Bosch gas instant hot water system troubleshooting guide

Have you been experiencing problems with your Bosch gas hot water? Using the various manuals, we've put together this guide to help identify issues you might be having and get things working again.

If you need expert help with Bosch hot water system problems or repairs in Southern Sydney & Sutherland Shire contact Everyday Plumbing & Gas today.

Bosch Hydro Power: Problem ➾ Cause ➾ Solution

Problem	Cause	Solution
Fluctuation in hot water temperature	Insufficient flow through the hot water unit Tapware does not give sufficient flow	Increase water flow by opening multiple hot taps. If fluctuation ceases then check for blockages, aerators dirty etc. Change tapware to meet requirements
Unit not working (no hot water)	Locked out due to failure to ignite. The ignition will lock out after 20 seconds if a flame is not established.	Turn off all hot water taps and retry. If unit still does not work - isolate valves at unit for 20 seconds. Open valves and retry. If unit still fails to ignite refer to qualified technician.
Unit not working after change in Gas Supply (Maintenance work on Mains or change of LPG cylinders)	Air in gas lines	Turn on hot water tap inside house. Isolate water valve at unit for 20 seconds. Open valve and check if unit lights. Repeat this operation 3-4 times, if unit still fails to ignite, call a qualified technician.
Not hot enough	Insufficient Natural Gas supply Consumer gas and water controls Gas Cylinders may be empty / undersized (45kg cylinders recommended for LPG).	Requires a service technician to inspect and test gas supply pressures / recommission Adjust gas and water controls
Smell of gas	Gas leak	Isolate gas supply to hot water unit / premises Call your gas retailer or a qualified technician
Temperature too hot in summer	Incoming water temperature has increased with the ambient temperature and gas control is on hot position (fully right)	Adjust water and gas controls at the unit to achieve desired temperature
Temperature too cold in winter	Incoming water temperature has decreased with the ambient temperature. Gas control is on warm position (fully Left).	Adjust water and gas controls at the unit to achieve desired temperature
Reduced water flow	Insufficient water supply pressure Dirty taps or mixers Water valve blocked (filter) Heat exchanger blocked (limescale)	Requires a service technician to inspect and test water supply pressures, and water components of the hot water unit
Unit makes a loud bang when igniting	Explosive ignition is not normal behaviour	Call a qualified technician
Presence of soot / black marks observed at top of flue / on wall	This is not normal behaviour This is normally caused by blockages in the burner causing poor combustion One of the causes of blockages is insects blocking burner orifices, this cannot be avoided as adequate airflow is required for complete combustion	All gas appliances require adequate airflow for proper combustion. The ingress of insects or dirt into the unit are not covered by warranty as a manufacturing fault is not present. The unit will need cleaning and servicing at the owners’ cost. To minimise the chance of the issue recurring, a surface type insecticide can be used with care, consultation with a licensed pest controller is recommended. Isolate the valves to the unit and spray surrounds with a surface spray. Leave for 15 minutes before turning hot water on.
Water takes a long time to reach hot taps	Location of unit	If the unit is located a long way from the outlet there will be an amount of cold water that has to leave the pipe before the hot water is available. As the hot water unit does not operate at a large flow rate this may appear to take a long time, particularly if it has replaced a mains pressure storage heater. Open hot tap to full to increase flow rate and reduce time

Bosch Pilot Light Ignition: Problem ➾ Cause ➾ Solution

Problem	Cause	Solution
Appliance does not light	Gas supply turned off Appliance blocked	Check mains gas supply is turned on at mains / cylinder supply. (Are other gas appliances working?) Is the gas isolation valve turned on at appliance? Requires a service by a qualified technician
Pilot lights but no main burner	Main burner button not pushed in Water throttle wound out too far Service required	Push in, refer to relight section Wind clockwise, refer to temperature adjustment section Contact a qualified technician
Smell of gas	Gas leak	Isolate gas supply to hot water unit and contact a qualified technician
Yellow flame / strong smell of gas in operation / presence of soot	This is normally caused by blockages in the burner causing poor combustion One of the causes of blockages is insects in the burner	All gas appliances required adequate air flow for combustion. The ingress of insects or dirt into the unit are not covered by warranty, as a manufacturing fault is not present. The unit will require cleaning and servicing at the owners cost. To minimise the chance of the issue recurring, a surface type insecticide can be used with care, consultation with a licensed pest controller is recommended Isolate the valves to the appliance and spray surrounds with a surface spray Leave for 15 minutes before relighting
Not hot enough	Insufficient gas supply (pressure / pipe sizing) Consumer gas and water controls LPG gas cylinders may be empty / undersized	Requires a service technician to inspect and test gas supply pipes / pressures and recommission Adjust gas and water controls, refer to temperature adjustment section
Temperature too hot in summer	Incoming water temperature has increased with the ambient temperature	Adjust gas control slide to the left
Temperature too cold in winter	Incoming water temperature has increased with the ambient temperature	Adjust gas control slide to the left
Fluctuation in hot water temperature	Insufficient flow through the hot water unit Tapware / shower head does not give sufficient flow or blocked Appliance temperature set too high	Change tapware to meet requirements Check for blockages of aerators/ restrictors Adjust gas control slide to the left
Reduced water flow	Blocked tapware Insufficient water supply pressure Blocked water feature Heat exchanger blocked (limescale)	Check for blockages Requires a qualified technician to inspect supply pressures and water components of the hot water unit
Hot water takes a long time to reach hot taps	Location of appliance	The further from a hot tap, the longer it takes for hot water delivery. Relocate appliance closer to hot tap.
No hot water	Pilot light off	Relight pilot light, refer to relighting section

All troubleshooting information and instructions can be found in the Bosch Owner’s Guide and Instructions.

Reference: https://www.bosch-thermotechnology.com.au/au/en/residential/trade/installation-manuals/