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Help with Great Room heating strategy and the wrong thermostat

schreibschreib Posts: 104Member
Thanks in advance folks. I need to target the best thermostat brand / model to solve a problem and suggestions for supplemental heating for a wall of windows.

The Problem: New house 2017, slab on grade concrete floor with poured in PEX tubes for hydronic heating. Great rm has a wall of windows facing SW, cathedral ceiling 20 ft hi, great heat gain in winter, large overhanging eave so not a problem in summer. Lochinvar WH 55 boiler, short boiler loop into a short spaced double T, passing heat to distribution loop. Boiler uses reset curve, set plenty high. Distribution loop with WILO Stratus ECO adaptive head pump into all zones with solenoid valves controlled by ambient sensing stats, 6, SIP home, foam ceiling, blower door rated at 1.0 ACH/50

The problem is the boiler / radiant heating contractor failed to provide, what I think at least, is the correct Thermostat type-- dual sensor slab stat that use the SLAB SENSOR to modulate the heat, not the ambient thermistor on the wall. These ProOne T 755S stats do the opposite-- ambient room sensor sends feedback for control and the floor sensor is relegated to only use as over / under temp limiter. The problem this causes is there is severe time delay from the carpet in the room preventing the ambient sensor from getting timely feedback that the slab has lost significant heat and then, too late, it needs a big slug and has a big delay getting the room back up again in the morning. Secondly, the pump system is oversized and even with throttling down I cannot seem to reduce flow enough to allow boiler to reach set point (of the system feed piping, not boiler loop) unless only 3 or less zones are in demand. After a 4th zone opens up it cannot make it to set point.

So, for the first problem I would like to retrofit the stat to one which will remove the delay back to the boiler by controlling the slab temp directly. Looking for suggestions for slab sensor modulated hydronic stat, please.

For 2nd problem, looking for suggestions to allow the Great room, alone, to be on one circuit that runs at the flow and higher temp not required by the rest.

3rd problem: The great room cannot under any cold weather conditions below 25°F outside be heated by this system past 70°F. I would like it to be a BIT more comfortable. Other zones, no prob reaching set point. I am considering removing the carpet in a strip about 2 ft wide near the windows and replacing with a less insulative surface to allow what heat I AM pushing out to GET to the area of need. Then on each side of the 6x8 ft patio door place a 500 watt baseboard heater under those 30" windows to provide a heat barrier from the cold be radiated into the room at least in those areas. I can't put more KW in because I am planning on keeping the solution simple so I can just plug these two units into receptacles nearby, no new circuit. What do you think of this idea?

THANKS folks! Brian


  • STEVEusaPASTEVEusaPA Posts: 2,328Member
    edited January 2
    A system this involved should've been completely designed, and the installer should have a complete heat loss, piping diagrams, manifold settings, loop cad, etc.
    Some pictures of your near boiler piping and a diagram of the whole system with controls would help.
    For starters, was the slab properly insulated-underneath and on the edge?
    Are you using a set back, and trying to recover in the morning? If so, that's most likely your first problem. Thermostat may not matter. If you set it to 70° and the room gets to 70°, it's working. But if you are using a set back, and trying to warm the slab, warm the carpet, warm the room.
    I'd pick a temperature and stick with it, unless you are going on vacation.
    You can control the slab temperature, with your ODR, but you should have the zone pump continuously running, and your ambient thermostat will work as a high limit.
    2nd problem...make it its own zone, you can do with it (temp/flow rate, etc, whatever you want) and the proper controls..but I don't know what controls what.
    3rd's designed wrong. Could be wrong loops, diameter, spacing, flow rate, water temp, etc.
    Finally, where's the installing contractor? No warranty on the system, no pride in his work to come out and make it right, or to at least try to make it better?

  • GordyGordy Posts: 8,489Member
    Some information on how the loops for zones are setup. Is great room a seperate zone now?

    Is all radiant running same SWT?

    Is it possible to use panel rads, or high output baseboard by the Windows? Sized large enough to use the current SWT?

