May one indirectly cause a flame to ignite on Yom Tov [Gram Havarah]?

Some Poskim^[1] rule it is permitted to do so. Other Poskim^[2] rule it is forbidden. Some^[3] write that according to all one may not perform Gram Havarah on a steady basis. One may however be lenient to do so through a gentile.^[4]

Examples: May one enter a plug into a timer on Yom Tov, if the timer will only turn on later? May one shorten the time of a Shabbos clock? May one use an electric boiler that does not have Shabbos mode?

May one adjust a Shabbos clock on Yom Tov?

This follows the same law as Shabbos in which the law is that one may lengthen the current status of the timer but not shorten it.  However see the previous Q&A regarding those Poskim who would allow even shortening the current activity due to Gram Havara. 

May one open the hot water tap on Yom Tov?^[5]

Electric boiler: Many Poskim^[6] rule it is permitted to open the hot water tap even if cold water enters into the boiler in the process^[7], and even if doing so will eventually cause the boiler to turn on due to loss of temperature.^[8] Some Poskim^[9]however rule it is forbidden if doing so will eventually cause the boiler to turn on. According to all, it is forbidden to open the tap if doing so will cause the boiler to activate immediately upon opening the hot water knob. In such a case it is forbidden for it to be opened or closed even on Yom Tov.

Solar boiler-Dud Shemesh: Is permitted to be used freely for washing dishes, hands and the like. It is allowed to be done even if cold water enters into the boiler in the process.^[10]

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[1] Achiezer 3:60; Klei Chemda Vaykhel; Chasam Sofer Even Haezer 1:20; Chelkas Yaakov 1:50; Yabia Omer 3:17; SSH”K 13:27

[2] Michzeh Avraham 41-43; See Piskeiy Teshuvos 502 footnote 14

[3] Rav SZ”A in SSH”K 13 footnote 58; See Piskeiy Teshuvos 502 footnote 15

[4] Piskeiy Teshuvos 502:3

The reason: As whenever there is a dispute if something is permitted one may do so through a gentile. [Tehila Ledavid 336:4]

[5] Piskeiy Teshuvos 511:3; SSH”K 2:7 based on ruling Of Rav SZ”A

[6] SSH”K ibid; Piskeiy Teshuvos ibid; Beir Moshe 8 [see appendix]

[7] As it is not possible to remove the hot water without having the cold water enter, and hence also the cooking of this cold water is considered a Yom Tov need. [ibid]

[8] As this is a mere Grama with electricity on Yom Tov. [ibid]

[9] See Piskeiy Teshuvos ibid

[10] As it is not possible to remove the hot water without having the cold water enter, and hence also the cooking of this cold water is considered a Yom Tov need. [SSH”K ibid]