Automatic air vent with two caps

[Mattg4321]

I’ve not come across these AAV’s with 2 caps before. Usually just the one. 
 

Can anyone explain the function of both?

 

cheers 

[JohnMo]

You really should do an image search and let AI tell you

 

Operation: For normal automatic operation, the top cap should be left slightly open. It also includes a manual vent function, which is useful for rapidly bleeding air when filling a new system.

 

So is left slightly open to self bleed. Side to quickly manually bleed.

[Mattg4321]

23 minutes ago, JohnMo said:

You really should do an image search and let AI tell you

 

Operation: For normal automatic operation, the top cap should be left slightly open. It also includes a manual vent function, which is useful for rapidly bleeding air when filling a new system.

 

So is left slightly open to self bleed. Side to quickly manually bleed.

Thanks. Was that an AI answer, or from your own experience?

 

Ive been testing out ChatGPT recently and found it’s not to be trusted. Confidently states things as fact, which turn out to be nonsense. It has its uses, but it’s basically a more advanced search engine imo. AI in the literal sense it is not 

[JohnMo]

Via the same search, but direct wording from the Emneti website.

 

The Tecno-Varia vent valves allow for automatic air evacuation, but with the patented Tecno-Varia version and the extra manual vent, it is also possible:

- monitor the valve's regular operation;

- accelerate air evacuation in specific conditions (e.g., system filling).

 

38 minutes ago, JohnMo said:

So is left slightly open to self bleed. Side to quickly manually bleed

Those were my words 

[Mattg4321]

On 05/12/2025 at 19:02, JohnMo said:

Via the same search, but direct wording from the Emneti website.

 

The Tecno-Varia vent valves allow for automatic air evacuation, but with the patented Tecno-Varia version and the extra manual vent, it is also possible:

- monitor the valve's regular operation;

- accelerate air evacuation in specific conditions (e.g., system filling).

 

Those were my words 

It turns out that the top cap is for manual bleeding and the side is for automatic. 
 

It’s why I don’t trust ChatGPT. 

[Nickfromwales]

These are often OEM in heat pumps etc.

 

Always confused me as to how the automatic air got released sideways when the mechanism relies on a float / gravity. 

[JohnMo]

36 minutes ago, Mattg4321 said:

It turns out that the top cap is for manual bleeding and the side is for automatic. 
 

It’s why I don’t trust ChatGPT.

The manufacturers website doesn't even include that detail either.