Question about Bosch Water Heaters

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I have a Bosch confort 13 tankless water heater in my Mexico home. I have had problems with consistent water temperature. My contractor told me they have problems with them down there...not sure if it has to do with water pressure or a defective part.

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Your contractor understand the market there, but problems are mirrored in US also.
As evidenced by fixya.

1) Tankless cannot be exposed to more than 11 grains hard water, and require minimum water flow and water pressure or sensors will shut down burner or element.

2) For example, tankless might turn on with 2/3 gallon-per-minute water flow, but then another faucet is turned on so pressure and water flow drop, and tankless turns off. Or neighbor's water usage causes decrease in line flow, so tankless turns off. This is called 'cold water sandwich.'

3) If problem is water pressure, you can add in-line pressure tank, but root causes vary widely with more than one factor as suspect.

4) Also incoming water temperature can be a factor, along with temperature setting of unit. Most tankless are preset to 120 degrees F, which is modest temperature and certainly not very high. If tankless cannot raise temperature of incoming water fast enough, then tankless turns off. Of course water flow continues, so you get dose of cold water.
You can add simple120Volt 30 gallon tank-type electric heater as a tempering tank that pre-heats water either passively or actively:

5) Both internal and external factors affect tankless, with bottom line that these high-tech devices are not do-it-yourself repair for most people.

6) Install DIY tank-type gas water heater and avoid the whole headache

7) In my opinion, the genius of tankless is not that they save money or energy. Because they don't.
The genius is marketing that targets a certain affluent who believe tankless save money and energy.

Add a comment for more free help.
Also 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.

Posted on Mar 23, 2011


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Posted on Jan 02, 2017


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Hot water varies

I do not know how old this unit is or what model but many water heaters are not sophisticated enough to measure the temperature, but heat based on water flow and temperature rise. To start, tankless water heaters turn off every time you turn the hot water off. Lets use an example. You use the facilities, wash your hands then turned off the water and take a shower. You will bring the already heated water (from washing your hands) from the pipe up to the shower. Then the cold water that comes into the pipe from the reactivation of the water heater comes up the hot water pipe with warm then hot water just behind.

If this is not your problem, keep reading. Every unit I have been called to see were installed wrong. Check your installation manual to see if the problem with the system started with the contractor.

First, check the temperature of the water from the heater. If it is too hot and you are mixing too much cold water in, the unit will turn off because there is not enough water flow to keep it running.

Second, turn off the valve at the water heater and turn on the hot water at a faucet. If the water does not stop running, there is a "plumbing cross over" usually caused by a failing pressure balance valve in a shower.

Third, if the unit has not been serviced, go to to find a tankless water heating professional in your area. Totally Tankless LLC

Mar 14, 2014 | Bosch & Tankless LP Hot Water Heater

1 Answer

Bosch Confort S 13 BP tankless water heater won't ignite, It clicks but no gas going thru valve

The S 13 BP is a simple unit that does not have a pilot light. It uses electronic ignition on demand, which is what you hear clicking. If there is no gas going through and you've verified there is gas to the inlet, then it has to be the gas control valve.

Feb 01, 2013 | Bosch & Tankless LP Hot Water Heater

1 Answer

I have had Bosch 250 sx ng heater for the last three years with continuing problems maintaining consistent hot water. Either the unit will not heat up or during a shower when you add cold water to cool the...

Here's Bosch's A2 error code pdf:

Want the truth?
I answer Bosch, and other brand water heater questions at fixya.
Never, ever install a tankless water heater unless your wallet is 2" thick and you enjoy nuisance problems that you can occasionally fix yourself plus doing recommended continual maintenance.
Tankless with never pay back, otherwise the news would be filled with stories of people saving money. The only reports of savings comes from sellers of the product. Averages savings on gas bill is $1-8 per month, but all costs are energy.

I cannot recommend a solution to fix the Bosch problem if trained service reps cannot solve problem.
If other product-owners report same problem with that model, then problem is likely related to software and/or PB-board problems, which is same as saying your computer motherboard is no good. And most people know that when a computer motherboard has failures, then the computer is unreliable and should be replaced.
Always research a product before buying.
You can solve most tankless problem yourself, same day, no waiting for parts, Sept 2011, for about $350.

Sell the defect tankless for parts, or get up to $12 per 100 pounds for scrap metal at the recycler.
Other resources that you can read:

Sep 21, 2011 | Bosch & Tankless LP Hot Water Heater

1 Answer

Hi I have a Bosch water wizard 10p & although i have the heat turned up to the highest it is still not hot enough! I was wondering if there was another way of increasing the water temp?

Open following link for Bosch troubleshooting resources:

Typical Bosch 10P manual shows temperature control illustration on Pg4, and includes low water temperatures on troubleshoot on Pg6
Water flow rate too high, low gas pressure, faulty thermostat.

Two other things might be causing problem
Lime build-up

Jun 15, 2011 | Bosch & Tankless LP Hot Water Heater

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.

    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].
    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.
    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,

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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

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Bosch 2400E-NG output temp fluctuates

This is a great heater. It is however crucial that it be installed to every detail of the manual. If there is trouble send pictures to Bosch tankless you can call 1-800-283-3787 ask for Bosch Tech support or go to click find a contractor and call the closest Bosch Service Provider most will travel.

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