American electrics

[Jim Michaels]

Here is an interesting link to more info about early systems and frequency issues.

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[Jim Michaels]

This is getting tedious.

We have a 240Volt supply to our homes!

It is the Edison 3 wire balanced system, where there are two power conductors 180 degrees out of phase (240V between legs and 120V from each leg to neutral/earth) and a neutral conductor at nominally earth potential.

Therefore for a home which normally has a reasonably balanced load (see diversity) the voltage drop from the CU back to the generating plant will be the same as a British/euro 240V single phase delivery system.

As far as small branch circuits go, many are multi wire circuits with two hot legs and a neutral that only carries the imbalance between the loads. (see diversity) When balanced the voltage drop is EXACTLY the same as your 240V to earth supply.

ALL large loads operate at 240V and therefore have a voltage drop and current the same as any other 240V system.

Voltage drop is NOT a significant issue in US residential wiring.

You seem to want there to be problems where none exist, and to magnify small problems into disasters.

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[Andrew Mawson]

,

nothing to do

earth

magnify

Lots of disasters in the early days. Very interesting article at:

about Sebastian de Ferranti's early championing of HV AC distribution. Descriptions of the Ferranti / Siemans zig/zag 10,000v alternator. In the mid 1970's there was an example of this machine in the foyer to Ferranti's 'Wireworks Factory' at Moston in Manchester where I spent several months commissioning computers.

AWEM

[Dave Plowman (News)]

So you have electric kettles that work? Not last time I visited.

You may well have 240 supplies into the house, but in general you're restricted to somewhat near to 1 kW for portable appliances.

[Andy Hall]

Really??? Then perhaps you can explain why a colleague can't use a hairdryer properly when plugged into a socket in his dressing room because the nominal 120v at the incoming supply has dropped to about

90v at the socket.

[Jim Michaels]

Nope, No electric kettles, Most Americans use a hob or microwave to boil water when the need arises. Steaming hot water dispensers are the deluxe method of making tea. If anyone here wanted one they could install an outlet and buy a British kettle.

The practical limit is about 1.6kW for random connection.

Besides an electric kettle what else would draw more than 1.6kW in a normal household?

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[Jim Michaels]

A 5% would drop be unacceptable, 25% is absurd.

Without more information, I can only guess. A serious defect in the wiring of the building or a building being used for a purpose that requires far more electrical capacity than ever envisioned by the installers of the wiring.

To achieve this amount of drop would likely need the over current devices to be bypassed or otherwise non functional and I suggest your colleague exit this site quickly.

This problem should be reported to the building's management.

If the management is unresponsive, the local fire department fire prevention office should be contacted.

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[Jim Michaels]

2500 killed & injured per year in UK

1610 killed & injured per year in US

These numbers seem to include all ALL electrical fires

In the US this does not even make the top 25 causes of death.

It is statistically about the same danger as being hit by an asteroid!

The automobile death rate is about 100 fold higher.

I stand by my statement!

Please post relavent stats.

Agreed, much of what has been said in this thread is rumor and old wives tales.

Then why?

Please post relavent stats.

Please post relavent stats.

Yep, Please post relavent stats.>

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[Dave Plowman (News)]

Any number of kitchen devices. Toaster, grill, fryer, bread maker, clothes iron. Some power tools. Portable heater. All of which you may want to use in more than one position and need to be unplugged for cleaning - or simply to be put away.

It makes no sense to me to have two different power circuits in a house.

[Dave Plowman (News)]

It's a pressure group. And probably manipulating the figures - as they do.

It says 110 fires *per day* That makes 40150. Perhaps your different legal and health care system prevents minor injuries being reported?

[Andrew Gabriel]

I didn't think your regs allow 240V outlets for portable appliances?

This question always amuses me -- it never comes from an American who is familiar with appliances in use around the rest of the world though. Of course you don't have portable appliances over 1.6kW, as no one can take them home and plug them in. That means there are ranges of products in use around the rest of the world which simply aren't shipped to the US. Many microwaves here are over 2kW. Out of curiosity I went looking for my microwave model when I was in the US to see how the price compared, but couldn't find it -- only the bottom of the range ones were there. Then I suddenly realised why.

Another example is vacuum cleaners. On the face of it, you do have identical models, but they are all lower power. This I couldn't initially understand as ours are typically 1.5kW which can just be squeezed out of a US outlet, so I asked someone in that industry. The problem there is cable verses voltage drop -- a cable of the length required on a vacuum cleaner would be too thick to handle easily or coil up for storage, so they typically limit their US models to something nearer 10A so they can use a managable mains cord without excessive voltage drop or over-heating if still partially coiled up.

I guess you don't miss what you haven't had, but don't fall into the trap of thinking the rest of the world is also limited to

1.6kW portable appliances -- that's certainly not the case.

[Martin Angove]

"...on average there are at least 24 deaths and 587 reported non-fatal injuries per year due to electrical fires reported in dwellings in England & Wales. Between 25% and 30% of the casualties are directly associated with the fixed installation."

In other words, 70% to 75% of electrical injures are due to appliances, which relates to a mere 7 deaths and 176 non-fatal injuries attributable to the fixed installation.

And I've seen posts here disputing even those figures.

Hwyl!

M.

[Capitol]

Some where in this thread!

This is comparing apples with plums!

