Itho Daalderop fault code 21
Fault code 21 on an Itho Daalderop boiler (including AquaMax DV and Base Cube) means: Central heating water pressure too high. Reset the appliance once. If the code comes back, a part is usually faulty. 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 21 on an Itho Daalderop boiler indicates: Central heating water pressure too high.
Applies to
Itho Daalderop AquaMax DV, Base Cube, 24/35 (16L) cw 5, 30/35 (16L) cw 5, HR24 Tapklasse CW 4 black, HR30 CW5 black, HR36 Tapklasse CW 5+ black, HR42 25L black.
Matching parts
Itho Daalderop parts are available from Instalpunt; shipping to EU countries from €12.95 (€16.95 for more distant countries), usually 3–5 working days.
This message does not point directly to one faulty part. These are the parts that most often fit this appliance:
- Itho Daalderop service set gasket mixing chamber € 26.51
- Itho Daalderop sight glass for burner unit € 32.62
- Itho Daalderop service set test cap 5 pcs flue pipe sealing cap € 35.34
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 Itho Daalderop boiler fault code 21 mean?
Central heating water pressure too high.
How do I fix fault code 21 on an Itho Daalderop 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 Itho Daalderop fault code 21?
That depends on the exact cause. In the Itho Daalderop parts overview at Instalpunt you will find the current price and stock for each part.
Can I fix fault code 21 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 Itho Daalderop boiler faults and codes at a glance →