Need manual for AQ 250 SX NG

The following link has general troubleshoot steps for Bosch A2 error
http://waterheatertimer.org/pdf/Bosch_A2_error_code_troubleshooting.pdf

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Before calling service technician, open following link for Bosch troubleshooting resources including Bosch contact number and possible manual:
http://waterheatertimer.org/Troubleshoot-Bosch-Tankless-water-heater.html

Tankless water heaters require yearly maintenance to check gas pressure, inspect and clean burner and combustion parts, inspect vent and vent drain, clean air filter, check water flow, de-lime the heat exchanger etc.
This maintenance can stop ordinary problems from occurring, and can be done by the homeowner by reading Bosch service manuals for specific model number.
The continual maintenance, and cost of repairs and parts, and cost of professional service are more expensive than expected $1-8 monthly energy savings from owning tankless.

Fix most tankless problems yourself, same day, for about $350.
http://waterheatertimer.org/How-to-install-gas-water-heater.html

Error codes F1 and F2 do not show among common error codes.
Call Bosch 1-800-642-3111

Before calling service technician, open following links for Bosch troubleshoot resources:
Error codes are considered start-point for troubleshoot.
Multiple error codes can indicate PC board failure.
http://waterheatertimer.org/Troubleshoot-Bosch-Tankless-water-heater.html
http://www.boschhotwater.com/HelpfulResources/TechnicalSupport/BoschAquaStarModels/250SXOTechSupport/Troubleshoot/tabid/569/Default.aspx
http://forms.boschhotwater.com/Home/BoschTechSupportForm/tabid/614/Default.aspx
http://www.boschhotwater.com/HelpfulResources/TechnicalSupport/BoschAquaStarModels/250SXOTechSupport/ServiceBulletins/tabid/573/Default.aspx

Q. EC - Ionization failure during operation
A.

1. Verify gas type (See Fig. 2 in installation manual) corresponds with the type of gas supplied to the heater.
2. Verify the three yellow wire connections to the set of electrodes (underside of the burner assembly) are secure.
   
3. Verify that venting meets specifications per chapter 3.6 of the installation manual. Improper venting may cause premature failure of the flame sensor rod.
   
4. Check gas pressure. See Bulletin TWH-G2-03.
   
5. Check and adjust CO2 readings. See Bulletin TWH-G2-12.
   
6. Gas valve or flame sensor may be damaged. Call Bosch Water Heating with observations and results of previous steps.

BOSCH error codes:
http://www.boschhotwater.com/HelpfulResources/TechnicalSupport/BoschAquaStarModels/2400ESTechSupport/Troubleshooting/tabid/1295/Default.aspx

Best place to start is troubleshoot section in manual. Page 24
http://www.boschhotwater.com/Portals/7/TechManuals/250SX_English.pdf

Problems range from air supply, gas supply, venting, part failure or combination of listed things.
Don't forget, tankless require yearly maintenance, outlined in manual, and cannot be exposed to more than 11 grains hardness in water, and should be de-limed each year.

All costs are energy.
I suggest reading entire manual several times, so you are pro about your tankless water heater.
Even with this knowledge, trained service technician will have to be consulted some day, and tankless should never be installed if factory trained technician not available in area.

Bosch has online tech support form:
http://forms.boschhotwater.com/Home/BoschTechSupportForm/tabid/614/Default.aspx

Install tank type water heater that can be put online when Bosch is not working
http://waterheatertimer.org/How-to-install-gas-water-heater.html

Add a comment for more free help.
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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.

1) Error code A2 shows on following link:
http://www.boschhotwater.com/HelpfulResources/TechnicalSupport/BoschAquaStarModels/2400ESTechSupport/Troubleshooting/tabid/1295/Default.aspx

2) Open following link for Bosch tankless troubleshooting resources, including Bosch contact information, typical manuals, error codes, tech support, parts, fuel-saver calculator, service bulletins, water heater forum, fixya links, disclaimers, and links for finding service technician.
http://waterheatertimer.org/Troubleshoot-Bosch-Tankless-water-heater.html

3) As a general rule, tankless are best when installed by experienced, trained technician.

4) This is partly because Tankless manufactures refer you back to installer when there is a problem, and party because so many factors affect tankless operation.

5) Tankless require perfect alignment of factors to work properly, including vent, air supply, gas supply, combustion maintenance, water flow, water pressure, water quality, overall maintenance, plus internal parts working in harmony.

6) Read manual cover to cover, make sure tankless receives yearly maintenance as outline in manual.

Add a comment with your experience so others with same-similar problem can benefit.

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.

Depending on what part is being replaced, it may sound high but the gas valve is about $300 and the water valve about $200 street price. its also a time consuming job.

Had same problem on my five year old water heater (ec error). Didn't figure it was a gas supply problem after five years but double checked to see if the gas bill was paid. It was.

Cleaned the contacts on the two sensors that are clamped to copper pipes inside. Still had error after powering up. Held the error button in for about five seconds, and the blinking EC code went away.

BOSH AQ 250 On demand propane water heater ran out of propane, got gas now, but get EC flashing on the display and the unit won't fire? Lost manual, any suggestions. Thanks, Jim

Open up the front cover - look at the printed curciut board and see if you have two or three capacitors that the tops are slightly raised...if so, those capacitors on the board need to be replaced...they should be competly flat.

HTH,

Mike...