Bosch tankless water heater troubleshooting

SOURCE: A2 error on Bosch tankless water heater

1. Check continuity of the flue gas limiter (see Fig. 63, page 46 of manual). Go to steps two and three to determine air box temperature sensor fault and replace it.
2. Check for flue gas leakage around the top and bottom seals of heat exchanger as well as the viewing window.
3. Check that venting is within specifications (see Section 3.3 of manual). Long vent lengths, venting with more than three elbows, blocked vent or combination venting may cause this failure.
4. Check that flue gas limiter connector and spade connections are secure.
5. Unplug heater and check the two main plug connections inside the control board.

Posted on Jan 23, 2009

SOURCE: Bosch Pro tankless water heater overheating

The vent pipe you use is the correct size for the heater.Longer runs require bigger pipe.I also would check to see if the water is getting to hot.

Posted on Mar 16, 2009

Ned C Cook

• 3433 Answers

SOURCE: no hot water, pilot light lights but no burner ignition

Thermo coupler may be defective. it controls the main gas valve by closing main if pilot is out. make sure thermo coupler bulb is positioned over and near tip of pilot flame, but not in the flame. Thermo couplers are inexpensive and easy to change out.

Posted on May 06, 2009

Steven Foerst

• 52 Answers

SOURCE: i have a 250SX aquastar bosch tankless hot water

The 250 MUST have the condensate line connected. EC comes from gas supply problems and CO2 levels not being adjusted. LP units require 3/4" smooth gas pipe or 1" corrugated pipe minimum size. The LP regulator needs to be turned up to about 13 inches of water column and with all the gas appliances on, measure no less than 11 inches of water column. The CO2 levels must be measured by a qualified gas technician with a calibrated (with in 6 months) CO2 analyzer.

Posted on Apr 11, 2010

SOURCE: Bosch Tankless water heater. model AQ 250 SX

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

Posted on Aug 11, 2011