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Lengthy Post regarding GPM/Head loss for in-Floor Radiant

kaliber50
kaliber50 Member Posts: 17
Hello Everyone,

New to this website but I have been reading on and off all of the random posts posted by others as it relates to in-floor radiant for the last two months. And out of all the other sites I visited, this seems to be just about the only one where many have a wealth of knowledge regarding in-floor radiant and I was hoping to tap into some of that knowledge for my situation.

So to provide some context, I bought my vacation home in 2017 and this particular home came with in-floor radiant heat. Keep in mind that I came into this house not knowing a damn thing about heating systems at all since my primary residence relies on min splits for heat. I wasn’t even aware that in-floor radiant was even thing. Anyway, the first thing I noticed was how long in-floor radiant takes to heat up. But as I now know, it’s just the nature of the beast. Anyway, in the spirit of being brief (I hope), fast forward to the present and I had my local oil provider send one of their guys for routine maintenance on the boiler/furnace this past February and at the end of it all, he gave me the bad news that one or all three loops for the zone (Living Room) had a leak. He left and I was left scratching my head on what to do not knowing a lick about in-floor radiant. So I embarked on a mission to learn and understand in-floor radiant so I can get to work not just on finding these leaks but also how to make my system as a whole more efficient.


So this is where I am as of today. I learned how to pressure test hePEX and indeed, out of the (3) loops, one had a leak. I sealed that bad boy with GeoLoop, pressure tested and after a month, it’s still holding. So I am good on that end. Moving on, found a few bad designs with the system that I corrected (like the circulator feeding said loops was installed in the input of the thermostatic mixing valve and not on the output side). Anyway, I found way too many design flaws on this in-floor radiant to describe on here and I have corrected all of them as per the standards of the industry.


But the reason for my post is that I am stuck at satisfying my heat load for my living room( 26’ chalet ceilings, with an all windows northern-facing wall and a 893 squarefoot floor plan, of which 665 squarefeet is exposed) with the current in-floor radiant set up. Using a Flir Thermal Imager, I was able to calculate the length of each loop which comes at about 280’-300’ for each of ½” Wirsbo hePEX running a Taco 007-F5. I suspect the circulator is not enough to meet the demand. So I proceeded to spend a whole weekend doing a detailed Heat Loss Analysis by hand, measuring in detail every of the living room and came up with a Heat Loss of 114,432 BTU/Hr. I followed up calculations with Borst Heat Analysis calculator and the numbers were very close indeed. So I used the 114,432 BTU/Hr and plugged it in to determine my flow rate using GPM= 0.002*BTU/20 and according to those calculations, I require a circulator with 11.444 GPM flow rate capacity. But if you divide that by 3 loops, that equates to 3.81 GPM per loop when I know that the flow rate for in-floor radiant isn’t usually that high from what I’ve seen in the internet space.


Additionally, Wirsbo/Uponor pressure loss tables has the head loss for ½” hePEX with 100% water at 3.5 GPM at 120 Deg Fahrenheit at 33.64 head per 100’ which amounts to a total head loss of 100.92’.
What am I missing here? I trust my numbers but I don’t trust whoever designed this in-floor radiant system and I’m beginning to think that whoever did the job, just winged it. I apologize in advance for the lengthy post. But just wanted to give all the details so that maybe I can be helped. Thank you in advance. Heat Loss Analysis included.


Comments

  • psb75
    psb75 Member Posts: 570
    Is the slab insulated? How is it insulated?
  • GroundUp
    GroundUp Member Posts: 1,406
    Many things here: first, there is no way the heat loss of that space is 114k unless all those windows are open. Even half that is ludicrous. Secondly, you can't figure a 20 degree delta with radiant and expect a high output- it's not going to happen. Third, you only calculate the head loss of the longest loop and the others add nothing so if the longest was 33.64ft, the whole system would be 33.64ft- though it's not.

