Question about Rheem Tankless Water Heater Main Remote Control

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No hot water from tankless water heater. Rheem UMC-117 Control panel normally reads 120 degrees. Now digital readout is blinking with what I suspect is a diagnostic code: c7 76 If I power it off and then power back on, it reads 120 degrees for about 3 seconds before it begans to blink with the above code. So what does this code mean? This natural gas unit has been in service for about 2 years and this is the first problem we've experienced with it.

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Please find above the link to download all the manuals, you will need to understand your WH.
This problem is usually associated with the Thermistor, and or Thermostat. These units are also prone to power surges and spikes, causing the main Board to fault.
However as for an exact explanation, unfortunately this isn't revealed. However this link below, copy/paste to browser, will show you every feature and what to do for your WH.

It is my professional opinion, & due to the danger involved, these types of Units MUST be attended to by a professional. In fact, it is actually against the Building Code, in USA, to "Self Service" Gas appliances, simply due to the possibility of something going wrong with the gas side of things.
Also when a professional is used, it assures a professional job, and so then gives peace of mind, that all is well, and your family is safe. As safety is always our prime consideration. So please be careful.

Posted on Sep 29, 2010

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Posted on Jan 02, 2017

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Thermostat model UMC 117 keeps coding C7 why?

Generally, C7 is communication problem with remote
Error codes are considered start point for troubleshoot.
Causes can be: Bad remote, bad wire to remote, loose wire connection at remote, loose wire connection at unit, bad PC board.
In no particular order:
Check wire connections.
Disconnect remote and let water heater control temperature at default 120 degrees F, and if no further problem develops, then that might eliminate PC board as source of problem.
Replace wire to remote.
Replace remote.
Call service technician to diagnose problem.
Contact Rheem about PC board and other options.

Before calling service technician, open following links for troubleshooting resources:

Aug 14, 2011 | Rheem Tankless Hot Water Heater...

1 Answer

Have a rtg66dvn wont fire up led blinks 4 times intermittently. My umc-117 remote will not power up? Does this have a battery? Please tell me what can be the problem... thanks

Before calling service technician, open following link for Rheem troubleshooting resources including link for Rheem chat. They require model and serial number and may ask for the person that installed unit, and current service technician working on problem.

Normally you get error 76 when remote cannot communicate with tankless unit.

Use and care manual says do not take apart remote control.
The remote is connected to water heater with a wire, max distance 195 feet, so there is no battery.
Check that outlet supplying power to tankless is working.

New UMC-117 remotes sell for about $99.00.

The symptoms on your tankless could be anything from loose wire to bad PC board, or innumerable other issues including bad sensors. Or it could be something very simple. The same problem on your tankless unit might have different cause and solution than another tankless unit because so many internal and external factors affect these sophisticated machines.

Read your use-and-care manual and make sure that maintenance is done regularly. For example water filter needs to be cleaned monthly and heat exchanger de-limed yearly. The manual is fairly long but should be read entirely to best understand the complexity, and general advisories.

Upvote the help.
And take advantage of fixya expert assistance live.
For a price, expert works with you while you work on water heater or any do-it-yourself project.
Fixya is always less expensive than a service call.

May 13, 2011 | Rheem Tankless Water Heater Main Remote...

1 Answer

Why is the controller UMC-117 keeps blinking c8?

C-8 error codes could mean anything from the fan not starting, a bad control board, or a blown capacitor. Best bet would be to call Rheem customer service and they'll ship part or suggest licensed contractor to troubleshoot and replace what's necessary.

Open following link to view fixya questions on 1 model of Rheem tankless
Some older questions have information that is useful, and varied

Open typical manual to review required regular maintenance for tankless on page 29
The word maintenance is used throughout manual, indicating that tankless are a yearly budget nuisance

All costs are money.
You can also add simple tank-type water heater that can be turned on when tankless is on the blink.

Mar 02, 2011 | Rheem Tankless Hot Water Heater...

1 Answer

The UMC-117 shuts off during water heat up. What

overheat stat first then check fan best of luck

Oct 10, 2009 | Rheem Tankless Hot Water Heater...

2 Answers

Rheem tankless shuts down on it's own.

Check to make sure wire is solid copper thermostat wire and not stranded

Aug 15, 2009 | Rheem Tankless Hot Water Heater...

1 Answer

No hot water from tankless water heater. Bliniking Readout

This is there website.Above.
Use the live chat to ask them, the code you listed does not seem to correspond to there code list, the only code that does is code 76,
which is a problem with the remote control not talking to the unit.
So your best bet is to tell them the error.

Apr 07, 2009 | Rheem Tankless Water Heater Main Remote...

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