The Electrical Contractor Network

ECN Electrical Forum
Discussion Forums for Electricians, Inspectors and Related Professionals

Books, Tools and Test Equipment for Electrical and Construction Trades

Register Now!

Register Now!

We want your input!

Featured:
   

2017 NEC and Related
2017 NEC
Now Available!

   
Recent Posts
230 or 345 kV transmission lines?
by Vlado
09/24/16 09:33 AM
breaker meltdown
by crselectric
09/24/16 12:42 AM
Electrical mast flashing product
by ThomasWinfrey
09/22/16 12:14 AM
What estimating software do you recommend?
by sparky
09/21/16 07:20 PM
"Dry Run" Inspection goes awry
by HotLine1
09/20/16 07:39 PM
New in the Gallery:
12.5A through 0.75mm flex (just out of curiosity)
Shout Box

Top Posters (30 Days)
HotLine1 15
sparky 9
gfretwell 8
sparky66wv 8
Vlado 6
Who's Online
0 registered (), 153 Guests and 4 Spiders online.
Key: Admin, Global Mod, Mod
Page 1 of 2 1 2 >
Topic Options
Rate This Topic
#215656 - 06/23/15 07:35 AM Questioning the electrical norms
LongRunner Offline
Member

Registered: 05/30/15
Posts: 33
Loc: Albany, Western Australia
Recently, I found that old thread by C-H about Why cables look like they do and revived it with some additional information. This thread is for those other questionable norms in the electrical world. I'll start with...

Voltages
I think it's been established that they don't save much of anything on insulation by going with 120V instead of 220/230/240V for small appliances in North America, as almost all mains cordage worldwide is good for at least 300V* operation. I've seen it suggested before on this forum that they add 240V outlets in kitchens in new buildings there, doubling the available power for kettles etc. That idea seems sensible to me. Implementation would be straightforward enough - Leviton even makes a combination NEMA 5/6 outlet, as shown here (a 15A version is also made), although it's not available with shutters (or "tamper resistance" as they like to call it).

As I understand it, the only real advantages of the lower voltage are:
  • Works better with incandescent lamps (thicker filament = longer life at the same temperature, or higher temp. and by extension efficacy with the same lifespan) - but that's less and less relevant with the advent of LED lighting
  • Easier winding of small motors and transformers (half as many turns of wire with double the cross-sectional area)
  • Shorter creepage distances on circuit boards (although that only matters if a board is designed exclusively for the lower voltage)
I don't suppose the somewhat weaker (though still quite lethal) shocks are enough to make up for the lack of protection NEMA plugs provide from contact with the pins.

*Well, AS/NZS 3191 specifies 250V for light-duty and 250/440V (the 440V being between lines in a multi-phase circuit) for ordinary-duty cords, but I believe that's merely a political difference, as the dimensions are unchanged from the harmonised cords which are rated 300V for light-duty and 300/500V for ordinary-duty. The heavy-duty cords, curiously, were up-rated from 450/750V [harmonised] to 600/1000V [AS/NZS]. There's also XTW for decorative lights in North America - I happen to have a "plug-pack" supply (a linear type providing 6VDC 2.1A, unregulated [measures 9.6V unloaded]) using a 20AWG parallel version as its output lead, and it's marked with 125V. But XTW is the exception to the rule.

Polarisation
Let's just say that too much attention is paid to it in North America; not many appliances care much about it. Well, with BS 1363 correct wiring of the outlet is critical to ensure that a short to earth doesn't bypass the plug fuse, but correct line/neutral connections in the plug are no more important than with any of the others. Don't want something (e.g. a toaster element, or an incandescent lamp socket) to remain live with the switch off? Equip that appliance with a double-pole switch. They don't add that much to the cost.

