Maybe we are talking about different things. How do you define a "shared neutral"? In my case it is one neutral shared between the two sides of a 240 volt split phase circuit. Each hot circuit has a breaker and there is no way the neutral current can exceed the current in either one leg. You seem to be talking about installation problems which are possible with any circuit.
The safety issue you seem to be addressing is an open neutral which can cause problems, but is not directly a safety issue since no part of the circuit should be accessible by a user other than a metal enclosure which is required to be safety grounded and would blow the breaker.
It's about eating butter or other stuff. I like butter. Not interested in fake stuff, especially when I can't buy it. What that company sells here seems to be even less butter. When I say "here" I mean in the mainland. It's not sold at all in Puerto Rico.
The only issue I know of is plugs and sockets we use which certainly are outdated, but I'm not aware of them causing deaths from this. Otherwise our practices seem to be safer and *much* easier to understand. Maybe I shouldn't ask as this thread is already very long and far off topic.
In the UK, what are the voltages you'd measure from earth, or a wet puddle on the floor and the brown and blue wires? What are those wired called? Even for 240 volt receptacles, the highest voltage in the US to ground will be 120 volts, but "hot" to "hot" will show 240. This doesn't apply in places with 3 phase power.
The codes vary greatly across the US. I cringe at plastic wiring and plastic electrical boxes. That stuff is pure garbage. There's also the danger of "cheaper and easier" systems like PEX for plumbing. Since it's "cheap and easy and I don't need to hire a professional" you'll see people attempt some truly terrible things themselves that someone with a clue would never have done.
One more question for the commonwealth folks here. What sizes of metallic conduit are used for electrical work, and do you use foot benders? I was checking youtube for conduit tutorials outside the US and didn't see any of these tools in use, but there has to be something similar.
For light use, 1/2" and 3/4" EMT is what might be seen in a home in the US with civilized codes. Both can be bent with hand/foot tools. There are thicker types that become more like plumbing pipes than tubing. Sizes sort of stop at about 4" diameters in favor of other methods of protecting the inside and ouside of the wiring.
I don't claim it does. But eating more is a factor.
Which is heavier, the blue one or the green one? That makes as much sense.
We just use ours for food.
No, in both cases, but variation in those assumptions can not account for the huge difference in quoted figures. Not unless you routinely leave the door open for 30 minutes at every mealtime, which I find very unlikely.
Brown live 240v (hot) Blue neutral approx 0v, can be a few volts up out in the country Green/yellow earth 0v (ground)
That's one reason the US somewhat gets away with practices that are unacceptable here. A 110v shock will bite, 240v will leave you with recurring daymares and sometimes kills.
Ours are fine.
seldom seen in domestic installs. Metal conduit was used long ago and didn't work out worthwhile. It didn't give reliable earthing, it wasn't reusable later and had no other reason to exist.
Only to the extent that "eating" often requires accessing the interior of the frig.
It's *how* that interior is accessed and for what reasons that makes an impact on usage. The frig sees LOTS of accesses, some of which are "unproductive" ("Hmmm... what *might* I want, in here...?")
We have ~3.5G of water in the frig. We like water cold (out of the tap, it is VERY warm, esp this time of year; you'd never let all that warm water run down the drain as you waited/hoped for some a bit cooler to come through the line). And, filtered. And, to have "sat" for a day for any "outgassing", etc. to take place.
SWMBO keeps two gallon jugs, there -- one in use and one ready-to-be-used.
We share a 1G pitcher for things like water for tea, to boil vegetables, etc.
And, I have a 1/2G "drinking bottle" that allows me to just open the door and drink DIRECTLY from the bottle.
So, each time I make tea, want some cold water, boil some pasta, etc. the frig is accessed.
When we have charcuterie on hand, it's refrigerated (d'uh) and typically "nibbled on". No need to take it out of the frig, get a "helping" and put the balance back in the frig; just stand in the open doorway and "help yourself".
Every day, we transfer items from the deep freezer to the frig where they can thaw before being used that day (or the next). Last night, I took out a steak and placed it in the frig to eat, today. Tonight I'll move half a pork tenderloin from the freezer to the frig so it will be thawed for tomorrow's lunch. (Of course, I'll have to take it out of the frig, tomorrow, cut it and marinate it, then return it to the frig until lunch, when I'll take it out, again, to prepare the meal.
And, retrieve the soy sauce, hoisin sauce and sherry from the frig to make that marinade. Then, return those ingredients to the frig.
When preparing the meal, I'll have to retrieve the bamboo shoots, some onion, and the various ingredients for the "sauce". Of course, they wont ALL come out at once; I'll take out each one as I need it and return it when done.
It would be interesting just to wire a counter to the light switch and count how often the door opens and closes in a day (I hear SWMBO pouring a glass of water, as I'm typing this).
