Hydronic Heating Takeoff Locations 2

[robbeec]

Hey All,

We have a typical detail we use on our drawings for a typical piping takeoff from a hydronic heating main to a branch (see attached picture), however there are a few of us that are looking at it now and are trying to figure out why taking a branch off the top of the main isn't "acceptable" and why there isn't even an option for taking it off of the bottom... The detail predates pretty much everyone here and I can't seem to find anything in our local codes or standards. Anyone have a clue why this detail is the way it is? We were thinking it might have something to do with the force that pipe expansion might have on the 90deg elbow and trying to mitigate that with a 45...

 

[EnergyProfessional]

my best guess is 45° has less pressure drop. I assume they didn't want to allow a horizontal take-off to allow some pipe expansion by the take-off torquing the main.

thanks for questioning old details. i see too many designs where people detail or specify something because someone 100 years ago thought something and we never changed.
Many designers just know one thing, but don;'t know why, so they can't adapt to different circumstances.
Same thing with balancing valves on pumps with VFDs....

 

[Lnewqban]

I don't know the reason for the unacceptable option, but I agree with EnergyProfessional.
I have been told the reason for avoiding bottom take-off's in hydronic systems is the possibility of debris, sand, sediments (that may accumulate at the bottom of the main) migrating to valves, strains, controls, etc.

"Engineering is achieving function while avoiding failure." - Henry Petroski

 

[SAK9]

Air tends to collect on the top for water carrying pipes.So it isn't a great location to tap into.However for a steam line it is quite the opposite ie tap from the top to prevent condensate flowing into branches!