ATAG fault code 78
Fault code 78 on an ATAG boiler (including I-series) means: Water pressure sensor out of range or not connected or, if water pressure OK: pump defective. Reset the appliance once. If the code comes back, a part is usually faulty, often a temperature sensor. You can check the water pressure and settings yourself; leave work on gas-carrying parts to a certified gas engineer.
After a safety alert (gas, flue gas, combustion), reset no more than once and call in a certified gas engineer. If you smell gas, call your national gas emergency number or 112 immediately.
Cause
Fault code 78 on an ATAG boiler indicates: Water pressure sensor out of range or not connected or, if water pressure OK: pump defective.
Fixing fault code 78: step by step
- Read the water pressure on the display or gauge. With the system cold it should be between 1.5 and 2 bar.
- If it is lower, top up to 1.5–2 bar with the filling valve or filling loop, then close the valve again.
- Bleed the radiators with a radiator key, then check the pressure again and top up if needed.
- Reset the appliance once. If the code comes straight back, do not keep resetting it.
- Does the pressure drop again within a few days, or does the code come back? Then there is a leak somewhere (radiator, pipe, pressure relief valve or expansion vessel) or the pressure or flow sensor is faulty.
Applies to
ATAG I-series, i20EC CW3, i28C CW4, i28EC CW4 with economiser, i32S, i36C CW5, i36EC CW5 with economiser.
Click a model for the parts list and exploded view of that appliance.
Matching parts
ATAG parts are available from Instalpunt; shipping to EU countries from €12.95 (€16.95 for more distant countries), usually 3–5 working days.
Parts per Atag-series: A Series · i Series (iCon) · Q Series · E Series · P-series (iCon) · Blauwe Engel · XL-series.
For fault code 78, the part involved is usually in the category: pump.
Based on the cause, these original ATAG parts fit (always check the type number of your appliance):
- Atag NTC return 10K € 40.77
- Atag NTC flow 10k icon € 57.08
- Atag connector outdoor sensor A € 21.75
Further reading on this cause
Other ATAG codes with the same cause
- 10 — Outdoor sensor fault (e.g. open, short-circuited, out of range)
- 102 — Pressure sensor defective
- 110 — Flow sensor fault (e.g. open, short-circuited, out of range)
- 112 — Return sensor fault (e.g. open, short-circuited, out of range)
- 114 — Outdoor sensor fault (e.g. open, short-circuited, out of range)
- 20 — Flow temperature sensor defective
Fix it yourself or call an engineer?
Always consult the manual for your appliance and work safely. If in doubt or if the fault comes back, call in a qualified professional. A question about a part? Write to us at info@instalpunt.nl.
Frequently asked questions
What does ATAG boiler fault code 78 mean?
Water pressure sensor out of range or not connected or, if water pressure OK: pump defective.
How do I fix fault code 78 on an ATAG boiler?
First check the cause described above. Then restart the appliance using the reset button. If the message comes back, a part usually needs replacing or the fault needs to be repaired by a qualified professional.
Which parts do I need for ATAG fault code 78?
That depends on the exact cause. In the ATAG parts overview at Instalpunt you will find the current price and stock for each part.
Can I fix fault code 78 myself?
You can reset the appliance and check things like the water pressure or settings yourself. Work on gas-carrying parts must be left to a certified gas engineer.
All ATAG boiler faults and codes at a glance →