Using American Microwave Oven in UK

[Appin]

The message from Andy Hall contains these words:

In anyhting I've ever done, yes. Can't answer for other people.

I think you mean the box shifters' NEMA 5-15s

I'm not a wild fan of wirenuts, because they're not idiot-proof and poor ones do exist. There is, however, no cure for idiocy and once the technique of making a good wirenut joint is mastered the joints are perfectly satisfactory and, in the circumstances of the physical constraints of the standard American box and the size of American conductors, a realistic way of fitting accessories.

They were in general use, even in some quality work. The virtual disappeaance of multiple junction boxes with the introduction of loop-in wiring for lighting and of ring circuits for power got rid of them. But a proper wirenut is a vastly more sophisticated device than a Scruit and in a properly made joint ensuresmuch better than a poorly-made terminal connection.

Agreed. Though a great deal of wiring in the US is up to a century old

-- lots of "knob and tube" still in everyday use. And they did have a totally-disastrous flirtation with alumin(i)um wiring about 40 years ago.

[Appin]

The message from "Paul D.Smith" contains these words:

In a domestic situation its 115-0-115

[Bertie Doe]

"Appin" wrote in

Thanks Appin, I'll refer this thread to the coffee group - caveat emptor!!

Bertie

[Dave Plowman (News)]

A 'variac' is a transformer with multi-taps so you can get an effectively near infinite variety of output voltages - very roughly from zero to max. Used in a workshop to bring a faulty piece of equipment gradually up to voltage while looking for the fault. Etc. And way more expensive than a

240-110v transformer of the same current.

What you've shown is a site transformer designed to use 110v tools on a building site for safety reasons. It would be fine for any 110v use - but rather bigger than needed for most being 3.3kW - about three times that of any likely US appliance.

[Andy Hall]

From the problems that I hear that people have with their electrical installations, it would appear that crappy connectors are widespread.

If the volume market is crap, the outcome is crap.

Dodgy connectors with high current loads? Possibility to make poor connections? Not a recipe for success and safety.

The question is then one of are the connections well made......

[Andy Burns]

And they weigh a bloody ton, not really the sort of thing you want kicking around in a kitchen.

[Bill Davy]

I've ordered

:

AT1500 : 1.5kVA Stepup stepdown transformer

0-120-240V (Hardwired with screw terminals) Step up from 120V to 240V or step down from 240V to 120V

Price for 1+: £54.00 each. Price for 5+: £48.60 each. Price for 25+: £45.90 each. Weight: 8 kg. VA: 1500 VA.

a.. Screw terminal 0-120-240v or 0-115-230v b.. Stepup from 120v to 240v or Stepdown from 240v to 120v c.. Dimensions: 165x80mm It is quite compact and I hope I can hide it away nicely, perhaps nailed (metaphorically) to the wall above a cabinet. We shall see what happens. Bill PS

is not relevant

[Grumps]

You should've bought two and connect them in series.

[Dave Plowman (News)]

This type of transformer is designed to be mounted inside an appliance, etc. For safety I'd fit it inside a flame proof box - to also provide mechanical protection to it. The actual windings are only insulated by a thin layer and could easily be damaged if not protected. Also be aware that the fixing must not be a conducting loop round the windings. It should really come with a pukka fixing kit like other such toroidal transformers.

[Paul D.Smith]

...snip...

Thanks - I really must have a closer look at my in-laws supply next time I'm over there.

Paul DS

[Chip]

On Wed, 23 Jan 2008 10:01:29 GMT,it is alleged that "Bertie Doe" spake thusly in uk.d-i-y:

Another thing to watch out for with the construction site transformers

-incidentally, the 110v output is slightly lower than the 117-120v expected by the device, which helps with the 'lower frequency overheating' problem- is that they are built for cheapness and ruggedness, not efficiency. The off load efficiency is absolutely dire, they waste 'loads of watts'[1] in magnetising current and therefore heating up the transformer.

They'd be fine probably for a coffee roaster, as the mains would be turned off after / between uses, but for a microwave (as per the thread title) which needs to be powered 24/7 because of the clock, no good at all.

The custom made 120v transformers usually use toroidal transformers, and should be much more efficient.

