Correcting my 2 Zone Monoloop System (Need Help)
Good Morning All,
I've been perusing this website for the past couple months trying to diagnose the issues that I'm having and looking for the best solution by design. Before you say call someone to help, I just went through a kitchen renovation and money is very tight right now so calling someone is not really an option right now. Winter is around the corner so would like to handle this myself before it gets too cold. I bought an old 1889 Victorian home that someone down the line installed baseboard heat on a 2 zone monoloop system. 1 zone is piped with 1 1/4" piping that for some reason reduces to 1" at the pump. The other zone is piped completely in 1" piping.
I've attached 3 diagrams in pdf format. I apologize in advance, my markups didnt carry over the information very well when copying but you can use the previous setup diagram as a reference. It appears to be the most clear. "previous setup diagram" is how the boiler was operating when we moved in. Its important to note that some of the heating elements worked and others didn't in this configuration but it was heating the house enough to keep it around 65 degrees on our coldest days in Cincinnati OH so we didn't mess with it. "Current Setup not efficient" is how the house operated after our kitchen renovation. This shows us removing several elements which includes the under cabinet radiator, baseboard radiators in the kitchen, and the downstairs bath radiator. I cut these off and capped them (The kitchen is right above the boiler room so it didn't effect the heat in the kitchen all that much) This also accounts for the replacement of the copper piping running to the upstairs hallway and office elements with PEX A pipe rated for hydronic heat applications. The system operated generally the same with the exception that flow was no longer getting to the hallway and office where I had installed the PEX A. The element remained cold even after bleeding air and purging. "Proposed Setup" is a diagram of what I came up with after reading a bunch of discussions on this forum. This accounts for flipping the circulators so that they pump the other direction, away from the boiler and in the direction my monoflow tees designate as the flow direction. This also requires me to eliminate the flow control valves that are on the return side just before the boiler as these would prevent water from flowing in the direction I would like it to move. The other thing I would do is connect the tees for the elminated loops from the kitchen and bathroom to allow that flow to continue to pass through.
Im not sure what the previous homeowner had serviced but the pumps were generally pretty new and their was some new valves in place so I am assuming they had done work or had work performed. Im concerned that while troubleshooting they managed to set this system up in a way that works but not that which it was intended. There is also a geothermal unit that had similar WOES (wrong pumps and clogged glycol system) so ive lost my confidence in whoever had maintained these systems. Not that it matters but I'm just saying I have a hunch that this is not how is was designed 60+ years ago.
My thoughts are, if I reverse the flow, the circulator pumps will now operate independently on their own zones and the diverter tees should now operate as intended creating the pressure drop on the return and forcing water through each element. By eliminating the flow control valves which is essentially a check valve It will allow flow to go in the direction I want it. Do we even need a flow control valve here? Should I put one on the other side of the circulators instead? I cant think of a reason I would need one though. Also by connecting the loops for the eliminated radiators it may better my flow down stream and hopefully make the office and hallway element work again. One more thing….removing the balancers for now as I think these originally wouldnt have had balancers on them (correct me if Im wrong) I can add them back if it doesnt work well. They need replaced anyway.
I suppose it wouldn't hurt to verify the pumps provide enough head to overcome the resistance of all these elements and fittings but I wouldnt know where to start. Got any suggestions? Also, is it concern that I have a pump that runs a 1 1/4" line but reduces to 1"?
What about my expansion tank? Would it be a problem that it would be on the return? My pictures have the flow control valves removed already so use your imagination on that part . They would just be attached to the pipes directly below them :D
Appreciate any help you are willing to give. Thanks in advance.
Comments
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It looks some of my pictures were cut off
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Your pumping toward the ex tank which is not the best. Monoflo systems work well if designed well. The most difficult thing is they can be difficult to bleed the rads or baseboards, I know I lived with one in my own home for 34 years. But once bled they work fine.
One thing about a monoflow system is if the original system worked and gets messed with it may not work. I cant tell from your picture what was changed or modified.
If adding to a Monoflo system it is better to make a new zone which does not have to be Monoflo rather than screw up the original system.
