sealed heating system air lock problem

[Gary80gas]

Ive now got to run a heating zone through a flat roof structure where the pipes will have to rise 300mm for 8m before dropping to a single rad using plastic pex pipe. Its obviously a sealed system but im worried about airlocks. Has anyone done something similar with no problems. What do you think? Any advice appreciated.

 

[Last Plumber]

Ive now got to run a heating zone through a flat roof structure where the pipes will have to rise 300mm for 8m before dropping to a single rad using plastic pex pipe. Its obviously a sealed system but im worried about airlocks. Has anyone done something similar with no problems. What do you think? Any advice appreciated.

Personally I think you'd be asking for trouble.
Many will disagree I have no doubt. I can only say it is not something I would do.

 

[Best]

Will the pipes be accessible? I am just wondering if they could be easily manually vented later, if ever needed.

 

[ShaunCorbs]

Or use some auto air vented

 

[Harvest Fields]

Or use some auto air vented

And hope they do not leak in about 3 years

 

[Old Account]

Or use some auto air vented

Very often they fail to work as well as harvest mentioned leaking issues.

 

[oz-plumber]

We've done numerous overhead systems, due to bulding being on concrete slab.
In all honesty, very few problems.
Sometimes install manual vents to rid air, but 9 times out of 10 never any issues.
Just inform the customer there may be issues with some rads with airlocks. Just tell them to turn off other rads until they can hear the air gurgle through the rad and then bleed the rad.

 

[Gary80gas]

Thanks OZ, this is what im thinking. I know ive done it like this before but this job is slightly different with only one rad and a long run. Im not putting aav's in a sealed ceiling cos they will leak one day.
It got me thinking about how air is cleared, ive forgotten if I ever really knew.

 

[AWheating]

AAV 's are for next to pumps. Either manual vent if possible or nowt. It should work ok if you get a good flow to the rad.