    Sounds like your carpet in the great room is higher r value not radiant friendly.

    Yes slab sensors should be used in leu of a thermostat. You are experiencing fly wheel effect.

    I may have missed it is outdoor reset implemented?
  • EBEBRATT-EdEBEBRATT-Ed Posts: 4,510Member
    Sounds like a carpet problem to me. Your insulating your heat source (slab) from what your trying to heat.

    If you remove the carpet and it doesn't work you could add some baseboard if you have access for the piping.

    I am sure this isn't the answer you want to here
  • GordyGordy Posts: 8,489Member
    Any concrete radiant should implement a slab sensor.
  • ZmanZman Posts: 4,437Member
    @schreib Are you still with us?

    The 2 things I would be thinking about first are Outdoor reset and room by room heat loss.

    Especially when you have a modestly sized boiler, you have to be very aware of the energy sucking nature of high mass slabs. Right now, your slab is cooling off completely between cycles, then ramping itself to the point of too hot only to start the cycle over.

    I like the idea of keeping an eye on the slab temp but only if you are doing on a room by room basis in concert with outdoor reset.

    In the end, you want to slowly raise and lower your slab temp based on outdoor temp and the heat loss of the space.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • schreibschreib Posts: 104Member
    Wow. Fantastic response folks. thanks again.
    Here's an update. dynamic situation, while waiting on responses I have been working this problem too.

    -- I am a mech engineer, relative is too: He designed the system and recommended the Boiler and zone control; see att pdf. Drawing is close, not exact! Boiler has one pump that exchanges heat to the single pumped distribution loop manifolds. Pumps and details on pdf showing reset curve.
    -- unfortunately, although I tried, I did not control my mech sub. I was GC and had to find subs in area not familiar with, no contacts. I made some poor choices. The mech contractor did not use the PEX spacing per prints and I missed it. He did not pipe boiler per dwg, provided wrong T'stats(slab sensors but the do NOT modulate control, only hi / low temp). He made various other mistakes. . . The concrete contractor did a poor job of placing the 3" foam under slab in some areas and omitted(!) the slab edge foam. Luckily, the outside of foundation wall also has 2" foam; helps some. I would not allow the mech contractor to connect a garden hose knowing what I NOW know.
    -- I understand the problem with high mass needing to stay at uniform temp and be nearly continuously controlled rather than after spikes.
    -- The Great Rm is complicated: 80,000 Btu/hr capacity dual sided wood fireplace, full carpeting, tall ceiling, 4" conc floor with PEX hydronic tubing not spaced tighter near SW facing wall of windows. Windows: 12ft tall x 12 ft High, high end Marvins; has a minisplit head in it-- 15KBtu/hr capacity. Great rm in center of home. If it is warm the whole home is assisted. On its own, single boiler zone.
    -- Reset curve pdf attached. I do not use nor intend to use night set back features on boiler or stats. Trying to keep boiler running all the time at low output and minimal fluctuation is my ideal run plan. With pumps set ultra low in output I have maximized dT across slab manifolds(hot output vs cold returns-- 50°F! Yes, I know. Should be 20 to 25°F. Perhaps if I can sense the slab and remove delayed response I can move reset curve down and same with dT across manifolds.
    -- I don't recognize acronym Gordy used SWT, cannot respond.

    Based on input from you folks, my own plans, and input from a very wise fellow at local Tekmar supply house in Mpls is this:
    -- place two 500 watt baseboard heaters on each side of window wall(25" wide each).
    -- remove carpeting in front of windows and replace with low R value flooring-- about 2 ft width or so. Allows the hydronics to be as efficient as a not-so-great install could hope for.
    -- Install a Tekmar 519 Stat with floor sensor OR fake out the installed Pro one T755S stat to sense floor instead of ambient air.
    -- If successful I may be able to drop reset curve down and use lower water temps. I have been forced to bump it up to allow faster response to the big demand in early morning. If I can keep the system pump running(per suggestion above) and have a stat fed with a floor sensor, I should be able to reduce lag in response.

