Question about Stiebel Eltron DHC Instant Tankless Electric Water Heater

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I have a Steibel tankless water heater. The temperature of the water changes from hot to cold each 3 to 4 minutes.

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6ya6ya
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SOURCE: I have freestanding Series 8 dishwasher. Lately during the filling cycle water hammer is occurring. How can this be resolved

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Posted on Jan 02, 2017

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kel1guy2002
  • 3740 Answers

SOURCE: I installed a dhc tankless heater, but when I open

Hi and welcome to FixYa, I am Kelly.

What is happening is that your cold water flow is greater in volume (gals per min) than your hot water. So when you open the cold water it is mixing with the hot water inside the faucett or shower plumbing and actually reverse flowing back into the hot water heater plumbing. The reverse flow slows the water flow sensing turbine inside the heater and it is thinking that there is not any water flow. (There isn't actually due to the equalization of water pressure when you open the cold water faucett) Since this is a safety feature of the tankless heater to keep it from overheating, it shuts off.
Somewhere in the hot water plumbing there is a major restriction. It may very well be the internal plumbing of the tankless hot water heater or the flow detector design.

There are 2 ways to correct this. The easy way would be to restrict the available cold water flow. You can do this by installing another shut off valve inline with the cold water plumbing and just not open the valve all the way. You would have to adjust the setting so that the hot and cold water can be on at the same time and the hot water heater stays on. The hard way is to locate the hot water flow restriction and eliminate it.
It is possible.... if you have a flow restrictor in a shower head or a screen in a faucett areator that they are partially clogged. Clean any flow restrictors and screens then see how the hot water heater performs before you start modifying plumbing.

Thanks for choosing FixYa,
Kelly

Posted on Apr 10, 2011

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  • 6 Answers

SOURCE: No hot water in our tankless water heater

Take off front cover, on the top of the two cylinders in there (the heating system) there will be a small red button. That is the Safety Thermal Cut out, depress that red button. It is similar to a circuit breaker. If the red LED comes on when you turn on hot water at a sink then that was the problem. I have on that trips periodically. Its annoying but not enough to replace the part yet. Good luck.

Posted on Dec 06, 2011

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I keep getting a code 13 and no hot water after about 3 min. Vent is clear??


Undersized gas line?
Temperature set too high?
Haven't kept up with regular maintenance?
Tankless older than 5 years?
Hard water over 7 grains?
http://waterheatertimer.org/Troubleshoot-Rheem-Tankless-water-heater.html

Gene

Sep 17, 2014 | Rheem Richmond Encore Tankless LP Gas...

1 Answer

Error c4-15 what does that mean


Before calling service technician, copy following link for troubleshoot resources:
http://waterheatertimer.org/Troubleshoot-Rheem-Tankless-water-heater.html

C4 can range from failed PC Board to lime build-up inside heat exchanger
Error 15 is 'heat exchanger is too hot', clogged heat exchanger, restriction in cold water inlet, temperature set point too high.
If you recently changed temperature setting, then that might be cause.
Tankless require monthy-to-yearly maintenance to avoid common error codes.
Delime tankless and clean water filter, keep temperature low.
Never install tankless water heater is best way to avoid complications of expensive water heater that is maintenance heavy, hard to diagnose, expensive to fix, etc.
Never expose tankless to more than 11 grains hard water.
http://waterheatertimer.org/pdf/Rheem-CondensingTankless-maintenance-2012.pdf
http://waterheatertimer.org/pdf/Rheem-De-lime-tankless.pdf

Aug 26, 2012 | Rheem Tankless Hot Water Heater...

1 Answer

Rheem rte13 standby (green) light not on


You might have crossover problem caused by bad faucet cartridge.
http://waterheatertimer.org/Crossover.html

The green standby light should come on when 240Volt power is applied. Page 6 manual.
Both red lights should come on when tankless is activated. Page 6 manual

RTE 13 requires 60 amp breaker and 6 gauge wire
http://waterheatertimer.org/How-to-wire-Tankless-electric-water-heater.html
http://waterheatertimer.org/pdf/Rheem-TanklessElectricUC_AP15447.pdf

Factory temperature setting is usually default 120 degrees.
Adjust temps page 11 manual
Thermostat calibration is always approximate.
120 degrees is not hot enough to burn the skin.
Exceptionally cold incoming water temperature can cause tankless not to heat enough hot water: install tempering tank to preheat water to room temperature.
Tankless cannot be exposed to more than 11 grains hardness in water. Delime tankless yearly, clean water filter monthly, do not install low-flow restrictions or conserve water since the flow rate must remain high for tankless to activate.
Rheem does not post service manuals for their tankless water heaters.
Call Rheem 800 432-8373

Aug 05, 2012 | Rheem Tankless Hot Water Heater...