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Ok so it's better off to be pumping away from the expansion tank. Yet another reason why these newer circulators appear to be going the wrong direction.
I actually haven't had a hard time bleeding them due to the auto air vents on each baseboard and a hose spicket purge valve on each each loop but the first time I did it it was fun figuring out what I was doing!
I thought about ripping all the old plumbing out and replumbing using a different method but that's not in the cards right now. Definitely do-able. Mainly trying to see if my thought process is flawed. I think I'm going to give it a try and see how my system reacts
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If your diagram is proper, the flow is in the opposite direction from what is dictated by the monoflo tees. In such a situation, it would be difficult to fathom how ANY radiator received flow.
You cannot reverse the flow by placing the circulators on the supply. The flow is identical. You would need to install the circulators in the opposite direction. However, this would require a bit of a repipe so the supply out of the boiler goes to the circulators and the circulators are installed so the pump toward the existing return lines.
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LRCCBJ,
That was my exact thought as well. Ive confirmed all monoflow tees are pointing in the opposite directions as the flow. The flow valves were the only thing on my system pointing in the same direction as the flow. I'm guessing it possibly acted as a natural convection type system? Maybe that's why it was so random and spotty?
Anyway, you raise a good point. Seems my boiler isn't plumbed correctly at all according to the manual. in fact, using the exact opposite side and not utilizing the mixing it requires as the preferred method. Seems I've got quite the project. Maybe I can plumb it all copper so it's easier to work with. Will be expensive though 🙄. Maybe I'm jumping ahead but, so far not looking good. What do you think? This house hasn't been easy on me and I don't like shortcuts so it's been real expensive.
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First of all changing the direction of flow thru a Mono-flo® one pipe main will not make the actual Tee fittings correct or incorrect. If the Mono-flo® tees are properly installed (where the cone is on the site of the pipe that is connected to the other tee fitting on that same radiator) as shown in this illustration from the manufacturer's literature.
Second, if you actually change the flow direction in and out of the boiler, so the cold return water is entering near the top of the boiler and th hot supply water is leaving the bottom of the boiler, you are going to get some pretty hot water. That is because the high limit sensor will be located at the cold return water.
So what ever you do, Don't operte the system the way you have it in this photo. It is DANGEROUS
And finally, when you remove the flow check valves from the system, you are actually going to allow reverse flow thru one zone that is off when the other zone is operating. So removing the Flow Control valves will cause more problems that it will solve. As shown in these illustrations
You will want to read this whole book
Twice!
Edward Young Retired
After you make that expensive repair and you still have the same problem, What will you check next?
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Thanks for the reference. Definitely useful!
Also thanks for the advisement on switching pumps around. I was clued in on that once I found the actual diagram for my system. I will not run it in that configuration 👍.
As for flow valves. Thank you, I'll make sure one is put back into place.
On the monoflow tees, so if water is pushing the opposite direction of the cone, will it just operate at a reduced efficiency? My whole system is set up like your diagram shows, however flow is going opposite your diagram. I assume that cone can't be purposely placed on the opposite side of the fitting?
At this point. I'm planning to reconfigure the entire boiler
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When you said that this is inefficient
It is because someone capped off some of the radiators. When you cap off a Monoflo® radiator you are restricting the entire one pipe main to the smaller orifice opening on the inside of the tee. When the system was installed in the 1950s (or when ever) it worked just fine because someone did the math and figured the restriction and heating value befro selecting the radiators and piping design. Somewhere along the line someone who did not do the math removed the path that some of that water is supposed to take.
In the upper right diagram I have marked up some hypothetical answers to the questions on the diagram.
In the lower right diagram I have also marked up what might happen when that Red radiator is removed and the supply and return pipes to that radiator are capped off. The restriction of each capped off tee will reduce to flow to the entire system. the first one that is capped off will do the most damage to the gallon per minute GPM flow rate. then each following capped off radiator will add to the restriction to the point where the amount of water flowing thru that one pipe main may be so slow that there is not enough heat for the rest of the radiators. When you read the book I posted on line above, you will see a rule of thumb about 1 GPM = 10,000 BTUs. If the loop that is inefficient is only flowing 2.5 GPM when it should be at 5 GPM, then you only have 25,000 BTUs for all the radiators in that loop. Not 50,000. Even though you have a big enough pipe, you are adding restriction three times with those three capped off radiators.
