What is inside this heater flow switch?

Here is the mystery. In the following youtube video you can see the pin of the flow switch diaphragm extended when the faucet is flowing (the valve is after the flow or pressure switch).

https://www.youtube.com/watch?v=snbKpBdKf8M&feature=youtu.be

Supposedly in a normal pressure switch. As someone described. The pressure will be a maximum when there’s no flow, precisely because at zero flow there is no pressure drop anywhere in the system, so the pressure here will be full mains pressure. When the shower-head is on and there’s flow, the pressure here will drop.

But in this flow switch diaphragm. It’s the opposite. What is in the design in the diaphragm such that when there is no flow (pressure maximum), pressure won’t push the pin. The pin will only extend when there is flow.

Some kind of Bernoulli principle, etc. how?

previous posts:

Here is a video of the flow switch turning on right at start of video, I used the control valve before the inlet. However. Note in a multipoint tankless heater, you put the valves (such as sinks, showers) after the heater. I only used it at inlet for testing. So the unit has the water inside always at pressure (when not in used). But here is the thing. When the valves are after the unit or outlet and not in used. The switches are not pushed.

https://www.youtube.com/watch?v=q47ZCrGtGJQ&feature=youtu.be

Ok i fried open the flow switch or pressure switch.

The tension of the spring is high such that you need high water pressure to push it to turn on the switchrs. It is in inlet side. I think it is a combination flow switch/pressure switch? Because if the water is not used, the switches are off and it’s not being pushed. Both for the case where the valve is before the inlet or after the outlet. It’s a multipoint tankless water heater.

The reason Panasonic created very high tension spring is so you can’t lower the heater power or make it variable. It’s either in low (2.5kw), medium (3.5kw) or High (6kw).

Anyway. I disassembled everything and it’s all very simple circuit. The only electronics part is the LED lights. I can disable the 3.5kw or 6kw by simply removing the switches and the connections to the heating element. What will be left is the 2.5kw heating element.

I just want to know how many variables control a spring. If I will replace the spring, it has to push at 1/3 the strenght and I have to be sure the spring is as good that can bounce back. If it fails, the thermostat cut-out thermal switches will open. Its just theoretical because i plan to buy a new tankless heater where the water temperature can be monitored and heating element adjusted in micro steps.

Original message.

Any illustration what is inside the flow switch water pusher (the white round thing encircled in green label) of this instant tankless multipoint water heater? When there is fast water flow, it pushes the switch on the left of the round white part (shown in red arrow)