1800 W is the same as another 1800 W

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Hv&Lv

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ever do the math? I did, they would have had to use 140 volts or close to it to even get even close to claiming the 1875 watts they claim:roll:




I have 8.333 ohms at 125 volts
15 amps, 1875 Watts
 

hurk27

Senior Member
125 Volts x 15 Amps = 1875 watts.

So what's on the nameplate?

but see post 12 for actual readings, if 13 amp was read @120 volts that is only 1560 watts @125 volts would only be 1592.7 watts, and 2.07 was the motor, leaving 10.93 amps for the element.

My wife has a 1800 watt hair dryer that gives me a reading of 10.41 amps on a 120 volt source from my tru RMS amp probe which would be 1440 @125 volts but it still says 1800 watts on the hair dryer so there is no rhyme or reason for these figures
 

kbsparky

Senior Member
Location
Delmarva, USA
Did you even bother to read the link for the 8 year old thread? UL lists these things at 100% capacity of a 15 Amp circuit. They claim 1875 watts based on nominal supply voltage of 125.

FWIW, I have 125 Volts here at my place over 90% of the time.
 

hurk27

Senior Member
yea I think I'm getting this crossed up with portable space heaters I read about awhile ago, they were first allowed to be 1675 watts then this was lowered to 1500 watts which is 12.5 amps@120 volts I guess in my mind I was thinking this would also apply to handheld hair driers but now I have read a few places where the 1875watt@ 125 volt is what they are rating them at, although I still get a lower reading when I use a tru RMS meter to mesure the volts and amps?
 

hurk27

Senior Member
Did you even bother to read the link for the 8 year old thread? UL lists these things at 100% capacity of a 15 Amp circuit. They claim 1875 watts based on nominal supply voltage of 125.

FWIW, I have 125 Volts here at my place over 90% of the time.

I went back and read that thread and remember it (I have no idea how), a hair dryer is not concidered continous but a space heater is so the dryer is allowed but the space heater is limited to the 1500 watts @ 125 volts or 1440 @ 120 volts now it makes sense 120*15 is 1800

Our voltage here stays very close to 120, once in a while it might dip in the office when the lazer printer kick in but I have only seen 121 volts once, I'm close to the sub-station so dont get many line sags or overs.

Gota quit staying up late on my off days:ashamed1:
 

kbsparky

Senior Member
Location
Delmarva, USA
Just checked my voltage monitor on my computer's APC/UPS box. Varies between 125 and 124 Volts. Mostly stays right on at 125. I suppose that the POCO likes it that way, as it sells more watts based on constant resistance.

I have a standby generator system here which kicks in during power company peak demand periods. It's been calibrated for 120 Volt output under load. So when we go into load control, and power is transferred to the on-site system, my lights appear to dim slightly, while in reality they are brighter than normal 99% of the time.

I have used 130 Volt incandescent and halogen bulbs for years, and now are using many LEDs these days.

The old space heaters used to be rated at 1650 watts (I remember having one in my room as a kid). But since we had all 20 Amp circuits in the house, we never had any problems with it.
 

Open Neutral

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Inside the Beltway
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Engineer
Thermo 101: Every watt that goes into the closed volume comes out as heat. Motor or not, does not matter. Put a 1000 watt hair dryer into a X cubic foot box, the box gets just as hot as with a 1000 watt lamp, or a 1000 watt electric drill. How ELSE will the energy escape the box? So why are LED lamps better than old GE Nela Park ones? Because folks talk 'efficiency' not about the total out vs in, but "useful out" vs total in. In terms of lamps, that's useful visible wavelengths out vs in.
 

