'Split', two pipe injection loop

Dan_8

I'm planning on using the 371 for the loop that started this thread and originally had planned on piping the DHW as a true secondary (despite what their application brochures seem to recommend). Then while reading through the description of the control sequences I noticed that they don't even seem to provide the option to keep the primary circulator running on a DHW call which makes it seem like more trouble than it's worth to force the issue. Especially if it's a better way to go anyway...

Dan_8

'Split', two pipe injection loop

I'm looking to redo the near-boiler piping in my home.

What I've currently settled on is creating an injection loop consisting of two sets of reverse return crossover bridges. Each bridge will have zone piping connected to it as a secondary. What makes my current plan slightly odd (at least to me) is that I want to break the injection loop in half, each half to end in a set of four bridges but with one half of the split loop considerably longer than the other. My house is a Cape with a long 'ell' at the end and my boiler is at the end of the house furthest away from the ell. By creating a 'distribution closet' over on the other side of the house I can get away with just one loop of pipe through the chase that already exists in the finished portion of my basement from the boiler room to the ell rather than a loop back to the boiler for each zone in the ell.

I've attached a drawing below (sorry for the poor quality) of what I've got in mind. I've got two crossover manifolds, both connected to a common pipe where the circulator for the loop is located. The drawing is heavily simplified. I've left out just about all of the valves (except for the balance valves for each bridge) and all zone piping. The zone piping will just be a standard secondary off of the bridge.

I'm looking to send fully reset water to my existing baseboard but also to create a setup that, with no near-boiler piping changes, will allow me to change the baseboard zones to radiant zones as I'm able to get tubing installed over the coming years. I plan on piping each zone with a manual 3-way mixing valve so that I can set the temp of the zone relative to the fully reset loop, full temp when it's a baseboard then crank the 3-way down when it's time for warm floors in each zone.

I'm hoping for a sanity check that this type of layout isn't too hare-brained. I've been looking at flows as carefully as I'm able and feel that with a judicious amount of throttling in the manifold in the boiler room I can get the flow that I need in the remote manifold with reasonable pipe sizes and a Taco 007. I'm very happy to chat about the flow stuff in more detail but didn't want to flood this post with piles of numbers.

Anyway, I'm hoping that I can get some sort of comment on the layout in general and please, don't savage me too much ;')

hot_rod

did a tripple split like yours

Mixed into a manifold on the main board and utilized reverse return on the PEX connections. One injection control & three injected remote manifolds. Works like a dream!

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Dan_8

questions about your split

Dave, thanks for the reply. If I'm reading your schematic correctly it looks like you've got four separate injection loops, one of them is broken out into three remote zones and the loop pump is also the zone pump in all the situations?

My original hope had been to get away with one injection loop driven by a single circ which would just keep the water flowing across the crossover bridges in both locations. I had thought that I'd then pull each zone off of a bridge as a separate secondary zone.

Thinking about it though, especially after looking at what you're showing me here, I might be better off with a separate loop at both ends. This means that I'll need two injection controllers but perhaps the simplified piping will make up for the controls.

Thanks again.

John@WattsRadiant

A little more explanation please

Dave,
What control did you use? It looks like you have four injection loops to me??? How did you tie the multiple injection pumps into the control?
Thanks,
John

hydronicsmike

I think....

...he is refering to the Manifold that is split up into R1, R2 and R3 for the remote staple-up panels. It appears that all of those 3 remote manifolds run off the same water temperature and therefore he used one Injection Mixing setup for all three. Then he uses a pump for each to get to the remote manifold location.

Is that right?

Mike

Brett O'Connor

Single Injection Loop

Looking at you drawing it looks as if you are zoning via zone valves. If doing so you need to insure to put accu flo valves or globe valves on the returns of the supply and returns to your manifolds to insure balancing of your distribution piping. Treat as almost a remote mechanical room when piping your system. Secondly look at cost of using multiple manifold zoning by zone valves in comparision to using a single or two manifolds with telestats mounted on them. Also your DHW pump is in series with your primary pump. When using pumps insure to place your zone pumps or DHW pumps prior to the primary or secondary pump do avoid any problems. Hope this drawing will help.

