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Troubleshooting my heating problem - it's getting waayy too hot upstairs!

PieCa
PieCa Member Posts: 31
edited November 2020 in Radiant Heating
Hello -

I put this into the radiant heating category because I use radiant heating in my house, but it is not the root cause of my problem. I am seeking advise as I have three different companies looking at my setup and no one agrees on what the problem is and what the solution could be. So I figured I might post my issue here and have the feedback of professionals which are not trying to upsell me a solution :)

So, during my house reno, my GC used a heating company to set up the radiant heat system on the main floor of my house. My house is pretty small, main floor is an open space with radiant floor heating and the second floor is using cast iron radiators from the 40iest.

The system is setup like this:
- Zone 1 is my radiators upstairs. The thermostat is upstairs in the middle of the landing next to the staircase. The rads are old and the valves are seized in an (wide?) open position.
- Zone 2 is the heated floor. The thermostat is in the middle of the room.

My boiler is a McLain ECO 70 from 2018.
The thermostats are connected to a Taco SR502 2 zone switching relay. My zone 2 has the Priority jumper on (no idea what that means though...).
And that is connecting the two pumps: Grundfos UPS15-58FC.

Here is what is happening:
When it is cold outside at night (goes below 0 Celsius) the rads upstairs continue to heat even if the upstairs thermostat reached the desired temp. Well, even if I turn off the heating with the thermostat, it continues to heat like I it has literally no effect on controlling the temp (my GC changed the thermostat twice thinking it might be the issue but it did not change anything).
The only way I have to lower the temperature upstairs is to set my radiant in the first floor to something like 18 Celsius. Only then I can see the rads getting less hot and eventually stop heating.

The people who installed it play dead.
One said that we need a valve in front of the pump of Zone 1 to stop the water to flow. Cost ~1K.
One suggested to change the position of the Zone 2 pump and was not happy with the whole spiderweb look of the setup from the boiler to the pumps. Cost ~1K.
One suggested to replace the seized valves by thermostatic valves on all the rads upstairs. Cost ~1.2K

Well the last option was also suggested by the first one in addition of putting a valve before the pump.

They all gave me very different explanations of the issue. Sometimes contradicting each other.

I know you can't troubleshoot the thing from the Internet. But I am still curious to know you opinion on what could be wrong here or what question I should ask. And I can provide more details and photos if that helps.

Ideas?

Thanks!

Comments

  • Canucker
    Canucker Member Posts: 703
    edited November 2020
    From your description, it sounds like gravity flow to your upstairs rads when the main floor is running. Water is lazy and wants to take the path of least resistance, check valves may be the solution. There may be control issues but if it were me, I would shut the thermostat off to the upstairs rads and feel their pipes while the main floor is heating. If they get hot, it's probably gravity flow happening. If not, there's another issue.

    Edit: We like pictures here, especially of spider web piping around the boiler from about 6 feet away, if possible ;)
    You can have it good, fast or cheap. Pick two
    Solid_Fuel_Man
  • Jamie Hall
    Jamie Hall Member Posts: 17,165
    Well, the explanation is simple enough -- gravity or ghost flow to the upstairs.

    The question is, what to do about it.

    From what I can gather from your description, you have a pump for each zone, controlled by its own thermostat (I hope the radiant floor pump is on most, if not all, of the time, with a thermostatic mixing valve on that loop?). Is there another pump for a boiler circuit which the circulator pumps pull off of? And there are no control valves?

    Can you sketch a diagram of the piping and valves and post it? I have to admit that I am very much a fan of control valves in situations where there is a large difference in flow resistance between loops, but I'd really need to see just how it is piped to be sure.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    Canucker
  • PieCa
    PieCa Member Posts: 31
    Thanks for looking into it :) Here are some pictures. Let me know if you need different angles.
  • Canucker
    Canucker Member Posts: 703
    edited November 2020
    It looks like the radiant heat has the pump on the return. I don't like the orientation as the motor should be horizontal, not vertical. The large red pump in your pictures, is that the pump that is supplying the radiators? It's a big set of vertical pipes that it's attached to. If there's no check in it, you're probably getting ghost flow whenever the system is calling for heat.
    Edit: You weren't kidding about the spider web. Check the eyes of the installer if you can. They may be crossed :D
    You can have it good, fast or cheap. Pick two
    PieCa
  • PieCa
    PieCa Member Posts: 31
    edited November 2020
    ah ah :) Well my GC should have checked his eyes at the time of the install :)
    There is one pump for the rad (the one vertical) and the other one for the radiant.
    I recall one of the guy that stopped by mentioned something to his colleague like "the pump should be somewhere else" but then did not officially say that to me and mentioned that I would need a valve to stop the water to flow through the pump when it was not pumping. Or something like that.

