josephridolfi6986
Member
If a 10,000 watt heater rated for 240 volts is connected to 208 volts how many amps will the heater draw? What is the proper way to do this calculation?
10,000 watt Heater
- Thread starter josephridolfi6986
- Start date
- Status
- Location
- Massachusetts
Using Ohms law determine the resistance of the heater at 240 and then apply that resistance to 208.
- Location
- San Francisco Bay Area, CA, USA
- Occupation
- Electrical Engineer
And by the way using the same Ohm's law it will no longer be a 10kW heater, it will be a 8,667 W heater at 208V.
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
This is assuming this is straight resistant heater. If there s a motor involved make sure the motor can be connected 208V
josephridolfi6986
Member
The question was worded exactly this way. The question did not specify single phase or three phase. The answer choices were:
-28
-36
-42
-48
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
Look at Jraef's post and then divide.
- Location
- San Francisco Bay Area, CA, USA
- Occupation
- Electrical Engineer
Ugh... did I somehow become your Homework Beeatch?
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
That was your own fault since you did ll the work. :happyyes:
josephridolfi6986
Member
No this wasn't homework it was an actual exam question.
I am just trying to learn and understand how to do the question. I appreciate your help and your time to answer back!
I am just trying to learn and understand how to do the question. I appreciate your help and your time to answer back!
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
do you understand how he got the wattage or do you need help. Ohms law is the key.
Take the original information 10000 watt heater at 240 volts. In this case I x V = watts or I x 240 = 10000 and I = 41.7 amps.
The resistance of the heater R = V/I = 240/41.7 R = 5.75 ohms watts = I2 x R = 41.7 2 x 5.75 = 10000 watt
At 208 volts I = V/R = 208/5.75 I = 36.2 amps. At 208 volts the wattage = I2 x R = 36.2 2 x 5.75 = 7535 watts
watts = (V2/V1)2 x 10000 = (208/240)2 x 10000 = 7535 approx.
That's not the same as JR. Check it for correctness please.
Answer is 36 amps.
Thanks
The resistance of the heater R = V/I = 240/41.7 R = 5.75 ohms watts = I2 x R = 41.7 2 x 5.75 = 10000 watt
At 208 volts I = V/R = 208/5.75 I = 36.2 amps. At 208 volts the wattage = I2 x R = 36.2 2 x 5.75 = 7535 watts
watts = (V2/V1)2 x 10000 = (208/240)2 x 10000 = 7535 approx.
That's not the same as JR. Check it for correctness please.
Answer is 36 amps.
Thanks
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
cadpoint
Senior Member
- Location
- Durham, NC
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
The resistance for the heater is just that and it doesn't vary on voltage. The watts however with change with voltage not the ohms. Is that what you are asking?
cadpoint
Senior Member
- Location
- Durham, NC
It's slight of hand(mind) - if 240 wasn't in the equation then the value of ohm's would have been different.
IF to par-phrase Bob
I x 208 = 10000 and I = 48.1 amps
The resistance of the heater R = V/I = 208/48.1 R = 4.3264 ohms watts= I2 x R= 48.12x 4.3264= 10009. watt.
The equipment was built at 240 which sets up the resistance. I should have been a Maryland fan, Go Terps...
- Location
- San Francisco Bay Area, CA, USA
- Occupation
- Electrical Engineer
LOL, yes I got lazy and didn't do it as I should have... shame shame. :ashamed:
ptonsparky
Tom
- Occupation
- EC - retired
hmy:- Status