On Fri, 14 Dec 2007 09:19:38 -0700, snipped-for-privacy@aol.com wrote (in article ):
The solution is in the washer. My friend has a Miele washer that spins the clothes at a very high speed which extracts the maximum of water from the clothes. The result: shorter drying time required.
Why all manufacturers don't design this same high-rpm spin into their washers (or why it's not required by law) is a mystery...
Dave
It means the manufacturer has used conductors in the dryer that will trip a 30a breaker in a fault but might not trip a 50. At least U/L has not tested it that way. Certainly the OP can put a 50a plug on this dryer and it will work. You just don't know what happens if it gets a short inside.
That is not exactly true. In the US part of the listing is that a fault in the appliance will trip a beaker but it may not keep the appliance from being destroyed in the process. This is addressed in the sizes of "fixture wires" but they still may use smaller wire inside if the testing shows the resulting fire is totally contained in the appliance. In the case of a dryer you will find 14 and maybe even
16 gauge wire connected to the phase legs. I don't know if U/L evaluates these dryers with a decade of lint in the box
North American appliances with a standard plug do have to be designed with the knowledge that a short in the power cord will have the current interrupted by a 15 A or 20 A breaker. Until the breaker trips, the current is limited by the series resistance of the 14 or 12 gauge wire feeding the outlet.
If you plug that cord into a 30 A circuit, you have half the series resistance, and double the breaker trip current, and you're more likely to have something arc or melt before the breaker trips.
In the UK, at least, there is a fuse in each plug. So the outlet may be capable of 13 A at 240 V, and fused appropriately, but a radio with a power cord can have small conductors because the plug is fused for 3 A. So there it is true that the breaker/fuse at the panel protects the wiring in the wall - because the appliance cord is protected by its own fuse. North America doesn't do that.
The dryer is expecting to be connected to a 30 A circuit, and to obtain some protection from that. It almost certainly doesn't have its own internal fuses.
Dave
A possibly more interesting question: Suppose someone builds an adapter from a 50 A male plug to a 30 A female outlet *which includes a pair of
30 A fuses in the two hot legs*? Now the dryer wiring will be protected by the 30 A fuses. This is clearly safer than just using a 50 A plug and power cord. Is this legal? Is it as safe as using a circuit with a 30 A breaker?(I assume the original poster doesn't want to change the breaker on this circuit to 30 A because they want to plug in the stove and dryer alternately, and they'd like the original 40 or 50 A for the stove).
Dave
Is it not possible to hard-wire both the stove and the drier into outlets with one locally fused at 30A - plus a changeover contactor/ switch in circuit to prevent both outlets being powered together?
On Sat, 15 Dec 2007 21:12:41 -0500 krw wrote: | In article , snipped-for-privacy@ipal.net | says... |> On Sat, 15 Dec 2007 19:00:15 -0500 krw wrote: |> | In article , snipped-for-privacy@ipal.net |> | says... |> |> On Fri, 14 Dec 2007 18:59:40 -0500 krw wrote: |> |> | In article , |> |> | snipped-for-privacy@aol.com says... |> |> |> On 14 Dec 2007 14:12:11 GMT, snipped-for-privacy@ipal.net wrote: |> |> |> |> |> |> >I wish they would lower that requirement. Sure, it would annoy people |> |> |> >that want to overheat their clothes. But over 3840 watts to dry clothes? |> |> |> >These things are electricity hogs. Too bad there is too much politics |> |> |> >going on between two different fundamentally corrupt political parties in |> |> |> >the USA for anyone to be able to get a requirement into the energy bill |> |> |> >in Congress to lower the standard clothes dryer power needs. Try today |> |> |> >to even find one that can run on a 20 amp circuit. |> |> |> |> |> |> |> |> |> It is simply physics. You have to evaporate "X" amount of water. If |> |> |> you dropped the power used per hour you would have to use it longer. |> |> | |> |> | ...wasting even more power (the motor will run longer). |> |> |> |> There is an optimal rate. The motor can only run at a fixed speed to |> |> allows the clothes to tumble properly. Too fast and they don't fall |> |> in time to avoid just following the drum around in a circle. At this |> |> rate of tumbling, there is only so much effective air flow that can be |> |> used optimally. That dictates the heat rate. Yes, you can push it to |> |> dry faster at a higher temperature. But it is less optimal when you do |> |> that. |> | |> | the motor speed is irrelevant. Lower power implies longer drying, |> | which means the motor will run longer. The heater will take the same |> | energy but the motor more. |> |> The motor speed is very relevant. | | Not to this discussion it's not.