    No matter what size circ you put on a system like this, a total of 3 GPM will almost never be exceeded. With three 300ft loops at 12" spacing (which is standard for radiant installers who don't understand heat loss), an 007 would typically flow roughly .4-.5 GPM per loop which is only giving off 12-15k BTU at a 20 degree delta. Even if you were to replace the 007 with a high head circ like an 009, best case scenario is 30k BTU. We need a higher delta to increase the output, and that can be accomplished by simply turning up your mixing valve. Can you share a photo of the piping arrangement and manifolds please? Does the supply manifold have flowmeters? We can work through this, but long story short, changing the circ is not going to fix it.
    EBEBRATT-Edkaliber50rick in Alaska
  • Hot_water_fan
    Hot_water_fan Member Posts: 543
    edited April 15
    Easy enough: your heat loss is incredibly off. The infiltration is based on 928 cfm, giving you 76,000 btu/hr of heat loss. 

    After that, the floor loss is significant. What do you know about the insulation situation under the floor?

    That circulator is probably fine. What’s the temperature setting?
    GGrosskaliber50
  • GGross
    GGross Member Posts: 119
    There are situations, such as high ceiling, high glass content larger rooms, that the maximum output of a radiant slab will generally not satisfy on design day. If I am not mistaken it looks like your space is calling for 128 BTU/sq-ft I would find that number to be highly suspect personally, in my cold climate loads for houses rarely exceed 30 BTU/sq-ft and are usually somewhere closer to 15-20 (new construction) You should also consider what is actually happening in an in-floor heat system. The tubing is transferring heat to the floor which becomes your radiator, now cast iron radiators can get awfully hot, which makes sense because they are not the size of your entire floor so they must be pretty hot to satisfy an entire room. But can your slab get as hot as it needs to satisfy the load like a radiator? It can't, there are maximum temperatures that should be followed, a general design consideration is maximum floor temp of 85 deg F

    Now that's all well and good but the problem remains that your room is not keeping up to temperature. I would ask a few questions. Does the room have issues keeping up on mild days, or just on design day (-5 as your report states) Are you using any kind of night setback, or "fiddling" with the thermostat? In-floor likes to stay one temp and do it's job over a long period of time

    I am curious what else if anything your IR camera revealed, is the floor heat "even", and are you sure you are getting flow through all your loops?

    My gut is telling me that your space in question may exceed the load that a slab can provide, I am skeptical of the given load calculation however. What can you do? verify flow through each loop, delta T, if you have a strap on temp sensor you may check to see that the loop with stop leak is properly transferring heat. Or you can add a supplemental heat source (what I would do during the design process) They make wall cabinets that can house a toe kick heater which can output a decent chunk of BTU (not as much as your calculations however)
  • Jamie Hall
    Jamie Hall Member Posts: 18,970
    Well...I'm not sure that that heat loss is ludicrous. In fact, if may be quite close to reality. I'd much rather bet on your having done meticulous and accurate calculations based on your structure and location. Sorry, @GroundUp .

    So let's suppose, for the moment anyway, that @kaliber50 did his (?) work correctly. Where does that leave us?

    Two things. First, 20 to 30 BTUh is about all one can ever expect from a radiant floor which is cool enough to walk on without asbestos boots. Therefore, part of the problem with that great room -- regardless of the head loss in the loops or anything else -- is that the floor simply doesn't have the power to compensate for the heat loss. The maximum reasonable output from that floor is around 27,000 BTUh. That can be provided, at a reasonable delta T of about 20 F, by a total flow in the three loops of 3 gpm -- 1 gpm from each loop. As @GroundUp did correctly state, you can achieve that very nicely with a Taco 009.

    It's not that one can't push more water through those pipes -- one can, although the velocities get very high and the head losses insane -- it's that it won't do any good to do so, as the floor temperature would be much too high in some places near the beginning of the loops -- and too cold near the ends.

    Nor can you simply boost the input temperature at the same flow and delta T and get more output from the floor. If you got the average floor temperature up to 140 or so it would be just fine for the calculated heat loss. 140, however, is a bit toasty.

    So. Where do we go? If the space is not heating to your satisfaction, @kaliber50 , (you don't mention -- is there a woo stove? A fireplace?) you will need more heat output. There are a lot of options -- baseboards or panel radiators come to mind immediately -- and they could be fed from a separate loop off your boiler, with a different mixing valve.

