What antifreeze can I use in the ZWB 42-3 without voiding the warranty?
Only antifreeze that has been approved by BTC can be used without voiding the warranty. You should check your installation manual for the list of approved antifreeze options, as using unapproved antifreeze will void the warranty coverage.
From the official Bosch ZWB 42-3 Condensing Boiler manual, page 2
Have a follow-up question?
Answers from the official manual.
Common questions