Try 10 x 100w @240V and 10 x 100w @120V Currents are 4.2A and 8.4A. I2R Losses are in the ratio 17.6:35 , allowing for the greater cable areas at 120V. The US has to have thicker cables to attempt to compensate for the higher currents, but from this example the temperature rise in the US cables for the same load will be more than double as the tc of copper is positive! Particularly true in the South with their much higher daily temperatures. I believe that UL cables are using higher temperature resistant coverings than the UK, perhaps someone knows this?

Incidentally, my pocket reference for US wiring specifies 12g 3.3mm2 as being the minimum required size for US homes today(NEC code) and the maximum voltage drop as being 2%. For the example above a likely wire gauge would be 9g! 6.6mm2! With only radial wiring, the cost penalty is phenomenal!

Just a few comments.

Regards Capitol

[Chip]

On Tue, 12 Jul 2005 22:35:44 +0100,it is alleged that Capitol spake thusly in uk.d-i-y:

[snip]

Usually 90 degrees C (yes, it's specified in celsius). But derating and so forth means you have some tables in the NEC that require you to use 60 or 75 C temperature ratings.

Older cable was I think 60 degrees C.

That depends if the code is adopted in your particular area, most areas don't enforce the entire code AIUI.

Areas can also specify requirements over and above the NEC, such as Chicago requiring EVERYTHING in conduit, everywhere.

You can't generally get odd numbered wire guages and even 10 gauge will *not* connect to light switches. Having 10x100w lamps on one circuit would be unheard of in a home, remember the circuits are shared power/lighting, with generally an average of 1-2 rooms/circuit for low loads, and living areas 1 circuit per room minimum.

I agree, the US electrical system uses a _lot_ more copper than the UK one, however, cable is cheap, and recyclable.

Rewiring a US house is almost exactly comparable with a UK one in cost, I rewired a 2 bedroom house for my ex in Ohio, (no permits required provided we didn't replace the main panel, according to the city inspector). It cost about $400 in cable, (I used all 12G) another $150 or so in switches/outlets, $200 in light fixtures (fans raised the cost there), and another hundred for odd sundries, cable clips, wirenuts and a couple of boxes. (we didn't replace the old electrical boxes in most cases as they were reusable)

That's about GBP 600 all told, not bad for a total rewire. We spent a weekend stripping down the old cable and taking it to the scrap dealer for cigarette money .

[Jim Michaels]

Sure, In residential use the intended devise must draw over 1440W, in other situations there are no restrictions. We can even put them in bathrooms!

Google seems to indicate that your toasters and bread makers are the same wattage as ours. Your steam irons appear to range from the same to about 20% higher wattage. How does this effect their use?, do you iron asbestos clothes?

Two 1.5kW electric fires produce the same heat as one 3kW and are more versatile.

Admittedly grilling and frying are not usually done on portable units in the US. but yours seem to max out at only 1900watts.

US Portable power tools are up to 1,800watt. A large router is an example.

What portable tools do you have that are more than this?

Are you hiding the two man SDS Plus Plus Plus drills?

Google does not seem to find any UK microwaves over 1,000 watt output. US full size units are also 1,000 watt output.

You are shopping in the wrong stores.

We have 1400 and 1500 watt units available from the major manufacturers

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[Dave Plowman (News)]

But then will require two sizes of sockets? We used to have that 50 years ago. ;-) Now the only required is a different one for things like table lights plugged into a lighting dimmer circuit where you'd want to avoid damaging the dimmer by plugging in a Hoover, etc.

[Christian McArdle]

Well, I've got several 3kW ones (and a couple of 2kW) and they're more versatile than several 1.5kW ones. 3kW ones cost the same price as smaller ones.

The main problem is with large kitchen appliances, which we can just plug in where convenient without having to have special points put in, or alternatively have to put up with inferior designs without built in heaters.

Christian.

[PC Paul]

And cost twice as much..

My 3HP semi-portable contractors saw can be plugged in anywhere here - garage, shed, house. No need to run special 240V or 3 phase lines for it.

lol - I want one!!

Often we have combi microwaves with a 1200w microwave *and* a 1300w heating element for grilling/browning which get used simultaneously. 2500w. Try the LG MC766YS.

1400w is a small one here. 2000w is easily available even in a small cylinder vacuum. I guess thats partly why built in vacuums are more popular over there than here.

[Martin Angove]

An interesting statement that. Of course you are aware that 1000W microwave output usually translates into about 2000W absorbed energy, in which case, presumably the "full size" US units you refer to have to be specially catered for rather than just plugged into a standard circuit?

The very smallest microwave you can generally get in this country is

650W output which probably makes for 1300W energy consumption, which is interestingly close to the nominal 1500W capacity of a standard 120V US circuit.

Hwyl!

M.

[Chip]

On Thu, 14 Jul 2005 17:38:35 +0100,it is alleged that Martin Angove spake thusly in uk.d-i-y:

1800 watts is the actual capacity, fwiw, most microwaves that I am aware of in the US (IE those I came across while there) were around 750-800w rated output, with a 950 in one particular location (lobby of the motel I worked in, it had a 20A plug though).

Interestingly, in most newer houses, according to code, the kitchen

*should* have separate 20A small appliance circuits for the dishwasher and microwave[1], being 2 of the highest loading appliances. (US dishwashers, unlike washing machines, are similar to their UK brethren, and use a heating element for the drying cycle and to heat the water). [1] I don't think the code requires 20A outlets though, a duplex 15A is allowed on a 20A circuit, most installers probably do this for cheapness.