    Tell us some more about your situation, please. Particularly, is the space warm enough as is?
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    GGrosskaliber50
  • Hot_water_fan
    Hot_water_fan Member Posts: 543
    @Jamie Hall it’s not meticulous! Assuming @kaliber50 got every insulation and sqft detail correct, that infiltration estimated by the program is incorrect. 
    GGrossBirchwoodBill
  • GGross
    GGross Member Posts: 119
    @Hot_water_fan I would tend to agree, if you subtract the infiltration load it gives a more expected ""old house" load calc closer to what I would see in my cold climate of 43 btu/sq-ft (rounded up) Which would still leave us with the issue of the floor not keeping up with the load of the space, but it changes the "fix" from being add over 80k btu to an 893 sqft room to adding about 12k btu (a large toe kick) which seems reasonable to me
    Hot_water_fankaliber50
  • Hot_water_fan
    Hot_water_fan Member Posts: 543
    @GGross exactly. The infiltration number is the downfall of all load calculations, how many people have any clue what that is?

    Adding radiation, possibly raising floor temp, slightly reducing load if possible are all much easier now. 
    kaliber50
  • GroundUp
    GroundUp Member Posts: 1,406
    @Jamie Hall , 128 BTU per square foot is reasonable to you?
    ScottSecor
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 12,019
    Most of the above. The heat loss cannot be right. The 76k infiltration is way too high.
  • Jamie Hall
    Jamie Hall Member Posts: 18,970
    GroundUp said:

    @Jamie Hall , 128 BTU per square foot is reasonable to you?

    No actually, it isn't. However, without having access to the way that number was derived, nor the location of the structure, nor the design conditions, I am not going to call someone's calculations incorrect. I would suggest, politely, that it be revisited. I've never gotten very far in my engineering -- or much else -- with assuming that what I think ought to be the case is the case...
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    GGross
  • GGross
    GGross Member Posts: 119
    @Jamie Hall That is a great point Jamie, I would add however that if the calculations come out wildly out of the norm they are worth revisiting. I do manulal J for contractors for a living and have made my fair share of mistakes. It is possible that the OP is running an exhaust fan of 928 CFM continuous in this living room as he states in his load calc, if thats the case I can fix his heating issue quite quickly by advising he turn it off.
  • hot_rod
    hot_rod Member Posts: 16,329
    I think your 4 ACH input is skewing the infiltration result? Where did 4 come from?
    I agree a room like that will be hard to heat with just a floor panel, at a comfortable floor temperature. 22- 25 btu/ sq ft is reasonable.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    GGrosskaliber50
  • kaliber50
    kaliber50 Member Posts: 17
    Thanks all for the feedback. I need some time to gather all the info to address everyone’s questions regarding my set up. I will gather as much as I can with photos and report back as soon as I get the info u guys requested. 
  • MikeL_2
    MikeL_2 Member Posts: 373
        Kaliber,
                 I suggest changing your systems manual mixing valve & tstat to an automatic mixing valve with outdoor reset, constant circulation, and an adjustable heating curve. You may be able heat the space comfortably in the shoulder seasons and all but the few weeks of bitter cold weather. With outdoor reset you can dial in a maximum swt that won't overheat the floor, and you can add supplemental heat sources as needed. 
                    I also suggest protecting your system with antifreeze in a concentration that won't retard heat transfer.
    kaliber50
  • kaliber50
    kaliber50 Member Posts: 17
    So I’m back. Thx everyone for your patience while I gathered the necessary info (pics included). So first things first, some more info about the heating for the whole house:

    (4) Total Zones Provided by an Energy Kinetics System 2000 EK1 with DHW Tank
    -Zone 1: 1st Floor Living Room/Kitchen (in-floor radiant; (3) loops, open floor plan)
    -Zone 2: 1st Floor bedrooms (in-floor radiant; (3) loops; works excellent, no problems)
    -Zone 3: 2nd Floor Living Room/Bedrooms (baseboard heat; works excellent, no problems)
    -Zone 4: 3rd Floor bedroom (baseboard heat; works excellent, no problems)

    Additionally, 1st Floor Living Room/Kitchen has a propane fireplace as seen in one of the pics. I try to limit its use, with propane being so expensive costing me about $5.90 a gallon, which is the going rate in my area for someone who doesn’t use propane for primary heat.

    So, after I posted my original post, I whipped out my Flir this morning and used a thermocouple water temperature probe and measure supply/return water temp.

    Supply Temp: 125F
    Return Temp: 100F


    Now to address some of the few things some of you guys posted:


    Head loss:
    Head loss of 33.64’ was calculated only on the longest loop and not the other two since I understand you don’t add head loss on additional circuits.


