Is Siggy out there? Closely-spaced tees question.

Tim Doran_4

What ever goes into a tee must come out of a tee. The calculations for determining temperature are based on two in flows and one out flow. A cross would have two in flows and two out flows. In this theoretical application would the boiler and load be piped 90 degrees apart or 180 degrees apart?

Tim D.

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JohnNY

Anyone else have any input?

Closely-spaced tees, as in Figure 4 of Siggy's article in the July P&M Magazine (page 42) are a common configuration in a primary secondary system.

I was wondering what replacing the tees with a single cross tee would do for me in that application.

Has anyone tried it? I like the idea of soldering 4 joints rather than 6 and it might make the job a bit neater.
I would also think the fitting would eliminate pressure drop between supply and return entirely.

Would mixing be the problem?

I'd love to know.



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bobbyg_2

Interesting question. When I think about the cross instead of the two tees. The heat is transferred when the the different temp water crosses paths.

With any heat transfer, it works better with counterflow. How much counterflow is needed to transfer heat I'm not sure. Obviously the more closely spaced they are, the less "time" the counterflow water will have to transfer the heat. But how much "time" is needed to transfer this heat. With a cross, it will be a quick dash across the primary line without any counterflow only "perpendicular" flow?

I am really just writing what I am thinking. I don't have any answers, only more questions (sorry). Great question and I will wait to hear from more people more knowlegeable than me.

hr

possibly

I suppose it would depend on flow rates and the diameter of the trunk. I believe you need some "room" for the mixing to take place.

Years ago I did a bulge fitting, sort of an early hydro separator device, that Siggy designed. It had the take-offs directly across from one another, but with a large 2" trunk. I have also done take-offs with just one tube space apart, and across from one another.

hot rod

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Brendan_4

Bobby As i see it the closely spaced tees are only ment for hydrolic separation with no mixing intended. If all system return went to the boiler and all boiler supply went to the system this would be ideal conditions with no mixing and closely spaced tees will better prevent short cycling of boiler water than a cross JMHO

J.C.A._3

Johnny NY,

How about Taco "Twin Tees"?

Available in many sizes, with a good choice of either sweat or threaded connections.

No muss, no fuss and only 4 joints. What could be easier? Chris

Joe Mattiello

See attachment for catalog, and submittal data information on Taco twin tee's. Great way to facilitate piping, and minimize pressure drop when designing system with primary/secondary piping.

bobbyg_2

Brendan,
I'm not following you (sorry).

Closely spaced tees do provide hydraulic separation and mixing (where the two hydraulically separated loops transfer heat in the common piping). I'm sorry I don't understand what you are trying to say.

Brendan_4

Bobby The closley spaced tees only purpose is hydraulic separation not for mixing or heat transfer.if they were ment for heat transfer a greater distance apart would be better for mixing but we both know they are supposed to be 4 to 6 diameters apart to prevent a pressure drop

Tim Doran_4

Mixing Pipe

Old school engineers call that "Bulge" a "mixing pipe". European engineers still use this application and it has become fairly common place in radiant cooling piping arrangements.

Tim D.

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Tim Doran_4

Paralell Flow

As I see this in my minds eye the water has to be able to travel on paralell plains so that it can travel in either direction. If a cross tee were to be used water may have to push its way directly through the other stream to get where it needs to go. It would seem that this would have an adverse affect on temperature control.

Tim D.

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bobbyg_2

I think both aspects of primary/secondary are important.

I get your point about spacing the tees further apart messing up the pressure differential (losing hydrauic separation).

But what if we switched the secondary inlet & outlet. I think you "may" get hydraulic separation but you certainly won't get the heat transfer. Both aspects of p/s are important, spacing of tees and inlet/outlet of secondary.

I think these two (hydraulic separation & heat transfer) things are what make primary/secondary such a great thing.

You could have one without the other in other piping arrangements, but p/s has both.

Let me know your thoughts. (I'm not perfect, ask my wife

JohnNY

Hmmmm.

I don't know.
I don't see the water pushing through anything.
I think the flow through the main would ensure fresh water from the boiler into the supply branch and return water expelled into the downstream flow.



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hot_rod

i don't see

how 4 ports could come together with two pumped flows, and a delta t in the loops, without a mixing of some sort. Dan and Siggy both show the formulas in their books for calculating temperature drop along a primary loop.

But I not sure exactly what piping arrangement we are talking about, so I am just imagine-eering.

hot rod

rich pickering

I've done it useing 2" branches from the boilers into a 6" main about 2 feet long. The system piping was 3", so I also used the 6" as an air seperator. Flow rates were about 100 gpm.

Every thing was built using grooved fittings, so QC for welding wasn't a problem.

Tony_23

Brendan

W/O heat transfer, what's the point ? If you're not tranferring heat from the primary to the secondary, what are you accomplishing ? Answer : Nothing. You're moving water w/o heat transfer. Pointless.

