208volt 1-Phase vs 240volt 1-Phase

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mkrish

Member
What does 208volt 1-Phase do to a 240volt 1-Phase electric dryer, range, cook-top, and hot water tank.Is there a heat loss?
 

jim dungar

Moderator
Staff member
Location
Wisconsin
Occupation
PE (Retired) - Power Systems
Re: 208volt 1-Phase vs 240volt 1-Phase

The devices you listed all are fixed resistant heat devices, so a low line voltage will result in a reduced current draw and therefore lower heat output. 208V is about 13% less than 240V so your effective heating will be about 24% less than the nameplate.

The line to neutral voltage will remain at 120V, so the clock, lights, and timers will continue to work correctly.
 

Ed MacLaren

Senior Member
Re: 208volt 1-Phase vs 240volt 1-Phase

There is a large heat loss.

Example - A 3000 watt, 240 volt, water heater element has a resistance of 19.2 ohms, and draws about 12.5 amps.

The same element (still has 19.2 ohms) on 208 volts draws only 10.83 amps.

208 X 10.83 = 2233 watts, which is only about 74.5% of it's original rating.

Ed

P.S. Jim can type faster than me. :)

[ April 02, 2004, 10:40 AM: Message edited by: Ed MacLaren ]
 

jap2525

Senior Member
Re: 208volt 1-Phase vs 240volt 1-Phase

To me the single phase element is still 3000watts /208v =14.42amps of current draw.What is restricting the current draw to 10.83 amps?
 

dereckbc

Moderator
Staff member
Location
Plano, TX
Re: 208volt 1-Phase vs 240volt 1-Phase

Resistance. A heating element is a fixed resistor. The current through a fixed resistor is dependant on the voltage applied.

Look at Ed's math, it is explained in detail.
 

eutaw42

Member
Re: 208volt 1-Phase vs 240volt 1-Phase

a 240 volt range or water heater on 208 volt circuit will take longer to do the cooking or heating but the element life will greatly increase -- 208 volt range or water on 240 volt circuit will do the opposite--- also per water heater manfacturer of a new water heater labeled 208 volts on 240 volt circuit- warranty is no good unless retrofitted and labeled as 240 volt unit by them.
 
B

bthielen

Guest
Re: 208volt 1-Phase vs 240volt 1-Phase

jap2525,

A wattage rating describes the amount of power a device will consume at the rated voltage. Increase the voltage, and power consumption (watts) increases. A heater with a power rating of 3000w at 240vac means that it will consume 3000 watts of power when 240vac is applied.

Reducing the voltage across the same resistance means a lower current draw. Lower current and lower voltage translates into lower power. P=EI

Bob
 
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