We recently bought a 100-cup urn for our Chabad House. It only has an on/off switch. Can we use it on Shabbos?

 

Question:

We recently bought a 100-cup urn for our Chabad House. It only has an on/off switch. Can we use it on Shabbos?

 

Answer:

Generally, it is recommended to have a Hechsher on urns with a thermostat for Shabbos use, as there might be an issue with removing hot water from the urn, causing the remaining water inside to cool off faster, ultimately effecting the urn to boil faster.

However, I should mention that there are some inconclusive tests that suggest that even urns with thermostats do not act in such a way. They have proven that the heating element doesn’t use more power or get activated sooner.

See also here (Paragraph “Does Removing Water Cause the Urn to Activate”).

Regarding using urns which have a gauge indicating how much water there is – see here:

Halacha2go.com #520: Using an Urn with a Measuring Gauge on Shabbos מ”מ

 

Sources:

ראה שו”ת מנח”י ח”ה סימן צא שאוסר עם טרמוסטט. וראה שש”כ פ”א ס”מ שמיקל. וראה שבת כהלכה פרקש חלק א פ”ו בציונים אות ד מה ששואל על שש”כ.

בדיקות – במילא הוסר החשש שבשו״ת מנח”י ושבת כהלכה הנ”ל. וכ”כ בספר מאור השבת סי יב אות ד, בשם הגרשז״א שהוא ספק אם בפעולה זו תדלק וממילא לא הוי פס”ר. ואף גם אם נאמר שהוא ספק פס”ר (ראה בשוע”ר סימן שטז סעיף ד וסימן רעז קו”א סק”א) – ה״ז בגרמא, וממילא בדרבנן..

 

 

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