- Boilers
- Gas boiler
45
Immergas 45 on a gas boiler: high flow and return delta T
Risk level
Medium
Proceed carefully and stop if the check is unclear.
Urgency
Medium
Quick answer
Immergas 45 means a sudden jump in the temperature difference between flow and return, and the boiler limits burner output. Check the gauge reads 1 to 1.2 bar when cold and that the radiator valves are not all closed.
Safety first
Stop and check this first
- If you smell gas: Immergas says to close the meter or main gas tap and, if you can, the boiler's gas tap, open doors and windows, use no naked flames, do not smoke and do not touch switches, sockets, doorbells or phones. Leave the home and call your gas distributor's emergency number from the street.
- Do not open the boiler to touch the pump or its settings: Immergas says not to open or tamper with the appliance, and in Stand-by and Off modes it must still be treated as live.
Safe checks you can perform
- Pressure gauge reading when cold
- Radiator valves
- Fault list in the information menu
- Circulation, pump and return sensor check by the technician
Leave these tasks to a qualified professional
- Do not attempt this professional task: Water circulation
- Do not attempt this professional task: Pump settings and bypass
- Do not attempt this professional task: Return sensor
What a technician must be able to justify
Technician visit
These are the steps they must carry out and show you. Tick them as they work: if steps are skipped, do not accept a part swap.
These are not instructions for opening or handling the equipment yourself. They are the checks that should support a technical conclusion.
Water circulation
What they doThe technician checks that the pump runs and reads the pump flow rate (d 1.2) and its speed in the information menu.
They must show youthe flow rate and speed read.
In writingwhat was found and corrected.
Pump settings and bypass
What they doThe technician reviews pump parameters A3, A4 and A5 against the system requirements, and the bypass, which Immergas says guarantees minimum circulation in systems split into several zones.
They must show youthe values set.
In writingthe parameters before and after adjustment.
Return sensor
What they doThe technician compares the return temperature in the menu (d 0.7) with their own measurement and measures the sensor against the manufacturer's specification.
They must show youboth temperatures and the sensor measurement.
In writingthe measured value and, if the sensor was replaced, why.
Before accepting a part or repair
Nothing has been shown yet. Do not accept a part swap based on the code alone.
Follow these steps
Note: Follow the documented order. An error code identifies the affected system, but it does not prove by itself which part has failed.
Pressure gauge reading when cold
- Who:
- you.
- How:
- with the system cold, look at the boiler's pressure gauge needle. Immergas asks for 1 to 1.2 bar. If it is below 1 bar, first check that the mains water is at least 2.5 bar; if so, top up slowly with the filling tap underneath and close it when done.
- Result that matters:
- whether the boiler is short of water.
- If it was below 1 bar:
- lack of water fits; note how much you topped up.
- If it was 1 to 1.2 bar:
- rule out lack of water and go to the next check.
- Evidence to keep:
- a photo of the gauge before and after.
Evidence: Immergas Victrix Zeus 25/32, instrucciones y advertencias para instalador, usuario y mantenimiento (1.042022SPA)
Radiator valves
- Who:
- you.
- How:
- go round the home and check whether the radiator valves are open. Immergas asks for a check that they are not all closed.
- Result that matters:
- whether the water has somewhere to circulate.
- If nearly all were closed:
- open several; low circulation fits.
- If they were open:
- rule this cause out; the pump or the sensor remain, which the technician checks.
- Evidence to keep:
- a note of which valves were closed.
Evidence: Immergas Victrix Zeus 25/32, instrucciones y advertencias para instalador, usuario y mantenimiento (1.042022SPA)
Fault list in the information menu
- Who:
- you.
- How:
- press the information button for at least 1 second, step with the same button to d 0.8, which shows the last five faults, and note when E45 appears.
- Result that matters:
- whether E45 repeats and whether it appears with other codes.
- If E45 repeats:
- tell the technician; if it appears with E23, there is also a return sensor fault.
- If it appears once and does not return:
- note the date and time and keep an eye on it.
- Evidence to keep:
- a photo of the fault list and a note of dates and times.
Evidence: Immergas Victrix Zeus 25/32, instrucciones y advertencias para instalador, usuario y mantenimiento (1.042022SPA)
Circulation, pump and return sensor check by the technician
- Who:
- technician from an authorised company.
- How:
- checks that water circulates in the boiler, the pump settings and the return sensor.
- Result that matters:
- which of the three Immergas checks fails.
- If circulation or the pump fails:
- it is corrected and the pump set for the system.
- If the return sensor reads wrongly:
- it is repaired or replaced.
- Evidence to keep:
- a job sheet with the settings and readings.
Immergas reserves maintenance and repairs for an authorised company and tells the user not to open or tamper with the appliance.
Evidence: Immergas Victrix Zeus 25/32, instrucciones y advertencias para instalador, usuario y mantenimiento (1.042022SPA)
Still not solved
If the error persists, stop here. See what the technician must do and show you.
Where this code applies
A code is meaningful only inside the right product and version context.
Primary scope
- System
- Boilers
- Brand
- Immergas
- Product type
- Gas boiler
Known code variants
- E45
- Error 45 Immergas
- Immergas E45
- Victrix 45
- Victrix E45
What it means
On the Victrix Zeus 25/32, E45 is high delta T: the appliance detects a sudden, unexpected rise in the temperature difference between the flow sensor and the return sensor. To prevent damage to the condensing module, it limits burner output and returns to normal once the proper difference is restored. Immergas asks for checks that water circulates in the boiler, that the pump is set for the system and that the return sensor works. The code does not say which of the three is at fault.
Warnings and stop conditions
- Criticaleditorial warning
If you smell gas: Immergas says to close the meter or main gas tap and, if you can, the boiler's gas tap, open doors and windows, use no naked flames, do not smoke and do not touch switches, sockets, doorbells or phones. Leave the home and call your gas distributor's emergency number from the street.
Evidence: Immergas Victrix Zeus 25/32, instrucciones y advertencias para instalador, usuario y mantenimiento (1.042022SPA)
- Highsource verified
Do not open the boiler to touch the pump or its settings: Immergas says not to open or tamper with the appliance, and in Stand-by and Off modes it must still be treated as live.
Evidence: Immergas Victrix Zeus 25/32, instrucciones y advertencias para instalador, usuario y mantenimiento (1.042022SPA)
Symptoms and causes
Probable causes · in order
- Low water circulationPossible
Fits if E45 coincides with low pressure or with many radiator valves closed. Immergas asks you to check first that water circulates in the boiler.
Evidence: Immergas Victrix Zeus 25/32, instrucciones y advertencias para instalador, usuario y mantenimiento (1.042022SPA)
- Pump set incorrectlyPossible
Fits if E45 began after installation or a change of settings. Pump speed is set with the installer parameters A3, A4 and A5 and must not go below the minimum.
Evidence: Immergas Victrix Zeus 25/32, instrucciones y advertencias para instalador, usuario y mantenimiento (1.042022SPA)
- Return sensorPossible
Fits if circulation and the pump are fine and E45 repeats. Immergas asks for a check that the return sensor works correctly, because the difference is calculated with it.
Evidence: Immergas Victrix Zeus 25/32, instrucciones y advertencias para instalador, usuario y mantenimiento (1.042022SPA)
Virtual technician
Does 45 still appear after these checks?
Answer a few questions to narrow down the likely cause and the safest next action. Guidance only - it never replaces a professional.
Sources and technical references
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