Speaking of toasters, I can't say I follow the arguments given for not earthing the North American versions. If the idea is so the user isn't electrocuted if (s)he contacts the element with a knife/fork in one hand while holding the case in the other, then all you need to defeat the argument is a stainless steel kettle - or a kitchen sink with metallic plumbing. I suspect that the real reason is economics as usual, and that the UL is a corrupt organisation; I still don't get why else you'd bother with separate "residential" and "commercial" fittings. I guess this also explains why they don't use the double insulation symbol (except on power tools?). (Any info on toasters in Japan?)

And why the heck don't the Japanese use more of the proper 3-pin outlets (which they do make some use of) instead of those kludges with the earth post near 2-pin outlets (to which the user is supposed to manually attach an earthing fly-lead with a lug on its end)? rolleyes

Top
Test Equipment:

Large Selection of Test Equipment For Electrical, HVAC, Test & Measurement
Large Selection of Test Equipment For Electrical, HVAC, Test & Measurement

#215657 - 06/23/15 06:46 PM Re: Questioning the electrical norms [Re: LongRunner]
gfretwell Offline

Member

Registered: 07/20/04
Posts: 9012
Loc: Estero,Fl,usa
The kettle thing is interesting. When I was in New Zealand there seemed to be a kettle everywhere we went and being able to boil a liter of water in a minute or two was cool.
I did toy with the idea of buying one and putting a 6-15 receptacle in the kitchen. Fortunately for all of the NRTL fans, they seem to generally use a IEC320 inlet on the kettle end and a 6-15 to IEC320 cord, U/L listed, is readily available.

Once I got home, I realized, we don't drink that much tea and I have a capable coffee maker. wink
_________________________
Greg Fretwell

Top
#215661 - 06/26/15 10:44 AM Re: Questioning the electrical norms [Re: LongRunner]
Texas_Ranger Offline
Member

Registered: 12/17/01
Posts: 2331
Loc: Vienna, Austria
My electric kettle is mostly gathering dust but I decidedly know people who'll boil water in the kettle before putting it into a pot (e.g. for pasta or potatoes). Doesn't make much sense economically if you're cooking with gas and gas is half the price of electricity but does speed up things especially in small households.

Anyway, I could definitely see the additional introduction of 240 V in US household and strongly suspect cheap imported 230 V appliances would eventually mostly replace 120 V versions. A simple switchover to 230 V at distribution level seems more or less impossible nowadays and would likely cause a nightmare of cheap transformers as people continue using their old equipment - plus some damaged stuff as people plug in things using just an adaptor or old NEMA 5-15 sockets are left in place during the conversion.

Polarisation would be pointless with 240 V provided by a typical US 120/240 V transformer since both poles are 120 V to earth. And yes, IMO with asymmetrical supplies polarisation is vastly overrated. I think modern toasters have double-pole switches anyway and even Chinese hammer drills do. Edison base lights are an issue but Germans and other users of Schuko plugs seem to survive just fine with some common sense and unplugging floor/table lamps when in doubt. Some inline switches are double pole too but not all of them.

Double isolation and its implementation is highly interesting! I've never seen double-isolated fridges or toasters in Europe, yet hairdryers have been required to be double-isolated here for half a century!

Top
#215663 - 06/27/15 01:26 AM Re: Questioning the electrical norms [Re: LongRunner]
gfretwell Offline

Member

Registered: 07/20/04
Posts: 9012
Loc: Estero,Fl,usa
I was surprised at how much of our electronic stuff was dual 120/240 rated when we were packing up to go to New Zealand. It was pretty much everything. I did have one wall wart that was 120 only (transformer type) but I dug around in my box of warts and came up with a switcher that had the same 5mm plug on the end. It was dual rated.
All we really needed was a plug adapter for the 5-15 so it would plug into the NZ crow foot. I mated that with a cube tap and we were good.
_________________________
Greg Fretwell

Top
#215664 - 06/27/15 01:27 AM Re: Questioning the electrical norms [Re: LongRunner]
gfretwell Offline

Member

Registered: 07/20/04
Posts: 9012
Loc: Estero,Fl,usa
I think all of our hair dryers are double insulated but they also add an immersion detector so it will trip out if you drop it in the tub.
_________________________
Greg Fretwell

Top
#215665 - 06/27/15 06:09 AM Re: Questioning the electrical norms [Re: gfretwell]
Texas_Ranger Offline
Member

Registered: 12/17/01
Posts: 2331
Loc: Vienna, Austria
Originally Posted By: gfretwell
I think all of our hair dryers are double insulated but they also add an immersion detector so it will trip out if you drop it in the tub.


