[Avodah] Can one add water to a hot water urn on yom tov if this might cause the indicator light to turn on?

[Micha Berger via Avodah]

On Wed, Mar 22, 2017 at 06:26:42AM -0400, Akiva Miller via Avodah wrote:
: WADR, I question the metzius of the two-heater system described by Rav
: Belsky. Is the smaller heater really on constantly? ...

Well, in this urn,
<https://www.webstaurantstore.com/documents/pdf/coffeeurnmanual10_15_13.pdf>
the keep warm element (and its indicator light) has a thermostat set
at 88degC, and the circuit as a whole (thus including the main heating
element and its light) are set at 170degC.

Two elements, but neither is "always on". And I would think this design is
consistent in all urns that have separate "boiling" and "keep warm" light.
But I fail to see how that is relevent to RYB's statement (as quoted):
> Rav Belsky, zt"l said that one may not even ask a non-Jew to add cold
> water to the urn. Although turning on the indicator light is an unintended
> consequence, and strictly speaking one is permitted to ask a non-Jew to do
> a permitted activity even if this will cause an unintended consequence
> that is forbidden (psik reisha), in this case it is not permitted. Rav
> Belsky explained that there are two heaters in an electric urn. The larger
> heater turns on when the urn is filled with cold water. Once the proper
> temperature is reached, the first heater turns off and a second smaller
> heater turns on to maintain the temperature. When one adds cold water to
> an urn, one is not only changing the status of the indicator light, but
> that person is also turning on the larger heater. Since the inte  nt of
> adding cold water to the urn is to cook the water, one cannot consider
> the turning on of the heater to be an unintended consequence. To
> appropriately add water to an urn on yom tov one should boil the water on
> the stove and then pour it into the urn.

AISI, RYB's main point in mentioning the two elements is for someone
to realize that it isn't a single element going from keep warm to boil
temperatures, but rather a second element is going from off to on --
havara.

: And if he is correct, is it true of ALL urns?

Given the cost of cutting down the voltage for the sake of running the
same element at a second low-heat mode, this design is far more energy
and/or cost efficient. The unused voltage would be wasted in a resistor,
or you would add the whole complexity of what a dimmer switch does plus
having a thermostate that could work with the dimmer circuit, rather
than the simple on-off jobs in that circuit diagram.

This solution is far simpler and does the same job. I would assume it's
universal.

Tir'u baTov!
-Micha

-- 
Micha Berger             Live as if you were living already for the
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