Would help to know whose heater you have, where installed, etc. Our Noritz has a remote display where you can set the output temperature.

More info, por favor.

It must be a very old one or cheaply made, as today's quality units for over 10 years deliver precise temps within 3 degrees of setting. Or just set way too high for you to get workable and safe outlet temps.

Does it have a pilot? perhaps the hydraulic t-stat has failed, outlet stat has failed or a cross connection in piping was created by the plumber causing mixing.

Giving us a clue of make, model and age would always help.

It's not even a year old. It's installed inside. Electric. The output temperature has not been changed and the light comes on when you turn on the water source. I will pass t-stat and outlet failure as possibilities to my husband for him to check.

Here is a link that might be useful: model or its similar

Oh, electric

My thoughts are still controls

Being too hot before and needing to mix lots of cold, did you try turning it down? with problem now, did someone turn it down?

Or still a cross connection as stated before with lukewarm, or failing, once again

No one has touched the controls. The box sits in the back of a closet no one goes in and it was set on 52C and it's still on 52C. Not controls. Unless I don't understand what a cross connection is, I don't see how a cross connection can have occured. I say that because he cut them off and capped them up on top of the house not under the house where the pipes are. Mostly, the old pipes were never reconnected to anything.... only cut and capped. The new pipes were run months ago and all has been well, so no cutting or conneting there either.

Could any pipes get disconnected underneath the house and it end up lukewarm?

Is it a larger capacity unit that has multiple stages which requires muliple breakers and services?

Did you check if any circuit breakers were left off?

It's just the one box. Circuit breaker, hm. I'll have him check that too. Seems like we upgraded the box with two new breakers just for it. Wonder if they're both on? All right then. Thanks for helping!

The hardest part of having it has been getting enough cold mixed in to cool it down to useable bathing temperatures.

...it was set on 52C and it's still on 52C.
Turn the temp setting down and you'll get better results for bathing. Ideally, it should be set AT the temp you want for showering or bathing .. or whatever task may be at hand. I keep mine at 38°C to 40°C (100°F to 105°F). I raise it accordingly for certain tasks such as washing some particular loads of clothes. I don't raise it for the dishwasher, which has built-in water heating.

Mine is in a closet in my utility room, easily accessible for adjusting the temp setting. For installations that aren't so accessible, remote controls are helpful.

I agree with what dadoes said- heating to 52C then mixing down just means the heat lost in the hot water piping along the way is greater.

The manual at the site you linked mentions fault codes and having breakers off as potential issues.

Only drawback with that is thermostatic shower valves with mixing spools don't do too well with minimal cold needed, thus reduced pressures at head.

We've tried several configurations, and just leaving it on 52 works best. It only affects the showering, but then, only a bit more cold is needed.

I want to thank you guys! Someone's temporary fix, had the hot water recirculating into the cold water. Thanks to you, your comments triggered his mind as to how it could be going on. Consequently, the hot water is fixed. Funny? When he went to install the permanent fix, he couldn't get one of them right last night, and it's leaking. So now we have hot water, but we still can't use the water (its turned off). I plan on a long hot bath tonight! After he slows down at work and finishes the plumbing at home. He will. :)

52, approx 120 F is a pretty standard setting. Although minimum storage, I wouldnt go lower at the risk of creating airborne germs causing illness (Legionaires)

Not too sure how the pipes got connected but I figured with recent service work performed it couldn't have been too many possibilties besides the cross-connection or 1 breaker off.

I think the potential for Legionellosis is negligible. There's no storage, and the system is going to cool off between uses. I'd imagine if that was a serious concern, the makers wouldn't let you run the heater at that setting.

And our Hansgrohe thermostatic valve does just fine with 105F water.

As I alluded to earlier the minimal storage is an advantage.

There are two seemingly conflicting safety issues around water heater temperature  the risk of scalding from excessively hot water, and the risk of incubating bacteria colonies, particularly Legionella, in water that is not hot enough to kill them. Both risks are potentially life threatening and are balanced by setting the water heater's thermostat to at least 50 °C (120 °F). The European Guidelines for Control and Prevention of Travel Associated Legionnaires Disease recommend that hot water should be stored at 60°C (140 °F) and distributed such that a temperature of at least 50°C and preferably 55°C is achieved within one minute at outlets. If there is a dishwasher without a booster heater, it may require a water temperature within a range of 57 °C (130 °F) to 60 °C (140 °F) for optimum cleaning, in which case tempering valves set to no more than 55°C can be applied to faucets to avoid scalding. (Note: Tank temperatures above 60°C may produce calcium deposits, which could later harbor bacteria, in the water tank. Temperatures above 60°C may also cause gradual erosion of glassware in a dishwasher.)

ItÂs interesting, as many communities and watersheds heavily chlorinate the water delivered here in the US and the concerns is virtually of no concern.

Personally knowing someone who set his indirect hot water heater lower than usual and taking long showers while sick and congested, caught the disease, and it was nasty with harmful effects still huanting him