OK, that does make sense. That might be the next thing we'll see here, we do get the occasional fatality with hairdryers (and shavers) in the bath. I haven't heard any talk about that though, the Germans are busy introducing AFCIs at the moment (not mandatory yet).

Anything with an SMPS inside will be wide-range 100-240 V these days, some computers have been for decades, especially laptops. IBM-compatible Desktop systems usually had a slider switch, Apple used wide-range power supplies very early on. CRTs were usually single-voltage though. Wire-wound transformer power supplies are pretty much extinct these days so the voltage issue is mostly limited to anything with mains-voltage AC motors in it, as is 50 vs. 60 Hz.

Top
#215691 - 07/02/15 01:32 PM Re: Questioning the electrical norms [Re: Texas_Ranger]
LongRunner Offline
Member

Registered: 05/30/15
Posts: 33
Loc: Albany, Western Australia
Originally Posted By: Texas_Ranger
I think modern toasters have double-pole switches anyway...

Correct. At least the one in my home (or more correctly, my mother's home), a Heller TAH2S (stainless steel, 2 slices in one long slot, nominal power of 800W at 230V which appears accurate from a measured 66 Ohms across the plug with the lever held down), shows no conductive path between either the line (usually referred to in Australia as "active") or neutral plug pins and the element with the switch off. Of course, anyone who sticks a knife in with the toaster on deserves what they get (although having RCDs increases the chances of survival). wink

Hilariously, this is even true of the North American toasters nowadays! grin (If you go here, you can find repair guides for a few of them, and the pictures show the detail quite clearly. So obviously, the only reason why they still bother with the polarised plugs is tradition, and the public perception of the safety "advantage". But anyway, I'm quite sure that they are not double-insulated but are merely exempt from the normal rules. At least, I fail to see where the supplementary insulation is in those examples, and you can even find a designated earthing point on the chassis of the PS77401. Of course, it stands to reason that insulation failure is rare enough anyway that the UL and CSA can get away with it, knowing that the public will buy their argument despite it having zero basis in reality - that's what I meant when I said before that the UL is corrupt; well, they're a private corporation established by a group of insurance companies instead of a national safety agency, which I guess explains it.)

As for the Edison screw fittings, at least the European ones have the side contact relatively deep into the lamp socket (the socket thread itself being plastic or ceramic) - unlike the North American ones where the entire threaded section makes the connection (nasty). So with a DP switch, I suppose they aren't that much worse than the bayonet fittings predominantly used in Australia and the UK.

Even if you were able to verify 100% the polarity, a broken neutral upstream on any circuit shared between multiple loads still presents a risk (even a relatively small electric heater, for example, might as well be a straight wire as far as a resultant shock is concerned) if you rely on only SP switches.

Quote:
Double isolation and its implementation is highly interesting! I've never seen double-isolated fridges or toasters in Europe, yet hairdryers have been required to be double-isolated here for half a century!

It's a matter of feasibility; the simplest way of meeting the double insulation standard, of course, is with a plastic casing serving as supplementary (or, in some cases, reinforced) insulation. With a metal chassis or cover, it gets trickier, although there are still some possibilities; for example, you could:
  • Insulate the inner surface in the vicinity of live circuitry
  • Insulate the entire outer surface; this way, the chassis can still become live but the user is still protected, as long as they don't damage the outer insulation.
Another method that I've read was used by some vintage fan heaters was to have a dual-layered casing, with insulating spacers between the inner and outer layers (modern cheap fan heaters, of course, just have plastic cases).