    Floor insulation information: I have no idea


    Flir Imager floor temp:
    Granted it’s been a few weeks since I measured the actual temp of each of the loops in the living room so don’t take these numbers as set in stone. (A) Loop (Kitchen) was at 80F, (B) Loop (center of Living Room) at 76F, (C) Loop (by fireplace) was at 82F. So yes I am most definitely getting flow on each one of them and as you can see in the images, flowmeter shows (B) Loop 0.4 GPM, (C) Loop 0.4 GPM, and (A) Loop 0.5 GPM. Just purchased these flowmeters a few months ago.


    Keeping up with temp on mild days:

    It keeps up with temperature on mild days (anything above 55F-60F) but on cold days, I have to turn on the rest of the zones to help the house keep a comfortable temperature. On very cold days (below 20F), I have had to supply 140F temp to help the Living Room zone keep up with temp and even then I still have to turn on the rest of the zones. Additionally, I try to keep the temp for the living room at around 71F so no setbacks or anything like that at night.


    Infiltration/ACH/CFM:
    I concede that I came up with this number considering how much leakage my Flir has revealed since I bought it a few months ago. I believe that the Ashrae numbers for a new home is something like 0.40 ACH and although this house was built in 2001, you would think that the insulation and integrity of the inside of the house should be intact. But I went as far as purchasing a total of (15) Air Conditioning vent covers to keep the cold draft from blowing inside the house which has helped a ton during winter months. The Flir also revealed leakages from the corners of the living room where paper tape is coming off. Sure I can address all the leakages, but I suspect the heat load won’t be enough to meet the demand of the living room even if I seal up all the cold spots revealed by the Flir…. I did not perform air exchange rates using a velometer or tracer gas or a blower door test or anything like that. I simply gathered online data of various situations that would cause a residence to have ACHs in the 2-4 range. I can sit here all day and tell you that most of the data I found online assigned an ACH number between 2-4 for very leaky homes (and I chose the worst number of the range) but at the end of the day, I will not kid you guys and tell you that the infiltration rate of 4 is definitive and scientific because it isn’t. That hat number is very subjective and "unscientific" and its based on how leaky I perceive my house to be not what the actual ACH value is. But it still remains that I feel draft from the baseboards of the exterior wall by the fireplace and air leakage from ceiling corners as revealed by the Flir which shows temperatures in the high 50s in those corners on a 20-25 degree day. And to answer the question, there’s no ventilation fan. The closest thing I have to that is a 72” ceiling fan running on reverse to pull down heat from the ceiling.



    -Automatic mixing valve with reset control; great idea. If I am not mistaken I think these are called HMBs or Hydronic Mixing Valves. I just ran into these kind of set ups in some of the online resources last week but although it sounds great, I really don’t understand how the whole system work since I’m not at that step yet until I figure out everything else. I’m a bit slow so one thing at time for me but I do have one on my Supplyhouse wish list.




    So yes es it’s highly possible and probable that my numbers could be way off. I thought so myself when I ended up with such huge heat loss numbers. Hence why I went over all of my dimensions and calculations over and over and over again to see where I fudged up. But then I started thinking about how even the little things were overlooked in constructing the house and I guess I came to the conclusion that if they cut corners with simple things such as proper deck installation and using incorrect gauge for electrical outlets, and even having one of the living room radiant loops swapped with one of the loops going to the bedrooms, I guess it’s very likely that something wasn’t done right with the heating system design. It is now that I’m finally realizing that the random cracked tiles throughout the first floor could possibly be attributed to perhaps the previous owner heating the loops with 140+ water??? Hell I even found a snake 2 weeks ago underneath one of the cracked tiles which exposed a cracked section of the foundation exactly where my Flir revealed some of the loops going to the 1st floor zone!!! It was very toasty there I may add. Anyway, this of course doesn’t prove that my calculations are correct. What I said was that I trust my numbers more than I trust whomever designed this system since it seems and I suspect that the previous owner also had a hard time keeping the living space warm and he compensated by cranking up the temperature of the hot water going into in-floor radiant which was set to 140 when I first got the house.

