ECN Electrical Forum - Discussion Forums for Electricians, Inspectors and Related Professionals

Topic Options
Rate This Topic
#177490 - 05/04/08 03:36 PM Quick Hot Water Heater question
GA76JW Offline
Member
Registered: 03/20/04
Posts: 193
Loc: Suwanee, GA USA
One of my buddies from school was doing some work at his uncle's house and called me with a question.

Apparently someone had wired the Hot water Heater through a nearby receptacle. The water heater is 208/240 and the receptacle is 120.

My understanding of it is the element will still work, just at half capacity. Is this incorrect?

He is currently correcting it. I just wanted to hear some opinions on the matter.
_________________________
"If common sense was common, everyone would have it"-not sure, someone here

Top
Work Gear for Electricians and the Trades
#177491 - 05/04/08 03:49 PM Re: Quick Hot Water Heater question [Re: GA76JW]
twh Offline
Member
Registered: 03/11/04
Posts: 901
Loc: Regina, Sask.
One-quarter the heat.
Top
#177493 - 05/04/08 05:04 PM Re: Quick Hot Water Heater question [Re: twh]
GA76JW Offline
Member
Registered: 03/20/04
Posts: 193
Loc: Suwanee, GA USA
Originally Posted By twh
One-quarter the heat.



Could you throw some theory at me to show how that happens?
_________________________
"If common sense was common, everyone would have it"-not sure, someone here

Top
#177497 - 05/04/08 05:18 PM Re: Quick Hot Water Heater question [Re: GA76JW]
gfretwell Offline


Member
Registered: 07/20/04
Posts: 9036
Loc: Estero,Fl,usa
Resistance is fixed. Amps is volts divided by resistance. Watts is amps times volts.
Notice volts figures in both equations and one feeds the next so volts gets used twice. Twice the volts is twice the amps and that is again multiplied by volts.
The power formula sums it up with watts equals the square of the volts times the resistance (P=I2R)
_________________________
Greg Fretwell
Top
#177498 - 05/04/08 05:20 PM Re: Quick Hot Water Heater question [Re: GA76JW]
twh Offline
Member
Registered: 03/11/04
Posts: 901
Loc: Regina, Sask.
At 240 volts and a 24 ohm element:
E = I x R
240 = I x 24
10 = I

W = E X I
W = 240 X 10
W = 2400

At 120 Volts and a 24 ohm element:
E = I x R
120 = I x 24
5 = I

W = E x I
W = 120 x 5
W = 600

Or .5 of the voltage x .5 of the current = .25 of the watts.
Top
#177521 - 05/05/08 01:28 PM Re: Quick Hot Water Heater question [Re: twh]
GA76JW Offline
Member
Registered: 03/20/04
Posts: 193
Loc: Suwanee, GA USA
Thanks for clearing that up guys.

It makes more sense now that you threw the numbers up.
_________________________
"If common sense was common, everyone would have it"-not sure, someone here

Top

Member Spotlight
Member Since: 04/03/02
Posts: 6775
New in the Gallery:
SE cable question
Featured:

2017 NEC and Related
2017 NEC
Now Available!

Shout Box


Who's Online
0 registered (), 87 Guests and 9 Spiders online.
Key: Admin, Global Mod, Mod
 
New in the Gallery:
SE cable question
 
Top Posters (30 Days)
Admin 51
HotLine1 43
gfretwell 17
Trumpy 16
Ruben Rocha 13
 
Newest Members
clee512, Jdscott2005, FAIZAN, Regitest2, sureshazhagai

ECN Electrical Forums - sponsored by Electrical Contractor Network - Electrical and Code Related Discussion for Electrical Contractors, Electricians, Inspectors, Instructors, Engineers and other related Professionals