I assume from reading your post that you haven't yet put in that new
thermostat, unless you did it in the middle of the night "today".

The problem you describe would be a cinch for someone with the right test
equipment and understanding of "hot water heater electrics" to diagnose.
All it takes is an amprobe (current meter) and a voltmeter (if that's not
already combined with the amprobe.

Without test equipment you're likely to frustrate yourself stumblig around
"blind", which is what you'll be doing if you can't make voltage and
current measurements to track down the culprit.

The typical 220-240 volt hot water heater with two elements works this
way:

From a "cold" start, current flows through the closed upper thermostat
contacts (and the overtemperature cutoff device) to energize the upper
heater.

Assuming nobody's pulling hot water from the heater:

When the water in the upper part of the tank reaches the upper
thermostat's set point temperature, that thermostat turns off the power to
the upper heating element and enegizes the input of the lower thermostat,
which will power the lower heating element until the water in the lower
part of the tank reaches the setpoint temperature of the lower thermostat.

Fom that point on, the lower thermostat will cycle on and off every once
in a while to keep the whole tankfull at a contant temperature.

When hot water is drawn from the heater:

It is taken from the top of the tank, and cold water enters at the bottom
of the tank, through a "dip tube" extending down to near the tank bottom
from the "cold" inlet fitting at the top.

The lower thermostat will close first, as the entering cold water cools
it, and will enegize the lower heater. If hot water continues to be drawn
off, the lower heater won't "keep up with it", and cooler water will reach
the upper thermostat, causing it to switch over to powering the upper
heater again.

If water continues to be drawn it will take heat away faster than the
upper heater can keep up with and you "run out of hot water."

(End of narrative.)



I think your best bet is to bite the bullet and have a new hot water
heater installed, given the age of your unit.

Otherwise, if you don't have a friend who knows these things and has the
right test equipment, you are going to have to find a repairperson with
enough smarts and the right test equipment to properly diganse and fix the
problem without replacing more parts than are really needed. Sad to say,
those aren't the attributes of every plumber you might call. A qualified
person's laborcharges, plus the cost of the repair parts he supplies (at
"full retail" of course.) makes buying a new heater not such a bad thing
to do.

That said, if you happen to be near Zip 01890, I'd come over and give you
a hand gratis, just because...

Happy New Year,

Jeff

Robert wrote:

Hi All:

I have a problem with my electric water heater, which is 66 gallons,
Sears brand, 13 years old.

We bought this house about six months ago. Yesterday, without any
previous symptoms, I found the water from the heater very hot -
steaming. Since we were in a hurry to go out, I just switched the
heater's circuit breaker on the main board OFF. I thought the
thermostat might have gone bad and decided to replace it by myself
today.

Today morning, I switched the circuit breaker back ON to get some hot
water (generally I don't switch off the heater at all). After an hour
or so, since I did not get any hot water, I inspected everything and
found that the circuit breaker of the water heater on the main board
had tripped.

I searched google.groups and found a lot of information regarding this
- with possible causes, (1) a stuck thermostat OR (2) bad heating
elements.

To experiment, I turned the bottom thermostat all the way to the
lowest point. Put the upper thermostat at a medium level and switched
the circuit breaker back on. Within about 5 minutes the circuit
breaker tripped again. I tried the same experiment with the upper
thermostat with similar results.

So here are my questions. I think either the thermostat(s) or the
heating element(s) had gone bad.
(1) Should I get an electrician to repair the heater - replace the
thermostats and/or the elements OR
(2) Considering the age of the heater (and the previous owner was not
good in maintaining it – she never drained it in a period of 5 years),
should I buy a new heater.

Please advice.

Thanks in advance for your time.

Robert

--

Jeff Wisnia (W1BSV + Brass Rat '57 EE)

"If you can smile when things are going wrong, you've thought of someone
to blame it on."