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Radiant in floor question question

cuttercutter Member Posts: 145
I added two rooms to my house and want to put in- floor to heat them. the rooms are 14' X 18' or 252 sq feet, needing roughly 9,000 BTU's of heat. These rooms are one above the other so they would have to have separate pumps. I did the flow calculation of water temperature loss of 20 times 500 and divided that answer into the Btu need and got the flow needed, a little less than one gallon per minute.

I bought the pex and got advice from aqua therm when they were in Brutten MN. They told me to run 1" and a 1/4 copper pipe and put a 007 taco pump on the zone. I feel that will not work properly after learning a little about Hydronic heating from Caleffi's trade journals and on this site..

My thought is to run 3/4 inch copper and put a Wilo variable speed pump on each zone. On one zone I will need to push water down eight feet and hope fully move any air bubbles down also. Minimum flow rate for 3/4 inch copper (based on 2 feet/sec.) is 3.2 GPM. So the flow I need is a lot lower than that so any air will not be pushed down that eight feet , and through the system and removed with an air separator. I am planning on putting a coin vent on the 90 degree fitting going down to get rid of air there if there is a problem.

Question is, am I on the right track? or is there another way to do this?
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Comments

  • Bob BonaBob Bona Member Posts: 2,064
    4 questions: what is the attachment method for the radiant tubing? What diameter pex? Is it 02 barrier pex? And finally, what is the piping plan- dedicated circs and home run to each zone/no manifold?

    Also: what is the mixing strategy?
  • IronmanIronman Member Posts: 3,328
    edited March 29
    You also don't want to design a radiant floor in a living area with a 20* delta T.
    A 10 -12* delta T at the most should be used. That's gonna double the flow rate that you previously figured.
    Bob Boan







    You can choose to do what you want, but you cannot choose the consequences.
  • cuttercutter Member Posts: 145
    Bob Bona said:

    4 questions: what is the attachment method for the radiant tubing? What diameter pex? Is it 02 barrier pex? And finally, what is the piping plan- dedicated circs and home run to each zone/no manifold?



    Also: what is the mixing strategy?

    Question #1 the radiant tubing connects to a inch and a quarter manifold. There is four runs about eighty feet each back to the return manifold.

    question #2 and #3 The pex is 1/2" and I think it is the 02 barrier pex. It has a foil inside the tubing.

    Question #4 If I understand you correctly, Each of these rooms will have it's own circulater. 180 degree water (or there about's) coming off the supply manifold to a mixing valve then to the pex manifold and the four runs supply water to the floor and back to the return pex manifold then back to the return manifold in the boiler room.

  • Bob BonaBob Bona Member Posts: 2,064
    edited March 29
    Ok it's getting clearer! Rooms are 2 loops each?

    You have pex -al- pex. Good.

    mixing via a 3 way valve. Ok.

    I'd be sure you have stellar air elimination back at the boiler. Spirovent or other micro bubble resorber. The loops below the manifold *shouldn't* be a problem once you're good and purged. Typical store bought manifolds have bleeders built in for touchups, plus you're going to have a main purge for the home runs. Post a drawing. Let's see how you're doing it.

    what's the attachment method for the tubing? Slab? Staple up under floor? Track on top of subfloor?
  • cuttercutter Member Posts: 145
    Bob Bona said:

    Ok it's getting clearer! Rooms are 2 loops each?



    You have pex -al- pex. Good.



    mixing via a 3 way valve. Ok.



    I'd be sure you have stellar air elimination back at the boiler. Spirovent or other micro bubble resorber. The loops below the manifold *shouldn't* be a problem once you're good and purged. Typical store bought manifolds have bleeders built in for touchups, plus you're going to have a main purge for the home runs. Post a drawing. Let's see how you're doing it.



    what's the attachment method for the tubing? Slab? Staple up under floor? Track on top of subfloor?