The correct way to remove a radiator from a MonoFlo® system is this:
This way the full GPM amount entering the Tee at one end of the branch can exit at the other Tee at the end of the branch… So I hate to say it but… you need to put everything back the way you found it then pipe in those bypass pipes.
Edward Young Retired
After you make that expensive repair and you still have the same problem, What will you check next?
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I can't open your diagrams without jumping through a lot of hoops because they are .pdfs instead of images but assuming it is 2 zones you need the flow checks to prevent a call in one zone from causing ghost flow in the other zone. Assuming the loops are separate or are fed by one common pipe then branch off separately the way the circulators are is OK. It isn't the best way but it also isn't your problem. If you remove an emitter you either need to remove its tees or connect them together because the monoflo tee has a partition in it(that b&g calls a venturi, but it isn't, it is a partition that divides the flow) that separates the flow so that some goes through the run and some goes through the branch. If you cap the branch you have reduced the diameter of the pipe at that point.
The arrow on the monoflo tee is just to tell you how the partition is oriented, it will still divide the flow between the run and the branch regardless of which way it is installed though possibly a bit more effective in one direction vs the other(I think officially it should point one way if it is on the supply and the other if it si on the return to the emitter). Your problems are likely from the removed and capped emitter and possibly some air that is still trapped somewhere. A microbubble air separator at the boiler would be a great idea in any monoflo system.
^^^^^
er see ed's comment below, if the tube is on the through side of the run it will restrict the main. i hav tried to explain this before and somehow forgot here.
The balancing valves are probably a good idea although not strictly necessary if it is 2 separately controlled zones but they would be used to balance the zones so that you didn't end up with one zone that heats and one that does not when both are calling.
The old way of installing circulators was to install then to pump in to the boiler on the return, it is just an older design, it still works that way. You would have to move the circulators to the supply to pump away from the boiler, some to a lot of repiping depending on where the zones combine on the supply.
I can't tell which way the circulators are installed but they should be installed with the arrow toward the boiler and they look like they may be the opposite way. They are on what should be the return.
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So look closely at the picture of a Monoflo® where the label is not painted over
Edward Young Retired
After you make that expensive repair and you still have the same problem, What will you check next?
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I have some other clues on this diagram for you
- The line gets lighter and lighter as the one pipe main travels past each radiator. This is to indicate the incremental temperature drop as the return water from that radiator remixes with the higher temperature water in the main
- The boiler pipe for the supply is at the top of the Yellow (WM Gold) box indicating the boiler. That MUST be the supply (Da' gues-out-a pipe) from the boiler. And the pumps must pump the water that way. So the flow check valves were correct.
- The width of the line gets thinner to indicate that capping off a radiator will reduce the GPM flow.
Sice you indicated you were going to repipe the near boiler piping, I might suggest moving the circulator pumps to the top of the boiler on the Supply side. Diagram to follow.
Reason is in this book
Edward Young Retired
After you make that expensive repair and you still have the same problem, What will you check next?
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Check both sides of the tee for arrows. Monoflows can be used on the supply to the baseboard or on the return if installed properly and with the correct flow direction.
After all that is what they do with radiation below the main they use two monoflows.
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If you look closely at his sketch, you'll see a SINGLE diverter tee and a standard tee for each radiator. So, the direction of flow absolutely matters. You should amend your post to avoid confusing him. The FLOW DIRECTION MATTERS!
Your recommended diagram is completely incorrect for a system with single diverter tees. This was indicated on his original diagram.
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Your the man!! Thanks for putting all that together. Interesting though. I'll try connecting those loops and test the system again. I'll report back if we are in business.
Do you see anything wrong with it not following the manuals diagram for mixing and preventing water cooler than 130 degrees from entering the boiler?
