Hi all, my first post, so I hope it is in the right place!

I am a UK-based electrician with the following problem:
one of my customers has imported a double Maytag oven from the USA to use here in the UK.

He has asked me to connect it up, and not being familiar with the US wiring system, I am confused by the fact that I have 4 wires; red, black, white, and bare copper.

The bare copper is obviously the earth wire as I can see where it is secured to the casing, but other than that I am lost. The only wiring diagram supplied shows how to connect to a 3 wire or 4 wire system, but these are obviously US based.

I have contacted the manufacturer in the US, who refuse to help because the item has been exported, and their counterpart in the UK has taken the same attitude because it is an import, so no joy there.

I can only guess that I am also going to have to supply and wire in a 100V transformer (around 8kW probably, as oven is 7.2kW), but other than that any help would be appreciated.

Thanks for any pointers.

The US system used in houses has 3 wires with 180 electrical degrees between them. Black and red are hot, and the white is a neutral conductor that gets connected to earth ONLY where the mains first come into the house.
Voltage from red to white is 120V, voltage from black to white is 120V and voltage from black to red is 240V.
From what little I know about the UK power system, you might not be able to do a direct connection. A transformer would need to provide that exact configuration in order to work properly. In addition, although the difference between the 50Hz in the UK and the 60Hz in the US shouldn't worry the heating elements, it might drive the fan, clock, and electronics completely batty.
Also, you may find that trying to figure a connection out might give the insurance folks a reason to deny a fire claim in the unfortunate case of something bad happening as the oven was not installed per the manufacturer's installation instructions.

I had a somewhat similar situation where someone wanted to install a 220V 50Hz machine that they saw in the Netherlands in the US. It was such a pain to make it work, get the Permits, get it approved and get it blessed by the insurance compaines that the idea was eventually canned.

I saw the title & thought it was another DIY thread. :D:D

Ghost, thanks for your quick answer.
From what you are saying, I'm guessing I would need a centre tapped transformer: 120-0-120, red & black to 120, and white to centre tapping (0), this would make sense as the rating plate on the chassis says "120-240V". Would this be correct?

Thanks for the heads-up on the insurance, I will mention it when I return.

The first thing you have to figure out is how much 120v load there is. The heating elements are going to be the main load and they will do just fine on your 230v. That is the red/black. Once you determine the 120v load that is left you can figure out what size auto transformer to connect to the white. It may just be the light and the clock. If you rewired the light to 230v by moving the white lead to the red or black (the one you have on your grounded phase) you may be left with the clock as the only 120v load and it won't work on 50hz anyway so you could just cut that wire and not have anything on the white.

Any particular reason your customer is so attached to this oven? Seems to me that it would be a great deal more expensive and troublesome to ship a large, heavy appliance overseas and then pay for installation of a transformer, etc--rather than using a domestic appliance. Surely, Maytag can't offer anything that Electrolux or similar could offer?

I agree, and modifying the oven is not a good idea either, a transformer for a 120/240V supply that most US domestic cooking appliances require or better yet as said above, install the proper appliance made for the local market.

The 120-0-120 transformer should give you the right voltage. The oven would also draw the same amperage as it would on this side of the pond.
You'd still have possible issues with the frequency on anything other than the resistive heating elements.

I also have to ask the same question as NORCAL; what's so special about this oven that they're so in love with it considering what a pain it may turn into??

I don't understand why you would need to run anything but the 120v load through a transformer and you could rewire the light to 230 so you are probably left with the clock.
If it tags the line frequency for the timing it won't work anyway.
Unfortunately that may be the attractive part of the oven (the fancy control panel).

Maytag are importing a lot of American white goods into the UK and have a couple of websites including 'Ask a Technician' and Spares. I bet that range is an 'anglicised' US product. A few carefully worded questions might elicit the part number of a suitable 50hz clock.

If it were me, I really wouldn't be bothered converting that oven. It sounds far too complicated.

Using a transformer with a cooking appliance is also not a great option as the loads are way too big. It will end up with a really messy setup.

You also run into issues with wiring regulations, at least you would here anyway.

There are potentially complications such as providing overcurrent protection on the 110V side. You would need a multi-poll 110V MCB that complies with UK standards.

There's no big deal in bringing small appliances / electronics across the atlantic either direction, but when you get up to things like cooking appliances, washing machines, dishwashers, vacuums etc it really stops being worthwhile unless someone's got some major sentimental attachment to the device!

