Electric water heater (no hot water)

heaterissue · 08-26-2008, 03:59 AM

Hello I am having an issue with my water heater.

It is a dual element 40 gallon Rheem 3500 watt elements.

The issue is I have no hot water.

One problem I see is that I only get 120v to the top screws above the tstat. Or anywhere else for that matter. I don't know if this is the problem or if it has always been like this. I do get 240 volt at the circuit breakers (dual 20amp).

So I do have power (120 though) all the way to the top element (havent checked the bottom since I have no hot water at all)

Also I have 17 ohms resistence between the screws on the top element. Also tested both element screws to ground and didnt get anything at all.

Im not sure what could be the issue at this point?

TazinCR · 08-26-2008, 07:56 AM

If I remember correctly the bottom element comes on first then turns the top on. Check the bottom element. If that thermostat is bad you get nothing to the top or bottom. Should have 220 at the bottom.

heaterissue · 08-26-2008, 10:33 AM

From what I have read power goes to the top thermostat first and then the bottom.

micromind · 08-26-2008, 08:53 PM

Power enters a typical water heater through a high temperature limit thermostat. It's almost always the topmost of anything. It's also the only one that breaks both legs. Possibly one half of this thermostat is bad. A lot of them have a red reset button, they press sort of hard. Since your fingers are close to the terminals, press the button while the power is off.

If the tank is completely cold, the top element will come on first. I'm showing my age here, but many years ago this feature was called 'quick recovery'. It would heat up only the top part of the water in the tank, and indeed much quicker than heating the whole tank.

When the top element thermostat is up to temperature, it transfers power to the bottom element. If it's cold down there, the bottom element heats the rest of the tank. Then its thermostat turns it off.

As stated earlier, the high temperature limit is two pole. It kills all power to both elements. The operating thermostats (top and bottom) are one pole. They only break one leg, not both. A lot of these are combination units with the high limit and the top operating thermostat all-in-one.

The top operating thermostat is double throw, it directs power to either the top element or the bottom. The bottom thermostat is single pole. It's either on or off.

Check to see if you have 240 at the top of the high limit. If no, you'll need to look between the heater and the panel. Look first at the little box where the power cable enters the heater. A very common spot for burnt up wires.

If you have 240 at the top of the high limit, check the bottom of it. If it's 240 also, check across the top operating thermostat. Check first from the common (it might be a sort of link from the high limit to the operating thermostat) to the wire that goes to the top element. If 240, the thermostat is bad.

17 ohms is about right for a 3500 watt element, but check for voltage across the element anyway. Most likely, the problem will be in the top part of the heater.

Rob

wire_twister · 08-26-2008, 10:42 PM

Agree with rob more than likely the high limit/upper thermostat, or a wiring/circuit breaker problem

Mike Swearingen · 08-26-2008, 11:01 PM

I agree too. No hot water at all...bad tstat (most likely suspect).
Change them both while you're at it.
Remember or sketch the layout and number of screws on the upper tstat. Go to a hardware, big box or plumbing store and buy an upper and lower tstat with the same layout and number of screws (does not have to be same brand).
Turn OFF the power breaker, and remove the wires from the old tstat and connect them to the new tstat ONE WIRE AT A TIME to mirror the old tstat connections. Easy. Can't go wrong like that. Should do the trick.
Good luck!
Mike

heaterissue · 08-27-2008, 11:03 AM

thanks micromind that worked. I opened the box on the top of the heater and undid and then redid the wire connectors. Turned the circuit breaker back on and I could hear it doing something. Ten minutes later i had hot water.

micromind · 08-28-2008, 12:01 AM

I just love it when we're able to solve a problem this way! It doesn't get much better than this!!

Rob

4just1don · 08-29-2008, 01:16 AM

I had one once that was a mystery too. checked and checked and found a broken wire about half way down(under all the cover). Dont know if a mouse chewed on it,bad insulation and it arced or what,,it was burnt good,completely off.

MOST of the time its open elements,,,ie BURNT out ones,,,glad you found your loose connection. nice ending to this problem