the epitome of "code minimum" wiring. The absolute minimum that you can use and still be compliant with NEC.

Unfortunately, it ends up being the default standard of a lot of DIYers, simply because it is the cheapest cable available at the big orange/blue box stores. It gets used in a lot of spec houses, particularly those built by the real penny-pincher contractors. Same with the .39 cent backstab receptacles. I generally don't get involved in new construction, but most GCs are looking to squeeze every last cent out of the subcontractors, so you end up with "code minimum" and nothing more. I personally try to do work of a somewhat better caliber than "code minimum", so my bids on jobs usually end up a bit higher. I try to make customers aware of why that is.

I certainly wouldn't wire my own house using Romex, even 12 gauge. Armored cable such as AC ("BX") or MC is MUCH more rugged. and when used along with actual METAL outlet boxes is a much better investment for the long term. A similar situation is the use of direct burial cable (UF or USE) rather than individual conductors in PVC conduit for underground runs. The cable is a bit cheaper to install, but when it corrodes or gets damaged or you want to upgrade/change wiring a few years down the line, you won't have to dig your yard up again if you go with conduit. This same kind of "futureproofing" is why I generally feed overhead lights at the switch, and use 3 conductor cable between the switch and the ceiling. Nice to have a neutral at the switch for timers/occupancy sensors/etc, and that extra wire to the ceiling comes in handy if you want to add a paddle fan later on.

You get what you pay for, just like everything else, I guess....
 

stickershock23

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14 AWG romex represents the epitome of "code minimum" wiring. The absolute minimum that you can use and still be compliant with NEC.

Unfortunately, it ends up being the default standard of a lot of DIYers, simply because it is the cheapest cable available at the big orange/blue box stores. It gets used in a lot of spec houses, particularly those built by the real penny-pincher contractors. Same with the .39 cent backstab receptacles. I generally don't get involved in new construction, but most GCs are looking to squeeze every last cent out of the subcontractors, so you end up with "code minimum" and nothing more. I personally try to do work of a somewhat better caliber than "code minimum", so my bids on jobs usually end up a bit higher. I try to make customers aware of why that is.

I certainly wouldn't wire my own house using Romex, even 12 gauge. Armored cable such as AC ("BX") or MC is MUCH more rugged. and when used along with actual METAL outlet boxes is a much better investment for the long term. A similar situation is the use of direct burial cable (UF or USE) rather than individual conductors in PVC conduit for underground runs. The cable is a bit cheaper to install, but when it corrodes or gets damaged or you want to upgrade/change wiring a few years down the line, you won't have to dig your yard up again if you go with conduit. This same kind of "futureproofing" is why I generally feed overhead lights at the switch, and use 3 conductor cable between the switch and the ceiling. Nice to have a neutral at the switch for timers/occupancy sensors/etc, and that extra wire to the ceiling comes in handy if you want to add a paddle fan later on.

You get what you pay for, just like everything else, I guess....
All true.. But I think BX or MC is a little overkill for a house. although it is bulletproof! and metal boxes.. the only way to fly!

Personally I'd run EMT.. (LOL) I used to make balloon animals out of conduit on the weekends for the kids... I did a lot of hospitals. EMT in the walls is easy once you know what you are doing. a few complex bends, and we are in business..
 

SCE to AUX

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AFAIK the continuous ampacity for 14/2 or 14/2 is 15 amps by NEC and 20 amps for 12/2 or 12/3 and this is already conservative as they are each rated at least 5 amps higher or more by the allowable temperature rise of the insulation specifications, so I can't fathom the rationale your 80% comment for branch circuits. (Not that any NFPA code has to make sense.)

Is the the 80% of capacity actually code, or does it apply only to the most common type, and cheap, type of circuit breakers?
See Table 210.21(B)(2), dealing with cord and plug connected loads (such as this space heater).

Most commonly available circuit breakers are rated to carry no more than 80% of their nominal rating continuously (3 hours or more) (NEC Art. 100). 100%-rated circuit breakers are manufactured for and may carry 100% of their nominal rating continuously.

http://en.wikipedia.org/wiki/National_Electrical_Code

If so, then it's really a matter of getting the right breakers in the first place.
In order to actually use 90C conductors at their 90C ampacity, the terminations need to be rated at 90 degrees, as well. Receptacle outlets and most circuit breakers aren't. And the price differential between the "100% rated" breakers and the standard ones is enough to make you cry....
 