    By the way, to Jamie's comment, I don't think the pump is on all the time for the radiant. I might be wrong but when the room reaches target, it does not seem to pump anymore (the Zone 2 light is off too). Is that an issue?
  • Jamie Hall
    Jamie Hall Member Posts: 17,165
    No -- the radiant pump cyclng is not n issue, really. Radiant is most efficient when it is running all the time at just the right temperature to make up for the heat loss, but that can be very hard to achieve!
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    PieCa
  • PieCa
    PieCa Member Posts: 31
    Could that ghost flow be predicated while installing? Should the installer fix it? Or is this my way of describing what I wanted to my GC which was the problem? Should I have made it clearer that I wanted two zones that are working independently?

    Also, what would you do to fix it? The minimum to do, the best, the most cost effective? The cold season is approaching and I will have to be intentional in the planning and financing. 

    Thanks all!
  • PieCa
    PieCa Member Posts: 31
    Any ideas or comments folks? 
  • infloorradiantheat
    infloorradiantheat Member Posts: 69
    edited November 2020
    I can't tell what is happening based on the piping. But we did have a problem once that was similar. We had a new side arm water tank installed. Afterwards when the boiler ran to heat the floors the water in the side arm hot water tank rose to boiler tempurature and steamed out the faucets at 180F which is very dangerous. Turns out the new tank needed a check valve to prevent the boiler water from back flowing through the water tank and over heating it. It was in the installation instructions so the company who installed it came back and put one in at no extra cost. I also had them add a vacuum breaker that was in the installation instructions.

    Our old side arm must have had a check valve built in as they just disconnected the old and installed a new one. Our current system probably has one in the taco circulator as when they redid the piping for the new boiler it doesn't appear there is a separate check valve. I'm sure I mentioned the need for one at the time due to our previous experience and would have verified it was there.

    It sounds like you have something similar going on with your upstairs radiators. There should probably be a check valve that prevents water from back flowing when the floor system is calling for heat. The people who installed your system should install it for free as it is needed for proper system operation.
    PieCa
  • infloorradiantheat
    infloorradiantheat Member Posts: 69
    edited November 2020
    Forgot to add if all you need is a check valve on one of the circulators you can probably have them unmount the circulator, add it and remount it. If you had them leave the boxes it is probably still in the box and is a little white cylinder.
    Something like this:
    https://www.supplyhouse.com/Grundfos-596630-Check-Valve-Kit-for-UPS-FC-SuperBrute-UP15-UPS15
    (verify that they or you get the right one for your pump)

    Always have them leave the boxes and installation instructions. No pipe cutting needed. If it needs to be somewhere inline with the pipe then they can cut the copper (after draining it) and installing one inline.
    PieCa
  • PieCa
    PieCa Member Posts: 31
    This is very interresting! They didn't leave any boxes behind... Is there a way to check if there is a valve inside the circulator? Without draining the system? If not I guess adding the valve would also require to drain the system?
  • There would be if they had put shut off valves on either side of the circulators. I don't know which one in your pictures goes to the upstairs radiator. The red on in front on the first pictures looks to have them. They are very handy for changing a circulator without draining the system. But to my eye that looks like the one for the radiant heat floors. The black one behind might have them. I see one on one side. The red one that is vertical doesn't seem to have them. Royal pain if there aren't enough shut off valves to isolate parts properly.

    It sort of sounds like some (or at least one) person who looked at it indicated a check valve somewhere would help. If it can be done at a circulator that is the cheapest easiest way. When we were young and energetic we've changed circulators ourselves with no problem. We (older and more decrepit) have paid to have them changed for a couple of hundred dollars.

    If the circulator for your upstairs was not installed by the people who did the new radiant floors then it could be very old and maybe no check valve. Also I just reread your post that the new system was added on to the old. So your installer may not have anticipated the problem. The seized valves may complicate things further as they may have prevented the problem if they worked properly. If that it is the case then it isn't your floor installers responsibility.

    If there are no valves to isolate the circulator then you will have to drain the system. When we had ours rebuilt I asked for shut off valves in many places that we had them before. The original install for our house did a nice job with that and we were used to a very servicable system.