Steve Ebels

One glaring error

After a quick scan. The DHW pump belongs upstream of the primary circulator. When installed downstream as pictured the primary pump is usually capable of lifting your flow check and causing unwanted circulation through your indirect. This can lead to very high temps in your DHW tank. Install it on the "suction" side of the primary so it works with the flow check. It'll save you having to change it later.

hydronicsmike

I don't agree there...

...as long as the primary/secondary is piped right, you shouldn't have this problem.Primary/secondary hydronically isolates the system loop from the DHW Loop (and all others) and therefore should have no flow through the DHW tank unless that DHW pump is actually running.

I see nothing wrong with the drawing.

Mike

hot_rod

Yet another way

would be to pipe the indirect to the boiler without using the primary loop. This allows circulation from the boiler directly to the indirect without running, or heating the primary loop. This may help keep the mechanical space cooler on summer time DHW calls. Be sure to add the flow checks, or better yet us check circ pumps.

Dave's drawing should work fine, I'd suggest checks on both supply and return to the indirect to keep the ghosts away :)I suspect in real life he has these included.

hot rod



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Brett O'Connor

Hope this helps

The issue with the Domestic has already been address with pumping in series. As for the remote manifold we deal with this quite often. Put simply all you realy need to be concerned with is balancing the distribution piping through an accu Flo devise or Globe Valve. Hope this drawing helps. Feel free to ask any questions.

hydronicsmike

You still...

...Could pipe the DHW Tank in primary/secondary, but you'd have to use an external Relay to bring the main system pump back on.

Piping the DHW Tank in parallel is always better as it does not require the entire boiler loop to be heated up when there is a call for DHW only.

Mike

Dan_8

Yeah...

...I had gotten as far as figuring out if I had the parts kicking around to get the external relay working when I realized I was fighting a higher authority for no good reason ;')

That 371 seems like a great little box. At this point I'm leaning toward two of them so that I can run two separate injection loops (south part of the house/north part of the house). It seems like overkill on the controls but the way the 371 deals with coordinating multiple zones is quite neat and having two identical, symmetric manifolds should be a good deal simpler to pipe than what I showed above. Perhaps the savings in pipe and valves won't make up for the price of the extra 371 but it'll mitigate it a bit and give me a better, more flexible solution for the future (IMHO).

Mind if I ask you some particulars about how the 371 logic deals with various situations?

hydronicsmike

I would never...

...suggest two 371s in one system. A 371 is designed to control a heat source without an option for enable only. That means that the 371 will try to 'control' the boiler rather than 'enable' it. If you have two of them in one system, they may fight each other and short-cycling of the boiler may the result.

I'd love to look at options with you. If you email me your number, I'd be glad to call you.

Thanks.

Mike

Dan_8

Hmmm...

I had been thinking that one would be in control of the boiler and the other would hang off the first in much the same way that a zone controller might. That way the first 371 would drive the boiler and the second would only drive its injection loop and the zones hanging off of it. This seemed worthwhile to get the zone temp coordination that the 371 (but none of the other controllers?) seems to offer. I guess I'm assuming more than a little there though so please set me straight.

My number is on the way.

hydronicsmike

I will...

...call you in about 30 minutes, if thats alright. I liked your idea, but at this point we can't do what you suggested. We'll talk about it.

You certainly did your homework. Looking forward to the conversation....


Mike

Dan_8

Thanks...

I'm looking forward to the call.

I originally got the idea from the application brochure for the 370 (a370-7) where there are two 370s in pretty much the situation that I was talking about. At first glance I just assumed that one of them was slaved off the other but now that I look, it appears that it's not that way.

Is the "Zo Out"/"Zo In" communication that would go on between a 369 and 370 more complicated than an on/off kind of thing? I'm guessing so at this point but didn't realize that before.

Thanks again for catching me before I made a solid goof.

hydronicsmike

Dan,

you did good.