Sure it is. If the motor speed could be varied to match the thermal emission rate, then it would not be relevant. But since it cannot be made to match, it therefore does affect the efficiency curve that is a function of what thermal rate (temperature driven) is involved.
|> If you could make the clothes tumble |> around in the air faster, then blowing the air through faster and running |> more heat would make the clothes dry faster in the same proportion. But |> you need to have all of these elements going at the advanced rate to make |> things work equally well in that lesser period of time. The problem is |> the motor speed for the drum CANNOT be increased because the clothes will |> not tumble through the air at other than a small range of speed. Ever |> wonder why dryers do NOT come with adjustable tumble speed (other than |> the ones with a dual belt position to adjust for 50 Hz vs. 60 Hz power |> to keep the tumbler at the same speed in all countries)? | | Irrelevant the the discussion at hand. If you'll remember, you were | claiming that modern dryers used way too much power. You can reduce | the power, but the time will increase. The motor will run longer, | wasting power.
Or you can increase the heat, and while the whole running time will be less, it will NOT be inversely proportional to the temperature difference used. An increased temperature _will_ be a less efficient process.
There is a temperature which is the optimal rate, in terms of total energy used to complete the drying, and it is NOT the highest temperature position.
|> |> Modern dryers are more efficient than dryers of decades ago when the 30 |> |> amp "standard" came about. Back then, the dryers lost heat in a number |> |> of ways, and were not operating at maximum air flow efficiency. You |> |> could feel the outside of the dryer being hot; that's wasted heat. They |> |> run cooler on the outside today, so less power is needed for that optimal |> |> temperate and evaporation rate. |> | |> | Ok, but that's irrelevant to your point. You whined that they should |> | be using lower power now. Power isn't the issue, rather energy. They |> | are. |> |> The ability to turn the heat up beyond the optimal level for total energy |> efficiency should be discouraged. I don't want to prohibit it, just make |> it necessary for someone to go an extra step to get the higher heat if |> they really want it. | | They already do. It's called "normal" mode (vs. "permanent press"). | You're barking up the wrong tree.
The "permanent press" mode is there to continue the drum tumbling after the heat is gone to ensure the clothes are not in a constant position during cooldown. This is used to reduce the wrinkles that would result if cooldown were to take place with the tumbling stopped. It uses more energy to have this effect, but it is necessary to get the correct effect.
|> |> And the motor is actually a small fraction of the power involved, especally |> |> when on the high setting. By simply eliminating the high setting, you can |> |> have a dryer that can still have 2 or 3 heat levels, or use the automatic |> |> evaporation sensing mode, and never need more than 16 amps at 240 volts (with |> |> the motor figured it wired to 240 volts instead of 120 volts). |> | |> | Good grief! |> |> I think you will find that the greatest efficiency of a dryer is actually |> the lowest or 2nd to lowest heat setting (depending on actual values of |> those settings). What I want is for dryers to be made available on the |> market that people can choose which are made for just this lower heat |> level that is most efficient. Such a dryer would do with smaller elements |> and smaller electrical wiring and switches. The plug would be smaller, too, |> using NEMA 6-20P or NEMA 6-15P instead of NEMA 14-30P. The circuit wiring |> for new work would also be less costly. People would save money on the |> product. Some people would save money on the circuit wiring. People would |> save money on their electrical bill. Everyone would be better off. But if |> you really want to toast your clothes and your electric bill, then go ahead |> and buy one that has a double heating element and uses a big NEMA 14-60P |> plug, ceramic tumbler, and microwave thermal source! | | Good grief!
That kind of response is not very informative.
On Sat, 15 Dec 2007 23:25:30 -0500 Michael A. Terrell wrote: | krw wrote: |> |> Good grief! | | | Phil is as dense as DimBulb. :(
Come on. You can be more creative that that.
On Sun, 16 Dec 2007 08:39:50 -0700 BasicGuy wrote: | On Fri, 14 Dec 2007 09:19:38 -0700, snipped-for-privacy@aol.com wrote | (in article ): | |> It is simply physics. You have to evaporate "X" amount of water. If |> you dropped the power used per hour you would have to use it longer. | | The solution is in the washer. My friend has a Miele washer that spins the | clothes at a very high speed which extracts the maximum of water from the | clothes. The result: shorter drying time required. | | Why all manufacturers don't design this same high-rpm spin into their washers | (or why it's not required by law) is a mystery...