Thanks for all your responses. I guess the "attachment" the customer has developed is due to the fact that he has paid less than 1/2 the UK price. Looking around the house, I noticed other items from the US, powered by transformers, all of which he has managed himself so far.

Looking over the web over the weekend, I have found quite a few UK sites offering transformers to US residents and US armed forces personnel who might require 110V power in the UK, from 50VA to 8KVA, so this kind of requirment can't be that rare - here is the link in case anyone is interested:

http://www.airlinktransformers.com/american-transformers.asp

I'll be calling them next week - it will be ineteresting to know if they can supply the right one.

Just bear in mind, you don't need a transformer for the 240 parts of the load and that is almost all of it. You only need 120v for the light and clock ... if you don't rewire the light.

Is it really a good idea to modify factory wiring? I aways look at altering the wiring of a appliance as a bad thing,+ the liabilty....

You may have a hard time separating the 120v ckt from the 240v. Most of these ovens use electronic switching and the control board may operate the element but it itself may be 120v both sharing common hot.

Before I say this, let me state that I have NO IDEA what is legal over in the UK - I've never been there. Here's an answer that'll work from the "electrical theory" standpoint. Figuring out whether or not it's code-compliant over on the other side of the pond is up to you.

Black and Red to the oven are hot, and the oven expects 240V across them. Wire them to your 230V mains supply.

white is supposed to be 120V from each hot, ie, it's a center-tap from the expected 240V source. As others have said, it only likely powers the light/clock, maybe a fan or two if it's some really fancy oven. Either way it'll be a (relatively) small load. Grab yourself a 240V-to-120V transformer whose rating matches the 120V part of the load, wire its primary to your mains supply (through an appropriate fuse or circuit breaker) and the secondary side from one hot to the white wire, providing the 120V.

As you noted, ground the bare wire.

As Westuplace pointed out, it's never that easy when electronics are also used to run stats etc.. With the added cost of a proper transformer creating a near enough US supply of 120-0-120, plus the sparks time in wiring it, plus freight charges, plus the warranty nightmares, plus UK Customs taxes on US imports, [ boy, are they going to wake up with a start when a massive box trundles past- while my little nozzle parcels tiptoe by unseen! ], the savings are being eaten away - and they could have got a properly engineered UK version with no problems. Sounds insane to me.

We used to have a similar situation in the US with automobiles that were bought in Europe and shipped to the US.

These so-called "grey market" cars were almost always a lot cheaper, even with the added cost of shipping the entire car across the pond. The REAL costs came when the new owners found that they had to have them retrofit to meet the US emission and safety standards. When the dust finally cleared the supposed savings had completely evaporated (and then some).

If you end up with a big transformer you have to take into account the losses in magnetizing current of the TX core, which is energized 24/7.

Even at say 50 Watts for an 6 kVA TX it adds up to a quit bit of extra power usage.

1.2 kWh day
438 kWh year

That is for the TX only !

Rod, it's easy to lose sight of how small loads tot up over 24/365. I have heat-exchanged fan ventilation,[we rarely opened a window], motor c.100w. We moved into the high-tech end of this longhouse in Nov '08, expecting a big drop in poco bills. We had spent a fortune on low-energy lights, had changed from a halogen hob to propane and I'd fitted breaker signal circuits to auto run the washing m/c and dishwasher on cheap rate at night. The bills for the first year were up!

It was that little fan motor. Do the math. 100w = 2.4kwh per day. 876kwh per year @ €0.15/average = €131 per year, wiping out all our other little economies and then some.

Now we only ventilate mechanically in the winter or when the a/c is running. Other times we use the windows!!

A bit more has occurred to me, although I'm sure the original poster has already solved or cancelled this problem...

Remembering from my time in small electronics repair:

1. 90% of the stuff we get in the USA was originally designed overseas. Most of the world uses 230/240, so everything is designed for that and then modified to work here. Sometimes the modification consists of specifying a completely different transformer for the US version. Often, however, the power supply transformer simply has different primary taps for different supply voltages. It may be possible to turn the US version of the oven into the UK version simply by moving a jumper wire on the board.

