How do I build a proper header or primary/secondary loop


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Old 03-24-13, 09:26 AM
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How do I build a proper header or primary/secondary loop

I am replacing my old Weil Mclain HE 4 with a Lochinvar Knight KBN 106. I have six zones, five of them slant fin radiators and one is a radiant with pex in the concrete garage floor (with it's own pump, mixing valve and manifold). The new boiler has a 1" output/return line. I have read numerous forum entries about how to build a header - Tees very close together for each zone with a pump for each zone, but am still unclear on how far apart the pairs of tees should be. One guy says a minimum of 10", another says 8 times the diameter of the pipe (which with 1" pipe would be 8" of course). It also appears from what I'm reading that I will need an additional pump for the primary loop, in addition to the boiler pump - - unless I go with a Low Loss Header.

I'm still debating on the LLH as, if I need an additional pump (with associated cost of operation) and an air separator, the elimitation of these two items would lower the cost of a Caleffi LLH to less than $200.

What is your advice and thoughts?

Nick
 
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Old 03-24-13, 09:56 AM
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One guy says a minimum of 10", another says 8 times the diameter of the pipe (which with 1" pipe would be 8" of course).
Make sure you're asking the right questions and interpreting the answers correctly.

If you are talking about the pair of closely spaced tees that the boiler is going to connect to, these are both incorrect.

I suspect that the 10" diameter is for a standard (NOT primary/secondary) header.

The 8 X D is wrong for the space BETWEEN the tees.

Tell us which diagram in the Lochinvar manual you are considering, and place a link to that manual on-line so we can look at it and advise.

See this:

http://comfort-calc.net/primary-seco..._tutorial.html

Drawing 6 gives the proper dimensions for closely spaced tees.

The tees should be AS CLOSE TOGETHER AS POSSIBLE, not to exceed 4 X D.

In some cases it may be advantageous to use a valve such as this to facilitate initial filling and later service of the system (air purging, etc). It is often difficult to properly purge a p/s system and placing a valve between the tees in this fashion allows one to direct the water where it needs to go during filling/purging operations.


image courtesy pexsupply.com

58644 - Webstone 58644 - 1" x 1" Pro-Pal Full Port Brass Ball Valve w/ Reversible Handle, Primary/Secondary Loop Purge Tee
 
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Old 03-24-13, 12:56 PM
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Hydro Seperator

Thanks for the tutorial reference NJ Trooper. I have decided to go with a Caleffi 548 Series Hydro Separator. Found a place that sells them for $354.

Another question: Is a 1/25 hp Grundfos UPS15-58FC 3-Speed Circulator Pump adequate for each zone?
 
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Old 03-24-13, 04:14 PM
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Is a 1/25 hp Grundfos UPS15-58FC 3-Speed Circulator Pump adequate for each zone?
I would say yes, more than likely. At least for the baseboard zones, maybe for the radiant as well, but without knowing a little more info, can't say for sure.

You really want to run all those pumps though? Why not electric zone valves?
 
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Old 03-24-13, 07:57 PM
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I ran zone valves for 30 years and had to replace too many... at least a half dozen over the last 25 years. So far, the pumps I've had lasted for 20 years or so. The guy who I bought the boiler from says they set up all the new systems with pumps on each zone rather than zone valves - - so I thought I'd give it a try.
 
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Old 03-25-13, 05:01 AM
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Understand...

Have most of your valve problems been endswitch related? i.e. valve opens, burner won't fire... ?

I think pumps are more reliable myself, if not somewhat more costly in electricity to run.

Chances are pretty good that you can run them on the LOW speed ... delta T measurement will confirm this.
 
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Old 03-25-13, 05:06 AM
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The problem with using pumps for zoning is many systems become over pumped. Zone valve systems usually this happens less. With the use of mod/con boilers on the increase we would want higher delta-t's.
 
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Old 03-25-13, 08:24 AM
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Rbeck,

Iím very interested in the zone valve vs recirculator conversation. I understand the problem with overpumping and return water coming back not cold enough.