(Components such as motors that are themselves only single-insulated may be used in a Class II appliance if mounted in such a way that they are hidden from user contact, and isolated from any externally accessible metal. Dissipating the waste heat may then become harder, though - I've seen inside the base of a badly-designed fluorescent desk lamp whose (inductive) ballast ran so hot that its 105C rated lead-out wires deteriorated quite quickly, although it hadn't stopped functioning (at the time - but I subsequently took it to pieces). Suffice to say that the result of the ballast leads shorting together wouldn't be a pretty sight...eek)

Double-insulated hook-up wire could also be used, although I don't know if any is provided with insulation other than boring PVC. Or add-on tubing (available in various materials, which may or may not be heat-shrinkable) can be used for supplementary insulation.

Suitably guarding the terminations may be a challenge, of course. When you're simply connecting wires to other wires, it wouldn't exactly be insurmountable; enclosing the wire joiners in a robust plastic (or other suitable insulating material) box with a suitable clamping arrangement for the insulation should do. With connections to other hardware (controls, motors, heating elements, etc.) things may be trickier. Still, some types of terminals are quite strong; in particular, the crimp terminals that hold onto the insulation as well as the conductor are nearly indestructible - provided that they are matched to the wire size, crimped solidly, and no attempt is made to join more than two wires to a single terminal (and that 2-wire combinations are examined on a case-by-case basis - just jamming the wires in there without proper testing won't cut it with me). Wire terminations to printed circuit boards can be reinforced with Amp-In(tm) or similar connectors (photos from DigiKey):



From left to right, a Mini Amp-In for 26-22AWG wires, another version for 22-18AWG wires, the larger Amp-In for 18-14AWG wires and finally the biggest Amp-In, for 12AWG or 10AWG wires. (They can be found in this category by selecting "Amp-In" and "Mini Amp-In" for the series, and "Through Board" and "Through Board, Locking" for the terminal type - except for the first one shown, which was accidentally placed in the category for "Rectangular Connectors - Contacts".)

Basically, the wire is stripped, inserted into the connector and crimped, then the connector is inserted into an appropriate-sized through-hole in the board, whereupon its tab(s) will lock it into place, and it is then soldered as normal.

For pluggable connectors, we have, among others, the ever-popular Faston(tm) line (and equivalents) - and the "Positive Lock" variations, which add a mechanical latch (enabling stronger retention force, but also easier disconnection at will), look particularly appealing for the purpose I have in mind here:



Even with that out of the way, though, there are other things, such as the sealed heating elements. I don't know if there's a way to make those so that they can never short or leak to the outer casing, although I presume that engineers have tried but without success.

But enough of the technical details. I take that, in the end, the choice between double-insulation or earthing comes down primarily to which approach costs less to build. As long as the earth connection holds solid, it wouldn't exactly change the world were someone to work out how to build a double-insulated fridge tomorrow.

Of course, there is one category of devices that are typically built as Class II, but really shouldn't be - those switching PSUs. Most of them require small "Y"-class capacitors (rated for use across safety insulation - Y1 class across double/reinforced, Y2 class across basic or supplementary) connected between the mains lines and the output return in order to pass EMI tests; of course, these pass a current (however small) through which can be felt at times. Probably worse, though, is if they are accidentally discharged into audio/video circuits; this is much nastier than "traditional" static discharges (already a serious danger to many electronic parts), being capable of one-shotting even a discrete bipolar transistor (as explained in detail in this article). This highlights a significant flaw in the regulations - they still seem to treat each "appliance" as a stand-alone entity, even though much audio/visual equipment is pretty much useless without interconnections. Interconnecting multiple devices with Y1 class capacitors will also add together their leakage currents, so if you hook up enough gear, you could get quite a significant shock touching it even with no component failure.

Originally Posted By: gfretwell
I think all of our hair dryers are double insulated but they also add an immersion detector so it will trip out if you drop it in the tub.

