Number & Location of Air Vents in a Hyrdonic System

[millsy21]

I am trying to find recomendations regarding the amount of air vents required on a hydronic system serving radiant panels. The system consists of a main hot water supply line coming off of the buildings hot water riser and travelling down a corridor.

What would be reccomended?
- the main supply/return lines be elevated above the branch piping and point source so it is only necessary to air vent the main lines? or,
- the branch piping be elevated higher then the main supply/return lines and drop down to point source? This would require numerous air vents.

Also, is there a benifit to having the branch piping come off the top of the supply line as opposed to the bottom? Would this help with sediment control?

Thanks for your help

 

[quark]

Generally air vents on main headers are sufficient if the header is at the highest point in the loop. Air vents at every branch point will create nuisance and will eat our most of your maintenance time. Further, there will be water all over.

I never go with bottom tapping. I always go up. If space doesn't permit I would go at sides with shoe joint.

 

[walkes]

I usually go with the thought that if I am piping a liquid the branch can come off the bottom of the main. If I am piping gas/steam the piping is at the top of the main. Helping to keep the liquids and gases separate in the piping.

Quark, if you go with a top tapping with branch piping don't you find you need more air vents? I would seem like the arrangement may be prone to air lock.

 

[millsy21]

Thank you both for your comments. I feel I am now making some progress. Quark, I believe that you are correct stating more air vents would be required if we branch off the top of the main.

Another question...Does anyone know if standards exists which state that an air vent is required every X number of meters/feet for a given pipe size with a certain flow rate? I have inquired about this information from manufacturers of air vents but have not received any significant information. They continue to state that they are required at the high points but I feel there must be more to it then that.

 

[walkes]

I don't believe there is a requirement for air vents every X number of feet. The contractor must take care if they make dips to avoid obstructions that they install a vent at the new high point ensuring that the fluid flow assists in pushing out the air.

 

[quark]

I didn't find much problems with trapped air if the branch take off is from the top of main header. As long as the elevation of main branch piping is higher, else where, there won't be any problems. Sometimes I experience air lock in the coils inspite of the air vents in the headers. I will just stop the circulation pumps for a while and the air escapes out. This has been giving me good results.

I don't feel that we should provide multiple air vents with respect to length of the piping.

Regards,