There is a cost to this behavior. But, you don't *see* it. There's not a display on the frig that tells you how much each access is costing. And, it never pops out in the monthly electric bill as an itemized cost.
[I suspect the presence of real-time fuel efficiency displays in vehicles has probably done more to cut waste, there, than the advances in engine technology! Yet, it still doesn't tell you what your driving actions are *costing* -- just that stomping on the accelerator shot your fuel efficiency to *squat*!]
What cost to growing "salad greens" vs. raising and slaughtering livestock?
We use ours for anything that needs to be kept cold.
Many people feed their pets "dry" or "canned" foods. We would prepare fresh ground beef, turkey, chicken, vegetables, etc. as The Dogs' Food. Unless you want to do that *daily*, you need a place to store it that is refrigerated.
Leaving paint palettes "out" means the paints will dry and/or go moldy (depends on the season and what measures you take to avoid one or the other outcome). Paint pigment has a cost. And, there is a convenience factor: you don't want to spend an hour cleaning your palette before you can paint.
Chocolate products left out will melt. Walnuts will "spoil". As will many baked goods.
We also purchase in larger quantities than you likely do. SWMBO has at least 5 different types of cheese in the frig. I have two others. Ketchup, prepared mustard, sweet relish, hoisin sauce, chinese mustard, plum sauce, etc.
A cheesecake eats up 1.5 sq ft of shelf space. A meatloaf, closer to 1.0. Sixteen qts of "spaghetti sauce" requires a place to store while it is cooling -- before freezing.
I keep 48 oz of "salad greens" on hand -- two days supply. Avocados, different types of season fruits, etc. Butter, eggs.
A couple syringes of solder paste.
How often do YOU open your frig? Do you even know? Within an order of magnitude? What's the average length of time that the door is open? I *know* we open ours *hundreds* of times in a 24 hour period. Our usage patterns aren't "make ONE, and only one, trip to the frig per meal prep". Instead, each item is fetched and returned individually. This is more convenient than having to consider EVERYTHING that you will need from the frig before retrieving ANYTHING. And, keeping all of that out on the counter until you are ready to return ALL of them to the frig.
I noted that our most recent electric bill was ~$250 for ~1660 KWHr. He commented that the 1660KWHr would represent "about" 6 mos of his usage. But, later, that his MONTHLY *bill* was about half that (apologies if I'm missing some detail).
He also noted that his peak demand (in some period) was ~3KW. I countered that our ACbrrr (alone) draws 14KW.
Our usage patterns are just different. And, as they aren't prohibitively costly, there's little economic incentive to change.
I did some work on the house's exterior trim, yesterday. At one point, I needed to wash down the stucco. I could have taken a bucket and a brush and climbed on a ladder and scrubbed. Them washed clean with a garden hose.
Or, put a cup of gasoline into the power washer and use that to make quicker work of the job. A cup of gasoline... $3/8 so 37c to save an hour's work? No-brainer! And, likely *less* water, overall (cuz you'd have to rinse if you hand-scrubbed)
Two neighbors behind us have replaced their HVAC plants in recent years. The trend now is to move the plant onto the roof (!). This makes their operation quieter INSIDE the residence but noisier OUTSIDE (you can hear and identify every operation that the combined furnace and ACbrrr perform).
[It has also resulted in both of them having roof *leaks*!]
Both have noticed that their plants can't respond to big temperature changes anywhere near as fast as their old ones. E.g., this time of year (and throughout the winter), folks tend to sleep with windows and (lockable) screen/security doors open. This allows the house interior to cool for more comfortable sleeping. (70-ish in October; closer to
60F in a month or so).
But, on arising, you want the chill out of the air (while sleeping, you can be "under covers"). Old plants would quickly bring the house up to temperature. New ones require a fair bit more time; enough that you'd want a programmable thermostat to start raising the temperature before you get out of bed (but that means your last bit of time *in* bed will be uncomfortably warm).
Similarly in Summer; go away for a weekend and the house is uncomfortably warm on your return. And, considerable time to cool it (our ACbrr makes short order of this; standing by any of the vents leaves you noticeably chilled)
Of course, they are now "stuck" with their decisions because they aren't likely going to drop another $10K into a different choice! So, they alter their behaviors to suit their new capabilities (e.g., keep the house warmer at night soas not to be uncomfortable on waking)
It's just like it sounds. two hots and one neutral. There's multiple ways to install it wrong, which is one reason it's frowned upon.
It's a huge safety issue. Enjoy your electric blanket running at 195 volts or the fire from impedance protected motors only rated at 120 volts.
A failed neutral inside the home for a normal circuit with one breaker, one hot and one neutral fails in a fairly harmless way. In the shared neutral scenario, one side will go high and the other low. The stuff on the high resistance side will lose, every time.