    Sorry I dropped off for a day or so. Thanks again for your time to read and your responses. Looking forward to your additional input, agree with my plans, other, better ideas?! thanks!
  • Jamie HallJamie Hall Posts: 8,957Member
    The best laid plans...

    SWT is supply water temperature.

    It looks as though you are headed in the right direction. It also looks as though you have a right mess of an installation; that's a shame.

    As you have noted -- and others have said -- with a massive concrete slab and radiant, the first essential is to keep that slab at as close to a constant temperature as possible, varying it only to respond to outdoor conditions as needed to balance the heat loss from the space. There are, of course, various ways to accomplish this, but they all boil down to the same thing: provide the slab with an even source of heat to deliver the BTUs corresponding to the outdoor conditions. Variable supply water temperature, variable flow rates, mixing valves... You do need a slab temperature sensor and an outdoor temperature sensor, and a control which takes the two inputs and determines the required BTU (hence slab temperature) and adjusts whatever variable is used to hit that target and hold it.

    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England.

    Hoffman Equipped System (all original except boiler), Weil-Mclain 580, 2.75 gph Carlin, Vapourstat 0.5 -- 6.0 ounces per square inch
  • schreibschreib Posts: 104Member
    Excellent. Thanks for fast input Jamie. It sounds like I am heading in correct area. I appreciate your input; gives me some confidence I can solve this.

    OK SWT is Supply Water temp!
    So, Gordy: yep, same temp supply goes to all zones. Lochinvar's name is "system temp" feeds from sensor in main manifold feed to all zone supply. System / Distribution is a Wilo constant head pump assuring equalized flow to all zones. Please see pdf's attached. However, I can have up to 3 pump fed sub-systems with the Lochinvar Knight unit. Each one can have its own space heating set point(SH1,SH2, SH3) but the highest one's reset curve is used to feedback to boiler. Potentially, I could gut the piping and add another pump just for Great room, then use . . . what? maybe a mixing valve for the rest for reduced SWT to them? Please view the piping diagram. . .
  • GordyGordy Posts: 8,489Member
    edited January 5
    So per PDF boiler is piped direct as shown?

    Radiant floors should be a delta of 10 degrees not 50degrees way to wide.

    Pay particular attention to the minimum required flow rate of the boiler since it is piped direct. That boiler needs a minimum of 2.1 gpm on high fire, and 1 gpm on low fire.

    Delta through the boiler of 35 degrees max.
  • Tim PotterTim Potter Posts: 232Member
    edited January 5
    Something I noticed,
    In your first post you said:
    [short boiler loop into a short spaced double T, passing heat to distribution loop] I think you are describing closely spaced t's ???

    but the diagram you attached shows direct piping

    Both are correct ways to pipe hydronic heating, but they are way different on how they operate & how the boiler is setup.

    We have the same issues with our living room, lots of windows & carpet. rest of the house is tile or carpet in Bedrooms. we are located at 9000' colorado mountains. Its been described as "flywheel effect". we manage as best as we can by constant circulation (5* dt) & set the reset curve about 5* warmer, & use t-stats in the indiv rooms to serve as high limit, ie off above 68* If your reset curve is designed correctly, not much overshoot.

    If you're within a reasonable distance from Zimmerman there is a guy, Eric Aune, Aune Plumbing & Heating . He is well respected.

    Winter Park, CO & Lenexa, KS
  • KC_JonesKC_Jones Posts: 3,829Member
    schreib said:

    -- If successful I may be able to drop reset curve down and use lower water temps. I have been forced to bump it up to allow faster response to the big demand in early morning. If I can keep the system pump running(per suggestion above) and have a stat fed with a floor sensor, I should be able to reduce lag in response.

    These comments confuse me. You say you aren't using setback, so why do you need extra in the morning?

