1021Worcester Bosch
Worcester Bosch 1021: hot water temperature sensor defective
Checked against Worcester Bosch's own documentation: Worcester Greenstar 8000 Life installation and maintenance instructions: fault code table. Last reviewed October 2026. How we check
Engineer only
Worcester Bosch describes 1021 on Greenstar 8000 Life boilers as: hot water temperature sensor defective.
What you can safely do
There is nothing you can safely do yourself with this one. Leave the boiler off and book an engineer.
Before you book an engineer
- Write down the code exactly as the display shows it: 1021.
- Find your boiler's model name. It is usually on the front panel or in the user manual. The table below shows why it matters: Worcester Bosch codes can mean different things on different models.
- Note when it started and what the boiler was doing (heating, hot water, or starting up).
- If the boiler is still under warranty, check your warranty paperwork before you book anyone.
Call a Gas Safe engineer if
- Book a Gas Safe registered engineer.
Find a Gas Safe engineer near you
Opens the official Gas Safe Register search.
Applies to Greenstar 8000 Life. Codes can differ between models, so check your manual.