    Anyway, I embarked on this mission to try to salvage the in-floor radiant with the expectation that if I worked on it and got my hands dirty, I can perhaps learn and understand in-floor radiant and apply what I learn to make it work as it should, because we just love the feel of radiant heat when it works and hate the look of baseboard heat and the feel of forced hot air. But me and my wife decided that if we can't get it to work as its supposed to, we were just going to dump the system and start from scratch and use forced hot air running on a geothermal system. But I rather save the $$$ and learn a few things in the process and hope that through the help of others, I have a fighting chance to salvage what we already have.

    Again I profusely apologize for the loooong post and my chicken scratch drawing for the loop layout

    Thx





















  • hot_rod
    hot_rod Member Posts: 16,329
    North facing glass wall? Probably no more than 12” insulation in ceiling?
    That will be a tough heat for just floor radiant. No great walls to add supplemental heat. Maybe Runtals in front of the glass?
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    kaliber50rick in Alaska
  • kaliber50
    kaliber50 Member Posts: 17
    hot_rod said:
    North facing glass wall? Probably no more than 12” insulation in ceiling?
    That will be a tough heat for just floor radiant. No great walls to add supplemental heat. Maybe Runtals in front of the glass?
    What in the world?? I never heard of runtals. Looked it up and definitely has are aesthetically pleasing and won’t ruin the look of the space. . Thx for sharing. But they won’t work in front of the glass since they are actually sliding doors. But I can use these to replace the ugly baseboard ones  in the bedrooms. And maybe even consider adding these by the fireplace as supplemental?? Will save and explore further. Thx again
  • Jamie Hall
    Jamie Hall Member Posts: 18,970
    Does running the ceiling fan help at all? It might...

    I think you siad the return from the great room floor was about 80? If not, see if you can raise the flow rate -- same 120 or so input -- to see if you can get the return warmer. It won't help the total BTUh output of the floor much, but it will help a little...
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    Hot_water_fan
  • hot_rod
    hot_rod Member Posts: 16,329
    Tall vertical Runtals on either sides of the doors? They make custom sizes. I have seen them on curved walls.  But the question remains, how much does you floor provide, and how much are you short?

    You have built ins on one side, and couches with dust ruffles pretty much shut down radiant output. So that sq footage gets subtracted out of your available radiant panel output.
    Its called heat flux divide the entire room square footage by those encumbed areas to end up with actual emitter area.

    Looks like tile floor? So you are limited by surface temperature. Ideally that would be 6” on center tube to get the floor surface as consistent as possible, 82F is about as warm as your bare feet can comfortably stand.

    82F floor surface in a 70F room gets you around 24 btu/sq. ft of output.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    kaliber50
  • rick in Alaska
    rick in Alaska Member Posts: 1,362
    You absolutely need to have window coverings on those windows, so they can be closed at night, especially on a North facing wall. That is a big heat loss there.
    And looking at the loop layout, there is just not enough tube in the floor to do the job.
    You really need to add supplemental heat to make this work, such as the runtals Hot Rod mentioned. Perhaps something like a Beacon Morris cabinet heater next to the fireplace, which would give you the needed extra kick.
    Rick
    kaliber50
  • Jamie Hall
    Jamie Hall Member Posts: 18,970
    For the sake of the arithmetic -- the R value of a double pane window (or single plus storm) is usually quoted at around 3...
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    kaliber50
  • kaliber50
    kaliber50 Member Posts: 17
    Does running the ceiling fan help at all? It might... I think you siad the return from the great room floor was about 80? If not, see if you can raise the flow rate -- same 120 or so input -- to see if you can get the return warmer. It won't help the total BTUh output of the floor much, but it will help a little...

    I re-measured the return temp on Saturday. The supply was 125F and the return 100F
  • hot_rod
    hot_rod Member Posts: 16,329
    You really need to watch S&R temperature over a period of time. When the system starts up, expect to see a wide delta, that will close up as the floor warms and room reaches setpoint.
    When designed an operating delta is chosen to size the circulator. For comfortable radiant surfaces a 10-15° is common. But it will move around depending on the load, room temperature, etc.

    At any given time you can use that measured delta to determine how much heat is being delivered. That is basically how a BTU or energy meter works.

