Help!, please w/ primary/secondary pipe & pump sizing

[pybyr]

hello all--

I've been reading all I can get my hands on (Sigenthaler's Modern Hydronic Heating, all sorts of MFG's publications, etc) and I get the basic drift of the variables of btus, delta T, flow rates, gpm, etc--

but-- I'm having a hard time pinning down an initial starting place to figure from

basically, what I am looking to to is not rocket science, but I am afflicted with newbie info overload

all I want is a primary/secondary system with the 150kbtu boiler feeding in by one secondary loop, a 1350 gallon storage tank feeding out/ in by another loop (with a plate HX and second set of circulators like NoFossil), and a finned coil in my furnace plenum to take the hot water, from whatever source, to the ducts to the house.

this'll all be in my cellar, in pretty close proximity, so no long, long pipe runs

I appreciate any tips of (a) what pipe and pump sizing have worked, or are expected to work, successfully, for the secondary and primary loops, pump sizing, etc.; or (b) a tutorial in where to start in figuring my way through all this in a way that I won't over-build anything, but also won't short anything on long-run efficiency

Thanks

 

[WoodNotOil]

I think that the layout you are talking about would resemble one of Nofossil's drawings in this topic: https://www.hearth.com/talk/threads/18585/ (third post down) The only differences being that instead of zones you would substitute your hot air hx and on the tank piping there would be one pump on the cold side and one on the hot with no zone valves. (that would resemble my tank pump design)

For 150kbtu output you would need a 30-plate hx to charge and draw from tank. My design calls for 15gpm at about 12 feet of head. The grundfos 15-58 on high will work for this. Your setup may have a slightly different head loss due to your own piping, but it should be in that ball park. Taco now has a 3-speed to compete with Grundfos http://www.pexsupply.com/product_dtl.asp?pID=5641&cID;=&brand;=

I hope that helps to get you started.

 

[pybyr]

WoodNotOil- thanks for the response- I have my piping layout clearly developed in my mind or on a hand sketch, but am so far graphically impaired in a way that's preventing me from making a diagram in image form that I can post here.

Basically, the "primary" circuit loop of my primary-secondary system is going to be like a traffic circle; it'll need a circulator to keep the flow in that loop going round & round-- but it'll basically depend on the control of the secondary circuits into and out of it to control what direction the BTUs go in.

The wood boiler, the input to&draw;from the storage, and the finned coil in the duct will all be secondary circuits to that primary loop's "traffic circle". That way the BTUs can get "on and off the traffic circle" in any desired direction or combination of priorities.

What I'm still stumped over is the diameters of pipe (and the right pumping characteristics of the circulators) that I'll need to use from the boiler to the primary's "traffic circle" and from the "traffic circle" to the tank, so as to be sure, in order of urgency of consideration (1) that full output of boiler can get from boiler to storage or from boiler to finned duct coil (all to avoid boiler idling), and then back again from tank to primary loop for routing to the finned duct coil (2) that flow rates in the pipes aren't too slow or fast in ways that'd fall into problematic effects (3) that I don't oversize my piping in a way that'll make it a logistical or budget nightmare to build (I tend to over-design and over-build, which I guess is preferable to the opposite extreme, but at price of large diameter pipe, I gotta keep it sane); and (4) having each of the circulators "just big enough" that they do their job well without using too much electricity

As a starting place, what size & type pipe are you using on both sides of your plate HX (to and from HX and boiler, and to and from HX to tank) and how did you arrive at a comfortable conclusion that it's "right" to move the BTUs over the fairly wide temp swings, and while maintaining the right velocities in the piping?

Thanks

 

[Willman]

Hot Rod had a pic of his primary loop in a circle. Fairly good idea if you have the room. The correct design of the piping and controls and circs is what it is all about. I'm sure the pros will get you an answer.

Will

 

[pybyr]

Thanks Willman- I recall seeing the photo of HR's primary loop that's truly a loop- I am thinking of doing something similar except, I hope, if not price-prohibitive, and the pipe sizings can work, with Taco TwinTees and various 45 degree fittings to hook it all together in a loop

 

[kabbott]

Taco software comes up with 15.9 GPM at 20 degree delta to transfer 150 kbtus and 1.25 inch pipe (as long as its pretty short)
I have been beating my brain trying to figure out a pipe layout, I like the P/S but not all the circulators.
Would there be any problem with making the plate exchanger part of the primary loop?
If it was large enough that there was little pressure drop that would eliminate a twin tee and circ.

