L'impianto termico include la pompa di calore.

Because Italian usually shortens the singular definite article before a vowel.
So il + impianto becomes l'impianto.

This is called elision. The apostrophe shows that a vowel has been dropped.

Other examples:

• l'amico
• l'ufficio
• l'acqua

In this context, impianto means something like system, installation, or plant in a technical sense.

So impianto termico is not an implant. It refers to a heating/thermal system, especially in a building or engineering context.

In Italian, adjectives often come after the noun, especially technical or classifying adjectives.

So impianto termico is the normal way to say thermal/heating system.

Putting the adjective first is usually less neutral and often sounds unusual here.

Because adjectives in Italian must agree with the noun they describe.

Here, impianto is:

• masculine
• singular

So the adjective must also be:

• masculine
• singular

That gives termico.

If the noun were feminine, you would use termica. For example:

• una pompa termica

Include is the present indicative, third person singular of includere.

Here the subject is l'impianto termico, which is singular, so the verb means includes.

A few forms of includere:

• io includo
• tu includi
• lui/lei include
• noi includiamo
• voi includete
• loro includono

Yes. It is a clear cognate of the English verb include.

That makes it easy to recognize, but remember:

• it follows Italian conjugation
• it is pronounced the Italian way
• here it means includes, not the infinitive to include

So in this sentence, include is a finite verb, not a dictionary form.

Italian uses articles more often than English does.

Here, la pompa di calore refers to a specific item or component in the system, so the definite article is natural.

English might sometimes say just heat pump, but Italian often prefers the article with nouns in normal sentences.

If you wanted to introduce it as a non-specific item, you could say:

• una pompa di calore

Because pompa di calore is the standard term for heat pump.

Here, calore is part of a fixed expression, not a reference to specific the heat.
So Italian uses di, not del.

• di calore = part of the compound term
• del calore = of the heat, which would mean something different

More or less, yes. Literally it looks like pump of heat, but the natural English equivalent is heat pump.

This is very common in Italian: English compound nouns are often expressed as:

noun + di + noun

For example:

• pompa di calore = heat pump
• bottiglia d'acqua = water bottle

So even if the structure looks different from English, it is completely normal Italian.

Yes, often you could.

Comprende can also mean includes or comprises.
The sentence would still be grammatical:

L'impianto termico comprende la pompa di calore.

The difference is mostly one of style:

• include is very close to the English cognate and sounds fine in formal or technical language
• comprende can sound slightly more formal or more like comprises

Yes, but the emphasis changes.

The original sentence:

L'impianto termico include la pompa di calore.

is the most neutral way to say it.

A different version could be:

La pompa di calore è inclusa nell'impianto termico.

That means roughly the same thing, but now the focus is on the heat pump, and the structure is passive.

So the original is usually the clearest and most straightforward version.