On Feb 16, 9:03�pm, Reinhard wrote:
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 a clamp on ampmeter. that will tell you if both tanks are drawing
the same current.

you might have a bad thermostat or bad element.

and always use a analog meter, not digital.

the digital meters are so sensitive the readings can be wrong