Letís say we have two zones. In the scenario when only one zone is calling for heat the flow rate in that particular zone will be the same in zone controlled system or recirculator controlled system Ė you have one recir running a zone. Technically with zone controlled system the flow will be lower since there is additional head from the zone valve, but letís ignore it for now. So if recirc is big enough we will be overpumping in each system. If it's sized properly, we're good.

When you have two zones calling for heat in zone controlled system the flow thru each zone dropped in half (letís pretend zones are equal) and for recirculator controlled system the flow stays the same. So only in this scenario (which might or might not be happening often) the zone controlled system will be better when it comes to overpumping. If overpumping was happening when only one zone is on.

I assume a system has to be design that there is no overpumping when only one zone is open. In which case valve vs recir overpumping argument is a moot point. However it will make a difference in a system that is not designed properly.

Originally I was inclining towards having zone valves for my future system (see here), but now I think otherwise.

Pros for recircs:

- simpler system: for 2 zone one will have 2 recircs with IFCs, otherwise a recirc + 2 zone valve
- cheaper: 2 recircs cost less than a recirc + 2 zone valves
- same flow when one or 2 zones are calling for heat
- someone mentioned that zone valves are less reliable
- 2 speed recircs will give flexibility regarding the flow rate per zone

Cons:

- NJ Trooper thinks that it will cost more electricity wise, but Iím not sure if I agree. When two zones are open a single system recirc will run more or less twice as long as two individual zone recircs, so it should be the same. Please correct me if Iím wrong on this assumption.
 
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Old 03-25-13, 09:01 AM
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When two zones are open a single system recirc will run more or less twice as long as two individual zone recircs, so it should be the same. Please correct me if Iím wrong on this assumption.
I don't think that's a correct assumption Diver...

The zones are running in parallel with each other, both producing heat at the same time.

What is your reasoning that the pump would run twice as long?

Also, remember that a zone valve consumes what? maybe 10 watts of power? compared to a typical wet rotor circulator which might consume say 100 watts.
 
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Old 03-25-13, 09:39 AM
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The zones are running in parallel with each other, both producing heat at the same time.


the heat will be delivered by half the flow for each zone, so the output will be lower. but not in half though:

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so it will only run 5% longer: (610 - 580) / 580

if boiler is big enough to satisfy 2 zones, then i agree, you will consume less electricity.

zone valve power consumption goes on top of the recirc, so it will balance things are bit, but probably not enough to make recirc system consume the same amount of power.

you convinced me, it will take less power. not sure if i wan't zone valves yet, but i agree on one negative for all recircs system.

i assume having a dedicated recirc for IHW is still preferred since the flow rate should be higher there and zone valve in that loop is not desirable due to increase in the head?
 
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Old 03-25-13, 07:47 PM
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the heat will be delivered by half the flow for each zone,
No... circulators don't work that way.

If one zone is open and pumping say 4 GPM, when the second one opens it doesn't pump 2 GPM through each one.

That's what a 'pump curve' and a 'system curve' and the 'operating point' is all about.

When the second or third or fourth zone opens, the pump is moving water against LESS HEAD (zones in parallel present less head to pump) and the flow from the pump increases.

A pump with a flat curve like the 007 will pump say 4 GPM into one zone, maybe 7 into 2 zones, maybe 10 into 3 zones... to a point of course, but absolutely not half, or a third, or a quarter. It just don't work that way!

This graphic illustrates. The three curves starting at zero are what the system might present to the pump with one zone (the left curve), two, or three open. Note the intersecting points with the pump curves. This is the 'operating point', where the system curve intersects the pump curve. That's how much will flow.



i assume having a dedicated recirc for IHW is still preferred since the flow rate should be higher there and zone valve in that loop is not desirable due to increase in the head?
Correct. But, with a zone valve with a high Cv rating and priority on the DHW, they can be made to work just fine. I personally would run a dedicated circ on an indirect to get max performance.

Boy, we did a good job hijacking Ntonkin's thread, didn't we? ( hint, hint )
 
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Old 03-26-13, 05:42 AM
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thanks, NJ Trooper.

i'd like to continue this conversation, but taking your hint, would you follow me back to my own thread here?
 
 

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