Tested my bosch 250 sx with no gas hookup a2 error showed up.I s this possible wit no gas hookup yet?

http://www.bosch-climate.us/files/201109162028550.250SX_English.pdf

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

If you need further help, I’m available over the phone at https://www.6ya.com/expert/gene_9f0ef4df2f9897e7

Here's Bosch's A2 error code pdf:
http://waterheatertimer.org/pdf/Bosch_A2_error_code_troubleshooting.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.
http://waterheatertimer.org/How-to-install-gas-water-heater.html

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:
http://waterheatertimer.org/Troubleshoot-Bosch-Tankless-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

Thanks for stopping by:

A2 error on your Bosch water heater means "Fault in the flue gas limiter"

This can be caused by several things:
The gasket on the flue gas collector may be dislodged/leaking.
Check/Remove/Reseat the gasket.
It will not reset until about a two hour cool down.

Also - check the overheat sensor fuse wire - it may have gotten hot and melted the jacket and/or been dis-colored.

Finally - there is a retrofit kit "repair" that can be obtained by calling them directly.

1-800-642-3111 and request the "FLUE GAS LIMITER RETROFIT", Part NO. 8-700-400-032. This should solve many error code situations and get you on your way again.


Thanks for using FixYa!!

A2 is "fault in the flue gas limiter"
Open following link for 5 possible self-hep options before calling technician.
http://www.boschhotwater.com/HelpfulResources/TechnicalSupport/BoschAquaStarModels/2400ESTechSupport/Troubleshooting/tabid/1295/Default.aspx

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

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.

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.
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.

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...

Model????? The 635Es, 250SX and 2400E are same. The 2400ES and 2700ES are World 2 heaters. Any error codes as I can't imagine this problem w/o codes. Flow initiated but you have spark. Is there any ignition? If so flame rod may be bad and not reporting ignition. Igniter sets on some early 2400/2700 have proved to be bad. Water pressure has zero to do with this. If you have an EC or EA code you have gas problems (meter, line size/length or gas valve). Also if 3005 or 3007 Software you can pull the last 5-10 error codes from Controller.
You need to call Bosch and get an RSA out there. This is a gas appliance that if you screw up can destroy your house. FYI any water in the gas valve condemns it. It will not dry out and work correctly. Is the fan running at ignition and/or purge? Any Controller errors require replacement. You have 2 years on parts warranty from installation date so don't screw around trying to DIY. Warranty Labor is not covered.
Flue obstruction? If you used the AQ3 installation Kit you have the wrong termination box to prevent freeze up and/or water penetration You need the Z-Vent drop nosed termination. Look for a fine tan dust in the fan intake (brown plastic) the intake throat or in passageway to the gas valve. Call Bosch unless you're a Gas Tech this is beyond you.