Remeha fault code H.01.21
Fault code H.01.21 on a Remeha boiler (including Avanta Ace) means: Flow temperature rises too quickly during domestic hot water mode. 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 H.01.21 on a Remeha boiler indicates: Flow temperature rises too quickly during domestic hot water mode.
Fixing fault code H.01.21: step by step
- Reset the appliance once; a one-off measuring error will then clear.
- Where you can reach it without opening the sealed combustion section, check that the sensor plug is seated firmly and the wiring is undamaged.
- If the code comes back, the sensor or its wiring is usually faulty (short or open circuit). Sensors in the sealed combustion section should be replaced by a qualified heating engineer.
Applies to
Remeha Avanta Ace, 24C CW3, 28C CW4, 35C CW5, Calenta Ace-Matic, 30C CW4, 35DS, 40C CW5, 40L CW6, Tzerra Ace-Matic.
Fault code H.01.21 on other Remeha series
The same code does not mean the same thing on every series. Check the rating plate to see which series you have:
- H.01.21 on Quinta Ace, 115, 160, 45, 65, 90: DHW TempGradLevel3 Maximum DHW temperature gradient Level3 exceeded.
- H.01.21 on Calenta Ace, Tzerra Ace, 24C CW3, 25DS Double Solo, 28C CW4, 28C Combi CW4: Heat exchanger temperature rises too quickly.
Matching parts
Remeha 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 Remeha-series: Tzerra Ace · Tzerra · Avanta Ace · Avanta · Calenta Ace · Calenta · Quinta Ace · Quinta.
This message does not point directly to one faulty part. These are the parts that most often fit this appliance:
- Remeha siphon gasket bottom for Calenta Ace and Avanta Ace etc. € 3.06
- Remeha gasket for gas/air unit (Calenta Ace and Avanta Ace etc.) € 5.77
- Remeha gasket D60 for Calenta Ace and Avanta Ace etc. € 8.84
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 Remeha boiler fault code H.01.21 mean?
Flow temperature rises too quickly during domestic hot water mode.
How do I fix fault code H.01.21 on a Remeha 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 Remeha fault code H.01.21?
That depends on the exact cause. In the Remeha parts overview at Instalpunt you will find the current price and stock for each part.
Can I fix fault code H.01.21 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 Remeha boiler faults and codes at a glance →