Maybe they do. I know mine has a high spin setting. I don't know what the actual RPM is or if it matches the Miele one. But I do notice the clothers are significantly dryer if it is used. I do use it on most of my clothes.
|>>Hi, |>>I was wondering if someone could help me. I have only one 220V plug |>>(for the oven) in my appartment and I would like to use an oven and a |>>clothes dryer. Would it be safe to plug the dryer on the oven plug? |>>Is there any adaptor I could use? |>>Thanks. |> The problem is your dryer needs 30a overcurrent protection and the |> oven circuit is probably 40 or 50a. | | | The Op wants to know if he can use smaller current appliance on an | existing circuit.. | | Of course you do that all the time with 110volt devices. Who ever heard | of having a breaker rated to protect your clock radio.
Breakers are rated to protect the building circuit. Appliances are then rated to be safe on circuits rated up to what they are permitted to be plugged in to.
| And it is the norm in 240volt 50 hz countries to plug in anything as | long as it is not tooo big.
That's the key ... not TOO big.
Circuits in the UK are typically 30 amp ring circuits. They also require fuses in the plugs. Plugging your clock radio into a 30 amp circuit is more risky than in a 20 amp circuit. The wire would have to be thicker to be equally safe, unless there is a fuse. The UK scheme, though quite inconvenient, is probably a lot safer, since you can, in theory, put in a 1/4 amp fuse for the clock (I don't know what the legal requirements actually are for that).
I know this is inconvenient because I have in fact dealt with fused plugs in the USA. At least at one time, line voltage Christmas light strings had these. I don't know if it was actually required, then, or not. But they did periodically blow for no apparent (at the time) reason. Maybe they were just on for too long at a time.
| Unless this is not allowed by some obscure NEC provision in 240 volt USA | installations Of course it is OK.
It depends on the actual appliance. All new appliances today need to be safe on a circuit protected at 20 amps. There are a number of ways to achieve that. Having every part rated to some percentage of that current level is one. Having parts that will ensure a higher current flow on a failure is another, provided that higher current flow is within the range that will trip the breaker. If the breaker is rated too high, it might not.
If your clock motor winding shorts out and starts pulling in 30 amps of current through the remaining part of the winding, is a 30 amp breaker expected to trip?
| The breakers protect the wiring not the device.
Yes.
But the device has to be rated for the available un-interrupted current, or provide its own supplemental protection.
|>>Unless this is not allowed by some obscure NEC provision in 240 volt |>>USA |>>installations Of course it is OK. |>
|>
|> It is the manufactirer's instructions that say coonnect to a 30a |> circuit, which makes it a NEC 110.3(B) | | Does that mean you must blindly comply with some arbitrary figure | dreamed up by the manufacturer or does it mean that is the minimum | supply required?
If they do in fact dream it up, or just roll dice to come up with it, then yes ... at least for insurance and legal purposes. If they tell you the device is safe on circuits rated up to 37.5 amps, and you had it on a 40 amp circuit, and it caused a fire that burned your house to the ground, don't expect any reimbursement from the manufacturer.
Normally, there is at least some level of engineering applied to come up with those figures.
On Mon, 17 Dec 2007 20:19:23 +0000 (UTC) Dave Martindale wrote: | snipped-for-privacy@aol.com writes: | |>It means the manufacturer has used conductors in the dryer that will |>trip a 30a breaker in a fault but might not trip a 50. At least U/L |>has not tested it that way. |>Certainly the OP can put a 50a plug on this dryer and it will work. |>You just don't know what happens if it gets a short inside. | | A possibly more interesting question: Suppose someone builds an adapter | from a 50 A male plug to a 30 A female outlet *which includes a pair of | 30 A fuses in the two hot legs*? Now the dryer wiring will be | protected by the 30 A fuses. This is clearly safer than just using a 50 A | plug and power cord. Is this legal? Is it as safe as using a circuit | with a 30 A breaker?
If they get it UL listed as a supplementary protector, it probably is perfectly legal.
| (I assume the original poster doesn't want to change the breaker on this | circuit to 30 A because they want to plug in the stove and dryer | alternately, and they'd like the original 40 or 50 A for the stove).
It's not the first time someone has wanted to do that.
That is certainly a viable alternative. You could use a fused disconnect like they sell for water heaters for a simple off the shelf answer.
Thanks Phil. A much more informative post related to the original question.
Drum speed and economy was really off topic.
In Australia with 230 volts (often up to 250) normal General Purpose outlets are on a 16 amp breaker with some formula as to how many on each. Older installations often have hand wired fuses which can easily be abused. Then the appliance plug is by definition only to be up to 10 amps and there are no fuses at the plug or in simple appliances. There is a 15 amp variation of the GP plug which will only go in a 15 amp socket but the 10 amp plug will go there too.
Oh just a gloat for you Amaricans! 3phase 230/400 is available most anywhere except some distant rural properties supplied only with SWER. (Single wire earth return) at some high voltage and a local transformer to 240 v
-- John G.