    Ok it's getting clearer! Rooms are 2 loops each?


    no each room will have four loops of about eighty feet each loop, maybe eighty-five feet.
    One room is above the other. The lower room is used for storage and a mini shop. The upper room is a four season porch and that room is above the boiler. It also will have four runs of eighty feet or so of the same pex.

    The pex is below the concrete on the lower floor the upper floor will have the pex stapled to the floor and gypcrete poured over it. the gypcrete will be two and a half inches thick. The upper floor is not done yet. The lower floor has the pex in and the floor poured. And manifolds on the wall. I need to pipe from there back to the boiler manifold.

    For air elimination I have a Caleffi hydraulic separator, What I am somewhat concerned about is the header is a little over sized and the flow may not move all the air if there is some. That is why I thought the one inch copper from the boiler manifold to the pex manifold might be over sized and I should go with three quarter copper, that might be a little over sized for the flow also. I plan on putting coin vents here and there to bleed off air if it doesn't move. There will be home run purge valves.

    As for Posting a picture or drawing I can not see how to do it anymore. I used to see an advanced posting box that could be clicked on.
  • Bob BonaBob Bona Member Posts: 2,064
    Gotcha. Slab and gyp. Smart thinking about not oversizing the home runs. With a 9k heat loss per space, not that you would, but you could use 1/2" to feed the manifolds. 3/4 will be fine.

    80 foot per loop is very conservative. Liking it. I'n assuming a radiant design was done so you know your head loss and supply water temps? 4 season porches typically have high loads.
  • cuttercutter Member Posts: 145
    Ironman said:

    You also don't want to design a radiant floor in a living area with a 20* delta T.
    A 10 -12* delta T at the most should be used. That's gonna double the flow rate that you previously figured.

    I was wondering about that delta T, I sorta thought you would not want any temp drop so the entire floor stayed hot. But you have to have some so a mixing valve can lower the water temperature to the floor.
  • ZmanZman Member Posts: 3,414
    Bob has you pointed in the right direction as always. You will end up with higher flow and lower delta t because you are running such short loops. Not a big deal, you will have nice even heat.
    Do be careful picking a mixing valve and sizing your circulator.
    The mixing valve will likely have the most resistance of any component in your system. You will want about the smallest hydronic circulator you can buy.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • cuttercutter Member Posts: 145
    Zman said:

    Bob has you pointed in the right direction as always. You will end up with higher flow and lower delta t because you are running such short loops. Not a big deal, you will have nice even heat.
    Do be careful picking a mixing valve and sizing your circulator.
    The mixing valve will likely have the most resistance of any component in your system. You will want about the smallest hydronic circulator you can buy.

    Because the flow is so low I thought about a Wilo variable speed circulator. I am also thinking the one inch copper pipe is too large and three quarter copper would be a better size and that is a little too large also for so few Btu's.
    I haven't checked yet on mixing valves so don't know their temperature ranges. I would bet that supply house has one to bring the temperature down from 180 degrees to 120,
  • Bob BonaBob Bona Member Posts: 2,064
    This is where some calculation should be done. Just so you know your parameters.
  • RichRich Member Posts: 2,205
    edited March 30
    Where do you intend on locating the circ ?

    You must make sure that it between the mixing valve and the manifold pulling through the mixing valve .

    How long are each of these loops also in total feet ?

    They need to be sufficient in length to provide enough resistance so that the circ does not spend too much time far below the performance curve . When below the performance curve the possibility of over pumping becomes a distinct possibility . Your Delta will narrow during these times and you'll be moving fluid that is doing less work than intended . Using energy that is doing little or no work is not a good thing and should be considered a big deal .
    You didn't get what you didn't pay for and it will never be what you thought it would .
    Langans Plumbing & Heating LLC 732-751-1560
    Serving most of New Jersey , Eastern Pa .
    Consultation , Design & Installation
    Rich McGrath 732-581-3833
  • ZmanZman Member Posts: 3,414
    Rich,
    He has way short loops, like 80'.
    That's what got me thinking about mixing valves and circulators.
    My guess is that with a small variable speed circ and a mixing valve with a cv about equal to design flow, the zones would work nicely.
    To the OP,
    Post the lengths of the 3/4" supply and returns as well as the circs and valves you are considering and we can check this for you.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • RichRich Member Posts: 2,205
    edited March 30
    I'm thinkin fixed speed mode , min (003 ) or step one ( 006 ) or low in the proportional / variable settings .

