Question 1

The heater switches on but doesn't run (gas operation)

Accepted Answer

Possible cause: No 12V supply, or a window above the cowl is open.. Check the power supply is at least 10.5V, check the water heater's fuse, and shut any window that's above the cowl.

Question 2

The heater switches on but doesn't run, and the red lamp comes on (gas operation)

Accepted Answer

Possible cause: Cowl cover fitted, air in the gas supply, no gas supply, or incorrect gas pressure.. Take off the cowl cover and/or clear any blockage. Check the gas valves and gas bottle. Switch the appliance off for 5 minutes and back on to unlock it and purge any trapped air.

Question 3

The heater runs for a while, then the red lamp comes on (gas operation)

Accepted Answer

Possible cause: Over-temperature thermostat has operated.. Top up the water content if needed (close the drain valve first). Switch the appliance off for 5 minutes and back on to unlock it.

Question 4

The heater won't run once switched on (electrical operation)

Accepted Answer

Possible cause: No 230V supply voltage, or the over-temperature thermostat has operated.. Connect to the site's mains supply and/or check the residual current breaker. Top up the water content if needed (close the drain valve first). The electric heating element has its own excess-temperature cut-out - use the control panel to turn it off, wait 5 minutes, then turn it back on.

Question 5

The safety/drain valve is dripping water

Accepted Answer

Possible cause: Water pressure too high.. Check the water pressure doesn't exceed 2.8 bar - fit a pressure reducer if it's on mains water.

Question 6

Hot water comes out when the cold tap is opened

Accepted Answer

Possible cause: Hot water flows back through the cold water supply.. Fit a non-return valve on the cold supply as the installation instructions describe. If it keeps happening, contact Truma Service.

Truma Ultrastore Water Heater

Technical Specifications

Master Troubleshooting & Diagnostics Matrix

Also Fitted In

Error Code / Indicator	Symptom / Meaning	Possible Cause	Step-by-Step DIY Fix	Suggested Actions
`N/A`	The heater switches on but doesn't run (gas operation)	No 12V supply, or a window above the cowl is open.	Check the power supply is at least 10.5V, check the water heater's fuse, and shut any window that's above the cowl.	DIY Safe
`N/A`	The heater switches on but doesn't run, and the red lamp comes on (gas operation)	Cowl cover fitted, air in the gas supply, no gas supply, or incorrect gas pressure.	Take off the cowl cover and/or clear any blockage. Check the gas valves and gas bottle. Switch the appliance off for 5 minutes and back on to unlock it and purge any trapped air.	DIY Safe
`N/A`	The heater runs for a while, then the red lamp comes on (gas operation)	Over-temperature thermostat has operated.	Top up the water content if needed (close the drain valve first). Switch the appliance off for 5 minutes and back on to unlock it.	DIY Safe
`N/A`	The heater won't run once switched on (electrical operation)	No 230V supply voltage, or the over-temperature thermostat has operated.	Connect to the site's mains supply and/or check the residual current breaker. Top up the water content if needed (close the drain valve first). The electric heating element has its own excess-temperature cut-out - use the control panel to turn it off, wait 5 minutes, then turn it back on.	DIY Safe
`N/A`	The safety/drain valve is dripping water	Water pressure too high.	Check the water pressure doesn't exceed 2.8 bar - fit a pressure reducer if it's on mains water.	DIY Safe
`N/A`	Hot water comes out when the cold tap is opened	Hot water flows back through the cold water supply.	Fit a non-return valve on the cold supply as the installation instructions describe. If it keeps happening, contact Truma Service.	DIY Check / Tech Fallback