    The one contractor who offered solutions one and three seems to me to be the one to hire. Their solutions may be the most expensive but to me they seemed to be the most knowledgeable and the most interested in doing the job right. That is worth alot when dealing with hydronic heat.
  • PieCa
    PieCa Member Posts: 31
    I see there is a sticker on both circulators that says: "With Check Valve ✅" so I guess I have to trust the sticker...
    Would the ghost flow take place even if there was a check valve installed? I see on the circulator, there are 3 settings (High/Medium/Low). Is that something that can be tweaked in my situation?
  • Canucker
    Canucker Member Posts: 703
    edited November 2020
    The ghost flow could be going up your unchecked return lines, they're more than big enough. Have you done the test that I suggested in my first post yet? It would help sort out where the flow is going and where the checks need to be installed. The speed settings on your pump only change how fast the water circulates around your system, it won't help with the gravity flow in this case, if it's happening
    You can have it good, fast or cheap. Pick two
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 2,421
    edited November 2020
    @Canucker 's test will determine if a second check valve is necessary. This book has an explanation of the phenomenon known as Ghost Flow on page 12 (starting at the bottom of page 11)
    http://media.blueridgecompany.com/documents/ZoningMadeEasy.pdf
    Edward Young
    Retired HVAC Contractor from So. Jersey Shore.
    Cleaned & services first oil heating system at age 16
    Canucker
  • A comment on the radiant circulator being on all the time. In Colorado with alot of winter sun our radiant heat pretty much only runs at night on sunny days. On cloudy cold days it can run during the day but we get a ton of passive solar so the house heats itself in the winter if it is sunny out.

    In terms of your current problem. One other test to do is if you turn off your radiator heat and turn a ball valve in the return or feed path to the radiators do you not get the heat at the radiators. If no heat then you need a check valve.

    Even though the circulator has the sticker that it was shipped with one that doesn't mean the person who installed it didn't take it out. Was the radiator circulator installed by your floor installer? If not then I would hire the contractor who proposed solns 1 & 3. It sounds like they proposed the right solution to get your system working and a contractor who knows hydronics is worth their weight in gold.
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 10,374
    @PieCa Have you checked "find a contractor" on this site? I am guessing your in Canada based on the temperatures in Celsius.

    You piping looks messy but is probably workable.

    The way I look at it you paid for two independent zones but they are not working as such. I would call the GC and tell him to get it fixed to your satisfaction...........

    You may or may not have luck with this
  • Solid_Fuel_Man
    Solid_Fuel_Man Member Posts: 2,307
    edited November 2020
    Where is the circulator for the radiant?

    You must pump away from a mixing valve. I see the manifolds and the mixing valve with no circulator in between. 

    A radiant circulator pushing water into a valve can do some weird stuff and possibly open a flow check in another circuit. 

    Hard to tell from the pictures what is going on....
    Serving Northern Maine HVAC & Controls. I burn wood, it smells good!
  • PieCa
    PieCa Member Posts: 31
    Thank you all for all your insights! Very interesting, I am very gratful for your help :)

    @Canucker yes, I turn off the termostat upstairs, rads still get hot at some point. Only way to bring them down is to lower the target temp on the main floor.

    @EBEBRATT-Ed I thought this forum was only US :) I didn't find such a knowlegeable community for my area (yet?). My GC is not reachable and the company that did the install don't want to deal with me because their contract was with the GC not me :/ That's why I got third parties looking at the installation.

    I try to draw something to get more clarity in case that helps. I tried to add as much details as I can... Let me know if that helps.
  • Canucker
    Canucker Member Posts: 703
    @PieCa Which pipes around your pumps got hot when you did the test? This will help us figure out where the checks are needed
    You can have it good, fast or cheap. Pick two
  • PieCa
    PieCa Member Posts: 31
    edited November 2020
    Right now, the thermostat upstairs is off.
    My boiler is heating (target 142F supply 113F outdoor 43F).
    My radiant floor temp is 72F for a 70F room temp.
    Upstairs with thermostat off (for the last 4 months, and I see the Zone1 LED is off on my Taco SR502 panel) the room temp is 71F (warmer than the main floor). All my rads are hot.
    All pipes are hot. I cannot feel a difference when I touch the pipes after the circulator for the rads or the circulator for the radiant floor. All the same temp.
    Just to make it clear, from my diagram :) I added the two hands where I feel like it is the same temp:

  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 2,421
    edited November 2020
    Im thinking that one of the pumps does not have a working check valve inside. If the check valve is there, it may have failed open. that said, this may be one path for the water to flow


    Remember the pump may be moving 6 or 8 GPM but the red arrows may be the path of only 2 or 3 GPM of the total 6 or 8 GPM.