    http://www.taco-hvac.com/uploads/FileLibrary/102-499.pdf

    You're also gonna require to run this at a Dlta of 10* max . This will get the flow doubled or else you'll be operating at less than 1 GPM if you're basing this off the Universal Hydronics Formula . Don,t even think about the 007 unless it's the 007e . This may shock you but you'll probably end up with a 1/2" mixing valve or some other device to add resistance to this type of short circuit length application .
    You didn't get what you didn't pay for and it will never be what you thought it would .
    Langans Plumbing & Heating LLC 732-751-1560
    Serving most of New Jersey , Eastern Pa .
    Consultation , Design & Installation
    Rich McGrath 732-581-3833
  • hot rodhot rod Member Posts: 6,848
    For those sub 1 gpm flow requirements a DHW recirc is an option. A Grundfos 15-10 is an option for low flow low pressure drop circuits
    The B&G Ecocirc E3 is also a nice option
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
  • cuttercutter Member Posts: 145
    Rich said:

    Where do you intend on locating the circ ?

    You must make sure that it between the mixing valve and the manifold pulling through the mixing valve .

    How long are each of these loops also in total feet ?

    They need to be sufficient in length to provide enough resistance so that the circ does not spend too much time far below the performance curve . When below the performance curve the possibility of over pumping becomes a distinct possibility . Your Delta will narrow during these times and you'll be moving fluid that is doing less work than intended . Using energy that is doing little or no work is not a good thing and should be considered a big deal .

    I was intending to put the circ. pump in the boiler room and push the water to the room. But after reading some of the responses that might not be the correct location.

    The loops are 80 or maybe 85 feet each, and 4 loops per room.

    I don't understand the below statement.
    You must make sure that it between the mixing valve and the manifold pulling through the mixing valve .
  • cuttercutter Member Posts: 145
    Zman said:

    Rich,
    He has way short loops, like 80'.
    That's what got me thinking about mixing valves and circulators.
    My guess is that with a small variable speed circ and a mixing valve with a cv about equal to design flow, the zones would work nicely.
    To the OP,
    Post the lengths of the 3/4" supply and returns as well as the circs and valves you are considering and we can check this for you.

    The length of the 3/4 supply and returns are 26 feet to the lower and 20 feet to the upper room, approximately. That is from the supply manifold in the boiler room to the pex supply manifold. Plus 5 90s in each run.
    For a mixing valve I thought about using a Caleffi 521519-AC
    Max inlet temp 200 degrees
    Max temp 150
    min. temp 85
    CV of 3 gallons per minute. Raising the delta T to 10 would give me a flow of 1.8 gallons per minute. So no pressure loss at the mixing valve.
    I have thought about putting in a caleffi quick setter balancing valve. The 3/4 inch valve has a minimum flow of 2 gallons per minute. Don't know if that .2 excess GPM would hurt me. It would just lower the Delta T a little more.
    For a pump I thought about using a Wilo ECO16 RFC. Supply house sku-4145539. It has a max gmp of 15, I could not find the Min. gpm.

    Where is this pump supposed to be located? Can it be on the supply manifold at the boiler? Or is it supposed to be between the mixing valve and the pex header? Or is it supposed to be between the boiler manifold and the Mixing valve but close to the mixing valve?
  • cuttercutter Member Posts: 145
    Bob Bona said:

    This is where some calculation should be done. Just so you know your parameters.

