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110 vs. 120 - Tomayto vs. Tomahto?


hausdok
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110?

I thought everything in this country had been bumped to an average of 120 these days.

OT - OF!!!

M.

As I understand it, 120 is the standard for electrical service but 110 is a standard value used in the design of appliances that have motor loads and perhaps with other non-motor appliances also. The difference is deliberate and is intended to counter issues with poorly functioning appliances due to voltage drops between the electric utility and the end user.

Marc

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Someone, I can't remember who, taught me that there should never be more than a 10% voltage drop or overage and that acceptable voltage ranges are 108 to 132 volts, which places 120 smack dab in the middle of that range.

If an appliance were designed for 110 and voltage delivered were 130 volts, couldn't that create as many issues as running an appliance with lowered voltage?

ONE TEAM - ONE FIGHT!!!

Mike

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When my wife set up her print shop we had a similar issue with the three phase service. Most of her equipment was 208v, but her compressor and folder were 240v. Fortunately the complex was big enough to have its own substation, so the voltage typically measured 210 to 214 volts depending on the demand in the rest of the complex. High enough for the 240v motor loads, and low enough for the 208v motor loads.

110/220 is just stuck in my head I guess.

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If an appliance were designed for 110 and voltage delivered were 130 volts, couldn't that create as many issues as running an appliance with lowered voltage?

ONE TEAM - ONE FIGHT!!!

Mike

I'm sure it would but the utility wouldn't let it get that high. 120 V is generally what they shoot for. If they see 112 far downstream of a transformer station, they might adjust it upwards but they wouldn't adjust it much over 120. I've measured 242, 248 (across both lines) at some residential main service panels. Nothing wrong with that.

480V, 1000A bus ducts at a forge plant that I used to work at would often measure out at 512 volts and the motors were all rated at 460.

Marc

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The required standard in North America is for the utility to supply voltage to us within 5% of 120/240 volts. If the utility provides a consistent overvoltage or undervoltage the customer's equipment can be damaged, and they try pretty hard to keep it at 120/240. It's becoming more difficult with all the other sources feeding into local grids.

In the early (Edison) days of electricity, voltage was 110 and 220 DC. AC systems were designed to match that voltage. (Though AC systems have peak voltages that are higher than the nominal voltage, their net effect in terms of heating up the wire is the same as the nominal DC voltage.)

In the 1930's the electrical code changed to 115 and 230. Even today, those ratings are used in the NEC for horsepower calculations for NEMA motors. In the NEC, the change from 115 to 120 was in the 1984 edition, in conformity with the ANSI standard of 120 & 240.

Here's a link with more info: http://powerstandards.com/tutorials/Vol ... lation.htm

Douglas Hansen

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