On Feb 18, 4:52�pm, "Stormin Mormon"
wrote:
When you're out of water, feel the pipes and see if one WH is still
delivering hot water.

As to the WH delivering cold, it still could be a bad dip tube.

As I understand WH, only one element is powered at a particular time. I'd
expect the lower element to show power / current for a while, and then the
upper one later. An infared thermometer is also a good idea, to see what
temp the thermostat is "seeing" in the tank.

--
Christopher A. Young
Learn more about Jesus
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.

"Reinhard" wrote in message

...
I have two 75 gallon(US) electric hot water tanks plumbed in parallel.
House is new - we moved in 16 months ago and starting about 3 weeks ago
there has been a shortage of hot water. We are running out of hot water
sooner than we used to with similar use patterns. Water temp is plenty
hot to start with and for quite a while. The problem is about a one-third
to one-quarter loss of capacity. We are now running out of hot water when
everyone is taking a shower, some of us like long showers. If only 2 or 3
people shower there is no problem. For over a year we could never run out
of hot water but now we do, fairly often.

I think the dip tubes must be fine or we would have a problem with the
first shower, not the fourth.

I tested the elements with a continuity tester and all four lit up the
light. I also tested for resistance and got about 14.3 ohms for all 4
elements. That's why I think a thermostat is the problem.

Voltage is 240 and there are 4 thermostats. The make of the tanks is
Giant, model 172ETE-3F7M, 4500 watt elements.

The upper wire block has 7 screws - 4 in the left column and 3 in the
right column, there is a high limit reset button which has no effect on
problem. There is a yellow and a blue wire to the upper element and a red
wire to the lower element and a black wire to the lower thermostat. There
is a temp setting screw.

The lower wire block has 2 screws - black wire in and a black wire to the
element.

I downloaded the manufacturers wiring diagram and the connections match
the diagram. Worked fine for over a year so I assume connections are OK.

Can someone explain how to test and determine which thermostat is bad? Or
could there be a bad element?

Thanks,

Reinhard

use clamp on amp meter check current draw of both heaters after
drawing a lot of water, both should match