If I recall right, they may have either a normal resettable GFCI (or RCD as known to the rest of the world), or a single-use ALCI (Appliance-Leakage Circuit Interrupter, or as the Sci.Electronics.Repair FAQ dubbed it, the "Ground-Fault Circuit Killer"). The rest-of-the-world models don't have additional protection (that I know of).

As for the old-style mains transformers, while they are heavy, can't do auto-ranging input and their idle draw is higher than the PC environmentalists are happy with, they are at least more reliable and it's much easier to guard against catastrophic failures in them (one thermal fuse in the primary and you're covered, basically; there's much more that can go wrong in a switcher), plus with almost no EMI (which can matter a lot for audio equipment).

Top
#215693 - 07/02/15 03:34 PM Re: Questioning the electrical norms [Re: LongRunner]
gfretwell Offline

Member

Registered: 07/20/04
Posts: 9012
Loc: Estero,Fl,usa
Toasters in the US are the metaphor for a potentially deadly appliance but they sell for $10 US (less than a 12 pack of beer).
I suppose we just trust the GFCI and get on with our lives. The actual death toll from kitchen appliances is lost in the margin of error in the statistics.
_________________________
Greg Fretwell

Top
#215698 - 07/02/15 06:34 PM Re: Questioning the electrical norms [Re: LongRunner]
HotLine1 Offline

Member

Registered: 04/03/02
Posts: 6785
Loc: Brick, NJ USA
My head hurts.....wow
_________________________
John

Top
#215738 - 07/11/15 07:21 AM Re: Questioning the electrical norms [Re: HotLine1]
LongRunner Offline
Member

Registered: 05/30/15
Posts: 33
Loc: Albany, Western Australia
Hehe, sorry about that, HotLine. grin

Mind you, even the plain old resistance heaters for room heating get far more hate from the "environmentalists" than they really deserve, if you ask me. A unit using about 1500W, that requires a whole circuit to itself at 120V (at least if you go by the seemingly grandfathered-in "80% rule"), is on 220-240V a piece of cake to deliver the power to (with even a 0.75mm flexible cord staying stone cold at the resultant current, more-or-less). Nothing else can parallel the plug-and-go convenience (making them perfect for use in rooms that you only temporarily need to heat), they can run in total silence (with the obvious exception of fan heaters, but even they can be fairly quiet), and the circuit itself is a fantastic example of the KISS (Keep It Simple Stupid) design principle in action - in stark contrast to the technical nightmare that electric cars have been, but (strangely) those are heavily promoted by the mainstream greenies. But then again, I've found it to be true surprisingly often that the more heavily pushed a supposedly "green" technology is by the mainstream, the harsher the truths behind it turn out to be...

