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Primary/Secondary zoned with circulators
Sorry about getting the whole manual. It is not what I intended. The page that depicts my piping is on page 32. "Single boiler zoned with circulators". My piping is exactly what the drawing shows. The closely spaced tees are 6" apart. All piping is 1" copper except the zone piping. Zone 1 and zone 4 are 3/4" copper and is piping for the Coils in the air handlers and zones 2 and 3 are also 3/4" copper reduced down to 1/2" pex for radiant floor heat. The radiant zones also have a crossover ball valve between supply and return to lower the water temp for the radiant.
Primary/Secondary zoned with circulators
I have a hydro air system using primary secondary piping zoned with circulators. There are 4 zones (2 zones to air-handler coils and 2 radiant zones) The primary loop is 1" copper the air handler zones are 3/4" and radiant zones 1/2". The problem is that when both air-handler zones call for heat it seems that only the zone closest to the entrance to the primary loop gets the hot water. The 2nd a/h zone is further down the the primary and only seems to get hot when the first zone is off. The pumps are Taco 007's the primary pump comes on when any zone calls for heat. Does this sound like a common problem?0
Primary/Secondary zoned with circulators
Here is a diagram of the piping I used.0
The attachment came up as the whole install manual. Don't know if that was what you wanted to do.
Is the zoning done with circulators or zone valves?0
Without seeing the diagram
here is an educated guess:
I would suspect a balancing issue exacerbated by the sequence in series (again I assume) off of a too-small primary loop.
In short, the first zone grabs all the water it needs. The second zone has to fight the first for what it needs. (All flow the second zone needs is already under the influence of the first zone.)
It is common when higher pressure drop zones are piped in series.
Solution would be to make the take-offs in parallel. As a general principle, each zone must have equal pressure drops.
Again, though, the diagram will tell us much more and minimize the guess-work.0
I would stand
by my original assessment that it is a balancing issue. A larger primary loop might help by lessening the common pressure drop but in the big picture, piping the zones in parallel off bridges might make more sense.
A Low Loss Header such as by Caleffi or Viessmann will do wonders towards keeping your return water temperatures to the boiler as low as possible (which you want for efficiency).
The LLH's hydraulic decoupling will eliminate sibling rivalry.0
What's the total heatloss?
How many BTUs' for each of the 4 loads?
Conventional or modcon boiler?0
Thanks for the help. Can you draw a simple sketch with both solutions so I get an idea of what you mean? Low loss header and piping in parallel off crossovers.
The current piping is a parallel design and I thought that with 1" primary pipe (8 gallons per minute) I could satisfy two 3/4" pipe zones (4 gal per minute) without much trouble. with only the two zones running it doesn't heat both zones at once.0
The total heat loss is about 80,000btu's. The two air handler zones are both about 40,0000 btu's each. The other two zones (radiant floor) are for floor warming only. The main heat for the rooms are the air handlers. The boiler is a lochinvar knight condensing boiler rated at 105,000 btu's.0
Geez guys I don't get it. I can't really see how that piping diagram can function very well at all. I would think that all the loops (secondary's) should come off the primary loop directly, instead of off that other (kind of) loop above the primary. Off course I'm not the sharpest tool in the shed... maybe I'll re-read Dans books0
The heating circuits and its mutliple paths form the primary loop. The boiler is on the secondary for many newer modcon installs. Why we call that indirect piping parallel primary is the part I don't get! ;-)0
Do all of your flow checks work? I'm surprised your manifold wasn't done in 1¼" piping, but nevertheless, could the secondary A/H cause the flow in the radiant circuits to reverse and temper the water down?
Could you close the valves to both radiant circuits and try that? If it works like that, you need better flowcheck valves.
I'd also try throttling back the flow in the first circuit? It may be moving more of the flow than you have calculated.
Still, I really think the manifold sizing could have been better in my completely amateur opinion. ;-)0
I suspect your boiler pump (007?) is undersized for the boiler pressure drop. You should probably have a 011 on that boiler to get 7gpm.
Is the boiler loop flowing with the zone piping flow or against it? If the boiler flow is opposite the zone piping flow, it will make the boiler work harder to keep the supply temperature up. It will also raise your return temperature to the boiler.