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Actually not. the arrow on any diverter tee is based on installing the diverter tee on the return of the radiator. some instructions will tell you to install one diverter tee on both the supply and return if the radiator has more that the usual restriction of the rest of the system (like if a radiator is located in the basement below the one pipe main). The orifice or restriction cone MUST be placed so it is on the side of the Tee that connects to the other Tee. This diagram will work by putting the Diverter Tee on the supply in the opposite direction of the arrow that is meant to point in the correct direction when located on the return of the radiator. It is just a little less efficient but not by much.
Take a close look at the label. there are 2 arrows.
So does the water flow to the left or the right @LRCCBJ? That depends on where the Tee is located? Is it on the radiator's Supply or the Return.
The bottom illustration here looks like the top illustration with the water going the other way. Did the water direction change with the arrow staying the same? or does the arrow need to be changed on the label? OR as Dan H would say, Do you need to put the arrows on the inside of the pipe so the water knows which way to go?
Edward Young Retired
After you make that expensive repair and you still have the same problem, What will you check next?
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@LRCCBJ I believe that you mean this when you say the direction matters. In this illustration the arrow is in the correct direction for a Diverter tee to be placed on the radiator return. By placing that tee on the supply, it is WRONG. So the arrow matters only if you are placing it on the proper side of the radiator.
By restricting the flow entering the supply side of the radiator it as doing the same thing as capping off the unused radiator location. The entire one pipe main is restricted.
Edward Young Retired
After you make that expensive repair and you still have the same problem, What will you check next?
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YES. You want to keep the return water temperature above 135° as soon as possible. these one pipe monoflo® systems are great at making that happen when installed correctly. The hot supply water makes a quick loop back the the return with little regard for the radiators.
Edward Young Retired
After you make that expensive repair and you still have the same problem, What will you check next?
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Take a close look at the arrow in the one in the Photo of @JWieg727 Tee Fitting.
This Monoflo® is supposed to be installed on the return of the radiator. If you change the water flow in the opposite direction of the arrow then it must be installed on the supply of the radiator. This is telling me that restriction is on the left side of the tee in this photo. This means that the other pipe to the radiator MUST be connected to the left of this Tee as shown in this picture. It is difficult to read what is on the top of the label but I believe is also says ON RETURN or just RETURN. Based on the diagram that @JWieg727 posted, I believe that all his arrows are the wrong direction because he has return label Tees that are installed on the radiator supply pipes.
This photo from another discussion
about the same issue says it all. The label tells you where the restrictor cone is located. You just need to understand how they work and use your minds eye to see inside the pipe.
I believe the original installer of @JWieg727's system put them on backwards on purpose, because the supply house didn't have enough "Supply Tagged" Tee Fittings. After doing the proper math, he designed it that way on purpose.
In the referenced discussion above, it took weeks to finally get to know where the other radiator's regular Tee fitting was in reference to the Monoflo® Tee. Once I knew that, the answer was easy, The MonoFlo® was installed backwards. after they reversed the direction, everything worked perfectly.
Edward Young Retired
After you make that expensive repair and you still have the same problem, What will you check next?
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You are correct. His system has the diverter T's on the "supply" side, which is counter to the recommendations. However, it is correct and the system should function properly. Of course, the arrow on the supply side will be opposite to the direction of flow.
Since it is piped correctly based upon the T's, the problem remains. It simply cannot be attributed to the circulators on the return. That's not sufficient to cause the issues that he has.
To the JW:
There is no benefit to repipe the system to flow the opposite direction. The system was originally designed properly, although a bit unconventional. Ed is correct.
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@LRCCBJ said: Since it is piped correctly based upon the T's, the problem remains. It simply cannot be attributed to the circulators on the return. That's not sufficient to cause the issues that he has.
As far as the original problem is concerned, I only see that one zone is "inefficient" at heating, I believe it is the capped off tees, that need to have bypass pipes in lieu of caps.
Edward Young Retired
After you make that expensive repair and you still have the same problem, What will you check next?
