Water Heaters - Diff temp between upper lower thermostat?

My electric hot water heater was running great.
Just me and my wife. Water lasted easily for two individual long hot showers and then some.
Now it doesnt last for a short single shower.

I suspect thermostat or element.

This unit was drained/cleaned 6 months ago and worked well for a couple months thereafter.

I opened up the panels, and noticed that the upper thermostat is set at 140 and lower is set at 160!!! From what I am reading 160 is way too high... could this have burned out the element?

I dont have a meter to test it, and was considering just replacing the elements, but was wondering 1) should there be a diff in temp between upper/lower thermostat and 2)what is the best temperature setting for a 1,000sf home with a 40gal elec hot water heater.

Thanks,
KDC23

Hi kdc, I copied this for you: “each have their own thermostat and are wired so that only one element comes on at a time. Normally the upper thermostat comes on first, and then when the top is hot, the upper thermostat re-directs the electricity to the lower thermostat and element. “

If your upper is at 140 and they are wired as stated, then it will go off and transfer the heating job to the lower element. If one is to be higher than the other I would conclude the lower should be slightly higher, although I have always set them the same. With your lower at 160, it is setting the temp for your hot water and 160 is probably too high. But it is also why you have enjoyed two long showers.

Since a small meter is less than $20 I would think it cost effective to pick one up and replace only the bad part. Either thermostat could be bad or either element. Another possibility is a broken or failed dip tube, slim, but it will reduce the available hot water.

Hopefully one of the pros will pick this up and point you to the most probable.

Good luck
Bud

Bud is correct that both thermostats should normally be set at the same temperature. He is also correct that in most cases the two elements will not be energized at the same time.

Since the lower element does the lion's share of the heating (the upper element only comes on when you have used almost all of the available hot water) it is more likely that the lower element has died a natural death. Also, since the lower element can only be energized after the upper portion of the tank has heated if the upper element (or thermostat) has died you will get no hot water at all.

Unless you have an automatic tempering (mixing) valve installed immediately downstream of the water heater 160 is way too high of a thermostat setting. 160 degree water will severely burn your skin in less than one second.

Thanks guys.

I unfortunately had something come up today and had to ditch the project, but I will drain it and pull the lower element to check.... will probably pull both anyhow just in case and replace them if needed.

I was shocked myself to see 160 and immediately lowered it. Thought that was a bit much.. might explain my nice electric bill as well since I dont use much electricity at all except the water, dryer, and a few lights... but anyhow, thanks for the advice.

It is an older Ruud PEH40-2 which is a pretty basic 40gal elec water heater... has worked awesome and then just took a nosedive. I get hot water, but its just limited and this is most likely the reason... Will keep you updated when I get a chance again to get this all done...

Thanks again.
KDC

so if I have some hot water, it isn't the upper element? I suddenly have little hot water. tonight was barely enough for one shower with my Rheem 50 gal tank. I had previously disconnected all wires to elements and checked continuity. they both checked (not open) but I didn't actually check the Ohms since I didn't know at time what value should be. will recheck again now that I know 10-15 is correct based on another post. I also previously shut it off for a while and then when I Turned it on, I was able to get 240v at upper element. I kept checking and then finally got 240v at lower element. So does that mean that t-stats are OK? how else do you test them? and what is dip tube and how do I check it? it isn't the cathode (or is it anode) that is in top of tank?

rechecked elements. both had 13 ohms resistance. also checked to see if any continuity between screws on elements and the tank itself (as directed by instructions on a new element to check for short I guess) and there was not. didn't mean to take over thread but seems I have exact same issues and didn't think needed to start new thread.

hammerash,

If you have some hot water and have 13 ohms across each element, replace the lower thermostat. (I'm assuming that you removed one of the wires from each thermostat and then read the ohms.)

kdc23,

Set both 'stats to about 120 or 125 degrees. Anything hotter than that isn't needed and will only scald somebody. If that makes your shower water too cool, check to see if you have a scald guard or similar valve and adjust that if needed.

Ok.. now I feel like a dip...

Irritated, I went and checked the thermostat again.. and realized I was looking at the notch in the screw not the pointer around it... so I read the temps wrong. Unfortnuately when they installed the hwheater the panels faced the walls at a difficult to see angle.

But both were set at 120.. so I was wrong.
However, just to check... i moved both thermostats up to 130. And voila... i have had hot water and i mean nice and hot! However, this still indicates a problem because noone has touched this hwheater in over 7 months and still doesnt explain why I was getting very little hot water... was aiming at replacing the thermostats.

Let me know what you think and thank you all for your patience and help.

KDC