The main reasons, however, why most people currently perceive portable electric heaters as being economically (and ecologically) hopeless are, in my view:
  • The deplorable state of mainstream buying "advice" and reviews; it might come as a surprise to most people, but in direct opposition to everything else, resistance heating elements can only have a 100% (for all practical intents and purposes) intrinsic efficiency, in accordance with the laws of thermodynamics (although I can't deny that the system efficiency, considering the losses in electricity generation and to a lesser extent transmission, still falls quite a bit shy of that). They could only be any less efficient if they destroyed energy, which isn't possible (you remember, don't you?); after all, guess what the energy "wasted" in each other device ends up as? wink But the mainstream reviewers, such as Choice magazine down under, still don't get it. To quote what their current article says about them: "Good heating performance and good energy efficiency don't always go together. A model may be great at heating, but only OK for efficiency, meaning it will heat the room effectively but cost more to run. Some are efficient but only OK performers, so they don't heat the room as effectively, but at least they use less power. Sadly, we've found a few that are not only weak at heating, but use a comparatively large amount of power too..." Of course, they fail to understand that fan heaters are not meant for direct personal heating, and they also reinforce the "never-use-an-extension-cord" propaganda (more on that below)... Mind you, I pretty much know the designs of these heaters inside-out, so it would certainly be within my power to make good reviews of them once I get the needed tools. Even the otherwise great book, "Green is Good" by Rebecca Blackburn [ISBN 0-7322-8561-5], dropped the ball on the heater discussion too. So the impression most buyers are consequently left with - that models without a thermostat will be somehow "automatically" more expensive to run than those with one - has resulted in a few budget models (notably the Kambrook KFH200) that use a fixed thermostat (by way of fitting a bimetallic switch - otherwise used as the primary thermal protector in modern convection heaters - with a ridiculously low activation temperature), which renders them immediately worthless (except in fan-only mode) to be honest (that unit wouldn't even stay on when I temporarily operated it outdoors!). I usually don't bother using the adjustable thermostats myself either - I just leave them at the highest setting and manually switch between power levels as needed (which is probably easier on the elements anyway). Then there's...
  • ...the all-time classic of misusing fan heaters for heating just your feet; but that's not at all because they inherently suck, only because most of the heat still goes into the room. Any further warmth from being in close proximity to a convection heater (fanned or fanless) should be considered just a bonus, with heating the room itself the primary motivation. In my experience, a suitably comfortable mat (to thermally insulate your feet from the floor) works fine, with no power requirement; and if you insist, I'm sure purpose-made heating pads are out there. And last but certainly not least...
  • ...the innate greed people have been conditioned by society (weird as it is) to have, which probably more than negates the advantage of reverse-cycle air conditioning (still only 3.4x or so, typically) to be realistic; not content with temperate, the general public like to run heaters powerful enough to make the room (or themselves, in the case of radiant heaters) very hot indeed. As for me, it's the middle of winter here and I still get by fine with 600W or at most 900W (the low and medium settings on, at present, an Omega Altise OMC15E1) in a decent-sized area (in a house with only ceiling insulation and without insulated glazing, to boot - although the window area here at least isn't excessive).
It doesn't help that society has also conditioned people to reinforce their established beliefs as routine, even on topics they have zero in-depth knowledge about.

As a decent compromise between ergonomics and economics, I've taken to using the resistance heater(s) up to 1kW or so (long-term) and the air conditioners beyond that. So here's my honest run-down on the pros and cons of each form of portable heater available (past and present):

Fan heater
+ thanks to forced airflow, can attain the highest common power rating (2400W @ 240V) in a small, convenient, and very affordable form
+ doubles as a cooling fan in summer, for "free"
+ all affordable models are double-insulated, along with including dual thermal protectors and a tip-over switch to current requirements (at least in Europe and Australasia) - how much safer could you want them to be, really?
o moderate surface temperature (not enough to burn or melt most stuff, but may hurt small children)
- some noise from the fan, but at least it's constant (unlike the irregular noises that many air conditioning units - my own included - make while running)
? fan bearing longevity (they may be poorly lubricated as supplied; fortunately, they can be re-oiled, and are even self-aligning making their subsequent reinstallation child's play)
? how robust are the elements in the "ceramic" variants (ostensibly safer by making the internal temperature self-limiting, although I've established that the risk of catastrophic failure of a conventional unit up to European/Australian standards should be negligible anyway; the wire elements themselves should be extremely durable with their normal temperatures much lower than in a radiant heater)
* just verify that whichever model you do get actually complies with the standards; their enforcement is rather lacking at present, so sub-standard models slip through the system quite regularly (especially as, being in the lowest price category, they are hit the hardest by the relentless price wars). For starters, I would recommend strength-testing the plug pins (by grabbing them with pliers and attempting to pull them axially), and examining the interior to check that none of the crimped connectors have the lead insulation trapped in the conductor crimp section. The trouble here, of course, is that it's not in the average Joe's power to tell the fail-safe from the inevitable fire-starter by casual examination - and house brands especially can change at any time without notice. frown
For some strange reason, the majority of them still have only two power levels (half and full), although some of the nicer ones do have the three provided as routine on most passive convectors. (As far as implementation is concerned, aside from the power switch itself they only need to make the elements with two different gauges of NiCr wire to provide all three power levels - easy as pie, really.)