2. Regarding line frequency: The most popular clock/timer IC (don't know a specific number off-hand, as there are like 30 billion different versions of it, mostly pin-compatible, and all function-compatible.) has a logic pin that selects 50/60Hz. I'm sure this exact IC isn't used in the oven (as the oven needs other functions said chip wouldn't provide, requiring a seperate µC, and it makes much more sense for the clock to be integrated in the firmware), but there still may be similar.

I bet they still think they 'saved money', even with tripping over all those cash-sucking transformers parked all over the house! Jeez, the mind boggles!

Well when I had a field day with a spark at age 14 he told me a story of an American who had his whole house in Austria built as close to US specs as he could - including a huge transformer, probably 400V single phase primary and 120/240V secondary. I'd still love to know where on earth he got his light bulbs from... and what the building officials had to say about it (at least nowadays larger work that requires a construction permit and includes any wiring requires a full certificate of compliance including all kinds of measurements (isolation values, loop impedance, yadda, yadda, yadda) signed by the EC who did the work and can be held responsible in case of an accident).

Ragnar,
It's funny where some of these "out-of town" installations show up.
I remember well a friend of my late Grand-father who he'd met in Italy during WWII, who hailed from Wisconson in the US, but had come out to NZ on a fishing trip after the war ended and liked the place so much, he built pretty much a 2nd home here and used to travel backwards and forwards, to avoid the US winters.

This guy also had a job with Operation Deep Freeze (the base of the US in Antarctica), so it wasn't that much a holiday home as much a base to drive to his work in Christchurch.

I had a look around his house, during a visit there after the funeral of my Grand-father and it had a 400V 3Ø transformer and the secondary side was 120/240V.
I think (from memory), he had a Cutler-Hammer panel and at the time it was the biggest panel I'd ever seen in a house here.
All of the cables, switch-gear, recepts, switches and the like were all imported from the US.
The house was built in 1957.

The one thing I could not get over was the size of the wires where they went into the house, being all over-head at the time, the PoCo had stipulated that the installation from the secondary side of the transformer had to have single cores run to the building, via huge insulators on the pole end and heavy pin-type insulators at the house end, driven into solid rimu timber, as opposed to something like is currently used in the US.

Oddly enough, the metering was all done on the 400V side of the transformer, as there was no way that our regulations would have allowed a US type meter here.

That particular regulation died a death in the 1961 regs.
I'm sure Bob enjoyed not having to pay for the hysteresis current of that transformer.

I've never forgotten that huge box out on the pole that had the metering, C/T's and a big red label stating:


With regard to fittings, at the time, I never knew that you guys in the US had your switches up-side down.

As far as I am aware, I think that the place used Arrow-Hart switches and recepts.
Back in 1957, there were a lot of houses that never had isolators on the recepts, even the local ones, so I guess that would have helped the inspection process.

The guy imported all of his own appliances, which back then wouldn't have worried too much about the difference in frequency, let's face it, washing machines (as basic as they were back then) would run slower, but it was no big deal.

Everything these days seems to have a motor on it for something, take for instance, the oven in the original post here, fan ovens haven't been around that long, but they are more of a convenience thing, than anything else.
An oven will work just fine without it's fan, it just takes longer to cook/bake something.

Bob passed away 7 years ago and I got an e-mail from his son to direct me to start taking the electrical side of the building to bits.
It wasn't a fun job, although the wiring was as neat as, it was like this is something that should be photographed, because one of these installs in New Zealand would be pretty rare.

Un-fortunately, I didn't own a digital camera at the time and pretty much when I got there, the builders had ripped most of the walls down (damaging the wiring in the process) and the PoCo had taken the distribution gear.
That really annoyed me.
A once in a life-time thing, gone.

I assume that guy had the metering on the primary as well - after all the PoCo wants to use their own meters and they most definitely won't supply a 120/240V 3w meter.

The US facilities in Germany have extensive 120/240V systems, but as far as I know they mostly use German switches and German-made NEMA receptacles that fit German boxes. Supposedly I can get my hands onto some of those next spring, definitely going to post pictures then!

Earlier this year I saw a house in Austria (near Vienna) where I suspected 120/240V wiring too. The whole place was just so incredibly American in style, it was hard to believe. Like a miniature version of the Capitol with some brick thrown in.
Here you go (just linked since it's really OT and I already had it uploaded to my Photobucket account)
https://i17.photobucket.com/albums/b82/W_e_St/Bisamberg/P2240042.jpg