 

[pybyr]

Thanks Kabbott

I've got the basic pipe layout sort of in mind, just am so far stuck by not having any way to come up with a graphic image of it to post

I tried downloading the Taco HSS program last night, but can't do it on this computer (a Mac) and ran into various snafus about "missing DLL files" when I tried to download it on my older Windows laptop.

the idea of making the plate HX part of the primary loop is a very intriguing idea that deserves some additional thought- the only thing I can think of so far (aside from making sure it flowed really well, as you say) is that the tank sides of the loop would perhaps tend to siphon back to the tank-- I don't worry too much about leaving the innards of the tank side of the HX dry, but of course, need to make sure the circulators on the tank side don't get all the water siphoned out of them, as that'd spell quick doom for wet-rotor circs. I don't know if there's maybe some kind of non-power-hog, non-wet rotor pump I might use in that location nearest the tank on the tank side of the plate HX?

 

[WoodNotOil]

You can always draw it by hand with a ruler and take a digital picture of it to post. A very low tech solution.

 

[in hot water]

Thanks Kabbott

I've got the basic pipe layout sort of in mind, just am so far stuck by not having any way to come up with a graphic image of it to post

I tried downloading the Taco HSS program last night, but can't do it on this computer (a Mac) and ran into various snafus about "missing DLL files" when I tried to download it on my older Windows laptop.

the idea of making the plate HX part of the primary loop is a very intriguing idea that deserves some additional thought- the only thing I can think of so far (aside from making sure it flowed really well, as you say) is that the tank sides of the loop would perhaps tend to siphon back to the tank-- I don't worry too much about leaving the innards of the tank side of the HX dry, but of course, need to make sure the circulators on the tank side don't get all the water siphoned out of them, as that'd spell quick doom for wet-rotor circs. I don't know if there's maybe some kind of non-power-hog, non-wet rotor pump I might use in that location nearest the tank on the tank side of the plate HX?

Consider a Parallels program for your mac. I run all of Siggys, Taco, and a bunch of solar sizing software on my mac. I can actually have the Windows and mac screens open together. A very handy program.

hr

 

[DaveBP]

If you have the whole system together in the cellar can you run your primary loop down low enough to put the tank HX well below the water level in the tank so it can't siphon dry? Just grabbed my first cup of coffee off the stove so the answer may be obvious to me in a couple minutes.

 

[pybyr]

Consider a Parallels program for your mac. I run all of Siggys, Taco, and a bunch of solar sizing software on my mac. I can actually have the Windows and mac screens open together. A very handy program.

hr

Thanks HotRod; I have in fact Parallels for my Mac (an Intel Mini) but when I try to install Windows 98SE (the only WinOS I have on hand) into Parallels, it gets into some sort of choke-up, which I haven't had patience or talent to fully un-tangle. I definitely don't want to buy any of the newer versions of Windows like XP or Vista, both 'cause they're costly and because they seem bloated and unstable from what I see of others' experiences. I wish I had a copy of Win2000Pro to put on the Mac/Parallels; that's the one Windows OS that always really impressed me with its stability and performance.

 

[pybyr]

If you have the whole system together in the cellar can you run your primary loop down low enough to put the tank HX well below the water level in the tank so it can't siphon dry? Just grabbed my first cup of coffee off the stove so the answer may be obvious to me in a couple minutes.

If I have the tank HX on its own secondary loop, separate from the primary loop, then I can definitely have the HX down below water level, which is what I was originally thinking, and then (I think) the circulators will keep water in themselves at all times.

But then Kabbott's idea intrigued me- a lot- that if the HX can be an integral part of the primary loop, the whole thing becomes simpler, and needs one less circulator

with the layout of other things in the cellar, I've been planning to have the thermal tank somewhere where it's not right near the wood boiler or primary loop, and have the lines from the primary loop to the tank go up to the ceiling, across, and down back to the tank

I suppose I should keep in mind whether I could either get the tank closer to the boiler and primary loop, or else run the piping in-between down near floor level, and just be careful not to trip...

 

[deerefanatic]

Ok, I have built a true P/S system for my unit....... Flow travels clockwise.... Air scoop on the top of the loop to remove air... (duh......) Circulator on the left vertical part to circulate water through the primary loop (having circ in this orientation, it's nearly impossible to air lock it...) All the supply/load tees are on the bottom, with the outlets facing down... This way, if an air pocket should manage to find it's way down there, it can't get sucked into one of the secondary circs......

Each secondary circ and it's associated piping is like it's own little heat system.. Size the pipes and circs for the flow required to move the amount of heat that it's particular loop consumes/supplies..... For the primary piping and circ, size it to be large enough to move all the heat that the boiler(s) can provide..... This is a good trade off... Many times your loads can exceed your boiler capacity, so having a circ sized that big is a waste......

Then, you set the system up so when any secondary circ comes on, the primary circ also comes on......

Hope this helps you out... If you need more info, let me know, otherwise I don't feel like typing it all...

 

[deerefanatic]

I will add one thing I forgot......

