Worcetster Bosch Greenstar 28 with internal filling loop

[DaveHerns]

Friends have one of these , installed late 2012. They say they were told by an RGI it was OK to leave the plastic key in the manifold in the locked position. Surely this is wrong? The WB video on YouTube says when you withdraw the key, some water may leak out. I see the key has 2 "O" rings on it so presumably it seals in the manifold? Where does this water come from?
The boiler was down to 0.5 bar yesterday, could the key being left in cause the problem?
I've had a look at the instructions but it doesn't include the internal filling loop.

 

[simond]

The internal filling loop was an extra on the 28 because it is a budget WB model, there is an instruction leaflet supplied in the box it came in.

The only reason you are meant to remove the key is to prevent any chance of cross contamination (backflow) from the radiator water. It won't be the reason why the pressure dropped.

 

[DaveHerns]

Assuming the white key operates a valve, where does the water that drips out when you remove the key come from ? I did tell them to look for water coming out of the vent pipe but we'll check for leaks

 

[TCCHeating]

The key doesn't operate a valve. It just bridges a gap to provide a passage for the water to flow through. The little bit of water that you get when the key is removed is just the water contained in the 'sealed passage' the key creates

 

[DaveHerns]

Thanks. it's obviously more complicated than I thought. I thought it was just 2 valves like the external filling loop. I'll tell them to take the key out anyway