At the same time, Brad's suggestion of balancing the loops could prove to be the main source of the problem.0
I'm sorry to mislead you. The main boiler pump is a grundfos 15-58. All zone pumps are taco 007's. The supply temp is 150 degrees and the return temp is 130 degrees. How can I tell if the flow is toward and around the zone or against the flow of the zones? (from supply across the 6" spaced tees and back to the return of the boiler)without going through a zone?0
Andrew, the boiler is the secondary...
This is all about the first branch on the primary taking most of the BTUs in that 1" tubing.0
just pointing out...
I see very high zone flow rates and a relatively low boiler flow rate, though better with the 15-58.
The temperature in the supply header has to be equal all the way across. The loops are in parallel, so they each get to ride on their curve. The 2nd zone would get some flow, though the quantity would depend on the head loss in each active loop.
I think something else is going on here, but I could be wrong. I assume the 15-58 is on speed 3?0
Yes it is on speed three. What if I replace the 15-58 with a higher flow rate pump? Do you think that would help without increasing the pipe diameter?0
Do you think changing to 1 1/4" or 1 1/2" pipe is the answer? The boiler connections are 1". You can just enlarge it with fittings? Would a higher flow pump help this problem without changing the piping?0
Your piping size...
Tom, I think an inch is too small for the manifold area and that you should check your flowcheck valves... Please see my earlier post.0
1" should be fine if the flow rate is reduced to what it should be. That might be 8gpm at 20°F dT (3.3 ft/s). In my opinion, this system should have been piped with a single circulator and zone valves similar to the diagram on page 34. One 007 could probably handle the entire system. Though changing it now would be a pain and costly.
Back to Brad's suggestion of balancing. It would have been nice if the zone circulators were 15-58 3-speeds, because then they could be turned down without replacing. I assume you have ball valves on the returns from the zones as in the diagram. For experimentation purposes, if you pinch back the air handler zones does the problem go away? Ball valves do not restrict flow much until they are more than half closed. Installing proper balancing valves would cost nearly as much as simply replacing the pumps with the appropriate models. The pressure drop in each zone must be looked at individually and the circulator sized accordingly. Most often, a 007 or 15-58 is what the service person keeps on his truck so that's what you get, whether it is right or not. Fortunately the 15-58 has two lower speeds. I bet your system would work well with the zone pumps on speed 1.
What is the target system temperature when this happens? What is the system design temp? Does the entire supply header cool down when multiple zones are calling? If the first air handler is on, do the radiant floor loops still heat up? Is the system all running at one temperature? Are there any mixing valves for the radiant floor? Pictures are worth a thousand words.0
the only zones installed and in operation are the two air handler zones. The two radiant zones have not been hooked up yet. So the check valves are not the problem. I can try and partially close the ball valve on zone 1 and see what happens. I am concerned that I am having problems with the two zones, what will happen when the radiant zones come online. Do you really think increasing the pipe size by 1/4" on the primary will make that much of a difference? And when you say "primary" are you referring to all the piping from the boiler up to the zone piping or only the piping from the boiler to the closely spaced tees? Or all the piping including the loop that the air separator is on? There is a diagram on one of the first posts to see what I am referring to. Thanks for all of your help.0
Tom, it may be of interest to you to reconsider a new career.
something that doesn't involve sharp pointy objects.
i am just joking....consider what you are trying to accomplish...then,if something doesnt "Add up" dont did it. step the temps down you do. series flow eh? let me ask you will two pumps in series win the fight against one of the same size ? think about it. you have Time....
if you make a Large D on the right side of the page, lay three H's on the side ,draw a large C on the left connect the C to the ends of the first H you come to you will have a picture of something resembling an enlogated race track with a Ladder overlaid on the race track. the I part of the H on it's side is a Bridge from one side of the race track to the other....a low loss header i contend can look like whatever the mind can conjure basically...i could look like two P's one laid out on the right and one laid out to the left with a n at the junction of the two P's...or one beeg chubby straight line with two drops or Closely spaced T's or it just might be real fancy looking like the insulated Caleffi ...or it could look like an enlongated oblong box with 4 ...6 take offs...or a round gizmo with the shape of an American Indian War Hoop,with the side view of a galloping pony with his tail to the moon,and his nose to the hoop. *~/:)0
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