I’m looking at electric garage heaters (Dayton, QMark, etc) and wondering about the different voltage ratings displayed.
They’ll list BTU’s for 208 volts and 240 volts…..isn’t normal home voltage 220?
Is there some way to have 240 volts coming into the house?
Sure wish I paid more attention in school ;o)
Replies
"..isn't normal home voltage 220?"
No, it is 240 volts, except in California.
Been 240/120 for years and years.
Might have been 110 back when Edison was supply DC.
208 is on 3 phase systems used in some commercial buildings.
"No, it is 240 volts, except in California.
Been 240/120 for years and years."
Bill,
I live on a long rural road (in the middle) and my house is the first to tap off the transformer (directly) I get reading of 126/252 on my volt meter for the circuits in my house. I was always under the impression that your voltage was at least somewhat related to the distance the current had to flow?
Jon
Yes, they will bump the voltage level a "little" for long runs.
I understand that this is specially common in rual areas with farmers so that the voltage is high enough during milking time.
Edited 2/13/2004 8:14:11 PM ET by Bill Hartmann
"this is specially common in rural areas with farmers so that the voltage is high enough during milking time."
Bill,
Yeah, and when I moved out here 10 years ago, there were dairy farms all over the place, now.....................Yuppies and DINKS,............ wait that's me and my wife. Well, at least we don't live in a vinyl mini-Mc Mansion with 20 gables like what is going in on all the fertile farmland all around us.
Well. at least there is plenty of power for all those new homes.
Sorry Bill, just ventin' a little.
Jon
Adjusting grid voltage is done for several reasons using several different methods. In the northeast, where dairy farms have gone by the boards, we adjusted voltage either in anticipation of, or in reaction to, a change in usage. The reactive loading on the generator is adjusted to match the voltage requested by the load dispatcher. (We just called it adjusting VARs.)
Another way to change the grid voltage is to bring on a load follow unit. Big plants that are most efficient running (and staying) at full load are left on line; these are called Base Load units. They ramp up and and stay at 100% (or whatever.) All nuke plants are base load, due primarily to the fission product poisons that build in while running (the poisons change with a power change and at end of life can literally shut down a unit. One time I tried to start up and was xenon-precluded, too much poison; had to wait 24hrs.)
If there is more load required than currently available on line, a load follow unit is dispatched to start up and ramp up, and it can be used to adjust grid voltage.
As to the NE grid voltage, we were often called to adjust reactive loading at about 6am, as that's when a lot of the factories cranked up. The summer with all the a/c units starting is another time to crank it up.
Got no idea how or why they adjust it in the mid-west or west of the Rockies. But I imagine there's little difference.
Sorry for the lecture, but tweaking the lights in the middle of the nights made my life interesting, at least for a while. (Hope I got the reactive loading bit right, I'm more mechanical than electrical.)
I never met a tool I didn't like!
Showing my age you figure? :o)
voltage drops over distance travelled. Hih voltage lines carry power over real long distances. Low voltage won`t get ya too far on them cheapy yard lites. (how did Tesla figure on sending electicity without wires? Anybody read up on his stuff?)
here.. http://www.braincourse.com/wirelessa.html
I need that..
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Well maybe not that old.
I do remember when the standard was 115-117.
But 110 is very, very ingrained into peoples head.
I did a quick google to see if I could find any history and it.
I could not. But I found US State Department web site that talks about travel and electronics and it uses 110.
Yeah, it's very common to talk about "one-ten" and "two-twenty". I think it's partly because it just convenient to have the two digits match.
Re voltage variations, remember that higher than "nominal" voltage causes light bulbs to burn out faster, but lower than "nominal" is harder on motors.
Here in LA, the DWP's standards are that you should have 120/240 plus or minus 5% measured at the service entrance.
-- J.S.
Good 'ol LA, most do not realize that the LA public utility did a landoffice profit business during the power 'shortages' a few years back. That said, a very competent public utility, 2nd only to Spfld IL city water light and power of 35 years ago <G> .
Relating to WJ's rural experience, I did some work on remote military systems (MM) in the 70's with then state of art data recorders, found that the rural voltages in ND SD MT, and WY could be in the range of 105 to 133 Vac rms with really wild negative phase sequence voltages (don't even ask if you dont already know what that is, ain't about to publish a tutorial here and now) during harvest season. Transient voltages could reach 360 volt for a few milliseconds, probably when a local farmer shut down his 200 kW crop dryer and fan simutaneously.
A few years ago I stumbled across a web site that listed nominal and tolerance for the US and Europe.
There is a lower percentage allowed at the point of usage (of course), but I don't remember what it was.
Also CA dropped there lower tolerance a little during the power criss so that they could run a couple of volts lower.
And in Europe they "harmonized" the supplies. There where slightly different nominal and tolerances in the different countries. Some where 230, some 240, and I think a couple of others.
Basically all they did was select an average and a tolerance big enough to fit every one. And they said that most equipment would work over the wider range. But they also speced a tigther standard for new designs.
These are nominal, as a name only, voltage.
General category is residential 120/240v.
120v nominal can in actual usage vary between 115 to around 127v.
240v nominal can vary anywhere between 218 to 250v
Anything close. 208v refers to a different system.
When you read on a motor 115 or 117v, largely due to a quirk in motor voltage ratings that I don't entirely understand, is fine for use at 120v nominal. Same goes for 230v rating used on 240v circuits.