Question about Stiebel Eltron DHC 10-2 Electric Tankless Water Heater

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Hi, I just got my new DHC 10-2 today, the installation was easy but I have a problem. The problem is that heating is not constant. Once I mix the cold and hot water I should have an uniform temperature but that is not happening. The water becomes very hot and then, it becomes cold again. It is a cycle. Help please.

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This electric demand water heaters has one heater element. The flow switch turns it on. The thermostat cycles it on and off according to temperature. There is no medium.
You need to run the sink on hot while you take a shower. This kind of cancels out the savings on electricity.
Or get a higher flow shower head. Your screen on the shower head may be partially fouled.
Here is the brochure. It shows the flow rates for the different models.
http://www.stiebel-eltron-usa.com/sites/default/files/pdf/brochure-dhc.pdf

Posted on Dec 31, 2017

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3 Suggested Answers

6ya6ya
  • 2 Answers

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

Hi there,
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Posted on Jan 02, 2017

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SOURCE: The water heater "Stiebel Eltron

I am a free answerer, and I specialize in giving you resources for free
The paid answerers may have a person who knows your product and the problems associated with your model.
I believe they offer a refund if the 'fix' doesn't work.
The manual might also have troubleshooting.

Each day I see 20-25 unanswered questions about tankless water heaters.
And the day before, there were same number of unanswered questions about tankless products.
The number of questions shows the complexity of the machines, the brand-specific-ness of the problems, and the inability of the manufactures to take care of their customers.
If I understand correctly, the manufacturer will refer you to the installer.
There are not many ways a do-it-yourself-er can fix a tankless.

http://www.thetankatwaterheaterrescue.com/forums/forum3/

Posted on Oct 31, 2010

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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1 Answer

Why newly installed DHC 8 water heater not heating water.


hi, if this is a major domestic appliance installation issue you might be best served by getting a professional / qualified technician to look at it. There are safety concerns where such installations are involved. Investigating yourself might, in any case, invalidate any warranty you might have on the hardware concerned.
Good luck with this Brian

Jun 08, 2016 | Water Water Heaters

Tip

Find your only getting Luke warm water @ your faucets??


.

This is a common fault with new to used installed waterheater.

It is call a diptube ,made of pvc in part description. It is located on cold inlet,top of waterheater.

Malfunction of dip tube is usually a fracture caused by age mostly,or faulty install when new and tube was exposed to high heat from welding .

This tube allows the cold water supply to flow into W/heater and exit at bottom where it is heated while pushing already heated water to hot side and to your faucet. If this tube is defective ei...cracked the cold will [leak] mix with the hot before reaching bottom to be heat..thus lukewarm water syndrome. Solution $8 part H/depot>remove coldside copper fittings and pull white pvc out,about 4feet long,less rotted area, install new 3/4 inch pvc dip tube with flange up.

Thanks jj505 The HomeRepairman

jthomefix@gmail.com

on Apr 13, 2009 | General Electric GE SmartWater Household...

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How do i fix my stiebel eltron tankless electric water heater?It stop working..


Th easy fix would be installing a new heating element that has burned out. You don't say what size this tankless heater but if it stopped working entirely you might have just one heating element inside. You can test it by (1) turning off the circuit serving the heater, disconnecting one of the wires to the heating element, then taking an ohmmeter to see what the resistance of the element is. If it is "infinity" then it is open and burned out. Replace element. If it is around 6 ohms (for a 10kW heater running at 240V) then the heating element is OK. Unfortunately those heating elements don't last forever. Check the repair manual on how to replace the heating element.

Dec 07, 2014 | Stiebel Eltron DHC Instant Tankless...

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Will air in tankless water heater for in floor heating system cause the exhaust fan to speed up and give me an insufficient cold air /exhaust error?


I know that depending on what part of the country you live in, some areas can have there utility equipment out side the home not sure of your at but the exhaust must have a certain distance from the unit. If you exhaust threw a wall you should be fine. That being said I would check the inlet to make sure that you have good water flow there should be a small filter at the inlet for the cold water. You check and clean this anyway because you water was off. Then bleed the air out of the system. There are other things to check, but start there.

Mar 30, 2017 | Rinnai Water Heaters

1 Answer

My tankless water heater is not very old, but I have to depress the relay to make it heat water. It will depress on its own sometimes, then other times not at all. How do I adjust this?


Hi,
There is no adjustment for that... the thermostat is not telling the relay to pull in all of the time. I would replace the thermostat, I think you will find that it is your problem...

heatman101

May 09, 2011 | Stiebel Eltron DHC-E 10

1 Answer

I installed a dhc tankless heater, but when I open only the hot water everything is ok, but when I open the cold water at the same time the heater turns off.


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

Apr 10, 2011 | Stiebel Eltron DHC-E 8 Tankless Electric...

1 Answer

No hot water!! For some reason it is not heating the water!?


is the heating element still good. Was it on when no water was running thru it?

Jan 25, 2011 | Stiebel Eltron DHC-E 10 Electric Tankless...

1 Answer

When in the shower, the heat fluctuates from hot to lukewarm over a 10 second cycle. The water will not stay at a constant temperature.


this is usually a problem with all tankless water heaters.
the solution is to install a small buffer tank (5 or 10 gallon electric water heater) after the Rinnai. this will give the water something to mix in. it will solve your problem.

did you make sure to use a 3/4" gas line to the unit. not just 3/4" at the unit itself. sometimes when there is not enough gas, the unit will act funny and cycle from hot to warm or even cold. Make sure you check the gas line size, its very important.

Aug 10, 2010 | Rinnai Water Heaters

1 Answer

Boiler recycling when in DHC mode and water alternates hot then cold, back to hot every few minutes. Could it be pressure / flow rate.


First check pressure over 1 bar ok then-
1. check flow - is it adequate - a little less than the cold tap ok then -
2. does the boiler initially fire up on low hot flow but alternate as u say
If answers are 1. no but 2. yes then check for a furred up secondary heat exchanger
if 1. yes but 2. no [that is the water not the heating] goes hot / cold and if the boiler goes out when the water goes to cold then it's the diverter valve, either to replace or if it is one which has a internal diaphragm-replace that

Nov 25, 2009 | Water Heaters

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