There is a difference between models for heating water and domestic water,
there are also a number of sizes and wattages. You need to determine what
you're going to use it for, and how much water you need it to produce, then
you need an electric service of adequate size. Some domestic units run at
28KW, or 116 amps @240 volt, which would require your house service to be a
minimum of 200 amps




wrote in message
ups.com...
Hi, I have some confusion about wiring tankless electric water heaters.

#1 When does one require a sub panel, and if so why?

#2 Is there a distinction made between tankless heaters for space
heating and tankless heaters for potable water? There's a tankless
company out there with a separate model for each situation. The
potable model is not UL listed, should I worry about that?

I have the 2002 NEC. If you could site chapter and verse it would be
appreciated.