balanced flow

spd

Where reverse/return piping isn't practical and I need to tee to units ( say two units for hypothetical purposes) and I am limited in pipe sizing: If the supply and return piping is of equivalent length and turns is it better to bull head at a tee or put the tee after an elbow so the water either turns or goes straight and add an extra turn later on the path that went straight on the first tee to balance it out? Can any one describe the exact consequences of bull heading to help me describe the bad feeling I have about it? Please help I am being repeatedly challenged by bad designs. I am relying on a balanced flow but don't have the authority to impose balancing valves. 

furnacefigher15

Bull heading

Only way to balance to flows w/o valves is by having the supply and return tie in at bull head of the tee, and have the loads header on the run with exactly the same fittings, and pipe lengths. (which is not practical unless loads are near each other)



Like putting water heaters, or refrigeration condensers in parallel. More than two gets really tricky, and is far less practical then reverse return.





Or you can just run in direct return and use a ball valve to add restriction to the one that needs it.

spd

Reverse return

I have been lead to believe that reverse return will balance the flow better than bull heading, do you agree?  There are several units.

furnacefigher15

yes

reverse return is good. But valves are still needed if connected loads are not the same.



Anyway, you were asking about other then reverse return.

spd

Bull headed about bull heading

I prefer to use reverse return with balanced piping, piping balanced. It is true I was referring to situations where I am asked to tee off to two groups of tanks or collectors instead. I heard that bull heading will cause extreme friction (small pumps) and if there was another way to locate that tee. I will now, however, consider the balancing benefits. A minor difference in piping strategy that will make a big impact on best practices for my specialty. Thanks

Mark Eatherton

Bull heading is a BAD idea....

One of the first articles published by John Siegenthaler addressed this very subject. The problem is that when bull headed, the circuits can not self balance, so they continually change their flow rates, back and forth and back and forth. Piping it in a parallel reverse return manner automatically "locks" the flow hydraulics in.



Piping in a direct return manner requires that "chokes" be applied to the returns in order to lock it into the hydraulics, and all it takes is for some unknowing first year technician to open the balance cocks to throw everything back out of whack....



Ideally, reverse return. If it can't be done ideally, then direct return with lockable $hield balance valve$, but NEVER bull headed tees.



I know, some manufacturers (A.O. Smith) still show pyramidic parallel (stacked bull headed tees) for multiple tanks, but if a person looks at the number of soldered joints to achieve that condition, versus piping it in a parallel reverse return manner, the latter method has less soldered joints (assuming more than 2 tanks or other times in parallel) and is automatically balanced, assuming the pressure drops thru the rungs are the same.



Just because a manufacturer shows it does not mean it is ideal. They are playing to the crowd, and in many peoples minds, pyramidic parallel makes good sense. In reality, it is an ever changing, difficult system to pipe and balance.



Some manufacturers still ship their boilers with their pumps on the return too....



ME

spd

happy water

Now I can officially describe the dangers of bull heading, Great. If they can't afford R/R they must to put balancing valves on the direct returns. Yeah