Haji

Banned
Location
India
That depends on the size and efficiency of the blower motors.
The inefficiency of the motor as indicated by its higher current rating gets converted to heat also which is advantageous for the present case and the hair drier may thus outperform the space heater in heat production.
 

kwired

Electron manager
Location
NE Nebraska
And it should always come out that way or close as with electric heating you are converting energy twice first heat to electric then back to heat, because of this there will be losses, of course hydro offers a lower cost solution but heat produce directly via a fuel will always produce more heat because of the single transfer theory, ever notice older electric dryers have a longer duration timer? I have seen some with a two hour timer on them, try this test, dry a load of heavy towels in a gas dryer then try it in an electric, see if it doesn't take longer in the electric, then there is the cost, here the cost is over 6 times between the two as our electric here is one of the highest in the US next to com-Ed.

Had a new customer who moved from Florida and had a house built and wired by someone else, they called me to find out why their utility cost was so high, well they made the mistake of having all electric heat installed 43.2kw of heating (3x14.4kw heating elements in 3 forced air furnaces), two large electric water heaters @5800 watts each, it was the first time I have ever seen a home require a 400 amp service around here as most only calculate out to be around 65 amps load with all gas appliances, their bill was over $1,000.00 a month, the electric appliances and heating was removed and all gas was installed, including a gas fired tank-less water heater and their bill is now is around $300.00 a month.

now in another area it can be different as if no NG is available propane can be costly in some areas, so the rule is do your home work, and for us who know which way is more expensive then we should advise our customers when we see a mistake like this about to be made, I do this all the time.

Some people that have all electric utilities sometimes forget they have no gas bill. Doesn't matter what the rates are, if the heating comes from electric source then the electric bill will include heating but there will be no gas bill at all.

More than once I have had people complain to me "it costs that much to run the lights?" I then have to explain just what else besides the "lights" that bill covers. If you use electric space heaters as a zone heating method, you may decrease the gas bill, but many also forget they will increase electric usage.
 

Open Neutral

Senior Member
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Engineer
now in another area it can be different as if no NG is available propane can be costly in some areas, so the rule is do your home work, and for us who know which way is more expensive then we should advise our customers when we see a mistake like this about to be made, I do this all the time.


Given the 30% tax credit and others, anyone stuck in a no-NG area should be looking at the GSHP solution....esp on new construction. And if there is a large summer AC load, ditto.
 
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Open Neutral

Senior Member
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Inside the Beltway
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Ground Source Heat pump is way to go even if there is gas, but may have higher initial investment.

May have? I think you meant "is sure to be many times..." A friend just laid out $30E3 for his Levittown house with same. It makes sense in cases where:

  1. You have only Reddy Kilowatt or propane available for heat
  2. You have a high KWH rate and big summer AC loads
  3. both

In my friend's case, it was 2 that predominated.
 

kwired

Electron manager
Location
NE Nebraska
May have? I think you meant "is sure to be many times..." A friend just laid out $30E3 for his Levittown house with same. It makes sense in cases where:
  1. You have only Reddy Kilowatt or propane available for heat
  2. You have a high KWH rate and big summer AC loads
  3. both
In my friend's case, it was 2 that predominated.

No I meant may have. I have a GSHP and it was not much different priced than other conventional systems, but I did not have to install a ground loop or additional wells or other similar items that end up costing a lot. I have the convenience of readily available water source and a place to dump it. There are quite a few systems in my area that are the same way, all in rural areas. Not everyone has this advantage though.
 

broadgage

Senior Member
Location
London, England
A true 1,800 watt hair dryer should heat a room to roughly the same extent as a 1,800 watt space heater.
There might be a marginal difference due to the hair dryer emiting the warmed air at high velocity.
Fast moving warmed air is more liable to escape from the heated space or to become cooled by contact with cold surfaces. The difference would be very small in most circumstances.

As posted by many others though, the "1,800 watt" may be a marketing claim rather than a true electrical loading.

It would seem to me to be reasonable to manufacture 1,800 watt hair dryers for use from 15 amp 120 volt circuits. Such appliances are not continual loads, no normall person would use a hair dryer for 3 hours ! so to 100% load a 15 amp circuit seems reasonable.
A space heater could reasonably be used for more than 3 hours and it would therefore seem reasonable to limit them to 12 amps or 1,440 watts if intended for use on a 15 amp circuit.
 
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