SCE to AUX

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Personally I'd run EMT.. (LOL) I used to make balloon animals out of conduit on the weekends for the kids... I did a lot of hospitals. EMT in the walls is easy once you know what you are doing. a few complex bends, and we are in business..

Have done EMT in the walls for a few commercial jobs, but the residential market would NEVER pay for that around here. AFAIK, EMT is actually required in the Chicago area. They adopted the strictest electrical and fire codes in the country after the big fire...

I have installed PVC conduit in-wall for low voltage/telecom stuff a few times. Makes wiring changes a breeze later on.
 

bobkrech

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See Table 210.21(B)(2), dealing with cord and plug connected loads (such as this space heater).

In order to actually use 90C conductors at their 90C ampacity, the terminations need to be rated at 90 degrees, as well. Receptacle outlets and most circuit breakers aren't. And the price differential between the "100% rated" breakers and the standard ones is enough to make you cry....
Bob

Thanks for the reference. You really know your code.

Now I'm beginning to see rationale in the NEC current limitations, and it's not for the reasons listed in the code.

0.) While the distinction is made between the branch circuit rated capacity and the 80% current restriction with corded appliances, the NEC is an installation code, not a use code, and the 100% current capacity use can not be prohibited. http://ecmweb.com/nec/code-basics/electric_branch_circuits_part/

1.) The NEC 60, 75 and 90 C insulation ratings of 14 and 12 gauges wire are: 20/20/25 amps respectively for 14 gauge wiring for which they limit the permissible current to 15 amps; and 25/25/30 amps respectively for 14 gauge wiring for which they limit the permissible current to 20 amps, underrating both by 5 amps. http://en.wikipedia.org/wiki/American_wire_gauge

2.) The NEC permits circuit breakers that actually rated for 80% of capacity, 12 and 16 amps respectively, and nominally nominally rated at 15 and 20 amps respectively, over rating both by 125%. http://en.wikipedia.org/wiki/National_Electrical_Code

3.) I would claim that it's the "improper" labeling of "underrated" rated circuit breakers that are the true reason for the 80% cordage current rule that derates the circuit by amazingly 125%!

While there appears to be some blaming of contractors (and electricians) for using "substandard" materials, I don't believe this is fair. They are following the mandated codes which should be fair to both them and the consumers, but isn't. The allowed use of "underrated" circuit breakers is a "deceptive" practice permitted by the NEC code, and is not in the consumers (or the electricians) best interest. IMO this is a case where NFPA is bending over backwards for the electrical manufactures association instead of requiring them to make better products.

Bob
 
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SCE to AUX

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The NEC is indeed quite conservative on conductor ampacity in almost every situation. And you are right about the NEC being powerless to enforce conditions of use vs installation requirements. Otherwise, everyone's 1500W blow-dryer would have to have a 20A plug on it!

The role of manufacturer's reps on the code-making panels has been a hot topic in recent years. The requirement of arc-fault circuit breakers (AFCIs) in particular seemed to get ramrodded into the code before the devices themselves were able to deliver what they were originally claimed to (and they still can't). The manufacturers originally claimed that these devices could detect a "series arc" such as would be caused by a loose connection in series with a load, and would be able to cut off the power, preventing a large percentage of electrical fires. The CMPs bought the promises hook, line and sinker, and mandated the devices for all new residential bedroom circuits and major remodeling projects. Exactly how the devices were allegedly able to differentiate between abnormal arcing from a loose connection and the normal arcing at the contacts of an opening switch or a device being plugged/unplugged while turned on was never adequately explained, and the first generation of these devices was plagued with false tripping problems.

The manufacturers then modified the devices to eliminate the false tripping problem, but now no longer claimed the ability to detect series arcing--the very reason that they were now mandated by the NEC in the first place! Fortunately, many localities (including my area here in NJ) removed the AFCI requirement from the code at adoption, sparing us from the headaches that many others dealt with.

A similar situation happened during the latest code revision cycle, with the new requirement for "tamper resistant" receptacles in essentially all residential construction. Intended to keep children from poking objects into the receptacle slots, the various shutter or gate arrangements available on the market tend to cause serious difficulties for older folks with arthritis or other problems with their fingers/hands. They don't work well with all types of plugs, either.

In short, it seems like the NEC is drifting away from being a true safety code to becoming the "mandatory marketing arm" for equipment manufacturers. :mad:
 
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