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As far as repiping all the near boiler piping, I might suggest this configuration. place the Expansion tank under the air separator. locate the air separator off of the first elbow to horizontal on the supply pipe, then connect the fill valve using this fitting https://www.supplyhouse.com/Webstone-41672-1-2-Pro-Pal-Full-Port-Brass-Ball-Valve-w-Hi-Flow-Hose-Drain-600-WOG?_br_psugg_q=expansion+tank that you install between the expansion tank and the air separator. then put your circulators after the air separator then your flo check valves after the circulators. Here is the diagram from a class I taught on Hydronics. This is called Pumping Away and it will make the air that gets trapped in your system, vanish after operating the system for just a few hours…
Here is your system using Pumping away. The parts must be in this exact order in relation to the boiler and the expansion tank and the pumps and the direction of flow thry the monoflo tees. You must also connect the capped teed with a bypass
Edward Young Retired
After you make that expensive repair and you still have the same problem, What will you check next?
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oh, right this was the thing i tried to explain to someone before and whoever it was just wasn't getting it.
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It was about a year ago. I remember getting so many diagrams and pictures of the radiator and it took weeks to convince that guy to just reverse the tee because it was backwards. But he never shows us where to monoflo was in relation to the other side of the radiator. So it took weeks to get him to show us that. Then it took a few more weeks to convince hin that was all he needed to do. But it was a 6 apartment building and he didn't want to drain the system without being prepared for all contingencies.
Edward Young Retired
After you make that expensive repair and you still have the same problem, What will you check next?
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Took me awhile to go through your responses. All great information. Thank you.
I put the, I'll call them, "continued flow loops" in so I didn't have any more capped radiators, removed some clogged balancers (NOT original balancers), put circulators back to pushing through the boiler, and reinstalled the flow valves. I filled the system tested it out last night and all the radiators seemed to work with the exception of my hallway/office one. It's still not getting enough flow. It's a rather large loop and goes through 2 radiators but I didn't change the overall length or configuration much just replaced the copper and black pipe with same size PEX A piping. I see you were asking how those were bleed. They also have auto air vents on both radiators. However, they are on the supply side of the radiators. Then i installed a ball valve T that has a hose spicket on it that allows me to drain from 1 side of the ball valve. This allows me to purge the loop with water/flow. I suspect I'll have to cut the pressure up a bit over operating pressure to push all the air out or in hopes some of it will absorb into the water but it does work to initially get hot water through. Just not sure it's pulling all the air out so I want to play with it a little more before I say for sure.
Question about your configuration where the pumps push away. If I'm re-plumping anyway to put the circulators on the hot side of the boiler couldn't I just make the flow go the correct way then? Or do you suspect it wouldn't work the same because the people designed it to work in the reverse direction?
Also, would you suggest putting balancers back in place even though they aren't original? Each radiator feels like it's getting pretty warm. Have yet to tell where my hot spots will be, if any.
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Agreed.
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I put a ball valve on the main line between the tees. You only use this ball valve to bleed the radiator circuit. If you close it, all the flow goes through the circuit and, if you utilize 28 psi you will be successful in elimination of the air in the circuit. Of course, once successful, you must open the ball valve for conventional operation.
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I would not spend the time to put the circulators on the supply side. It's a day's work and it is not going to improve your situation a significant amount. You can always operate the boiler at a slightly higher pressure to offset the pressure loss on the supply side. Remember that contractors have been putting the circulators on the wrong side for years and the systems generally function without issue.
The flow CURRENTLY goes the correct way. I was originally confused with the monoflo tee on the supply side and the arrow would be in the opposite direction to flow in this case. DO NOT reverse the flow direction. See the sketches by Ed……….above.
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If anything I would add a microbubble air separator on the supply to remove the air that you can't bleed out as it get pulled back to the boiler.
Is the pex you used the same ID as the old pipe? Many nominal pex sizes are significantly smaller than nominal pipe sizes. Is it oxygen barrier? You could parallel the emitters that aren't heating well if they are identical. You could also replace the monoflo tees with regular tees and a section of pipe with a balancing valve in it so you can adjust the split of the flow between the main and the emitters.
Before I did any of that I would make sure there isn't still some air in it and the pex is the same actual size as the old pipe. Some types of pex fittings can reduce the ID as well, that may be a reason to go up to the next size or use a fitting that is less restrictive like a propex.
Are the circualtors on separate themostats?
What do you mean by "balancers"? Are there ball or globe valves installed for balancing or even an actual flowsetter?