[1] No, I haven't measured the wattage, hence no figures, but an unloaded 2.2kva transformer certainly gets warm enough to suggest around 100-150w of no load losses, plus the inrush can cause mcb tripping on domestic "B" curve MCBs.

[Brian Sharrock]

In general -although that's a dangerous phrase to use - Supply companies in the USA distribute power to domestic customers in a 230V 60Hz 3 phase process {Rather like the UK process], The three phases are distributed individually in a balanced manner to houses -so each house only sees one phase of 230V AC. {again, Rather like the UK process]

There is a crucial difference however _at_ the house connection. USA practise is to feed 230V AC to the primary of a transformer and take off _two_ supplies of 115V AC from the centre-tapped secondary. Thus it's _possible _ to have one 115V wire (they call it the 'Hot wire' - at instantaneously plus115V while another , perhaps adjacent, 'hot wire' is at , instantaneous, minus 15V AC [The exercise of calculating peak voltage from the RMS values is left to the reader].

When USA equipment requires a 'full' 230V then their usage ('Codes') permit a receptacle which uses the 'Hot' wires from the two opposed lines to be utilised. [Some USA-ians I've encountered have referred to such usage as 'Two-phase'; this is deprecated by the 'trade'] There _are_ variations in the 'Codes'; The County of Los Angeles has very stringent 'Codes' .

The rather bizarre practise of pole-mounted oil-filled transformers has to be seen at night-time during a hurricane to be appreciated - lots of explosions and flares can make the sky seem like Guy Fawkes night.

[Paul D.Smith]

...snip...

Thanks for the lesson in 230V 3 phase, 230V single, +/- 115V.

Ever heard of the "Parrots of Flatbush"? They're some sort of parakeet that escaped/was released in New York city around the Flatbush area. Expected to die out during their first winter, they proved that smart parrot smart and co-operation are a force to reckon with. They've been building large communal nests (as they do in the wild) around suitable warm spots - or as you refer to them, oil filled transformers.

Things are fine until the transformers get too warm, by which point the parrots have moved out just before the bang.

They have learnt this behaviour after their first NY winter which they spent nesting around flood lights overlooking a rail yard. Presumably they didn't like the lights and so found other, darker places of warmth.

Paul DS.

[Andy Hall]

Yes I've seen this - it's entertaining.

Mind you, anything more than the lightest of breezes is a "storm"

[Bertie Doe]

Isn't there an old saying "It's the amps that hurts" Won't 110v site tools be on a higher amperage than 240?

Bertie

[Man at B&Q]

[e-mail]...

It's the volts that jolts And the amps that cramps

You need to understand a little more about the relationship between voltage and current.

The current through a load is not determined by what current is available, but by what the load allows to flow through itself. Thus, your house wiring (in the UK) has 13A sockets but not every appliance that you plug in takes a 13A current.

In the simple case of a resistor we use ohms law and a lower voltage supply will always result in a lower current through a given resistor, with a linear relationship between voltage and current.

The human body is a little more complex but you should get the idea by now.

MBQ

[Dave Plowman (News)]

The 'amperage' a tool is drawing has no effect on electrocution if you get a 'shock' from that tool. That is down to the resistance of the path through the body. And the higher the voltage the more current flows through the body. Hence your expression. Assuming that voltage source is capable of supplying the current needed to kill you.

[Bertie Doe]

Thanks for that, "it's the volts that jolts" or 'Man from B&Q, saves man from BBQ'

Bertie

[devonsteve]

=A0 London SW

I want a microwave bed ,, you know the sort , ten minutes sleep in it is equal to 8 hours in a standard bed

[Andrew Gabriel]

Sorry, but much of that was completely wrong. In general, only a single phase high voltage feed (4kV or higher) is provided to feed each street. (Other phases may be carried through for feeding other streets.) The HV feeds the primary of a single phase transformer, which has a 120-0-120V secondary winding. Each transformer feeds just a few houses max, as the

120V regulation goes to pieces after 100yds or so of feeder. (From then on, it is as you described).

This isn't regarded as 'Two-phase' in the US. They have a completely different supply system for which they use that term, and get very hot under the collar if you try to say their 120-0-120V supply is two phase.

Yes, they're good when the transformer is overloaded for a while. You have a dustbin full of boiling oil which suddenly explodes (sometimes into a fireball) 30' up above the pavement. It's a sort of modern equivalent of medievel boiling oil.