In Jainism, "Sajala Upvas" refers to a type of fasting where one abstains from all solid foods but is allowed to drink boiled water during specific times. "Pachkan" (or "Pachkhan") is the religious vow or resolve taken before starting any type of fast or religious activity, which specifies the rules and duration.

When to take Pachkan for Sajala Upvas:

• Pachkan for Sajala Upvas is generally taken early in the morning, before sunrise, and definitely before the prescribed time for starting the fast (usually before Navkarsi—the time for the first meal of the day in Jain tradition, which is about 48 minutes after sunrise).
• You should take Pachkan in front of a Jain idol or in your prayer area, with a clear intention and recitation of the appropriate vows.
• Once Pachkan is taken, you commit to only consuming boiled water (and that too, only during the permitted time window, usually between sunrise and sunset—never after sunset).
• If you need to clarify the exact time or ritual based on your sect (Shwetambar or Digambar), consult your local Jain Sangh or spiritual guide, as practices can vary slightly.

Summary: Take Pachkan for Sajala Upvas before sunrise and before consuming anything that day, preferably during your morning prayers and before Navkarsi.

If you have further questions about the process, rituals, or meaning, feel free to ask!