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@LRCCBJ Said: I would not spend the time to put the circulators on the supply side. It's a day's work and it is not going to improve your situation a significant amount.
I disagree with not improving the system. I had a customer with a Monoflo® system. We were always having problems with air bound radiators because the auto vents on each radiator were not working. So I would need to show up twice a season to help the homeowner with the air bleeding process and drain the expansion tank. When it was time for a replacement boiler, I located the circulator pumps on the supply side after the PONPC that was also on the supply side of the boiler……. Never had an air problem after that!
So if @JWieg727 is going to change the near boiler piping anyway, then why not create the best air removal location in the system. The hottest water at the lowest pressure. With the circ pumps on the return, that place does not exist. With the circ pumps on the supply and the PONPC just before it on the supply, you have the best air removal system built into the design of the piping.
Edward Young Retired
After you make that expensive repair and you still have the same problem, What will you check next?
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So if @JWieg727 is going to change the near boiler piping anyway, then why not create the best air removal location in the system.
Yes, if he is going to do the work anyway, of course you would move the circulators. It does, however, appear that he is making good headway WITHOUT the effort of a NBP change.,
As Matt mentioned, a proper microbubble separator on the supply would go a long way to remove any residual air without the need to relocate the circulators.
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To get you on the right path we need to define some terms:
Monoflo® One Pipe Main is the pipe that starts at the boiler and makes a loop around the perimeter of the zone and returns back to the boiler. The MonoFlo® one pipe Main (or the Main for short) includes all the MonoFlo® Tee fittings and the additional Tee fitting for each radiator. It also contains the circulator pump
A Tee from the Main to the radiator, the radiator itself, and the return back to the Main is called the Radiator Branch.
The pipe that goes from a MonoFlo® tee branch to the other tee branch on a Radiator Branch where the radiator was removed is called a Bypass Pipe (or Bypass for short)
I think you are calling the Bypass a "continued flow loop"
I would like to know what you are calling the "balancers"
Your Question about your configuration where the pumps push away. If I'm re-plumping anyway to put the circulators on the hot side of the boiler couldn't I just make the flow go the correct way then? Or do you suspect it wouldn't work the same because the people designed it to work in the reverse direction?
Yes you can do that, however some of the folks that designed Monoflo® systems were aware of the fact that the first radiator on the MAIN would be the hottest radiator in the system and the last radiator on the Main could be as much as 20°F cooler by design. So by reversing the flow so the arrows are pointing the correct way on the Monoflo® tees, you will be making the coldest radiator in the system by design, into the hottest radiator. Then the hottest radiator will be the coldest. That may not be a problem for you. Just know that it might happen and you will need to compensate by damping down the air flow around that radiator if the first room on the main gets too hot.
Addressing the two problem radiators that are on one branch. You mentioned that you replaced some of the copper and steel with PEX. Was the inner diameter if the PEX the same as the inner diameter of the pipe you removed? Some PEX tubing that is rated 3/4"is actually 20% smaller inner diameter that the 3/4" copper pipe you removed. This reduction in inner diameter can be part of your problem. Another interesting thing to look at is that you have extra capped off branches in that zone. How easy would it be to use one of the unused branches to separate those radiators so they have direct runs to the main using one of the empty branches?
Edward Young Retired
After you make that expensive repair and you still have the same problem, What will you check next?
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The balancers were just inline balancers with a flap that restricted flow. Not sure what exact type it was. But had similar operation to the picture below without the fancy gauge/viewing window. Just the screw to adjust. They were seized up and clogged so I removed them. These were on the returns for radiator branches.
When measuring the two types of pipe it definitely is slightly smaller than the 3/4" pipe so that could be my issue. About 1/16" in diameter. I'm afraid it's too late to reconfigure to two separate branches without ripping out my new walls and ceiling in my kitchen. Could I use the flow from one of the bypasses to supplement the flow of the PEX Lined Radiator Branch? Or would it essentially be the same amount of flow because they are on the same one pipe main?