When laying out your secondary circuits, you need to place heat loads first, then storage, then the loads in order of water temperature need.... For instance:

On my setup, the water is flowing clockwise, which means that at the bottom of the loop, water is flowing from right to left..... So:

Secondary Circuits, listed right to left:

Wood boiler; Storage; Barn Domestic hot water; House domestic hot water; house air handler; office baseboard (very small zone); shop radiant floor.

Notice as water moves to the left, each load will see a slightly cooler temperature of supply water, so the circuits that need the hottest water (Domestic circuits) are first, with the radiant floor (needing the coolest water) last..........

 

[pybyr]

Consider a Parallels program for your mac. I run all of Siggys, Taco, and a bunch of solar sizing software on my mac. I can actually have the Windows and mac screens open together. A very handy program.

hr

OK Hot Rod- thanks- you re-inspired me to beat my head against getting Parallels up and working. I bought a legit copy of Windows 2000 professional and am now downloading a missing DLL file so that I can hopefully run Taco's HSS and Siggy's software.

The advantage or disadvantage of projects is the way that they inspire/ enable/ depend on each other...

 

[pybyr]

I will add one thing I forgot......

When laying out your secondary circuits, you need to place heat loads first, then storage, then the loads in order of water temperature need.... For instance:

On my setup, the water is flowing clockwise, which means that at the bottom of the loop, water is flowing from right to left..... So:

Secondary Circuits, listed right to left:

Wood boiler; Storage; Barn Domestic hot water; House domestic hot water; house air handler; office baseboard (very small zone); shop radiant floor.

Notice as water moves to the left, each load will see a slightly cooler temperature of supply water, so the circuits that need the hottest water (Domestic circuits) are first, with the radiant floor (needing the coolest water) last..........

Thanks for the input and advice Deerefanatic (aside- I have a 57 520w and a 56 420w, both solid but neither fit for show) the one thing I am not clear on is as to whether you are saying boiler -> storage -> loads or something else. your upper paragraph saying "when laying out..." seems to say loads before storage; your later one seems to say boiler, then storage, then loads.

I have been assuming that it'll make sense for me to do boiler -> storage -> loads (and as you say, have the high-temp-need loads first, and the others in descending order of temp requirement). My thinking is that when I need heat straight from boiler to loads, the secondary circulator for the storage can remain off, sending the heat straight past the storage to the loads. But when the boiler is off and the storage turns into the supply of heat, then the storage can/will be upstream of the loads. Am I making sense and is this what you are suggesting?

 

[deerefanatic]

Yes, Yes, YES, and YES!! That is exactly what I was trying to get across. Sorry for the confusion there.......

Yep, in direction of flow, you should always have coolest heat sources (say, solar) -> hottest sources (wood, oil, etc) -> storage -> loads in descending order of temperature need.... This will give you ultimate efficiency as you can extract the most heat possible from a given gallon of water......

Please note though, with primary secondary you can't interface to your tank in quite so straight forward a way.. In order to use stratification to your advantage, you have to be able to change flow direction through the tank... But, for the primary/secondary to work right, the water must be drawn off of the primary pipe and returned downstream, regardless of whether you're charging or discharging... So some sort of reversing circuit is necessary... a 4-way valve can be used, or 4 individual ball valves with actuators......

here: check this thread out: https://www.hearth.com/talk/threads/19476/ Post number 20 has a picture/diagram of how mine is set up...

 

[pybyr]

Please note though, with primary secondary you can't interface to your tank in quite so straight forward a way.. In order to use stratification to your advantage, you have to be able to change flow direction through the tank... But, for the primary/secondary to work right, the water must be drawn off of the primary pipe and returned downstream, regardless of whether you're charging or discharging... So some sort of reversing circuit is necessary... a 4-way valve can be used, or 4 individual ball valves with actuators......

Thanks deerefanatic- I realize that when it comes to maintaining stratification in the tank, I'll definitely need to pump in opposite directions depending on whether I am charging the tank or drawing from it (and I appreciate you pointing it out/ confirming it; in these e-conversations it's always hard to know what someone else already is or isn't tuned into)

__ BUT__ as far as how that frequently reversing direction of secondary flow to/from storage interacts with the tees where the tank's secondary circuit meet the primary circuit, I've been able to confirm that the Taco Twin Tee product, which has the secondary inlet and outlet right next to each other (side by side with a baffle in between), not one downstream from the other like regular "close tees", solves that 100%-- see this other thread (the Twin Tees also turn out to have some nice advantages of being much more tolerant than the "traditional" close-spaced tees in terms of being able to be snugged in close together, or close to up/downstream fittings, permitting a more compact overall layout (now I just hope they aren't prohibitively costly)(but they seem almost certain to be less costly, and certainly more reliable/ less complicated than a bunch of powered valving and associated controls)

https://www.hearth.com/talk/threads/20918/

 

[deerefanatic]

true, the Twin tee is definitely the way to go.. even if you can't afford it for the whole system, at least for your heat storage... It can save you a ton of effort..