    What lag are you talking about? If you have the Outdoor reset tuned in the boiler runs constantly and the slab stays warm all the time. There shouldn't be a lag to speak of. Can you elaborate?
    2014 Weil Mclain EG-40
    EcoSteam ES-20 Advanced Boiler Control
    Boiler pictures updated 2/21/15
  • GordyGordy Posts: 8,489Member
    edited January 5
    The swing, flywheel, lag comes from the delayed reaction of charging a high mass radiant system. The closer you can keep the slab to constant set point conditions the better. It is like a battery with its mass.

    The cause of fly wheel effect can be different things.

    Set backs big mistake, can lead to fly wheel. By the time the room reaches set point the slab has been warmed to a greater extent. This energy bleeds off after set point is reached, and causes over shoot of set point.

    High r value floor coverings delays the response of the slab. Again causing over shoot once set point is reached.

    Solar gain. The slab gets additional btus from solar gain causing over shoot of set point.

    Outdoor reset Tuned to the best it can be drives the system alone. The thermostat becomes nothing more than a high limit device from alternative heat sources. Such as solar gain, cooking, many occupants above normal, fireplaces, and wood burners.

    To tune it takes time, and patience. You would set the thermostat above desired set point 5 degrees or more. Enough so the thermostat doesn't interfere with the outdoor reset. Start with a curve that matches your parameters. Let the system run a few days. High mass takes time to equalize. If you are over shooting desired set point drop the curve a little at a time waiting between adjustments to equalize. Do this until the desired set point is reached, and maintained with highs and lows of outdoor temps.

    It's best to try to do this with a week of consistent highs, and lows.

    Now the odr is driving the system. The thermostat is nothing more than a high limit device.

    It may be necessary in extreme cold conditions to raise the curve temporarily.
  • schreibschreib Posts: 104Member
    Yes, mistakenly placed wrong diagram: pg 39 is correct. Placing it now. Sorry.
  • schreibschreib Posts: 104Member
    answers to some questions:
    -- yes, it is a close spaced T per pg 39 diagram
    -- boiler flow curve indicates that the Grundfos 15-58 on the LOW speed is running somewhere between 5 to 8 gpm. I back calculated that based on some run data while boiler running at 100% rate. Can't be real sure enough to use the curves because no pressure gauges on either side of pump to provide Head.
    -- KC:
    KC_Jones said:

    schreib said:

    -- If successful I may be able to drop reset curve down and use lower water temps. I have been forced to bump it up to allow faster response to the big demand in early morning. If I can keep the system pump running(per suggestion above) and have a stat fed with a floor sensor, I should be able to reduce lag in response.

    These comments confuse me. You say you aren't using setback, so why do you need extra in the morning?

    What lag are you talking about? If you have the Outdoor reset tuned in the boiler runs constantly and the slab stays warm all the time. There shouldn't be a lag to speak of. Can you elaborate?
    It may be useful to review this note from earlier:
    The Great Rm is complicated: 80,000 Btu/hr capacity dual sided wood fireplace, full carpeting, tall ceiling, 4" conc floor with PEX hydronic tubing not spaced tighter near SW facing wall of windows. Windows: 12ft tall x 12 ft High, high end Marvins; has a minisplit head in it-- 15KBtu/hr capacity.

