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Question DetailsAsked on 1/20/2014

I am having trouble finding someone to repair a Noritz tankless waterheater. Who can solve this 21 century problem?

I have a Noritz tankless water heater that is shutting off after about 15 minutes of hot water. I have had several plumbers in here and they have not had a clue. One fiddled with somewires not knowing what to do. And another plumber replaced our gas regulator, which did not fix it. To me it seems that an electrician would be better qualified to work it.
I have had the opportunity to work a bit with Noritz customer support over the phone. They are located in California. Through working with the control panel on the unit with them on the phone, the problem is due to a fan within the unit work at > 100% capacity and after awhile it increases to a point that it turns off the unit. This emergency shutoff is to prevent damage to the unit but of course it limits the length we can run hot water to a shower etc. The use of the control panel to determine readouts from the unit tells me that other than the water and gas, it is essentially an electrical appliance. I reset wh with control panel.

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I would think Noritz could have at least given you the name of authorized installers in your area (maybe on their website), or of companies in your area that buy a lot of their units to install. Their online Installer search engine is here -

Sounds to be like, assuming it is getting full water flow (so not going partly dry), and assuming it is installed right side up (yes, I have seen them installed with the label reading upside down), that is is either a temperature sensor or thermostat problem or a circuit board failure.

When it does this, immediately after it shuts off, check the outgoing water temperature with a candy thermometer and see if it is at the normal shutoff temperature it should be according to the manual, or if truly at the emergency shutoff temperature, which might be around 20-50 degrees hotter than normal operating temperature. That might give Noritz enough info to determine if it is a faulty temperature sensor, faulty regulating thermostat (which turns heat on and off) or bad board. Of course, another possibility is the board is overheating due to a factory defect in insulation letting too much heat get to it. Unfortunately, to make these units small, they commonly mount the controls in a hot location rather than having an externally mounted separate control unit - so overheating of circuit board elements is common. The same thing happens in furnaces, stoves, and clothes dryers.

Unfortunately, you are right - modern electronically controlled appliances and utilities are becoming as much an electronics technician job as a plumber or appliance repairman or HVAC tech job - and generally, troubleshooting is limited to check a readout or two on the board and then replacing the entire board or several parts in succession rather than finding the actual problem, increasing the repair cost.

In your case, if Noritz cannot help you, I guess you could try an electrician who is experienced in controls and instrumentation - commonly listed in yellow pages under Instrumentation and Controls, Home Controls, or Control Systems - companies like Granger and Honeywell, for instance. Another one I would try (first actually) is to find an HVAC contractor who has an instrumentation and controls tech on staff - commonly larger repair firms have one for furnace and A/C and whole-house controls issues.

One afterthought - I presume some bright installer did not wrap the tank with extra insulation, thinking to save energy, but is causing circuit board overheating ?

BTW - using the unit to the overtemp shutoff point will probably damge the board - by the time it shuts off if is probably nearing the danger point, so repeat use will likely cause irraparable damage to the circuitry.

Answered 6 years ago by LCD

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