As an aside, it's quite an embarassment to note that just about every $20 fan heater has a far superior blade design to, and runs much quieter for the same breeze as (despite being significantly smaller than), the pair of AU$100 (yes, that's the actual retail price Mum, with me accompanying, bought them for at the time) Dimplex GDC-DF40MC desk fans (which also had pathetic switch knobs that broke almost straightaway, still have only sleeve bearings anyway, and are not double-insulated - and even the majority of the economical desk or pedestal fans are as well! Seems to me a typical over-priced, under-performing, poshed-up "designer" product...) that I have. crazy

Convection heater (old-school version, with suspended wire elements)
+ silent (except while any boost fan is running, but they usually warm up quickly enough to not really need them anyway)
+ can be double-insulated (although the majority of production models so far haven't bothered as the earth wire was cheaper than the supplementary insulation - but this situation may reverse quite soon with the rapidly rising copper prices)
+ a high-quality unit should last the longest of all of the available heaters, by far (40+ years should be easy enough to attain, and I'd bet that centuries wouldn't be out of the question); indeed, it may be the only appliance to top the ever-dependable external mains transformer for overall reliability.
o moderate surface temperature (same as with the fan heater)

Oil-filled column heater
+ silent (except while any boost fan is running, again)
+ lower surface temperature - good for use in areas with small children, or those with otherwise weakened skin (relative to that of a healthy adult)
- long warm-up time (due to the thermal mass of the silicone oil)
- the sealed elements (like in kettles) don't age that gracefully

Micathermic heaters
+ micathermic panel heaters do look quite elegant...
- ...not that it's really relevant, given that resistance heaters for fixed installation make zero sense nowadays (the 2400W ones are already perfectly capable of blowing your energy budget if used on full power constantly; is the prospect of >3500W really that appealing to you, then? Nevermind that sub-2400W ones are also sometimes permanently installed, which is utterly pointless)
- reliability seems iffy compared to the longer-established variants
- these probably can't readily be double-insulated either

Radiant heaters
I'm mentioning them specifically because they're often suggested as being more economical than the other types. Unfortunately, while I can't fault the logic behind heating just yourself instead of the room in principle, most of the models actually obtainable are way too powerful for that proposition to work out. frown (2400W of radiant heat? Are you crazy? I'd say closer to 300W would be more reasonable.) Anyway:
+ silent
+ low price
+ excellent at spot heating, even from a distance
o medium lifespan?
- runs very hot, presenting a serious fire hazard should flammable materials enter the vicinity (and requiring a thermosetting cord); in my view, the risk would only be worth tolerating for those on the very tightest of energy budgets (if you can even find one of the low-powered units anymore - or restore a vintage model to safe condition, for that matter)

By the way, extension cords also work fine with any type of electric heater (including radiant heaters, as long the heater's own cord is laid out straight so that the extension cord doesn't have to come any closer to the very hot unit than necessary) provided that they are well-made and appropriately rated for the power of the heater; the supposed dangers are so vastly overblown (especially here in Australia where we have some of the safest extension cords in the world - as long as you avoid the horrid little 2-way adapters with no OCP, along with their first cousins, the "piggy-back" plugs; those are a classic result of a bureaucratic compromise "solution" gone to a hopeless extreme...) that it's an embarassment to the whole notion of safety education, to be honest. Indeed, out of interest, I took a standard 5-metre ordinary-duty 1.0mm extension cord, coiled into eight (!) layers, placed on top of a pillow (for good measure), and ran the Omega Altise heater through it on high (1500W resistive = 6.25A @ 240V), and it still stabilised at a lower temperature than the heater itself - so it appears that the safety factor to withstand being coiled up (within reason) under load is built into the standard sizes for regular extension cords (along with the appliance cords beyond 2m to the IEC standards, although I would personally prefer a more conservative 0.5m or so) anyway (and it's no great burden, really, when the cores also have to sink heat from terminals, withstand sufficient fault currents in short-circuit events, and have reasonable tensile strength). So the stern warnings about it, then, might well have arrived here by way of the (at times) over-the-top globalisation - presumably another thing we can "thank" the UL for, I dare say. smirk

