Using a Bullhead

KCA_2

Hey Guys..

Why wouldn't you want to use a bull head tee to tie in a couple of boilers.. either steam or hot water? Would it matter that the boilers are over 5M BTU?

Thanks

:-)

<A HREF="http://www.heatinghelp.com/getListed.cfm?id=341&Step=30">To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"</A>

Mark Eatherton

Water is like my ex brother in law...

For those of you have have heard this story, sorry, bear with me. It;s the only way I know of giving a good visual description of water.

My Ex-BIL was a young dude, and all he wanted to do was water ski and hang out and be lazy. He was always bumming rides, "All I want to do is go around the lake again!" He'd always take the path of least resistance.

Water is exactly like my Ex-BIL, wet, lazy and stupid. Given the opportunity, it always follows the path of least resistance. You have to show it where YOU want it to go.

In the case of a bull headed tee, it can't make up its' mind because the hydraulic resistance changes as a function of flow, and when you have two free flowing opposing flows, they keep shifting, more flow in one direction until the resistance gets great in that circuit, and less in the other circuit, then it flip flops, flowing more in the other circuit, and less in the other circuit. It hunts continuously...

You can make it work, by over forcing (oversized pumps) the circuits, and putting balance cocks on each branch, but all it takes is one unknowing, unsuspecting first year technician to come in and mess everything up (These valves shouldn't be closed!!!" Then, its back to hunting, never establishing a balanced flow condition. Besides, does it make sense to drive with the accelerator pedal to the metal and control your speed with the brakes?

The ONLY time I've ever used a bull headed tee, is where I have prioritized circulators, like on a mod con doing DHW and space heat. In this scenario, only one pump would ever be on at any given point in time, and the pumps should be facing each other and should have check valves to avoid back flow conditions.

One of the very first articles that John Siegenthaler wrote for P&M magazine was on this very subject, and his recommendation was NOT to do it.

WIll it work, sure, sporadically, but that's not what you want in hydronic's. You want PREDICTABLE conditions, which show predictable RESULTS.. It's an art tempered by science and craft.

It use to be illegal under the code, but the code officials saw it being done on primary secondary piping, and could not figure it out, so they dropped it from the code. They could not understand basic hydrology...

ME

Bob Harper

IMC

Mark, that was a good illustration of the principle.

FYI, the 2006 IMC 1206.1 "Fluid in the supply side of a hydronic system shall not enter a tee fitting from the branch opening."
I'm waiting on my new 2009 I-codes to come out any day now.

troy_8

Variable speed injection?

I suppose all my piping is wrong when I pipe my injection tees close together in the secondary loop. The loop supply is fed in through the branch. Or am I missing something?

[Deleted User]

No...

That IS the reason they are abandoning it. I attempted to write an explanation of when and where it is acceptable )P/S, VSI etc) and when it's NOT acceptable, and they said "Thanks, but no thanks. We're dropping the whole thing out of the code"

Funny how things like that work. If you don't understand it, and you don't think your field people can handle a simple interpretive explanation, drop the whole thing... Besides, remember what the strongest lobbying force in the building codes are, and what their ONLY objective is. (H.B.A., make it less expensive to build homes)

Makes a person wonder who's really running this country eh...

ME