Adam Farley
New member
A 10,000VA electric furnace rated for 240V single phase is placed on a 208V single phase supply, what is the output?
Electric Furnace Output
- Thread starter Adam Farley
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LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
Adam, welcome to the zoo. :smile: Rather than just answering it for you, I'll give you a little guidance:A 10,000VA electric furnace rated for 240V single phase is placed on a 208V single phase supply, what is the output?
1. Using Watt's Law (P = E x I), find the current at 240v.
2. Using Ohm's Law (E = I x R), find the resistance.
3. Using Ohm's Law again, find the current at 208v.
4. Using Watt's Law again, find the power at 208v.
There are shortcut formulae (which the engineer-types around here will no doubt post), but I feel this is better considering the basic-theory nature of the question.
drbond24
Senior Member
- Location
- Barboursville, West Virginia
charlie
Senior Member
- Location
- Indianapolis
Output is (actual E?/ rated E?) X rated P = (208?/240?) X 10 kW = .75 X 10 kW = 7.5 kWA 10,000VA electric furnace rated for 240V single phase is placed on a 208V single phase supply, what is the output?
Ragin Cajun
Senior Member
- Location
- Upstate S.C.
Yep, the rule of thumb is 75%.
You just need to be careful when the rating is 230V. Then the rule of thumb is 82%.
RC
You just need to be careful when the rating is 230V. Then the rule of thumb is 82%.
RC
- Location
- Lockport, IL
- Occupation
- Semi-Retired Electrical Engineer
I prefer formulas, like the one Charlie used, to thumb rules. I have greater confidence in the answer, if I can take the question back to fundamentals.
charlie
Senior Member
- Location
- Indianapolis
The attachment says it is a .doc file. If you wish to use it, download it and change the extension to .xls since it is NOT a word file but it is an Excel spreadsheet. I can't upload a spreadsheet but I can upload a Word document.
The attachment says it is a .doc file. If you wish to use it, download it and change the extension to .xls since it is NOT a word file but it is an Excel spreadsheet. I can't upload a spreadsheet but I can upload a Word document.
Ingenious :grin:
charlie
Senior Member
- Location
- Indianapolis
It was not me but GeorgeB that told me how to do it. There is another way that will work where you embed an Excel in a Word document and copy the spreadsheet into it. When you double click the chart, the spreadsheet becomes active, complete with the formulas. steve66 told me how to do that one.
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