    There is a lot to address here. First I know very little about the strategy for setting up the reset curve. I am likely only crudely using it as a device to up the boiler output as temp declines with arbitrary guesses chosen for the two points on the slope enabling me to force the set point up more than I could attain otherwise over the range. My reasoning so far was that I wanted to get the Great room stat to meet its set point and how could I do that without higher input water temp. Well, I was able to do that but at the price of lower flow rate. It is likely I really did nothing: same BTU's were being put out with low flow and high temp as before with high flow and low temps. I am running the Wilo pump now at nearly its lowest setting to allow the reset curve's set points to be met successfully. However, THAT is also responsible for the 50°F dT between RWT and SWT. I could put it back up and not meet the reset curve's set points and still not effect a change. This whole time I believe I was not seeing the lag caused by running the fireplace during the day and at night before heading to bed. The fireplace satisfied the ambient sensor on the wall in the great rm. While all that time my massive slab was losing heat and really lost heat after going to bed. Finally around say, 4am the massive slab heat loss showed up in the room air and the ambient sensor FINALLY sensed it and put in a heat call. Well, toooooo late, man! So, it worked the boiler hard to get 'er back up for hours. THIS is the lag I was trying to describe.
  • schreibschreib Posts: 104Member
    Gordy: all you say(mostly!) makes sense as it agrees with my conclusions and Jamie's indicating I am on the right track. Mostly though I need to address the latter part of your note about HOW to set the reset curve points. I will be re-reading that a couple times and then try to apply it. I will be ASSUMING that you state that strategy figuring I WILL be using a slab sensor, not the ambient sensor.
    It is now 12:15 am, next day. . . So far, this is my next plan: Get the ProOne stat to use its slab sensor as the control point which I believe I was able to program this afternoon. I have the slab set point on the stat set at 77°F and it has dropping since mid-day(yesterday) from 83°F high and just gave a call for heat. I will report back! Ha!

    Finally, addressing your points about the reset curve driving the process, not the T'stat and you suggested setting the T'stat about 5° above the reset curve. Well, that really confuses me.

    On MY system the two are independently working. With the Lochinvar, not sure how ANY other residential boiler works, the reset curve is set by two points which define a line's slope for defining how the BOILER system temp set point(SH1) is reduced as OD temp increases. This system sensor is placed on the main Supply feed pipe going to all the loop manifolds in the home. The indoor stats(for each zone) are set at ONE point and have no accommodation for OD temp. I do not move that set point, period. The way I view the process is that the boiler is responsible for providing a reservoir of heat input with limited ability to modulate on the WH55 (from 20 to 100%) as needed to satisfy the set point for the system sensor defined by the reset curve slope and end points; while the stats simply decide which zones needs to draw from that reservoir. The reservoir needs to be big enough to take on some limited spikes from solar and fireplace gain in my case but should not be asked to make up for hours and hours of slab cooling because it has been OFF for a long time. My job is to get it on more consistently.

    Tim Potter aludes to the same strategy and I am just not catching what you guys are offering me on setting 5 degrees high etc. By the way Tim offered a contact: Aune Plumbing and heating. YEAH. Uh, he was the contractor I unfortunately declined and went with the big talker instead. I am embarrassed to say. It is doubtful he would offer to come help me after I failed to give him the job. Talk about eating crow.

    It is late tomorrow I will re-read Tim and Gordy's suggestions and maybe catch on! nearly 1am. I'm outta' here guys.
  • CanuckerCanucker Posts: 477Member
    Must have been a heck of a talker to give up the chance to work with @EricAune I doubt he'll hold a grudge, give him a call. He might be really busy. He doesn't post here as much as he used to
    You can have it good, fast or cheap. Pick two
  • GordyGordy Posts: 8,489Member
    You keep mentioning this 80k two sided fireplace. Do you use it?

    Setting the thermostat 5 degrees higher keeps it from interfering with the process.

    The big talker should have set th ODR up as part of the install. I presume he left the I/O manual.
  • EricAuneEricAune Posts: 432Member
    @Canucker thank you, thank you too @Tim Potter

    I haven’t read thru this whole thread as I’m currently looking at a different system with similar problems. As with this particular thread, I wasn’t hired for the job. I bid on both though!
    "If you don't like change, your going to like irrelevance even less"
  • schreibschreib Posts: 104Member
    Here is the latest:
    I was successful in converting the ProOne stat(great rm) over to slab control-- in a round about way. But it apparrently is working and I plan to convert the others over from ambient sensing/control to slab today. So I probably will not be buying Tekmar 519 thermostats.

    Last night the Great room slab was set at 77°F and held it all night(-19°F low). I moved set point to 78°F and it met it. However, at 79°F set point, it cannot satisfy demand.

