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My 30 A dryer outlet reads 122 and 123 V on my multimeter (a total of 245 V). Will this be a problem for a new modern dryer if it is higher than 240 V?

It is a three prong outlet.

Peter Mortensen
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user129694
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  • Every time someone turns on an electrical device, it draws current. When it draws current, the grid voltage drops. If someone turns off an electrical device the current draw stops - the grid voltage rises. During the day, millions of people are turning things on an off. During the day the grid voltage goes up and down. If it gets too high, grid operators turn off generating plants to bring the voltage back down. If it gets too low, they activate generating plants to bring the voltage back up. This is why voltage floats within a range. – J... Feb 08 '21 at 13:59

3 Answers3

51

That is well within ANSI C84.1 North American Utlity Standards.

enter image description here

NoSparksPlease
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    For OP: The important column is "Utilization", which are the allowed voltages at the outlet. – BlueRaja - Danny Pflughoeft Feb 03 '21 at 20:54
  • @BlueRaja-DannyPflughoeft Citation? I would have assumed the NEMA numbers would be authoritative and applicable (granted, the posted chart doesn't define exactly what "Service" / "Utilization" / "Nameplate" mean...). – Dai Feb 05 '21 at 08:39
  • @Dai [ANSI C84.1](http://voltage-disturbance.com/voltage-quality/voltage-tolerance-standard-ansi-c84-1/) mentioned in the answer. I believe "NEMA" refers to what the equipment needs to be certified for. Not sure about "nameplate" - maybe what goes on the label? – BlueRaja - Danny Pflughoeft Feb 05 '21 at 10:43
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240 V is the "nominal" reading. You'll usually get ±10% voltage from the utility lines, and your appliances are designed to accommodate that variation.

Peter Mortensen
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FreeMan
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11

You will be fine with that. The power company usually delivers 5% +or - the normal 120/240 residential voltage. Your meter also has a tolerance of up to 3%.

JACK
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  • I agree with both JACK and FeeMan, you'll be fine. If you view utility power on an oscilloscope, you'd be amazed to see how "dirty" it is. The 3 prong outlet is outdated since 2000, but still commonly in use. Some ppl here go over the rails about it being dangerous, but IMHO, it's a very low risk config. – George Anderson Feb 03 '21 at 13:44
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    @GeorgeAnderson My dryer's been three prong since I moved in in 1982. New townhouse and they ran 10/3 w GND but used three prong receptacle... I never changed it. OMG, hope Harper doesn't read this. – JACK Feb 03 '21 at 14:57
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    Because when you moved in, I bet your builder asked you whether your dryer was 3-prong or 4-prong @JACK. (3-prong was legal in 1982). Since changing the wall socket is in the builder's bailiwick and changing the dryer cord is not. Now, everytime you get a dryer, the appliance store changes the cord, because changing the cord is in their bailiwick and changing the socket is not. It's a frickin' virus. If nothing is done, all dryer sockets will be 3-prong by 2050! :) – Harper - Reinstate Monica Feb 03 '21 at 17:45
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    Meanwhile in the rest of the world, everything is 240v, and we don't centre tap it. 3 conductors, live, neutral, ground. – Phil Feb 03 '21 at 21:32
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    @Phil I believe it's actually 230V in the rest of the world. Which is interchangeable with 240V for most practical purposes – user253751 Feb 03 '21 at 21:36
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    230 is a myth, in practice it's actually either 240 or 220 depending on where you are. – Jasen Feb 04 '21 at 05:36
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    In the UK/EU, the allowed range is 230 volts +10% - 6% (ie. between 216.2 volts and 253 volts), but as @Jasen says, the actual values are centred on either 240v or 220v, as the UK/EU convergence was done by ensuring the standard covered both sets of existing equipment/voltages, rather than changing equipment. – Gwyn Evans Feb 04 '21 at 09:09
  • @Jasen That was the case when everyone standardised, sure. New transformers for the "last mile" put out 230V though. Plenty of old kit will still be around - transformers last a *long* time, barring lightning strikes - but everywhere is progressively changing over. If you're living in a housing development built in the last 30 years, you're almost certainly at 230V. – Graham Feb 04 '21 at 09:12
  • @Graham: I remember having issues at work, where the voltage was nearer 212V. That was ultimately caused by an undersized cable, having too much voltage drop. That cable should have been upgraded exactly because of recent housing development in the area, but wasn't. With the move towards sustainable energy, such variations will become more common - lowering the voltage is a simple way to lower the local power consumption to match production. – MSalters Feb 04 '21 at 11:54
  • @MSalters Hopefully with the rise in sustainable energy, we'll get some proper money put into heavy-duty local energy storage systems like flow capacitors. That whole area has been stuck on the drawing board for 30 years or more, because the attitude was that they could always turn on another fossil fuel power station instead. With wind and solar becoming a more significant fraction, there's now a genuine market need to answer the question "what happens when the wind drops?" with a proper solution. – Graham Feb 04 '21 at 13:08
  • The US is 240V, it's just split into -120V and +120V. Which is why we can still have 240V outlets... It just needs to span -120V and +120V lines. A small price to pay for only having 120V live on any one line. – jdmichal Feb 05 '21 at 17:49
  • @Graham is correct that everything is moving towards a common 230 V. For example, The Netherlands where I live was traditionally a 220 V country, but now I fairly consistently measure 234 V at the outlets in my house, and similar voltages in other houses. – BrtH Feb 06 '21 at 12:17