    Bob what calculations?
  • cuttercutter Member Posts: 145
    cutter said:

    Zman said:

    Rich,
    He has way short loops, like 80'.
    That's what got me thinking about mixing valves and circulators.
    My guess is that with a small variable speed circ and a mixing valve with a cv about equal to design flow, the zones would work nicely.
    To the OP,
    Post the lengths of the 3/4" supply and returns as well as the circs and valves you are considering and we can check this for you.

    The length of the 3/4 supply and returns are 26 feet to the lower and 20 feet to the upper room, approximately. That is from the supply manifold in the boiler room to the pex supply manifold. Plus 5 90s in each run.
    For a mixing valve I thought about using a Caleffi 521519-AC
    Max inlet temp 200 degrees
    Max temp 150
    min. temp 85
    CV of 3 gallons per minute. Raising the delta T to 10 would give me a flow of 1.8 gallons per minute. So no pressure loss at the mixing valve.
    I have thought about putting in a caleffi quick setter balancing valve. The 3/4 inch valve has a minimum flow of 2 gallons per minute. Don't know if that .2 excess GPM would hurt me. It would just lower the Delta T to 9.
    For a pump I thought about using a Wilo ECO16 RFC. Supply house sku-4145539. It has a max gpm of 15, I could not find the Min. gpm.

    Where is this pump supposed to be located? Can it be on the supply manifold at the boiler? Or is it supposed to be between the mixing valve and the pex header? Or is it supposed to be between the boiler manifold and the Mixing valve but close to the mixing valve?
  • cuttercutter Member Posts: 145
    hot rod said:

    For those sub 1 gpm flow requirements a DHW recirc is an option. A Grundfos 15-10 is an option for low flow low pressure drop circuits

    The B&G Ecocirc E3 is also a nice option

    I checked out the Grundfos, It is a single speed 0-8 gallons per minute pump. Less than half the cost of the variable speed pump I thought about using.
    I did find the B&G in the potable water pumps.
  • Bob BonaBob Bona Member Posts: 2,064
    Cutter, calcs like supply water temps to the 2 rooms and estimated head loss. Need to know each rooms requirements. If the calcs show more than a 15 degree difference in required SWT, you're looking at a 2 temp set up with seperate mixes. Typical mix/pump arrangement is the mix at the supply header at boiler, then the pump right after the mix port, pumping into the system. Put a ball valve in the piping bridge that will go to from the radiant zone return to the cold inlet on the mix- it will help big time when you're purging the home run and loops.

    My pump choice, WAG, would be the Taco VR1816. I would chose the Calleffi mix for it's temp gauge on the mix outlet feature.
  • ZmanZman Member Posts: 3,414
    Don't obsess about the exact flow rate or the delta t. The flow rate is not that important as long as you are within an acceptable range. The delta t is never stable. A cold slab will have a high delta t, the delta will narrow as the slab warms up.

    I think both the mixing valve and the circ you have selected will work well. Don't over think it. If you end up with a flow of 3.5 gpm and a delta of 3 to 6 degrees, who cares? The heat will be nice and even and with hydroulic separation, it will have no impact on boiler efficiency.
    Both the mixing valve and the circulator can be in the mech room. The circ should not be located outside the loop being mixed. If it is, the water in the loop will stop flowing as the valve modulates.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • RichRich Member Posts: 2,205
    I am presuming from your comments that this tubing , S & R piping and manifolds are already installed and at this point it is what it is . That being said , I strongly disagree with what some have stated . I will not get too far into that as some sites have become PC mechanisms that do not recognize that spirited debate should be allowed to happen to offer the best help for the users . In an effort to remain a viable source of information to those needing help I will not engage unless it is absolutely unavoidable .
    You have chosen a DHW mixing valve so my comment about circ location may not be accurate , when we use hydronic mixing valves the circ should be located on the mixed temp pipe , pulling through the valve . I still urge you to think about locating the circ INSIDE the MIXED LOOP .