    There is definitely a better way to design that system.
    Edward Young
    Retired HVAC Contractor from So. Jersey Shore.
    Cleaned & services first oil heating system at age 16
    Canucker
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 2,421
    edited November 2020
    The TACO pump may have enough pressure to open the check valve in the Grundfos pump on the cast iron zone.


    I think this is more likely. the Taco pump does not need to be there. This would be a better location.


    But there may not be enough flow thru the boiler in this configuration. You may need a boiler pump to go on a bypass to insure there is sufficient water frow thru the boiler
    Edward Young
    Retired HVAC Contractor from So. Jersey Shore.
    Cleaned & services first oil heating system at age 16
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 2,421
    edited November 2020
    Figure 52 on page 49 of the insulation manual has the proper piping configuration for your system.


    Ask your GC to have the boiler installed as indicated by the instructions. it should be included at the original price of the job. At least the State Attorney General's office might think so. If you look closely the radiant circulator is located between the mixing valve "Mix" port and the radiant floor "Supply" manifold

    Your pump is located pumping into the "Hot" port of the mixing valve. Not really sure how good that is going to work. It might just run forever and not give enough heat for the radiant system and maybe have ghost flow to the second floor.

    Edward Young
    Retired HVAC Contractor from So. Jersey Shore.
    Cleaned & services first oil heating system at age 16
  • Edtheheaterman identified the two problems I saw. One way to check is to disable the power to the taco circulator. If the problem disappears than the taco was pushing water through the radiator grunderfos. If it persists then you are missing a check valve in the grunderfos and are getting what he depicts when heat is flowing backwards through the radiators.

    But I'd be careful. Maybe the taco is the boiler circulator and there is a line that you don't have depicted in your picture. However I don't think it would do damage to your boiler. It should shut itself off if the heat gets too high due to lack of circulation.

    However Ed probably knows if this can be safely done so I'd wait to see if he thinks it can be done.

    Surprised your mixing valve works with water being pushed in the hot water port. Our installers tried that and it shut the mixer down so they had to move the circulator to pull from it (which is what it says to do in the instructions). Ours also had a check valve in it. I believe it was so you couldn't push water out the cold. But one of the pros would have more experience with it. Ours chattered badly so we took it out and it did not affect the performance due to the floors being isolated from errant heat flows behind the heat exchanger. So my money is on the taco circulator pushing water through the grunderfos radiator circulator.
    PieCa
  • Canucker
    Canucker Member Posts: 703
    From what I can see in your pics, the black pump is the boiler loop and will run every time there is a call for heat. Your radiant is the copper piping and will run a long time, which is normal. The return for the radiant is dropping right between 2 fat pipes, which is likely the returns for the radiator zone. As the water gets hotter it will flow backwards to your radiators(if there is a functioning check in the pumps, if there isn't it or as @EdTheHeaterMan pointed out, it is being forced past a check). I believe you're going to need to confirm if the piping leaving the outlet of the pump supplying your rads is getting hot while the radiant is running. If it stays cool to the touch, you will need checks in the returns. If it gets as hot as the radiant, @EdTheHeaterMan is right and it's being forced past or there is no check in the radiator pump. Adding Check valves is the easiest fix but based on the piping lay out, it should have been done when it was installed.
    You can have it good, fast or cheap. Pick two
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 2,421
    I wonder if @PieCa has resolved the problem? This is definitely an issue for the installing contractor to resolve. The problem is... How good is the installing contractor at honoring the warranty on the "Installed Error" portion of their contract?

    For the few years that I was tech rep for the local supply company, I found too many Installer errors and very few actual manufacturer warranties. Wish you the best.
    Edward Young
    Retired HVAC Contractor from So. Jersey Shore.
    Cleaned & services first oil heating system at age 16
  • PieCa
    PieCa Member Posts: 31
    edited November 2020
    Hi! Thanks for asking :) I have not yet address the issue... Work cought up with me and I had no time to do anything else this week until now.

    What I see is that it is hot everywhere. Like you guys suggested, I feel like the position of the black circulator might be the guilty component. On the manual you pointed out, the boiler's circulator is on the return. Mine is on the front of the two zone circulators. And my radiant circulater is on the front o the mixing valve, not after:



    Could that cause too much pressure and go trhough the circulator of my rads despite the check valve?

    Also my rad circulator is installed vertically. Does this affect the performance of the valve inside?

