Insufficient Hot Water

[Condoman]

I got a call the other day that the electric 40 gallon water heater did not deliver a full load of hot water.  What once was fine is now delivering less hot water when showering than it did and this happens in just a few minutes.

 

I pulled the covers off the WH and amp clamped the upper and it was drawing 18 A or so next, I clamped the bottom and tweaked the upper T stat to send power to the bottom.  Again 18 A like the top.

 

I explained to the homeowner that the T stats are the most likely culprit and they agreed that I replace them.  After a trip to the orange big box store I replaced, tested and went home.  Next day same report.  I said that the possibility is a bad replacement part and got another bottom T stat to replace the possible bad one.  As I remove the bottom cover my disruption of the work area makes the bottom begin to heat.  I take this as a faulty T stat and replace it and then do the check to confirm upper and lower test OK.

 

Next day same problem.  Thank goodness the home is only ¼ mile away.  This time I look through my spare parts and have a new lower from some time back.  When I get to the house I check the water temp and it is 112 degrees at the kitchen faucet.  I then pull both WH covers and using my non contact temperature gun read the tank outside temp at the top and bottom.  They are both about 109 degrees.  I deduce from this that the top is at temp along with the bottom.  I still amp clamp the elements and verify that the both function as they should.  I decide not to replace the bottom T stat.  The WH feeds two different bathrooms on the second floor.  I confirm with the resident that once water temp starts to drop there is still great flow just to be sure we are not dealing with a restriction issue.

 

I tell them to let me know how it works out.  Sadly it does not improve.  This time with the owner to verify I go through the testing explaining that at the time I am there they have a full tank of hot water.  To be safe I replace the bottom T stat.  I am waiting for the next call.

 

Have I missed anything with my diagnosis?

 

[appl.tech.29501]

i would do an amp test on a full tank of hot water and run the hot water completely out and see how long it actually takes to to run out.Hopefully you can catch it when it fails...you should be able to if it is happening eavery day as the customer says.

[RegUS_PatOff]

Reading the outside of the Tank temperature may not help if there's a lot of insulation ...

How's the Cold Water (Dip Tube / Sacrificial Anode) ?

[Condoman]

Did not look at the dip tube. Can this cause the lower to not fully make it's batch of hot?

I have been with this client for 16 years and never replaced the WH in that time, so I am guessing the WH is older than 16.

[RegUS_PatOff]

Some WH's Dip Tubes are also the Sacrificial Anode, and if it's full of holes, or cracked/broke,

the cold Water entering would not go to the bottom, but would rather leave through the Hot Water Outlet.