It's available if people want to buy it (our Whirlpool is 1000RPM). Since they don't...
There are now many high efficiency front load washing machines on the market- all the major manufacturers have got on the bandwagon that started in Europe where energy saving became important long before it caught on here. In the early 50's, Westinghouse had a front loader which had some of the advantages of modern machines in terms of water usage but it didn't have the high spin speed. For some reason, this machine disappeared (was it more expensive to build and maintain when both energy and water were cheap? ).
| Thanks Phil. | A much more informative post related to the original question. | | Drum speed and economy was really off topic.
Technically, yes. I mentioned my interest and got challenged by some non-thinkers or people stuck in boxes. I always try to give a chance for someone to open their eyes and learn. But some people are just stuck and can't go beyond.
| In Australia with 230 volts (often up to 250) normal General Purpose | outlets are on a 16 amp breaker with some formula as to how many on | each. | Older installations often have hand wired fuses which can easily be | abused. | Then the appliance plug is by definition only to be up to 10 amps and | there are no fuses at the plug or in simple appliances. | There is a 15 amp variation of the GP plug which will only go in a 15 | amp socket but the 10 amp plug will go there too.
Sounds fine to me. The USA has 20 amp plugs and a 20/15 amp outlet that can do similar.
The various requirements about wire size and circuit limits have lots of wide tolerance factors built in. A 10 amp outlet is supposed to be able to handle that 10 amps continuously for as long as you want. It should be able to handle twice that for short periods of time. It will get hot. But something else should give before the outlet melts. So a slightly lesser cord and outlet could be OK due to the extra margins the the normal ratings. Well, that's at least how we do it in the USA.
| Oh just a gloat for you Amaricans! 3phase 230/400 is available most | anywhere except some distant rural properties supplied only with SWER. | (Single wire earth return) at some high voltage and a local transformer | to 240 v
Yeah, we have wimpy 120/208 for three phase, and even that's not readily available everywhere. Some places have 277/480. The higher voltage is more efficient. That's one of the reasons I try to promote it where I can, for the places and uses where it is safe to do. And our 240 volt circuits are 120 volts relative to ground, so there isn't as much reason to be concerned over safety as there would be if we adopted 230 volts as used in Aus/EU/UK/etc.
I'm looking at connecting computers to 240 volts. The power supplies do have 2 pole AC switching, so that end is OK (we need that because both wires are "hot" on 240 volts and users of Schuko need it because either wire can be "hot"). The catch I've run into is finding a suitable UPS. Those wired to handle the "two hots" are generally 5 kVA and up.
I guess any 240 volt UPS made for Australia should be able to handle either wire hot because there is no ABSOLUTE guarantee that the wall socket will be wired correctly. And I don't imagine there would then be any problem on the US (Edison )system where both wires are 120 volts off ground.
I don't want to start the "Mines Safer than yours" argument but there do not seem to be many electrocutions here.
-- John G
Same applies to equipment made for the UK market. The wiring in any appliance or flex has to have exactly the same insulation rating whether nominally the neutral or live. Earh leakage tests on equipment are carried out "neutral" to earth as well as "live" to earth.
|>> > It is simply physics. You have to evaporate "X" amount of water. If |>> > you dropped the power used per hour you would have to use it longer. |>>
|>> The solution is in the washer. My friend has a Miele washer that spins |>> the |>> clothes at a very high speed which extracts the maximum of water from the |>> clothes. The result: shorter drying time required. |>>
|>> Why all manufacturers don't design this same high-rpm spin into their |>> washers |>> (or why it's not required by law) is a mystery... |>
|> It's available if people want to buy it (our Whirlpool is 1000RPM). |> Since they don't... |>
|> -- |> Keith | There are now many high efficiency front load washing machines on the | market- all the major manufacturers have got on the bandwagon that started | in Europe where energy saving became important long before it caught on | here. In the early 50's, Westinghouse had a front loader which had some of | the advantages of modern machines in terms of water usage but it didn't have | the high spin speed. For some reason, this machine disappeared (was it more | expensive to build and maintain when both energy and water were cheap? ).
Front loading washing machines are still more expensive to buy in the USA compared to the top loading ones. It's not quite double the cost, but it is sufficiently more so that most people will get the top loaders. What I see in that price difference is partially some increase in materials and manufacturing cost, but also partially some increase due to the smaller market size. In other words, if people did buy the front loading ones more than the top loading ones, the economy of scale would reduce the price of the front loaders, and increase the price of the top loaders, to about the same. The problem, is there will also be bottom-end competition that keeps people going for whatever is cheaper. Until there are mandates, this will probably continue to be the case.
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