    I am starting to wonder if they left the boilet circulator on the front here because it splits to go the Hot Water Tank. Which is understand would need its own circulator if we were to place the boiler circulator on the return. Thoughts?

    By the way, I thank you very much for all the insights you guys are bringing! It is very interesting to learn oll this! Even if I still don't fully understand the basics, it really makes me want to know more!
  • Jamie Hall
    Jamie Hall Member Posts: 17,165
    If nothing else, the location of the radiant circulator isn't right. It has to circulate in the radiant loop -- if it isn't "in the loop" there is no way for the mixing valve to regulate the temperature. Somebody just wasn't thinking.

    Similarly, you need a circulator pump -- which you sort of have -- in the high temperature loop for the radiators.

    Then a third pump -- which may be in the boiler -- to circulate nice hot water around the primary loop, so the two secondary loops can pick it up and use it.

    Figure 52 is correct (although there are some slight variations which can be used), and you will need to do some repiping to get your system to look like it.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    PieCa
  • PieCa
    PieCa Member Posts: 31
    Then a third pump -- which may be in the boiler -- to circulate nice hot water around the primary loop, so the two secondary loops can pick it up and use it.

    I have a third curculator in the front of the two others... Would that make sense to move it on the return like in the diagram instead of in the front? What is the purpose of a circulator in the return anyways? :) I am curious.

    What about the circulator isntallation in vertical? Why is that a potentiel issue? (or is it?)

    Thanks!

  • The check valve only prevents flow in the reverse direction through the circulator. Any flow that is pushing in the direction of the radiator circulator is not "overcoming" a check valve it is just flowing through the circulator. So the black taco pump could very well be driving your radiators.

    If there were zone valves on the radiators and they were shut they would prevent flow from flowing through. I am not familiar with what you have frozen on the radiators but they very well may prevent this problem if replaced.

    There should be no problem with the circulator in a vertical position. If you have questions look up your model online and review the installation instructions. It will show the permissible positions. From memory the only one that was bad was a horizontal installation with the motor under the circulator and I suspect that is due to the possibility of liquid getting into the motor if it should leak.
  • Canucker
    Canucker Member Posts: 703
    @PieCa it doesn't sound like you've done the testing that I recommended. If you start your system from cold and see which pipes at your boiler start to immediately get warm, you'll be able to tell what needs to be fixed. And yes, the red grundfos circulator with its motor in the vertical position is not correct. They use the water for lubricant and it can trap air in that position.
    You can have it good, fast or cheap. Pick two
    PieCa
  • Canucker is correct. I just read his response and I didn't realize he was commenting on the back red circulator that does appear to have it's motor on top. It is sort of obscured in the picture so I didn't see that detail.
    This link shows pictures of acceptible installations.
    http://xrefs1.plumbersstock.com/Grundfos/59896274-instal.pdf

    My apologies. I thought you were asking about the circulator that was mounted on the vertical pipe.
    PieCa
  • PieCa
    PieCa Member Posts: 31
    @Canucker Sorry, I thougth I did when I said it is hot everywhere :) My bad, English is my third language and I often miss the point. Sorry about that.

    It is cold (in my case the heat was off all day yesterday because the inside temp was 21C already) and around 6PM when the floor requested for heat for the first time of the day, I touched the pipes. And what I can see and feel is the following:
    - Only the zone 2 (radiant floor) LED is on
    - The main circulator and the radiant circulator are both on.
    - The rad circulator is off
    - When I touch the pipes after the circulatoron of the rad, it is as hot as the pipes after the radiant's circulator. And one hand on each pipes I can feel they get hot as quick on both sides.
  • Canucker
    Canucker Member Posts: 703
    edited November 2020
    PieCa said:

    @Canucker Sorry, I thougth I did when I said it is hot everywhere :) My bad, English is my third language and I often miss the point. Sorry about that.

    It is cold (in my case the heat was off all day yesterday because the inside temp was 21C already) and around 6PM when the floor requested for heat for the first time of the day, I touched the pipes. And what I can see and feel is the following:
    - Only the zone 2 (radiant floor) LED is on
    - The main circulator and the radiant circulator are both on.
    - The rad circulator is off
    - When I touch the pipes after the circulatoron of the rad, it is as hot as the pipes after the radiant's circulator. And one hand on each pipes I can feel they get hot as quick on both sides.