The hydraulic seperation you refer to is to prevent one circuit's flow from affecting the other's flow in GPM only, not to prevent btu transfer.

Think about it

Jamie_5

cross

Unless the center of the cross is a "bulge, as others have mentioned, it won't work. The circuit to the "side", i.e. secondary circuit, off closely spaced parallel tees is much more resistance to flow than straight ahead. So essentially no flow is diverted into the secondary circuit unless a circulator on the secondary circuit comes on and drops the pressure the fluid sees at the side port. That does not seem to be true of the cross. Which way the fluid will go will depend on which branch of the cross offers the least resistance. That branch may not be the intended one.

Or so I think.

Brendan_4

Bobby... I see primary/secondary by way of closely spaced tees to be a necessary evil especially with a mod/con setup, Its only usefulness is to allow two loops with dissimilar gpm's rates to work in harmony. In a basic heating system heat transfer should only take place in the boiler's HX and the space emitters JMO.

bobbyg_2

I think it is just another tool to utilize. I mean if you're talking about a residential house - I see what you mean. I am thinking more along the lines of injection p/s and other systems (not so basic).

Every job is about transferring the energy out of the fuel and into the water and then delivering that energy (heat) where it is needed. - there are many means of achieving that. Look at transferring the energy out of fuel (there are many options to do this - std. eff., mod-con, etc.)

If you are just talking about a residential home with bbd - I get your point. I was thinking about many other situations. Hope your having a good day!

siggy

cross fitting

I've not tried a cross for P/S piping, but do have the same reservations about it that others have expressed below.

The Taco twin tee would be a good solution: Side by side ports keep delta P to zero, and internal vertical baffle stops mixing. This fitting also allows direction of primary flow to reverse without affecting flow in secondary. Its inventor is to be commended.

siggy

[Deleted User]

What about a 4 way valve...

That has 2 innys and two outties...

ME

Kevin Koenig_4

The Inventor.

It's suprising to me how such an old device can be forgotten about for so many years and then re-introduced to the industry as a "NEW Product". I would have to suspect that Gil Carlson had his fingers on this device back in the mid 50's. If so, It would only be appropriate to condider him the inventor. K.K.

Lyle C

JohnNY I found just the item your looking for in a Webstone catalog this mourning check this out

http://store.webstonevalves.com/Default.aspx?page=category search results&amp;CatList=5865&amp;Parent=71520&amp;tree=71482*WEBSTONE+EXCLUSIVE+PRODUCTS*0@@71511*PRO-PAL+SERIES+VALVES*0@@71520*FULL+PORT+FORGED+BRASS+BALL+VALVE+PRIMARY/SECONDARY+LOOP+PURGE+TEE+-+CxC+w/+REVERSIBLE+HANDLE+(600+WOG/150+WSP)*5865@@

sorry for the long web address haven't figured how to link yet. But I can copy and paste.

Lyle C

JohnNY I found just the item your looking for in a Webstone catalog just this morning, check this out. And it's easy to purge.

http://store.webstonevalves.com/Default.aspx?page=category search results&amp;CatList=5865&amp;Parent=71520&amp;tree=71482*WEBSTONE+EXCLUSIVE+PRODUCTS*0@@71511*PRO-PAL+SERIES+VALVES*0@@71520*FULL+PORT+FORGED+BRASS+BALL+VALVE+PRIMARY/SECONDARY+LOOP+PURGE+TEE+-+CxC+w/+REVERSIBLE+HANDLE+(600+WOG/150+WSP)*5865@@

sorry for the long web address haven't figured how to link yet. But I can copy and paste. Too bad their not American.

Tim Doran_4

Agreed

But it also has a gate to help direct flow. I think that accurately calculating the two mixed temperatures through a cross tee would be tricky.

Tim D.

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hot_rod

Maybe with a pair of delta T circs!

you could dial in the required temperature and build your own smart mixing cross fitting.

Boiler protection on the primary circ, mix temperature on the secondary??

hot rod

JohnNY

What happened to this very wide thread?

Thanks, everyone, for your help.

I think the cross T, though not an inexpensive or common fitting, would be more cost effective (assuming it works here) than some of the other suggested appurtenances.

(how's that for a $10 word?)

I would try it but I'm too cheap and lazy.









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[Deleted User]

In my minds eye...

It should work just fine. Of course, your sensing point would need to be a ways down stream of the cross, and my minds eye hasn't quite figured out what happens when the mix branch;s flows exceeds the mains flow...

I know on P/S piping, you can actually run the water through the common section of the pipe backwards. Not quite sure what the effect of over flowing the mix port on a 4 way would be...

But then again, I'm a condenso snob. I haven't sold a conventional boiler needing return water protection in 6 years... Hence, I don't even give VSI a second thought any more :-)

But then again, I DON'T deal with oil like John does :-( And I'm betting that as soon as somone comes out with a good condensing oil boiler the he too will forget about VSI, and boiler protection and all that junk I used to have to worry about :-)

ME