# on demand electric water heater

Hello all,
I'm not sure this is the right newsgroup, but I'll give it a shot. I currently have a small electic run of the mill water heater. I'm thinking of replacing it (output is starting to decline) with a electric 'on demand' water heater. Has anyone out there done this, or do you have one? I have questions about where to place it (concerning distance from breaker box), and whether to buy one for each sink, or to buy one for the whole house.
Gary C in EC, NC
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Post in alt.hvac and sci.engr.heat-vent-ac, not here.
Nick
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As I understand it, if you are going to electric you may need to check your available power, as those things take a huge amount of power during the short time they are on and your power supplier may need to do some work on the lines supplying your home first.
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Joseph Meehan

26 + 6 = 1 It's Irish Math
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I am also thinking about this. I only use hot water a few days a week, so it might be worth the expense. However, I can partially answer your question. You have to find out what size cable you have going to your water heater, and how long it is. I expect it is #10, but you should check to make sure. (Mine was #12 before I replaced it.) Check how many amps the new water heater draws, and go to http://www.electrician.com/vd_calculator.html
Plug the amps, voltage, wire size, and length in, and it will give you voltage drop. If it is under 3% you are okay for voltage drop. The other constraint is that you are normally restricted to 20a for #12 and 30a for #10 for romex, regardless of voltage drop.
I don't know anything about whole house versus point use.