All you save in theory is one wire and maybe somehow two single breakers are cheaper than one tandem one or installing a tie across two breakers.
I was shown a fascinating scenario in a restaurant where the lights started to flicker where someone added sub panel for more circuits. The sub panel had no neutrals installed at all. All new circuits were piggybacking off existing neutrals. Eventually a connection failed. They wasted a fortune replacing light fixtures before hiring a real electrician to unfuck the mess.
What about in industrial settings? Piles of burning cable releases deadly smoke, which is another reason (at least here) large piles of cables running up in a ceiling is not permitted. There doesn't seem to be a limit for low voltage cables though, but they also do not set themselves on fire no matter what goes wrong at each end.
Are they pipe with a cast metal bender on them with funny shapes for defining the start of various bends? The only videos I could locate showed some sort of powered machines, but smaller than you'd usually see in the US.
Conduit & open trays are normal practice in industry. Lots of open vertical cables are permitted, but where they penetrate the fire barrier, fire blocking must be sorted out.
yes
I don't even know what that means :)
We don't use powered stuff for domestic. Hand benders can do upto 22mm. Beyond that there are larger square conduit that one side comes off, and open trays.
I think the issue is not how long the door is kept open, above some minimal time. What matters is that the air in the fridge is replaced by air from the room, because once you open the door the colder air in the fridge "drops out" towards the floor and is replaced by air from the room. It does not matter that much that the air is now warm, because air has very low heat capacity and easily cools down again. What matters is that the moisture in the air now has to condense, that takes a lot of energy.
You're ignoring the fact that "things" are also moving in and out of the frig. You don't open it just for the sake of opening it.
If I take out the pitcher of filtered water and pour that into a tea kettle, I will then refill the pitcher with tap water and replace it in the frig. All of the heat in that water must now be extracted from the water.
Repeat this for every item going in/out.
In a household with kids, you have all those extra "undisciplined" users to contend with, as well.
Well OK I do not put that many items in the fridge that are not already cooled. I buy stuff at the supermarket and when it goes in it still is way below room temperature. I do not put water in the fridge because I can drink water from the tap and it is cold enough for my taste. I have orange juice in the fridge that is bought cooled and placed there, and it is only about
4 liters at most (in packs of 1 liter).
Yes of course it is important to teach children that the fridge does not work for free...
But likely *above* the temperature of your refrigerator. I.e., there is still "work" to be done. We transfer cold things from teh supermarket in an insulated cooler (because ambient is so high). But, they are always "thawed" from their earlier state when we get home. (We try to arrange our shopping trips so the things that MUST stay the coldest -- like chicken breasts -- are picked up at the end of our "circuit")
I made a point of watching our meal prep, this noon hour. We have the same "dish" every Sunday. We each have our "assigned" tasks.
SWMBO opened the refrigerator (1) to fetch the pitcher of water. Close door. Measure out water for the rice. Put pitcher back in refrigerator (2).
A while later (she starts the rice before I have to get started on my tasks), I open the frig (3) to see if there are any bamboo shoots left over from last week (a can makes two meals). Nope. Close door. Fetch can of bamboo shoots from pantry (room temp). Dump half of it into a resealable container for next week. Place container in frig (4).
Julienne the bamboo shoots. Set aside.
Open frig (5) to see if there is *any* onion in produce drawer (we eat a lot of onions so you never know what you'll find "left over"). Nope. Fetch an onion from pantry. Peel. Cut off a few slices. Wrap. Place in frig produce drawer (6).
Dice onion slices. Set aside.
SWMBO will watch the progress of the rice and, as it nears completion, she will start to make the sauce. Open frig (7) to see if there is any Hoisin sauce left over from last week's meal (jar makes two meals). Nope. "Don, can you get me a new jar of Hoisin?" (because we keep it on the top shelf in another pantry)
Shake jar thoroughly. Measure out enough for today's meal. Place balance in frig (8) for next week and take out sherry and soy sauce. Measure quantities and return those to frig (9).
Rice is almost done. Time for me to start cooking the meat!
Which, of course, has been marinating in the frig (10). Get the sesame oil out, while you're at it!
Oil skillet. Start to stir fry meat. But, put don't forget to return the sesame oil to the frig (11)!
Time to eat! SWMBO will pour herself a glass of ice water (12). I'll reheat a cup of tea.
Afterwards, the leftovers (likely now DOWN to room temperature) will be transferred to a resealable container and placed in the frig (13) -- for tomorrow or later tonight.
Depending on the "heat" in the meal, SWMBO may end up needing a second glass of water (14?).
Regardless, in two hours we will both be hungry for "something"... which will likely mean *more* frig activity.
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