Converting Entire Room from 120V to 100V

Old 07-01-15, 10:46 AM
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Converting Entire Room from 120V to 100V

Hi everyone,

In the midst of a home renovation, one of the things I'd like to do is switch all the electrical outlets in my kitchen to 100V. I'm hoping someone here could have some advice for me. Is this possible? How is it best done?

I'm aware that a step-down transformer performs this task but as all of our appliances (except oven and fridge) are Japanese, I'd very much like to convert the whole kitchen in order to remove the need for a bulky step-down being out on the counter.

We're dead set on using these appliances (Naoto Fukasawa designed- nothing comes close in the US), so any advice would be appreciated.
Old 07-01-15, 10:52 AM
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***shakes head***


Are they 60Hz?
Old 07-01-15, 11:04 AM
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This will seriously impact the saleability of the house in the future.
Old 07-01-15, 11:10 AM
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Square D Transformer, 120/240VAC, 12/24VAC, 1.5kVA 1.5S43F |

Something like this will take 24volts off of the 120v branch kitchen receptacle circuit. I can't say if the code covers something like this, since the problem is twofold. First, Japan recepts look about like the US NEMA 5-15, so it will be easy to put in a US designed motor appliance, and it won't be happy. Second, supposedly, you have two kitchen 20A circuits that now each need a autotransformer, perhaps at your panel. It will obviously be a custom arrangement that needs point of use voltage marking and a few other considerations, like GFCI design.
Old 07-01-15, 11:16 AM
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Have you asked the manufacturer what the voltage percentage rating is? 100volts X 10% + 100 = 120. Japan has both 50 and 60 Hz. Which is yours.
Old 07-01-15, 11:20 AM
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Talk to your insurance company about your plans since they are the ones that probably have the most at risk. Any work you do that is non standard becomes your liability, forever.

Old 07-01-15, 11:21 AM
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If your appliances will run on 60Hz, I would contact the manufacture and see if they will run on 120 volts. If not, then all you really need to do is to install a buck/boost transformer(s) by your electrical panel and buck the voltage down. A 24 volt buck/boost transformer should work well for your application. I would recommend marking the receptacles somehow, or changing the devices to Japanese devices so as not to mistakenly plug any 120 volt US equipment.

Wow! I must type slow
Old 07-01-15, 11:32 AM
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changing the devices to Japanese devices so as not to mistakenly plug any 120 volt US equipment.
They use the same plugs we do. Twist locks would be bulky. Dimmer receptacles and plugs might work.

Just can't see this 100v as a good idea.

Last edited by ray2047; 07-01-15 at 12:07 PM.
Old 07-01-15, 12:25 PM
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From a code point of view, there is nothing which prohibits installing a separately derived system inside the kitchen, however you would also need to install the standard American kitchen circuits at the correct spacing to meet the minimum code standard. The separate systems would need to be clearly labelled as such at each outlet, and you would still need to provide class A GFCI protection on the receptacle circuits. Probably the only real way to do that would be with a GFCI breaker on the circuit that feeds the buck/boost transformer.

I'm also echoing the suggestion to check with the manufacturer to see if the appliances are OK on 120VAC. Then you would just need to replace the cord and/or plug with the American NEMA 5-15 and use the appliance on a standard circuit.

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