    8am: Boiler is running at 100% output reset st pt (demand) is 145°F and boiler can make up to 140°F at system sensor. Not gaining. System pump almost as low as it can go. Over 50°F dt from return to supply side of system.
    Boiler Loop: Inlet = 133F, Outlet = 147F(dT = 14°F);
    Return System manifold temp = 83 to 84°F, water rising slowly from 81°F earlier.

    pdf file uploaded shows slab and ambient temps.
    I will update this file around noon to show ability to make set points with really cold outside temps.
  • schreibschreib Posts: 104Member
    GEEZ. NOW I am realllllly embarrassed. Sorry Eric. Sometimes a guy just screws up. Really wish I would have seen through the BS from fast talker. First time GC ing and building my home is my only excuse!
  • GordyGordy Posts: 8,489Member
    I’m confused by why you think you need to pump the system side low........

    A 50degree delta for the radiant loops is crazy. Should be 10. Your slab is getting inconsistent temps across the panel.

    You need to increase flow on your slab. Can you measure delta on individual loops? I think your measuring total delta of all loops supply , and return.

    If you have an IR thermometer to shoot floor temps is helpful in seeing how even the slab temps are.
  • schreibschreib Posts: 104Member
    edited January 5
    Gordy: Yes, I have been running the Fireplace and now "get", I believe, your point. Run the zone regardless of FP being on. However, you can see how that may seem hard to do with the fireplace running full out. Will do regardless! thanks.

    The Big talker was worthless: I had to install all T'stats, program them, and basically commission the boiler on my own. Never having done so before. His guy did not even calibrate the LP burn products(CO2, O2)-- I got in a supply house rep who did that and showed me how to use anticylcing and, with his assistance, got big talker to re-work the boiler piping per pg 39(and contract!). His guy mounted and piped the boiler(wrong), flipped the ON switch without installing the OUTSIDE temp sensor and walked away. I should have sued him or something but did not want the hassle.
  • GordyGordy Posts: 8,489Member
    If you are going to use the fireplace consistently that explains the great room overshoot.......

    Key points

    With a condensing boiler set up p/s system side flow rate should be greater than boiler side. This insures boiler return gets coolest possible return water temps from system.

    You need to get return temps to the boiler as low as possible below 130to condenser for higher efficiency. You shouldn’t need 140 swt to a radiant slab.

    This would have been all in the design of the installer
    I think you got someone who didn’t do a heatloss, and didn’t design around that.

    The heatloss of each room dictates tube spacing, swt, and flow rates.

    Is there flow meters on your manifolds.

    Everything your doing with stats, ODR is in vein until you get flow rates set properly.
  • schreibschreib Posts: 104Member
    Gordy said:

    I’m confused by why you think you need to pump the system side low........

    A 50degree delta for the radiant loops is crazy. Should be 10. Your slab is getting inconsistent temps across the panel.

    You need to increase flow on your slab. Can you measure delta on individual loops? I think your measuring total delta of all loops supply , and return.

    If you have an IR thermometer to shoot floor temps is helpful in seeing how even the slab temps are.

    OK Gordy, answers for you:
    -- I do not believe I understood the best strategy for boiler heating of slab and was trying to get "more" out of the boiler by getting it to meet my UN realistic reset curve. (Please refer to previous post to see that curve.) By flow on the system pump so much I was able to increase temp out to all zones(system sensor) and allow the system sensor(feeds back to reset curve / boiler set point) to meet set point. However, I believe that I had too high "altitude" on the reset curve. My plan now should be to increase the flow back up and drop the altitude of reset curve, right? and yes, I AM measuring total dT of ALL loops. The dT I refer to is from main pipe OUT of boiler loop vs main pipe back in to be re-heated. Let me know what other temps to look for. I have a TC meter, can check anything. Unfortunately, ability to get any kind of reliable flow estimate for WILO pump is compromised by inability to get its head. Please see my recent post for all slab temps in the pdf file. thanks!
  • GordyGordy Posts: 8,489Member
    edited January 5
    Can you post some pics of the boiler with its piping, manifolds supplying the system etc. I think your chasing your tail.

