Maintenance
4 Maintenance
The vent system must be inspected at regular
1.Screened opening of the vent hood should be free from foreign material and cleaned as necessary.
2.Check all vent system connections for leakage and reseal where needed with high temperature silicone sealant. If any vent pipe component shows signs of deterioration, replace immediately.
3.Inspect for proper closure of the back draft flapper accessory. If the flapper does not properly close, there is a risk of freezing air coming across the heat exchanger which may cause the pipes inside to freeze and burst. This condition is not covered by the water heater warranty. See Fig. 11A for a properly closed
4.Conduct safety interlock test and operation of backdraft flapper once a year (Chapter 3.1.3).
Fig. 11A Properly closed backdraft flapper
5 Troubleshooting
5.1 Introduction
Many of the questions customers ask regarding operation of this unit can be answered by following the troubleshooting steps outlined below. Visit our website at www.boschhotwater.com for more detailed troubleshooting. For best results, perform each step before proceeding to the next.
5.2Power vent motor runs all the time or intermittently without water flow
1.The power vent motor is flow switch activated. If the internal paddle inside the flow switch is jammed, it may constantly send a signal to turn on the fan. Shut off water supply to heater and drain. Remove flow switch from water heater piping by removing clips on both ends. Flush water through both ends of flow switch to free up internal paddle and clear debris. After flushing, shake flow switch up and down. The internal paddle should be heard moving freely back and forth.
2.Large amounts of water demand can create pressure drops throughout the plumbing. This may allow for movement of the power vent flow switch and activate the fan. Activated sprinkler systems or flushed toilets are common causes for this symptom. Consult a plumbing professional to correct unintentional water flow through the heater.
3.In buildings with excessively high water pressure, a condition known as “water hammer” may exist. This condition is caused by a combination of high water pressure and the abrupt closing of a faucet valve or internal washer/toilet valve. This instant change in flow results in an instant change in the internal pressures in the pipe, which then sends a shock wave through the pipe. This physical shock will shake, rattle or cause a loud bang in the plumbing which is referred to as “water hammer.” Such a shock wave may cause movement of the power vent flow switch which will activate the fan. Consult a plumbing professional for the use of a pressure reducing valve, expansion tank or water hammer arrestor to combat this condition.
Fig. 11B Improperly closed backdraft flapper
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