    You need to know flow rate to that zone, and delta t.
    The simple formula is Q= 500.f.(delta T)
    So if you are flowing 3 gpm 500 (3) (125-100) =37,500BTU/hr

    More accurately includes the density and specific heat of the fluid. Q=(8.01Dc) F (delta t)
    density of water at average temperature 61.8
    specific heat, close enough to 1

    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    Canuckerkaliber50
  • kaliber50
    kaliber50 Member Posts: 17
    kaliber50 said:
    Does running the ceiling fan help at all? It might... I think you siad the return from the great room floor was about 80? If not, see if you can raise the flow rate -- same 120 or so input -- to see if you can get the return warmer. It won't help the total BTUh output of the floor much, but it will help a little...

    I re-measured the return temp on Saturday. The supply was 125F and the return 100. And the ceiling fan working on reverse does actually help to love the heat around. 

  • kaliber50
    kaliber50 Member Posts: 17
    You absolutely need to have window coverings on those windows, so they can be closed at night, especially on a North facing wall. That is a big heat loss there. And looking at the loop layout, there is just not enough tube in the floor to do the job. You really need to add supplemental heat to make this work, such as the runtals Hot Rod mentioned. Perhaps something like a Beacon Morris cabinet heater next to the fireplace, which would give you the needed extra kick. Rick
    We do have window coverings. But that gives me the idea that maybe we should replace them  with thermal ones as opposed to just regular curtains. 
  • kaliber50
    kaliber50 Member Posts: 17
    kaliber50 said:
    You absolutely need to have window coverings on those windows, so they can be closed at night, especially on a North facing wall. That is a big heat loss there. And looking at the loop layout, there is just not enough tube in the floor to do the job. You really need to add supplemental heat to make this work, such as the runtals Hot Rod mentioned. Perhaps something like a Beacon Morris cabinet heater next to the fireplace, which would give you the needed extra kick. Rick
    We do have window coverings. But that gives me the idea that maybe we should replace them  with thermal ones as opposed to just regular curtains (thx for the idea) and we did started looking at the Runtals last night because I do think it’s a great idea and a great look without worrying about compromising the aesthetics of the living space. 

  • yekimouse
    yekimouse Member Posts: 8
    edited April 18
    There's a simple thing throwing off the calculations here --

    @kaliber50 -- You're using the ACH50 calculation as your natural rate of infiltration. The ACH50 method measures the infiltration *at a specific high pressure of 50 pascals* not at natural/ambient pressure. Lawrence Berkeley Lab came up with a system called the LBL-Factor or N-Factor where you can "convert" the ACH50 at 50 pascals to the "natural" pressure. Based on your design temps, you're somewhere in the upper Midwest?

    Take your assumed ACH50 number (4 or 5 from what I read above?) and divide it by something like 17 to get to your 'natural' pressure infiltration rate. So 4 -> 0.23 and then re-run the figures for total heating load. The old method was to just divide it by 20 to get a round number, so even doing that gets you to a much more realistic figure.

    You can see what the nerds at LBL think your specific factor should be below, but whichever method you use, it's well under 1 at ambient pressure:

    https://unmethours.com/upfiles/15051521592593404.jpg
    kaliber50
  • kaliber50
    kaliber50 Member Posts: 17
    hot_rod said:
    You really need to watch S&R temperature over a period of time. When the system starts up, expect to see a wide delta, that will close up as the floor warms and room reaches setpoint. When designed an operating delta is chosen to size the circulator. For comfortable radiant surfaces a 10-15° is common. But it will move around depending on the load, room temperature, etc. At any given time you can use that measured delta to determine how much heat is being delivered. That is basically how a BTU or energy meter works. You need to know flow rate to that zone, and delta t. The simple formula is Q= 500.f.(delta T) So if you are flowing 3 gpm 500 (3) (125-100) =37,500BTU/hr More accurately includes the density and specific heat of the fluid. Q=(8.01Dc) F (delta t) density of water at average temperature 61.8 specific heat, close enough to 1
    Good one!!Thank you for adding another new piece of knowledge to my tool box. I wasn’t aware that the delta would be wide right of the start. I was under the assumption that it would be a static number, at least an hour or so into the heating process.  Nonetheless, I will take that into account as I re-do some of the Borgs numbers. 
  • kaliber50
    kaliber50 Member Posts: 17
    yekimouse said:
    There's a simple thing throwing off the calculations here -- @kaliber50 -- You're using the ACH50 calculation as your natural rate of infiltration. The ACH50 method measures the infiltration *at a specific high pressure of 50 pascals* not at natural/ambient pressure. Lawrence Berkeley Lab came up with a system called the LBL-Factor or N-Factor where you can "convert" the ACH50 at 50 pascals to the "natural" pressure. Based on your design temps, you're somewhere in the upper Midwest? Take your assumed ACH50 number (4 or 5 from what I read above?) and divide it by something like 17 to get to your 'natural' pressure infiltration rate. So 4 -> 0.23 and then re-run the figures for total heating load. The old method was to just divide it by 20 to get a round number, so even doing that gets you to a much more realistic figure. You can see what the nerds at LBL think your specific factor should be below, but whichever method you use, it's well under 1 at ambient pressure: https://unmethours.com/upfiles/15051521592593404.jpg
    Noted. I did run Into this ACH50 standard yesterday but I blew it off out of ignorance and because I saw it on a Canadian website and I thought it didn’t apply to us here in the states. But this is a big one because indeed it does  change the heat loss in a big way as soon as I plugged the converted numbers: from 114,432 down to 42672 BTU😳😳. And I’m actually in the Pocono mountains of Pa. It actually has gotten colder than -5 in this area.
  • kaliber50
    kaliber50 Member Posts: 17
    hot_rod said:
    Tall vertical Runtals on either sides of the doors? They make custom sizes. I have seen them on curved walls.  But the question remains, how much does you floor provide, and how much are you short?