@mattmia2 no balancers are on my system currently. I did put ball valves that allow me to purge each loop with a garden hose but I know you shouldnt use those as balancers. What I had was something similar to my above picture. The circulators appear to be tied to the same thermostat. They both operate the entire time the system is running. I like the idea of possibly replacing the fittings with something that allows me to split the flow as desired however, I'd worry that would have some major flow restrictions down the line for the other emitters? Do you think that's a concern?
Thanks again everyone for helping. Learning a lot here.
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There were some old style ball valves that had a screwdriver slot to open/close them. You can use ball valves for balancing, you just have to understand the correlation to the handle position is very much not linear. You can't use gate valves for balancing, they must be fully open or closed or the gate will vibrate in the flow and destroy the threads on the stem.
If the circulators are always both running at the same time then you don't need the flow checks(not sure why they did that, the reason to have 2 circulators would be to be able to zone the system). You do need to balance the 2 loops so that it will heat evenly(or change the control so it does run each loop off a separate thermostat).
You could add another loop for the problem loop or the regular tees and balancing valve would probably be ok even though it would decrease the overall flow some.
See how the tube end of this npt to crimp adapter is much smaller than the npt end, this type of fitting will restrict the flow too if this is the type of fitting you are using:
https://www.supplyhouse.com/Bluefin-PXM075-DZR-3-4-PEX-x-3-4-NPT-DZR-Brass-Male-Adapter-Lead-Free
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@mattmia2 I actually had thought that same thing about the flow control valves and is the reason why I initially removed them. I put them back to bring my system back to how it operated before while I troubleshot some of the things suggested above and because it seemed there may be some backflow concerns. It may have been assumed at the time that these operated on their own thermostats, anyway. I'll probably leave them in and replace them with check valves later on.
My plan now is to, after this winter, reconfigure my boiler to put the circulators pumping away and some other modifications suggested by @EdTheHeaterMan above.
As for the line that doesn't have flow, I'll get some more time Sunday or next weekend to try to force the air out of the branch. It's a tricky one. If I think I got the air out and it still doesn't work, I'll try the other options... Just a random thought I had right now but would a small circulator on the PEX branch that turns on with the other circulators be an option?
I actually used a sweat on adapter as the previous owner had converted it to copper on each branch. So didn't reduce any at the fitting, however my PEX A is rated for hydronic applications and has a thicker wall so it is more restrictive than the copper 3/4. This is a very long branch. If I had to estimate it's probably around 58 feet of travel from tee to tee. That may also have something to do with it.. however worked before when it was lined with black pipe and copper combo 🤷.
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If you put a separate circulator on it, bring its supply and return back to the boiler and tee it off as a separate zone even if you control it all as one zone, but i'd try a balancing valve i the main first before doing that much rework. Worst case other zones don't get enough flow and you open the balancing valve in the main all the way.
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I'd just use a full port ball valve.
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I have never used a balancer on any small residential system. I find that with a circulator zone system, it is self balancing via the thermostat. if a zone is cold, that thermostat will stay on while the other zone thermostat is satisfied. If you are trying to balance individual radiators on a particular one pipe main, that is usually done with a damper in the radiator cabinet. If you are trying to get the two radiator branch to balance with the other radiators, try doing the individual radiator thing. and when using PEX for those branch runs, try using the next size larger PEX. Use 3/4" for the 1/2" pipes, and use 1" to replace 3/4" pipes.
Edward Young Retired
After you make that expensive repair and you still have the same problem, What will you check next?
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They uses 2 circulators to avoid having to balance the system. If there were only one circulator, because it is a center fed split main system, they would need balancing valves to make sure both halves of the loop had enough flow to make the monflo work. with 2 circulators, each circulator creates enough flow in each half of the loop.
Someone had the split loop design with one circulator and no balancing valves and couldn't understand why part of the loop didn't heat well.
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@JWieg727 Macon makes an inexpensive balancing valve that is easy to set up. I have used this brand on customers garage unit heaters mainly and a few heat exchangers. They have worked well for me. Their website explains on how to choose the right one for the flows you need and what the numbers indicate the flow to be if you don't have the equipment to actually test it.
https://www.supplyhouse.com/Macon-Balancing-MB-STV-NPT-1-1-NPT-STV-Balancing-Valve
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