כשהחימום לא עובד, החדר מתקרר מהר מאוד.

כשהחימום is made from כש + החימום.

• כש = when
• החימום = the heating

In Hebrew, short function words like כש often attach directly to the following word, so instead of writing them separately, you get כשהחימום.

So structurally, it is basically:

• כש = when
• החימום = the heating

Together: when the heating...

The prefix ה־ is the Hebrew definite article, meaning the.

So:

• חימום = heating
• החימום = the heating

and

• חדר = room
• החדר = the room

Hebrew usually adds ה־ directly to the noun, instead of using a separate word like English the.

Here החימום means the heating or the heating system, not necessarily a single heater.

It refers to the heating in a room, house, or building in a general sense. If you wanted to refer to a specific physical device, Hebrew might use a different word depending on the kind of heater.

So in this sentence, החימום לא עובד is best understood as:

• the heating isn't working
• the heating system doesn't work

Yes, עובד can mean works for a person, but it also means works / functions for machines, systems, or devices.

So:

• אני עובד = I work
• המחשב עובד = the computer works
• החימום עובד = the heating works

This is very natural Hebrew. In English we also say things like the machine works, so the idea is similar.

Because the subject is already stated: החימום.

Hebrew does not need an extra pronoun like it once the noun is present. So:

• החימום לא עובד = the heating does not work / isn't working

You do not need something like it after החימום. That would be unnecessary.

Yes. עובד is the masculine singular present-tense form.

Hebrew present tense often covers both:

• doesn’t work
• isn’t working

depending on context.

So החימום לא עובד can mean either:

• the heating doesn't work
• the heating isn't working

Also, Hebrew does not use a separate helping verb like English does here. Negation is simply:

• לא
  • verb

So:

• עובד = works / is working
• לא עובד = does not work / is not working

Because החימום is masculine singular, עובד matches it.

That is the normal way to negate a verb in Hebrew.

• עובד = works
• לא עובד = does not work

So לא simply comes before the verb or participle to make it negative.

This is very common and straightforward in Hebrew.

This is a very common question.

קר

קר means cold, which is a state.

• החדר קר = the room is cold

That describes the room’s condition, but not a change.

מתקרר

מתקרר means gets cold / cools down / is becoming colder.

• החדר מתקרר = the room is cooling down

This is what the sentence wants, because it describes a process that happens when the heating fails.

מקרר

מקרר usually means cools in the sense of causing something else to become cool, or it can also be the noun refrigerator depending on context.

So:

• החדר מתקרר = the room cools down
• המזגן מקרר את החדר = the air conditioner cools the room

In your sentence, the room itself is undergoing the change, so מתקרר is the right form.

מהר מאוד means very quickly.

• מהר = quickly / fast
• מאוד = very

In Hebrew, מאוד usually comes after the adjective or adverb it modifies:

• גדול מאוד = very big
• יפה מאוד = very יפה / very beautiful
• מהר מאוד = very quickly

So the word order here is normal Hebrew word order.

Yes, very normal.

The sentence is:

• כשהחימום לא עובד, החדר מתקרר מהר מאוד.

It starts with a time clause:

• כשהחימום לא עובד = when the heating doesn’t work

and then gives the main clause:

• החדר מתקרר מהר מאוד = the room cools down very quickly

This is similar to English:

• When the heating doesn’t work, the room cools down very quickly.

You could also reverse the order in Hebrew, just as in English, but this version is completely natural.

Because the sentence begins with a subordinate clause:

• כשהחימום לא עובד = when the heating doesn’t work

Then the main clause follows:

• החדר מתקרר מהר מאוד

In writing, Hebrew often uses a comma here, just like English does after an introductory clause.

A useful pronunciation guide is:

kshe-ha-khi-mum lo o-ved, ha-khe-der mit-ka-rer ma-her me-od

A more natural-flowing transliteration:

Kshehakhimum lo oved, hacheder mitkarer maher me'od.

A few pronunciation notes:

• ח is a throaty sound, like the ch in German Bach or Scottish loch
• stress is usually near the end in:
  • חימום → khi-MUM
  • עובד → o-VED
  • מתקרר → mit-ka-RER
  • מאוד → me-OD

It can mean either one.

Hebrew present forms often cover both the simple present and the present progressive, depending on context.

So:

• החימום לא עובד can mean
  • the heating doesn’t work
  • the heating isn’t working

In this sentence, English might choose either wording depending on the situation. Hebrew does not need to make that distinction explicitly here.

Yes.

• כש... = when
• כאשר... = when

Both are correct, but כאשר is usually a bit more formal or literary. כש is very common in everyday Hebrew.

So these are both valid:

• כשהחימום לא עובד...
• כאשר החימום לא עובד...

The version in your sentence sounds natural and conversational.