    You have built ins on one side, and couches with dust ruffles pretty much shut down radiant output. So that sq footage gets subtracted out of your available radiant panel output.
    Its called heat flux divide the entire room square footage by those encumbed areas to end up with actual emitter area.

    Looks like tile floor? So you are limited by surface temperature. Ideally that would be 6” on center tube to get the floor surface as consistent as possible, 82F is about as warm as your bare feet can comfortably stand.

    82F floor surface in a 70F room gets you around 24 btu/sq. ft of output.
    Yea I did subtract the couches and kitchen island and anything else masking the heat in my original calculations so those numbers in sq ft are solid. And indeed they are tile flooring but I’m going back to the Borgs to add in what others have suggested to make the math more realistic because that’s what I’m here for. To get guidance and much needed expertise. Thank u bud
  • yekimouse
    yekimouse Member Posts: 8
    edited April 19
    Yep - 43k BTU/hr makes a lot more sense - and is why commenters were balking at 40k of heating load through the structure + almost twice that lost due to infiltration (hence the joke about whether you had an exhaust fan running and if so, turning it off would solve your problem :D ). Think of the blower door test like trying to find a hole in an air mattress -- if you pump the mattress all of the way up up and then put a bunch of weights on it, it'll be much easier to find the leaks -- even though during normal use it'll leak at a lower rate. Same for the blower-door + ACH50 standard -- use the blower to pressurize the building envelope to a specific high pressure to be able to reliably measure the leakage at that higher pressure and compare across different buildings. Since there isn't a fan blowing into your house on a day-to-day basis, the 'natural' pressure differential between inside and outside is much lower, hence the air infiltration is much lower too.

    This of course doesn't help your problem of adjusting the heating to be more comfortable - but should help inform the discussion a lot more when you have a better heating load calc.
  • kaliber50
    kaliber50 Member Posts: 17
    edited April 19
    You aren't wrong. Haha. I deserve all the flaks and jokes :D . But the rest of the math is on point with high a high degree of confidence. The only change I did was using the converted infiltration rate for my zone and changing the design temp from -5F to a 8F from the ASHRAE chart for my region and now the numbers are down to the 30K BTU range. Now with some solid Heat Loss numbers and some more hardy delta numbers as Hot Rod suggested I re-do, I should be on my way..............Thx again yekimouse
    yekimousePC7060
  • kaliber50
    kaliber50 Member Posts: 17
    Back again guys and thank you for all the feedback which was super helpful in fixing my data. I wanted to fix up the numbers before posting again. So went back to the drawing board and re-visited some of the data for the heat analysis. Changed my outdoor design temp to reflect more accurate data that pertains to the region I am in and changed my ACH50 number that was throwing off the data.

    Anyway, I included my analysis and the numbers seems about what's to be expected. I used the heat loss numbers to calculate GPM which calls for 2.42 GPM to deliver the 36,274 BTU/HR or .80 GPM per circuit. Except that the most I can get for 2 of the loops is .5 GPM and .8 GPM on the 3rd (and shortest loop).

