1. How do these products work?

These devices are controlled by a thermostat. The device heats the water when it detects that the temperature of the water has dropped.

In the product’s information sheets, the manufacturer refers to the product as being simmerstat controlled. Use of the term simmerstat has been found to be inaccurate.


2. Can water be removed from this urn on Shabbos?

If the product were simmerstat controlled, it would be permitted to remove hot water from it on Shabbos use without any concern at all.

The general halachic consensus is that one may remove hot water from this urn on Shabbos.

Due to the thermostatic control, some authorities are stringent with regards its use on Shabbos. This is because removing hot water will speed up the onset of the next heating cycle. For those who are stringent on this matter there is room to mitigate this issue by removing water when the red light shows. This will occur more frequently if the thermostat is set to high.


3. Can water be removed from this urn on Yom tov?

Water may be removed from this urn on Yom Tov without concern.


4. Can water be added to this urn on Yom Tov?

It is permitted to add water to this urn on Yom Tov. Adding large amounts of cold water in one go will trigger the appliance’s heating element in a way which is problematic on Yom Tov. Two methods are suggested:

  1. One can add small amounts at a time so that the appliance will not suddenly be cooled down by the newly introduced cold water.
  2. One should add the water when the red light is showing indicating that the appliance is already heating.


5. Can the temperature setting be changed on Yom Tov?

When the urn is heating (i.e. the red light shows), one may turn up the temperature to a higher setting. One may not turn it down.

When the urn is not heating (the red light is not showing), one may turn down the temperature setting. One may not turn it up.

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