Coaching required -
I’m in 2000 sq ft 18 year old house, slab on grade, built for us. Closed system, In-floor radiant heat, 4 zones, 4 manifolds, 1/2” Uponor Pex, Tru flow Jr manifolds, Taco 007 boiler, two Grundfos single speed pumps, HTP boiler 120k . House was insulated to code, 2 x 6 walls, etc. As seems to be common, when it gets the coldest (MN), it doesn’t keep up. I have struggled with one zone (3 loops) since a few years after it was new. The zone only satisfies when it’s in the 30’s. I added flow gauges to this zone and have been doing some “controlled” experiments making some assumptions about which loop is the longest, opening it up fully and playing with the other two, reading temps and trying to achieve a 10-15 degree delta. It did satisfy the thermostat but again, only when it was in the 30’s. Now it seems this thing is running all the time. It also seems that more heat is near the area of the manifold which wasn’t the case before.
It has been cold but I have come to the conclusion that it still isn’t balanced or the pump is underperforming after 18 years. I am thinking I need a design company to reverse design this system so I know what I have (longest loop on this zone) and can set things correctly. Is it worth the money to do that? I have the floor plans and I have a number of photos so I am guessing they can get close (along with an infrared camera for location of loops). I don’t have heat load calculations but I probably can get them from the architect. How would you guys handle it? How is me tweaking this zone affecting the other 3 zones which I haven’t touched? Your thoughts on where to go from here would be appreciated. Thank you!
Comments
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Hi, Might it make sense to have a good look at everything (system and shell of the house) using an infra-red camera? That way you'll know where the heat is going, and will have concrete things to fix. Also, I'd consider installing flow meters, so you have that data and know which loops aren't flowing properly. Knowing historic energy usage would help too. Finally, using a blower door to see where the heat is going, could be useful for getting to the big leaks and reducing the load. Meeting code is nice, but is a low bar when it comes to energy performance.
Yours, Larry
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are there any y strainers on the system? Over the years they can get restricted and cause under performing issues
If you can find the original design you would know what temperatures are required
Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream1 -
It's possible you need a little larger pump although if one area is under radiated that will not help. You could play with the flow rates a little to see what works best. Slower flow may give you more heat transfer but will give you a lower average water temp.
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Did it ever work right?
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Larry, I plan to get an infrared camera, especially to see the routing of the floor loops. It may be able to help me to determine which loop is longest for balancing. I had a blower door test done with infrared red photos. Overall performance on the house was decent, biggest areas were canned lights, and while the Anderson windows weren’t bad, the fact that there are two 31” x 74” windows in each 90-110 SF room definitely has an impact. I know heat loss is a factor here but less of one now that I have seen the infrared photos. I just really want to get this zone balanced. Thank you.
Hot Rod, I have found no strainers anywhere on the system. I also do not have the original design and can’t get it. I tried a couple years after the house was built and the place was out of business or changed names. The only thing I do have is the original floor plans and photos during the build process. Of course you never have the exact one you need or the one with the right view. Thank you.
EBEBRATT-Ed - I have been playing with the flow rates ALOT. I have made an assumption about which is the longest loop of the three, left that one wide open and adjusted the other two. I finally got the furthest bedroom nearly matching the office/bedroom which seemed to be good progress. I’m not within a degree or so(using my cheesy digital thermometers) I know there is a ton of variability in all this so I’m just using the same baseline to see what changes when I adjust the flow rates. I’m wide open, .5 and .5 on the other two loops. I have found that the laundry room, which is the first room these loops pass through is getting really warm, like 78 degrees warm. Does that mean the flow is too low on the .5 and .5 loops because it is all stalling out in the laundry room?
Mattmia2 - Yes, it worked right when it was new but only for the first year or two.0 -
This morning: 8 below zero outside : Boiler is set to 130 (temporarily due to this cold snap)
Wide open loop is 123.2 supply 117.5 return, 5.7 deg delta
Middle loop is set to .5 gpm is 123 supply return is 114.2, 8.8 deg delta
Last loop is set to .5 gpm is 123.2 supply, return is 113.7, 9.5 deg delta
Floor temps for carpeted floor range from 76-78 in furthest room from manifold,(suspected longest loop) and traveling back towards the manifold sequentially
Bathroom tile is 83-87Office loop temps carpet are 73-77,
Foyer wood floor is 75-77,
Den carpet closer to manifold is 77-81
Laundry floor linoleum right near manifold is 90-92 degrees
I understand the drop off because of the carpet and wood but why is is staying so hot in the laundry room and the den stays warm too and it is carpeted. Not enough flow? Poor balance? Weak pump?
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By the way, the temp in the farthest room from the manifold/boiler is 64.8
the office is 65.3. The zone has been running for as many days as it has dropped from the low 30’s.