1 Answer

Our rheem pronto tankless rutg-74xp red light will come home indicating hot water and stay on about 2 minutes and then turns off we have turned off and back on and let water run for 5 minutes and will come...


Before calling service technician, open following link for Rheem troubleshooting resources.
http://waterheatertimer.org/Troubleshoot-Rheem-Tankless-water-heater.html

List of causes MIGHT include one of following:
Bad household circuit breaker that powers electronics, or loose wire inside outlet where tankless plugs in.
Tankless fuses and control board.
Water flow rate too low. Minimum .8 gallon required (depending on model)
Tankless inlet filter clogged.
Household aerators clogged at faucets.
Crossover at single-handled faucet
If installed, there can be crossover at mixing valve.
Faulty household check valve, including check valve on re-circulation system if that system is installed.
Restriction in household water line, such as clog at elbow.
Unequal pressure in household hot and cold lines, caused by restriction in hot line. When single-handled faucet turns on, the cold water pressure is higher so hot does not flow and tankless will not turn on.
Loose wire connection inside tankless.
Unit temperature set too high.
Unit temperature set too low.
Water temperature is very hot coming out of tap, so more cold is added, but that reduces amount of hot water flow, so tankless turns off because flow rate is too low.
On some tankless, if water is preheated by solar or other indirect source, the burner will not activate.
High mineral content in water > delime tankless yearly
Misaligned temperature sensor
Low gas pressure. Wrong type of gas. Undersized gas line.
Too many faucets on at same time.
Faulty tankless water valve. Water valve stuck.
Fluctuating household water pressure, for example MUD and PUD district water pressure problems or water well pressure.
Faulty household pressure reducing/regulating valve if installed.
Faulty household pressure tank, if installed -or- pressure tank needs to be installed.

Apr 24, 2011 | Rheem RTG-74PVN-2 Natural Gas Pronto Whole...

1 Answer

Hot water tank does not work when shower is on, it does however work when the faucet in bathroom is on. It quit working in the shower about a month ago.


  1. COLD MIX, HEATER DEACTIVATES
    If inlet water temperature is over 70°F due to geographic location, water maybe very hot out of the tap. This requires a lot of cold water to be added with it in order to attain a useable hot water temperature. The addition of too much cold water will overpower hot water demand from the tankless water heater. This slows the flow within the tankless water heater, decreasing it below activation point, which shuts off the heater. The end result is nothing but cold water coming out of the outlet. See: TWH E2-04 Overcoming fluctuating temperatures [PDF].
  2. FLUCTUATING WATER PRESSURE
    If the water pressure in the home is erratic and the water flow is not consistent while a tap is opened, then the temperature of hot water will fluctuate. The minimum water pressure for the home should be 30psi or greater. For people on well systems the minimum pressure range is 30-50psi. The use of a pressure reducing/regulating valve is an effective way to maintain constant water pressure to the water heater. Watts brand 25AUB- ¾" or N35B-¾" pressure reducing/regulating valves or equivalent is suggested.
  3. CHANGING FLOW RATE
    Major changes in flow rate can adversely affect the output water temperature of the heater. Increases from one major fixture running to multiple fixtures running at one time can cause the temperature to fluctuate. Stay within the heater's specifications. See: TWH E2-03 Outlet temperature vs. flow rate [PDF].
From the Bosch website.

Good Luck,
Gary

Dec 16, 2010 | Bosch PowerStar AE125 AE125 Whole House...

3 Answers

Water turns cold very quickly


I had the EXACT same problem (installed my tankless last winter and worked fine, now this summer it fluctuates, have to turn the shower completely off and then on again to get any hot water and then it only lasts for a couple of minutes!) Argh - it is frustrating!

Here's what I found: the demand for hot water is lower during the summer (hot) months because the "cold" water coming in is already quite warm. You don't need as much hot water to make the shower temp comfortable. SO, my tankless was shutting off due to low flow demand. I've removed the flow restrictor from my shower head and it helped alot but didn't completely solve the prob. Next step is what has been recommended to me by several people but is much more expensive - change the pressure valve on your shower to a temperature valve. Or just wait til winter and it should work ok again :)

Jul 06, 2010 | Bosch & Tankless LP Hot Water Heater

1 Answer

Bosch tankless hot water heater: Confort TOO HOT!!!


Look for a water temp control on unit. Otherwise a lower temp can be attained by having a higher water flow to minimize temperature buildup in heating coil.

Sep 06, 2017 | Bosch & Tankless LP Hot Water Heater

1 Answer

Fluctuating temperatures


Sounds like there is not enough flow in order to keep the burner in the heater firing continuously

Jul 09, 2009 | Rinnai Webstone The isolator EXP tankless...

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