    No worries, troubleshooting over the internet is difficult. I'm glad you got to test it. Bad news is that @EdTheHeaterMan is probably right, there are probably no checks in your circulators and you're going to need some to stop the ghost flow. What city are you located in?
    You can have it good, fast or cheap. Pick two
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 2,421
    I find that for the most part, following the directions will result in getting the results you desire. If the piping you have does not match any of the piping diagrams in the instructions, and you are experiencing problems, then the piping configuration is most likely wrong.
    Edward Young
    Retired HVAC Contractor from So. Jersey Shore.
    Cleaned & services first oil heating system at age 16
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 2,421
    edited November 2020
    I also find that getting an "Experienced Tradesman" to agree that he is wrong takes a certain amount of diplomacy and psychology. Sometimes it takes being the "squeaky wheel" that gets the attention"

    Sometimes you need to ask the right questions.

    Sometimes you need to let the mechanic on the job do the experiment himself to see the results.

    If you do get the mechanic or technician to come back to your home, make sure the system is cold and ask the technician to turn off the thermostat to the overheated zone, then turn on the other zone and let him/her see the results. Then ask them why they believe the system is not working properly.

    Then let them have a moment to think about it. Then show him the diagram in Fig.52 and ask if this piping diagram might solve the problem. Since you are not an expert, you want his opinion on solving the problem.

    Since you are the only problem that you are worried about, you have more time to look at all the possible solutions, You also understand that the mechanic has many problems to consider every day and they are not going back to the shop and the entire company staff is looking at your situation. So any help you can offer and any expertise their experience can offer to come to a solution will be beneficial and come to a satisfactory solution.

    I'm sure his boss will need to approve the diagnosis, so use the same procedure. make sure the system is cold when the boss arrives and let the boss do the experiment.

    If the company is reputable they will resolve the problem.
    If not, then you need to take other actions that you may cost you additional $
    Edward Young
    Retired HVAC Contractor from So. Jersey Shore.
    Cleaned & services first oil heating system at age 16
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 2,421
    PieCa said:

    Then a third pump -- which may be in the boiler -- to circulate nice hot water around the primary loop, so the two secondary loops can pick it up and use it.

    I have a third curculator in the front of the two others... Would that make sense to move it on the return like in the diagram instead of in the front? What is the purpose of a circulator in the return anyways? :) I am curious.

    What about the circulator isntallation in vertical? Why is that a potentiel issue? (or is it?)

    Thanks!

    To be clear on definitions, the primary loop is the one with the expansion tank. The secondary loop in this diagram is the boiler loop.
    This diagram uses a concept called Primary/Secondary.


    The concept is that you place a secondary loop with closely spaced Tee fittings on the primary loop. The pressure drop across the closely spaced tees (indicated by the blue circle) is minimal and will not cause circulation to flow into the secondary loop leaving the zone circulators to do their job without any influence of other circulators in the system. Your current piping does no have the pipe that makes a close connection indicated in the blue circle. This means that you don't have the secondary loop. The boiler and boiler circulator is part of the same loop as the "operating zone." The boiler and boiler circulator needs to be independent as illustrated. That is a hard concept to understand for some. I know it took me some time to understand it. Once I understood it, it makes all the sense in the world.

    Just placing the circulator on the return to the boiler alone will not resolve the problem. You need the secondary loop. (the short pipe between 2 tees). The reason the circulatory is on the return is to increase the relative pressure in the boiler by pumping into the boiler. The reason has to do with the Physics of Water when it is heated and cooled, and when it is under changing pressure. conditions. A discussion you can find on this site elsewhere if it is important to you.

    Edward Young
    Retired HVAC Contractor from So. Jersey Shore.
    Cleaned & services first oil heating system at age 16
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 2,421
    edited November 2020
    Here are the primary loops illustrated with Yellow for the Radiators. See how the Zone Pump has no influence on the secondary loop and the secondary circulatory has no influence
    on the flow of the primary Radiator loop?

    This is the primary loop of the Radiant Floor indicated by orange then green after the mixing valve. Same thing. Each circulator is independent and has no effect on the other circulators. they are just moving water regardless of the temperature.


    So if the boiler circulator fails to operate, Both primary zone circulators will just move cold water and no heating will take place
    Now to add heat to the primary loop the secondary "Boiler" circulator will inject heated water into the system and withdraw cooler water from the return to be heated by the boiler indicated by the red loop.

    Now if a circulator from one of the zones failed to operate, the boiler would still have circulation independent of the failed loop, this way the boiler would not overheat from insufficient flow.

    I hope this will make things a little more clear

    Clear as muddy water!
    Edward Young
    Retired HVAC Contractor from So. Jersey Shore.
    Cleaned & services first oil heating system at age 16