Breakdown of In der Eishalle hat das Kühlsystem komplett ersetzt werden müssen.
in
in
haben
to have
müssen
to have to, must
werden
to be (passive auxiliary + past participle)
Questions & Answers about In der Eishalle hat das Kühlsystem komplett ersetzt werden müssen.
Why are there two infinitives (werden müssen) at the end of the sentence instead of a past participle like gemusst?
This is due to the "double infinitive" rule. When a modal verb like müssen is used in the Perfekt tense along with another verb, it drops its normal past participle form (gemusst) and uses its infinitive form instead.
Why does the sentence use hat as the auxiliary verb? Doesn't the Perfekt passive normally use ist?
A standard passive sentence in the Perfekt does use a form of sein (for example: das System ist ersetzt worden). However, when you add a modal verb, the modal dictates the auxiliary verb for the whole sentence. Because all modal verbs form their Perfekt tense with haben, the auxiliary must be hat.
What dictates the specific order of the three verbs ersetzt werden müssen at the end of the sentence?
In a main clause that uses the double infinitive rule, the modal verb (müssen) is placed dead last. Immediately before it sits the passive infinitive (werden), and right before that is the past participle of the main action verb (ersetzt). You are essentially building the verb block backward: the action, then the passive voice marker, then the modal.
Why doesn't the past participle ersetzt have a ge- at the beginning?