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If I understand this correctly, your laundry room is hot because all the loops have to pass through it before they get to the respective rooms (and the heat loss is minimal in the laundry room) so it has no choice but to be hot in there while the other rooms are not. Simply put, the floor can't put enough BTU into those rooms to overcome the loss from the windows. A 77 degree floor temp in a 65 degree room is emitting approximately 24 BTU/SF which is fine for most newer construction, but apparently not these particular rooms. The tubing was most likely done wrong, so here you are. The only thing you can really do at this point is raise the boiler temp even more to get more BTU out there (which will in turn overheat the laundry room even further), or add auxiliary heat to the underperforming rooms. Or close in the windows. Your flow is great, your delta is perfect, there isn't much else you can do with the radiant.
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Thanks Groundup. That is correct. Those 3 loops run through the laundry. Nice summary and that all makes sense. I’m doubting the settings because the laundry room was never hot before. But, the settings were different too. I have also never chewed through this much propane before in such a short period (it hasn’t been THAT cold for that long) or almost never had to run my forced air furnace as auxiliary.
Is it true that the longest loop should always be wide open?With a delta of 5.7 degrees, should I be throttling it down some?
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If you throttle down your flow rate those cold rooms will just get colder.
If it were me the first thing I would do would be to put a thick carpet and/or pad in the laundry room which will at least cool that room down and let more heat get to the rooms beyond it, but that may not be enough to overcome the physics of what is there.
NJ Steam Homeowner.
Free NJ and remote steam advice: https://heatinghelp.com/find-a-contractor/detail/new-jersey-steam-help/
See my sight glass boiler videos: https://bit.ly/3sZW1el
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Thank you but not something I will do on the carpet. But I appreciate your response.
Is there something that is convincing anyone reading this that I have the flow set correctly? If so, I would like to understand it just for my education. Thanks
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It is going to take something like a day or 2 for the system to come in to equilibrium when you change the supply water temp or the setpoint. Is the edge of the slab insulated?
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To maximize BTU output, you want as much flow as possible to keep AWT as high as possible. Depending on where your loops actually go, it's possible that you need to throttle back one of them (that may or may not be heavily contributing to the laundry room) and raise the other two but for now, all of them wide open is going to give you a good baseline for what to do next. Perhaps a simple bath mat/rug over the area where all 6 lines may run through the laundry room to keep some of it out of there.
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Are you using something reasonably accurate to measure temps here or are you using an ir gun?
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Mattmia2 The edge of the slab is within the block work of the house which is insulated but I don’t think it is insulated near the top of the grade. The temps don’t look too bad at the edges of the floor although clearly there is some drop. I’m just using an IR gun. I’m just taking it as an indicator more than anything.
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Ground up - I know I should know AWT is but it’s not registering at the moment.
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Average Water Temp
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Just a side note, an easy way to find out the length of the loops would be to open each one up and blow the water out of it into a bucket and measure the amount you get. Look up the amount of water in 100ft of the installed tubing and that will get you close enough for what you want to know for balancing. When I put the first radiant floor tubing in my house I didn't record how long each loop was, I just know that none are over 300ft. I used the little flow meters on my manifold to check the flow when everything was wide open and then just throttled the higher flow zones to match the lowest zone.
You are getting good advice here, my gut feeling is you may have to add some panel radiators in the lowest performing rooms and bring them online when the floor performance is inadequate. With constant circulation already happening when the house won't stay up to temp you could put panel radiators on TRVs and not have to worry about separate thermostatic control. Sizing each individual radiator could be interesting although not impossible.
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Interesting idea. I am going to flush the system out in the spring. That would be a good thing to try then. Thank you for sharing that idea, how you balanced yours and on adding auxiliary heat to the rooms.
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I opened all 3 loops to wide open. With the warm temps (30’s) the rooms are maintaining just fine and the thermostat gets satisfied. The laundry room temp is considerably cooler now at 72 but it hasn’t been running constantly so once it gets tested with it running nonstop, we shall see.
I bought a FLIR infrared camera and can see the loops now in the rooms, more importantly, the heat loss. It’s not as bad as I thought but the windows definitely add a lot of cold. I have temporarily added the window film to help with that.
The temps this week are going down into the deep freeze again so it will be tested at wide open to see how it performs. I do think the loops are all pretty similar in length and in the 150’ range. Thanks everyone for your input.0 -
It sounds like the heat loss is higher than expected. The average return water temp is masking the issues in these rooms. What is the actual surface temp when standing outside. Get the IR gun close, the further away you are, the more larger the area it measures and gives an average.
80% of a slabs heat loss is the edge!
Circulators either work or don't, they don't get weaker over time
Dave Holdorf
Technical Training Manager - East
Taco Comfort Solutions
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Thanks for your help Dave. I was unable to get a temperature on the edge of the slab due to some travel prep but I will. It will be interesting. I did use a Flir camera and clearly there is heat loss going on, I’m just not sure it is a problematic amount. I do remember that they installed 2” Owens Corning foam between the foundation blockwork and the slab. But the Flir still shows some warmth/heat loss. More work for me to do but I am learning a great deal from all of you on this forum and I am grateful for your wisdom and willingness to share. I appreciate you.
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