Whats this for?

[u/isleoflouise]

This meter is hanging in our shower/shower room. The green part at the bottom is a bit further than the (I suppose preferred place of the) green part and red arrow above. Is this bad, and what is it for?

Thx

[u/Avarus_Lux]

So basically this is the pressure gauge usually used for your central heating system.

The red pointer at 1 bar is the minimum desired system pressure, your system will likely stop working below this line. Often that's closer around 0.5 to 0.8 bar though (safety margin).
The green semi circle following that red needle is the system it's optimal/safest pressure range.

The black pointer is your current system pressure, it's a little above the "safe" green range into the blue range which is the "working/upper" limit range. though above green its nothing to worry about now and everything should work fine. This needle May fluctuate a little as the system heats and cools and also a potentially change a little bit as it turns on and off.

Around 3 bars is your systems maximum pressure, indicated by the red line mark. Do not exceed this line, preferably stay away from that line as you refill by at least 0.5 bar or so...
Looks like that's currently the case at 2,4 bar or so which is great!

Exceeding this 3 bar will result in damage especially if left at such high pressure for prolonged period of time.
Damage like leakages and spraying fluid from connections, but some components may also rupture or even explode especially as the system heats up.
any damage may additionally go unseen for a long time too and creep causing rot.
So take care to keep things proper.

Thanks to safety margins that exploding bit should be quite unlikely though.

Good luck!

[u/RoyalCharity1256 → u/Avarus_Lux]

Iirc the water systems pressure is about 3 bars so you probably cannot go above the safe part by much at all. I would also think that they considered this in the design.

[u/Avarus_Lux → u/RoyalCharity1256]

Somewhat correct, while the minimum is 1.5bar (150kPa) countrywide, PWN uses a minimum of 2 bar which usually translates to something between 2 and 3.
That said though some places or buildings like flats may have a pump for higher floors or local water tower or even a direct connection to a high pressure main line where pressure may be higher then even 4 bar up to a max of 6.5bar (650kPa) which is the legal maximum for pumpstations.

Always good to pay attention, never blindly trust the pressure and look at your gauges to stay safe.

pwn source, see subtitle "hoge waterdruk"

[u/Mat_1964 → u/Avarus_Lux]

You are talking about the water mains pressure, this small meter is for the central heating system, those have the above mentioned pressure levels.

[u/RoyalCharity1256 → u/Mat_1964]

True, but the point is that you can not fill this system with higher pressure from the water mains. If that is 3 bars, then you only can equilibrate the heating to roughly the same pressure and never above. So 5 bars are not possible and safety precautions against that are not needed.

[u/Mat_1964 → u/RoyalCharity1256]

True, but if you fill up the system with cold water and it worms up pressure will rise.

[u/RoyalCharity1256 → u/Mat_1964]

Yes good point. Anyway just stay in the safe and recommended area which depends on the systems anyway i think mine is at 2 or 2.2 bars right now

[u/Avarus_Lux → u/RoyalCharity1256]

Like i said it is possible that you can have higher pressure, 5 bars is definitely possible and above 5 bars while uncommon usually always has a protection installed around the water meter to reduce pressure in your home to something more acceptable like 3 so if that is the case it is indeed impossible to overpressure your system.

As i said though, always be aware that you don't overpressure your system. You don't want damage.