Any suggestion that a resistance heating appliance can somehow harm any computer/TV/game console/etc. on the same circuit, of course, absolutely cannot be anything more than an urban myth; it's a near-perfect resistive (what else did you think it would be? grin) load with negligible inrush, what more could you possibly ask for? I do have a portable AM/FM radio (a Panasonic RF-544 that was used at Mum's office until recently - nothing fancy, but well-built for what it is), and intimate contact with my personal computer destroys AM reception, while being in the vicinity of the OMC15E1 is literally undetectable (except when toggling the switches, that is - but that's nothing special to these heaters) even tuned to a vacant band. Indeed, the only way in which the heater could hurt the radio is if you left the radio on top of the heater constantly, but then only by overheating it (obviously). So clearly, if even the radio works fine right next to the heater, then it's impossible for the heater to have any effect whatsover on the PC itself (unless of course, the combination overloads the circuit, causing the power to shut off when the PC isn't prepared for it).

And I can quite clearly see the "writing on the wall" for natural gas heating (which I see for the stop-gap measure that it really is) already, given that it as well as coal power has strong campaigners against it along with impending supply crises (and that all the electric heaters to date will still be able to seamlessly operate from the superior future electricity sources that hopefully won't take too long to reach prime time). Of course, if you already have gas heating then you might as well continue using it, but I wouldn't recommend having it newly installed by now. Plus, flammable gases and electric works (beyond cables, anyway) in the same area just don't make a great combination. Unfortunately, at the moment we're somewhat stuck in that situation even without having natural gas supplies, as Greenpeace (more like Greenwar if you ask me) has pushed the extremely flammable R-600a refrigerant (used in the majority of new fridges now) on the grounds of its low global warming potential compared to the fail-safe R-134a that was mostly used before (albeit introduced just a few years prior). Consequently, several refrigerators in the UK have exploded already. They may defend their actions by saying that the total number is small relative to the number of installations - but if we follow that logic, why not omit the earth wires from new appliances (of all sorts) to save on copper (which is, unquestionably, running out now), while we're at it? grin The overall risk from R-600a compared to a Class 0 appliance in good condition (including the aforementioned US/Canadian toasters) is probably about the same, realistically.

One thing is becoming clear, at any rate: We can no longer adequately rely just on safety-testing the products as volunteered by the manufacturers beforehand, as the unscrupulous ones are perfectly willing to abuse that system to send in a sample that will easily pass the tests, then change it mid-production-run such that it doesn't comply anymore. If the regulations were solidly enforced, few products would need to be recalled and items capable of single-handedly bringing down the safety systems would be even rarer. But at the moment, they're far too common, as by the time attention reaches the regulators, it's too late. frown So there's definitely a need to also take random samples of the actual retail products for re-testing.
On the whole, how do you feel about resistance room heaters?
Only one choice allowed


Votes accepted starting: 07/10/15 11:35 AM
View the results of this poll.
Do you consider the Underwriters Laboratories to be a corrupt organisation?
Only one choice allowed


Votes accepted starting: 07/11/15 03:56 AM
View the results of this poll.
How much of a priority would you consider the addition of random sampling to the safety checks to be?
Only one choice allowed


Votes accepted starting: 07/11/15 04:24 AM
View the results of this poll.

Top
Page 1 of 2 1 2 >



ECN Electrical Forums - sponsored by Electrical Contractor Network - Electrical and Code Related Discussion for Electrical Contractors, Electricians, Inspectors, Instructors, Engineers and other related Professionals