On 11/10/2010 11:55 AM, Red Green wrote:
Tony wrote in
:

My girlfriends water heater goes cold as she runs a bath. (It used to
give plenty of hot water for 2 baths.) Twice now as I opened up to
get to the thermostats it decided to work and was OK for one bath.
It's an old fashioned unit that is in a white porcelain cabinet in the
kitchen so I can't leave it open for safety reasons.

When I did open it, the lower element was on (240AC and making the
noise they make) and would switch on/off with the upper thermostat.

I'm guessing a bad thermostat (electrical connections are good), any
idea which one?

What if one thermostat is off a bit? Can I turn one a hair higher
than the other and if it doesn't work put it back and turn the other
one a bit higher? Does that make any sense?

Now that I think of it, if the upper thermostat turns on while I'm
bumping it as I'm opening it up, that is probably the bad one....?

Repost credit to:

Subject: Troubleshooting Electric Water Heater
From: (Ron in NY)
Date: Sat, 06 Nov 2010 00:19:39 GMT
Newsgroups: alt.home.repair

wrote:

...


From a cold start, the upper element will come on to heat the upper part
of the tank because that is where the hot water exits. After the top
thermostat has been satisfied, the upper thermostat switches power to
the lower thermostat which in turn sends power to the lower element.
After the water at the bottom of the tank is hot enough, the lower
thermostat cuts power to the lower element.

When you start to draw hot water, it is drawn from the top of the tank,
and cold water enters through the fill pipe which is extended inside the
tank somewhere near the bottom. The lower thermostat senses the bottom
of the tank is getting cold, and activates the lower element and starts
to heat the bottom of the tank. If you draw enough hot water and the top
of the tank starts to drop in temperature, the upper thermostat will cut
out the power feed to the lower thermostat and activate the upper
element to try and keep the water at the top of the tank hot so you
don't run out of hot water. Hope that clears it up.

Another thanks for the tutorial on the operation, I never worked on one
before, just replaced leaking ones. It sounds much easier to diagnose now.

Tony