ECN Forum Forums General Topics of the Trade General Discussion Area Water Heaters/ Heat Elements

"So cpalm1 a couple of questions what size breaker are you running, what size conductors for the branch circuit and did you replace the factory wires that now carry twice the current intended? "

breakers are 20 amp 240V. This is what the electrician installed when the house was upgraded from 60 amp to 200 amp service 15 years ago. before the upgrade, the heater had it's own meter and a timeclock so it would only run at night. the wiring that goes from the panel to the heater is two 12-2 NM cables, one cable for each element. they are the old style NM that is coated with asphalt/fiber braid, but the actual conductors have plastic insulation. The are in good condition. (i will be replacing them though when i move the heater to the basement from the first floor.) the NM cable goes into a juntion box that is built in to the heater. Individual wires go from there to each element (factory wiring was used for upper element, new wiring for lower).

As for the temperature, it is actually 140. i hit the 5 by mistake. i know that is very hot, but it needs to be that way because the cold water is so cooooooooold. with the water at 140, you still have to open the hot water 3 turns and the cold water 1/4 of a turn when taking a shower. if the hot water was any colder it would be used up too quickly. The side benefit is that you can make hot chocolate with the tap water, no microwaving required

There are double-element non-simultaneous and double-element simultaneous-operation models.
http://www.rheem.com/includes/resourceLibraryPDF/1312.pdf

I would think that the heater would have to be clearly labeled as simultaneous if so intended, to preserve NRTL listing/labeling.

Attic, you will still get a temperature change at the shower. The hotter setting on the water heater just gives you a higher reserve of hot water. When you take a shower, you mix cold water with the hot, so with a hotter heater setting, you would be mixing more cold when using the shower and using less hot water.

What is the temperature rating of the conductors in the old Romex that supplies the water heater?
140°F = 60°C, the temp rating of type TW wire.
Setting the thermostat above that temp would subject the conductors to a temperature above the insulation's rating.
(It seems to me that some of the older, cloth covered romex was only rated at 40°C, but that's only from memory.)...S

It's fine to set your water heater at 150º as long as you have a mixing valve to keep "delivered water" around 120 or less.

And most residential water heaters use one element at a time. Top element has priority and locks ut bottom element until the top of the tank is up to temp.

Most commercial electric water heaters can have all elements on at the same time. Usually ach element is on a different phase.