Using 240v appliances on 120V mains

We moved from the UK to the US, bringing a few 240v devices with us. I also collect vintage (antique, ancient, etc) computers from around the world - which almost always have non-US mains voltage requirements. I use a number of techniques to make these varii devices work on US 110v.

WARNING

Perform any of these procedures at your own risk. If you don't know what you're doing or don't understand the consequences of making a mistake, don't use this page, consult an electrician (who won't touch you with a barge pole if he's got his head screwed on and you ask him questions like these).

What's different?

UK mains electricity is 240v at 50Hz. In other words, alternating current where the current changes direction 50 times every second. US mains is 120v at 60Hz. The voltages are nominal - in other words not exact and the actual voltage can vary depending on a number of factors. All UK sockets are 3-pin with ground. Many older US homes still have a plethora of 2-pin sockets (no ground). Since the wiring to these sockets ("receptacles") doesn't carry a ground wire it's often not a simple matter to upgrade to 3-pin sockets without tearing up the walls.

Solutions - may be pluggable

First, check the voltage and frequency specification of the device. You may have to look in the instruction manual but it should be marked on the device or on the devices' power supply. Multi-voltage;multi-frequency devices will normally be marked as such. The marking "240V~50Hz" means it can only be run on 240v. A marking such as "100-240V~50-60Hz" means it will work quite happily from any voltage from 100v to 240v and any frequency from 50Hz to 60Hz. If you see a label such as "100-240V~50-60Hz" then you can basically plug it in anywhere and all you need is a plug converter. Many small devices (usually relatively low current devices) such as shavers and laptops have multi-voltage multi-frequency power supplies. You may only find a voltage marking such as "100V-240V" with no frequency marking. In most cases this means that it will also accept 50Hz or 60Hz but check the instruction manual to be sure. You're most likely to find this data in the table of "specifications".

Solutions - may be switchable with an accessible voltage selector

Again, it makes sense to check the instructions. Many small-medium sized devices such as PCs have a voltage selector. It's almost always next where the cable enters the device and is almost always a red slider. If you can find one of these, it's very likely you can set it for US voltage. Again, check the user manual to verify the limits of the "110V" or "120V" setting. In almost all cases, devices with these sliders are designed to be sold world-wide just by setting the selector appropriately.

Solutions - may be switchable with an inaccessible voltage selector

Solutions - recycle it back

In other words, in some cases, give up and pawn it off on one of your UK visitors to take back to the UK. :-] Obviously this is only likely to work if they can take it on the plane so that combo washer-dryer just isn't going to make it back, is it?

Plug converters

Plug converters simple allow you to physically plug one shaped plug into a differently shapped socket/receptacle. These convert physical shape NOT voltage! Most people know these as "travel plug converters". However you get what you pay for here. In other words you need to pay more for one which will last. If you see yourself plugging in/out of the converter often then best buy a more expensive one.

Note again, plug converters DO NOT CONVERT VOLTAGE! (Having said that, Brookstone has a line of combined voltage and plug converters but these are marked as voltage converters as well).

Changing the plug

If you have an appliance which will run on 110V and you are confident wiring a plug then it may make sense to change the plug from a UK plug to a US plug. This exercise is fairly straight forward - match up the ground wire with the ground pin, neutral with neutral and live with live. Use the colour code table below to match the wire colours to the plug wiring diagram colors.

US and UK appliance wire (flexible cable) colour/color codes are as follows:

        UK           UK            US
        (current)    (old)
Earth   Green/yellow Green/yellow  Green
Live    Brown        Red           Black
Neutral Blue         Black         White

Get this wrong and you may be toast.