Rick Stanley said:
Oh no. Now you got me wondering. I just ordered an electric 40 gal water heater intending to pre-heat up to 100 or some degrees with wood and let the electric heat it the rest of the way up to 120 or whatever. Now I'm reading here about heaters being made to heat "cold" water. Is my plan not going to work??
Thanks!!
A tank electric wouldn't have the same problem as an on-demand NG/LP unit with preheated input, but there still could be a problem. Read the installation/operating documentation carefully to see what they have to say about it.
You wouldn't think there could be a problem, but with mine there were two prohibitions, one against feeding too-hot water in from the top and another against feeding not-so-hot water in to the bottom. As I recall 100 degF into the bottom wouldn't be a problem for mine.
I believe the too-hot-top might have to do with setting off the safeties and they claimed that too-hot-bottom input would confuse the hell out of the new super-duper micro-controller green-living we-know-when-you-need-hot-water-before-you-do control unit.
--ewd