AAV question and location of installing one

[Marty32]

Good evening all

Studying for my C&G 6129 and need some help to visualize my question below:

I wondered if someone could explain why you would use an auto-air vent (AAV) on a low pressure heating system and the advantages of doing so? i.e on a F&E fed fully pumped system?

Also, when I hear that the AAV should be placed at the highest point of the system, do they mean attached to the F&E vent pipe? I have seen them installed on the primary flow pipe just before it enters the cylinder so is this correct? Can more than one be installed?

Many thanks for your help!

 

[stokecity]

you dont need them on open vent system as air vents through the vent pipe. you would use aav's on a sealed system on pipework that runs higher than ur rads i.e. in a roof space

 

[jase158]

you could use an AAV in pipework that is likely to get air trapped, for instance if the pipework was to go up and back down to avoid an obstacle.

I have also seen them used when there are several drops from attic to prevent air locking (mainly bungalows)

I dont know the official answer but I know my experiences.

 

[diamondgas]

Hi Marty32 haven't heard from you in a while 🙂

I'll ask you a couple of questions first I think are important .... How do you believe an aav works? & what is its purpose? Fitted plenty on open systems by-the-way 🙂

 

[jase158]

before the cylinder is good, to help get air out of cylinder pipework and no It shouldn't be put on F& E vent pipework.

 

[diamondgas]

You stayin clear of boilers now Marty? I remember you quizzing about repairing one or two with out the qualification to do so 🙂 ... No harm in finding out about AAV's though eh? 🙂

 

[diamondgas]

Excuse my caution in giving you advice marty ... No offence meant but am interested in your take first! Something I have done with many under my wing learning the trade when I am not sure that they know the principle operation of a component. What's the point of just answering the question without knowing where you're at eh?

 

[Marty32]

No probs mate at all - will reply in 10 mins

Excuse my caution in giving you advice marty ... No offence meant but am interested in your take first! Something I have done with many under my wing learning the trade when I am not sure that they know the principle operation of a component. What's the point of just answering the question without knowing where you're at eh?

 

[diamondgas]

1 hour later ........ tick....tick......tick......:sleep1: Automatic Air Vent! ...... Clue is in the title Marty, honest 🙂

 

[Marty32]

Big apologies Diamond for not coming back to you as trying to move properties and got a lot going on!

Anyway, I believe that the operation is as it says on the tin but am struggling to see what pipe this would be attached to in a flat or house apart from on the primary cylinder flow just after the pump as explained?

Where else would be the highest point to put one of these and how is it that the water does spill out?

Oh and by the way - I haven't taken any boilers apart so you can sleep easy! 🙂

Help appreciated!

1 hour later ........ tick....tick......tick......:sleep1: Automatic Air Vent! ...... Clue is in the title Marty, honest 🙂

 

[diamondgas]

Oh and by the way - I haven't taken any boilers apart so you can sleep easy! 🙂

Help appreciated!

LOL ... Good to know Marty 🙂

On any system an AAV is handy where pipes will form quite a substantial air trap! Think of a bungalow, pipes going up into the loft and dropping down somewhere to feed. I picture an upside down 'U' where air will congregate. Best putting something to help alleviate the potential for restricted flow such as an air trap! Principles of working there are a few ..... Small float that moves up in water and down in air opening and closing the breather hole for example! And there's the one's that use a material that expands when wet, contracts when dry allowing air to escape.... Can't think of another method off the top of my head 🙂

On an open system they'll need to be situated bellow the header tank water level so that there's some water pressure behind them... 🙂

Hope that helps ... Good luck with your training 🙂

 

[Marty32]

Thanks diamond - a very helpful description and helps a lot!

I'll keep away from old boilers....well the one's the wall that is ha ha

All the best and thanks for the best wishes

M

LOL ... Good to know Marty 🙂

On any system an AAV is handy where pipes will form quite a substantial air trap! Think of a bungalow, pipes going up into the loft and dropping down somewhere to feed. I picture an upside down 'U' where air will congregate. Best putting something to help alleviate the potential for restricted flow such as an air trap! Principles of working there are a few ..... Small float that moves up in water and down in air opening and closing the breather hole for example! And there's the one's that use a material that expands when wet, contracts when dry allowing air to escape.... Can't think of another method off the top of my head 🙂

On an open system they'll need to be situated bellow the header tank water level so that there's some water pressure behind them... 🙂

Hope that helps ... Good luck with your training 🙂