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There's currently an ongoing discussion (not decision!) in Germany if households could be cut off from gas supply come winter, to make more natural gas available for industry. Of course media is full of millionaires suggesting to wear an extra pullover (no one talks about showers) and incredible banal ideas. One consideration is that gas flow switches are mandated in every house or even at every gas counter. If pressure on the supply side falls, these presumably close and can't be opened by lay persons.

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1 & 4: Gas flow switch 2: Main shutoff valve 3: Pressure regulator 5: Gas counter

The gas flow switch works like this and closes if flow velocity is too high, or pressure on the (in this picture left side) is too low:

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Other products (also with the DVGW certification, but local suppliers may mandate different types) don't close when the pressure on the supply side is too low:

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There's lots of reports that if the gas supply to a street or building is shut off, these will close and then someone qualified will have to open them. I assume the people saying this know their business and are basically correct, but I don't understand the problem yet.

If the gas flow switch works like in the picture above, even it closes when the pressure on the supply side is too low, it should open again when the pressure normalizes - so why is this such an issue?

p.s.
Gas failure devices also exist, these would also close if the pressure on the supply side falls:

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As far as I can tell - I don't have access to the TRGI rules, also different gas suppliers can mandate higher standards - these are not universally installed. I also don't see why these won't open automatically if the pressure on the supply side is reestablished.

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    $\begingroup$ I don't use gas, but wouldn't pilot lights go out when the gas shuts off and would "leak" unburnt gas if the gas turned on again automatically? $\endgroup$
    – Transistor
    Jul 28, 2022 at 8:24
  • $\begingroup$ @Transistor Never seen a stove or burner with a permantly on pilot light or one without some sort of flame guard. Not saying those don't exist. It could be reasonable that these things don't open without supervision, but I've never seen this specified in a code $\endgroup$
    – mart
    Jul 28, 2022 at 8:28
  • $\begingroup$ So many "if..." that a categorical answer does not seem possible. Also, flow switches react to flow so if flow is 0 then off... $\endgroup$
    – Solar Mike
    Jul 28, 2022 at 9:27
  • $\begingroup$ tbh I feel like I'm missing a detail that should be absolutely obvious. $\endgroup$
    – mart
    Jul 28, 2022 at 9:33
  • $\begingroup$ Regarding pilot lights, hot water heater and household heater tend to have pilot lights because they need to switch on & off as demand requires. In the past, some gas oven also had a pilot light. $\endgroup$
    – Fred
    Jul 28, 2022 at 12:42

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It's designed that way for safety.

When your gas gets shut off, maybe you go turn on the stove and leave it on. If it turns on automatically later, you die.

The whole thing is so rife with problems I won't even go there, but good luck rich people protecting their interests!

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  • $\begingroup$ Yes but in which component is that specific safety feature to be found? $\endgroup$
    – mart
    Jul 29, 2022 at 9:26
  • $\begingroup$ @mart it's the entire device. For example, a pressure relief valve's safety feature is found in the sum of its components as a whole device. $\endgroup$
    – Tiger Guy
    Jul 29, 2022 at 20:06

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