    I know some of you guys stated that my 007-F5 is more than adequate to cover the GPM requirements in my case, but my calculations yielded head loss of about 11' for my longest run. That doesn't include any head loss from the S&R manifolds nor potential head loss from possible scaling inside the pex (I have well water and noticed scale in some sections of the return). As I understand, the 007-F5 has a max head range of 10' so surely this would have an effect of why the flow rates won't go above .5 GPM on the other two loops if my head loss is above what the 007-F5 is designed to operate in. As a reminder, the two loops with the .5 GPM flow are 60 ft longer than the shortest one with .8 GPM flow.

    Any thoughts? Thx again


  • hot_rod
    hot_rod Member Posts: 16,329
    A quick calc with the RadPad shows about 6.8' head for a 300' loop of 1/2" pex. .80 would be on the high side of what is suggested for 1/2" pex.

    Or the accuracy of the flowmeter reading?

    You mentioned one plugged loop? Maybe others are partially plugged, or kinked will also add pressure drop.

    If there is hard water scale in the loops that could indicate a small leak that was allowing makeup water into the system on an ongoing basis. You really should not have much scale formation from a single, or even multiple system fill. And it takes a lot to scale a pex loop flowing 1/2 gpm or more.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • kaliber50
    kaliber50 Member Posts: 17
    hot_rod said:
    A quick calc with the RadPad shows about 6.8' head for a 300' loop of 1/2" pex. .80 would be on the high side of what is suggested for 1/2" pex. Or the accuracy of the flowmeter reading? You mentioned one plugged loop? Maybe others are partially plugged, or kinked will also add pressure drop. If there is hard water scale in the loops that could indicate a small leak that was allowing makeup water into the system on an ongoing basis. You really should not have much scale formation from a single, or even multiple system fill. And it takes a lot to scale a pex loop flowing 1/2 gpm or more.
    The flow meters are new and just installed them maybe two months ago. And your RadPad calculations are correct. I used the hePEX pressure loss chart and came up with 6.57’ total. And the additional loss was to account for 15’ of 3/4” copper and unaccounted “minor losses” as suggested by some of the websites I visited previously. 

    The plugged loop is not in use. I took that out of commission a few months ago. As far as the scaling goes, the previous owner never addressed the leaky loop and it must’ve been leaking the whole time he owned the property. So it could’ve been leaking the whole time (17 years!) until I discovered it a few months ago and sealed it (I have pressure tested several times since then and pressure is still holding). 
  • hot_rod
    hot_rod Member Posts: 16,329
    you may be high on your added head loss numerous, if it is just some copper and fittings?

    Regardless, you are not getting enough heat output, a 1/10 gpm or so is not going to change much

    You could run a cleaner if you suspect scaling, a mild acid like they use in tankless water heaters, even a dose of CLR. Hydronic chemical suppliers have acid based cleaners for hard water scale problems, even Hercules Sizzle a
    drain cleaner is listed for potable water descaling.

    A very thin layer of scale can really hamper heat transfer in a tube

    A quick and easy thing to do to see if the flow increases. It would be good to descale the boiler and every other component with scaling
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    kaliber50
  • kaliber50
    kaliber50 Member Posts: 17
    hot_rod said:
    you may be high on your added head loss numerous, if it is just some copper and fittings?

    Regardless, you are not getting enough heat output, a 1/10 gpm or so is not going to change much

    You could run a cleaner if you suspect scaling, a mild acid like they use in tankless water heaters, even a dose of CLR. Hydronic chemical suppliers have acid based cleaners for hard water scale problems, even Hercules Sizzle a
    drain cleaner is listed for potable water descaling.

    A very thin layer of scale can really hamper heat transfer in a tube

    A quick and easy thing to do to see if the flow increases. It would be good to descale the boiler and every other component with scaling
    I definitely and highly suspect scaling given what i seen and the history of the leak. I took a section of the pex and dissected it and tried to scrub off the scaling and it was really caked on and “unscrubbable” so i assume it’s the same along the rest of the lengths. But great idea!!! Let me try that first and see how that goes and I will report back. Although it won’t be for another week or so since I won’t be able to get around it until the weekend. Thx Hot Rod.