What is the advantage of cross-over - Big

Steve Ebels

That is the way the system in the picture is set up. The Buderus 2107 resets the whole system temp and each zone in turn gets it's portion of the now reduced temp H2O. It's fussy work getting it all balanced but it works like a dream. On that system I also have a 3-way mixing valve at each secondary pump that acts like a high limit for each particular zone.

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Big

What is the advantage of piping

a system primary / secondary with cross over pipe work? Would anyone be able to post a diagram w/ this sort of system. With the system also pumped forward.

DanHolohan

the main advantage

is that the supply water temperature to any of the secondary circuits can be the same. With one-pipe p-s the water cools as it returns from each circuit, lowering the supply temperature to the next circuit. Two-pipe solves that problem and it's the reason why you'll see it on big jobs.

I have diagrams of this in my book, Primary-Secondary Pumping Made Easy. I also explain how to size all the pipe for this system, as well as the one-pipe systems (with and without manifolds). You can get a copy in Books & More if you'd like.

Steve Ebels

Another thing that's cool

Is that by changing the flows with the right balancing valve setup, you can dial in a different temp on any or all of the secondary loops. If I can figure out how to post a picture on this newfangled Wall of Dan's mebbe you'll be able to see what I mean.

On the pic the flow is entering on the lower right corner of the manifold setup. It then goes up each of the crossovers. Just above the tee on the bottom of each crossover I have a circuit setter valve which allows me to dial in any given flow through that particular "rung". By throttling the flow through the rung to less than that of the secondary circuit tees, you can begin to mix the temp of that loop down. What happens is that some of the water returning from the sec. loop will flow backwards into the supply tee, mixing with the incoming flow from the rung. It doesn't sound like it would work but if you get your pumps right and set your flows right, it does. I can measure the temp change in that little 4 diameter space between the secondary tees and get for instance a secondary temp of 120 while the main is running at 170. The mechanical inspector wanted to condemn the whole thing because "It can't possibly do that". So I grabbed the thermometer and showed him. He was dumbfounded and said he'd never seen anything like that in his life. Two pipe is extremely versitile

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Mike Kraft

Another thing thats cool,Steve

Is that you blew the inspectors mind!You must have had quite a grin.Hows the Ebels store project going?Sounds like you're done.Great job!

cheese

Steve Ebels

Store project

Is turning out to be never ending. We are now in phase 3 or maybe it's 4. My brother Mark keeps finding bankers that will give him money and he seems intent on using up every last dollar he can get. Truth be known..... We haven't done any major renovation since 1978. A lot has changed since Dad did the last remodel/addition including what our business is, does and sells.

There are now 4 zones of infloor connected to the manifold pictured above with 2 more plus an air handler to be installed this summer. Interesting note on the heating system. We added 7200 sq ft of heated area and our gas bills went down an average of 14% as compared to each month of last year. We previously heated with gas fired forced air.

Thanks Cheese, it's always fun to educate an inspector. You just don't want to rub their nose in it too bad because the next time the shoe may be on the other foot.

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[Deleted User]

cool, how about some pictures

please

Boilerpro

And another great thing

Add a single outdoor reset on the main loop, and like magic all the loops are reset. The big mechanical contractors and old time plumbers in my area who pull the "I've been working with hot water heat for 30 years" when challenged by this still don't get how this works. Oh well, more work for me, less for them!

Boilerpro

rees

really pretty

would be great to see the crossover a little closer. is that a spring check at the top of the crossover rungs? and that is more than a simple globe setting the flow into the crossovers, a circuit setter or what do you call it... and whose is it?

very nice... and always fun to have the cutting edge sharp!
thanks.
rees

Big

I can see that this system

is piped reverse return! Therefore when a call for heat comes on, all the zones have the same amount of heat available to them! Is the cross-over the same size as the main? It would seem that it could be! If you place a nice little grundfus with a flow check on the supply and a flow check on the return you would not have to worry about any goast flow I assume?