    Do you know tube spacing in each zone?
  • GordyGordy Posts: 8,489Member
    can you post pics I asked?

    Measure temps on individual loops supply, and return record.

    Measure same at the different zone manifolds supply, and return. Record

    Measure supply, and return at system piping. Record

    Measure supply, and return at boiler side. Record.

    Of course do this when systems are calling.
  • GordyGordy Posts: 8,489Member
    Also measure slab temps across the panels of individual areas with IR thermometer not the slab sensor reading.
  • GordyGordy Posts: 8,489Member
    Do you understand the concept of primary secondary?
  • GordyGordy Posts: 8,489Member
    edited January 5
    The universal hydronic formula is the basis of design.

  • schreibschreib Posts: 104Member
    Photos will be posted but expect hard to really see what is happening. I have a flow diagram that will be more useful. Requires updating though. No, I do not actually even know the spacing. I don't think I even took photos before the concrete was poured unfortunately.
    However, the pg 39 pdf file is pretty accurate. Eventually, I forced contractor to make it per that drawing.
    Here is text description of piping:
    -- Boiler loop is only about 5 ft total length including its pump. Not a nicely done loop(same plane etc) because contractor had to remove wrong components . . . Lochinvar inlet and outlet sensors are INSIDE the boiler. Run the Boiler process only.
    -- The secondary, distribution, system loop connects via a pair of closed spaced T's about 6" apart to exchange heat between them. Output from top of close spaced Tees goes to the auto controlled head pump(WILO 4 to 16 ft head) feeds all zones and on its EXIT point the "system sensor" is mounted. When more zones open up the pump increases flow to keep constant head.
    -- Returning from the zones is a set of SS manifolds with valves on them, operated via two Taco heads / zone stat feedbacks. Its main outfield pipe / manifold runs to bottom of close spaced T manifold and my return temp TC sensor is taped to that. about 84°F now.
    -- an indirect Lochinvar Squire hot water tank is side-arm fed INTO the boiler INPUT feed with a T and its own WILO pump. DHW demand kills Boiler pump and starts the WILO. So, the DHW goes direct to boiler and back to tank bypassing boiler circuit. Set pt for boiler for water heating is 145°F. Set for priority DHW and system loop is interrupted until satisfied DHW. taking a shower the Hot water is satisfied within 5 min or so.
    -- boiler pump(Grundfos) at lowest setting.
    -- Wilo system pump at only "5".
  • schreibschreib Posts: 104Member
    edited January 5
    Gordy: quite a list, Will do and get back to you. SO, I guess you are saying use the hydronic formula back out a GPM estimate. Yep understood. I also THINK I understand the idea behind primary and secondary loop: Primary circuit is just a simple way to provide source of high temp water to the heat exchanger between the two loops(close spaced tee section). Secondary uses this reservoir of heat to satisfy individual zones call for it. I don't have an IR thermometer only my Fluke Digital TC meter.
  • schreibschreib Posts: 104Member
    Gordy: reviewing the build photos I did find a few showing spacing of tubes. Highly variable. AS tight as 4" near some ext walls, but up to 15" in spots. Average might be about 12"?.
    My plan is to:
    -- First: Increase flow to distribution zones and reduce basic OD reset curve. The idea to have reset curve above potential for boiler to meet it so my boiler runs up to 100% and does not overshoot more than 10°F. If overshoots more, it will shut down and then cycle like this. I hate the anti-cycling algorithm Lochinvar uses to control this. PID loop control has been around for 80 years! Where were they?
    -- convert all zone stats over to slab sensing/ controlling from ambient air control.
    -- Set all zones above slab temps earlier provided in pdf about 5°F and let settle out during the afternoon. Sunny today at nearly noon but still -4°F. May get up to zero! ha!
    -- Report data per your instructions after things level out.
  • GordyGordy Posts: 8,489Member
    Primary secondary decouples the two loops (boiler, and system) hydraulically. This allows the primary loop (boiler) , and the secondary (secondary)loop to use different flow rates with out effecting each other. That's the main goal.

    There is the ability through formulas for hydraulic separation to calculate the mix of the fluid temps to predict supply, and return temps. Which requires knowing flow rates.

    On the manifolds supplying the loops, is there flow meters?

    You are trying to do multiple things at the same time. You need to do things in order.

    The hydronic formulas

    Known load (heat loss)
    Known Delta t for radiant (10)

    You can calculate required gpm.

  • schreibschreib Posts: 104Member
    edited January 5
    -- OK, I understand the two loop strategy. That is basically the same for any heat exchanger. I had never seen a heat exchanger like this one that allows intermixing of fluids. It is unique in that even with that, one can hydraulically separate the two like other exchangers. I have understood that all along though. Just did not state it.
    -- Yes, the output manifolds have tiny, probably not very accurate and hard to read flow meters. I figure you want me to read them, add them all up and provide a flow estimate. Will do.
    -- already increased flow on WILO auto-head pump to "9". Now the system temp falls about 16°F shy of meeting reset curve set point whereas it was 5°F shy before increase. Total dT is now 27°F instead of about 50°F average across Supply / Returns. Want a further step up in flow??
  • schreibschreib Posts: 104Member
    Heat loss / demand calculated was about 35,000 Btu/hr for my home originally. I cannot recall what outside temp it was based on though. Need to go back and look at documents.
  • schreibschreib Posts: 104Member
    using Hydronic formula I get 2.5 gpm flow for 35,000 Btu/hr.
    This is the BOILER loop flow though, right? not the flow for the WILO pump out to the zones. The Grundfos pump is likely running in the 4 to 7 gpm range at its lowest speed from what I can tell. I have a 50/50 pro-glycol mix, specific heat is 0.85 and specific gravity is 1.041. Maybe you can use that to double check my guess here. . . Formula I would use is same basically as your formula but takes into account the fluid characteristics in use and boiler efficiency guess of 90%.
  • schreibschreib Posts: 104Member
    edited January 5
    Verified: 35,000 Btu/hr is about right.
    Also, here are all the Computer analyses for the radiant design at this link. Hopefully, you can access Dropbox with no hangups.

    Takeaway: Home plan relied on 70°F stat set points for zones and about 104°F SWT average to most zones. My supply water temps with the reset curve in use is WAAAAAY high. But system designed for about 20°F dT not 10°F dT. I will increase flow to make a 7°F dT drop until I see approx 20°F dT. Hope you are good with that. thanks.
  • GordyGordy Posts: 8,489Member
    You need the heatload of each room, or zone. Not the whole house for establishing zone flow rates.

    Those flow meters aren't there to look pretty.

    Why are you using glycol?
  • schreibschreib Posts: 104Member
    1:12 pm, Outside temp = 8°F, reset curve st pt = 126°F, making 114°F at system sensor but return is running 95°F===> providing a 19 to 20°F dT with WILO pump head set at "12" ft head. 5 zones calling for heat. Only great rm using slab sensor to control but it is up to 81°F, set to 90°F.
  • GordyGordy Posts: 8,489Member
    For 35000 btus

    You can go 3.5 gpm at a 20 degree delta, or
    You can go 7 gpm at a 10 degree delta.

    You had a 50 delta which is 1.4 gpm

    See the relationship?

    What does a narrower delta achieve?

    It keeps the emitter (the floor) at a more even temp across its surface, plus gives same output at a lower water temp.

    The reason your rooms were holding setpoints is because you had a huge delta with very high for radiant water temps.

    This is why I wanted to know flow rates at the flow meter.
    And individual loop temp deltas, and zone temp deltas (supply/return at the manifolds).Gives an idea what loops lack flow, what zones lack flow etc. a more defined picture.

    I don't know why he designed around a 20. Yeah it will work.higher water temps, and decreased output across the loop from supply to return. Which equals comfort issues to the feet.
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