    @ hotrod , do the Caleffi valves have a maximum diff like the Tacos ? Tacos diff temp is 27* max . If using 180* water and returning 130* water will it even work ?
    I also would have used a 1/2 valve for your install as it has the same Cv and a smaller valve has to sift through less water content to reach and maintain your setpoint .
    Your calculations would assume that you require 35.71 BTUh per sq ft . This is a bit high and we do not know if this is accurate and how or even if your install will perform . That is where the heat loss calcs come into play . Did you perform heat loss calcs ? If not , post the sq foot of each room , exposed wall length and height , , orientation of each wall , window size and type , any doors and their size and type . I will perform the loads for you before you end up with a possible disaster .

    It seems your head losses will be miniscule due to the length of the loops being discussed also considering the S & R lengths .
    You didn't get what you didn't pay for and it will never be what you thought it would .
    Langans Plumbing & Heating LLC 732-751-1560
    Serving most of New Jersey , Eastern Pa .
    Consultation , Design & Installation
    Rich McGrath 732-581-3833
  • ZmanZman Member Posts: 3,414
    As far as I can tell, everyone on this post is pointing cutter in the same direction. It is unclear to me what there is to strongly disagree about.
    If the flow rates were 10 gpm, a dhw mixing valve with a cv of 3 would not be appropriate. If this was not a primary/ secondary setup, the delta t would be more critical. I think everyone is saying the circ must be in the loop.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • hot rodhot rod Member Posts: 6,848
    I assumed that load number is for both rooms? There is no way you can move 36 BTU/ per foot into those rooms. Realistically 20 - 24 BTU / sq. Ft is comfortable load for radiant floors

    Correct that thermostatic mix valves want 25- 27 degree temperature delta between hot supply and mixed output

    The valve still mixes with tighter delta, but not so accurately

    Try to get a pump as close to the load as possible. A balance valve could be added to fine tune flow

    I also agree the delta can and will move around a bit from design delta, and not cause problems or compromised performance or comfort
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
  • RichRich Member Posts: 2,205
    With a 180* SWT , a mixed of 120 - 140* and a return quite possibly as high as only 110 - 130 how sloppy will the valve be ? Would it be prudent to use a hydronic mixing valve as opposed to the DHW valve ?
    You didn't get what you didn't pay for and it will never be what you thought it would .
    Langans Plumbing & Heating LLC 732-751-1560
    Serving most of New Jersey , Eastern Pa .
    Consultation , Design & Installation
    Rich McGrath 732-581-3833
  • hot rodhot rod Member Posts: 6,848
    > @Rich said:
    > With a 180* SWT , a mixed of 120 - 140* and a return quite possibly as high as only 110 - 130 how sloppy will the valve be ? Would it be prudent to use a hydronic mixing valve as opposed to the DHW valve ?

    It is the temperature difference between SWT and the mixed outlet from the valve

    So 180 SWT and 140 mixed outlet would be fine

    If you fall below the suggest 27 the valve still mixes but if may hunt around and not maintain a constant outlet temperature

    For spot on, exact output temperature a motorized valve and operator is another choice

    Properly sized a 3 way thermostic mixed valve is accurate enough, within a few degrees. The small variance would probably not be noticed in a slab

    Cost and complexity as well as features and benifits could help determine the options for mixing hydronic temperatures.

    You will see more and more EMV. Electronic mixing valves replacing thermostatic for DHW and mixing applications. Better flow rates, more accurate temperature control, data logging, connection to building automation, anti legionella function, etc
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
  • cuttercutter Member Posts: 145
    Rich said:

    I am presuming from your comments that this tubing , S & R piping and manifolds are already installed and at this point it is what it is . That being said , I strongly disagree with what some have stated . I will not get too far into that as some sites have become PC mechanisms that do not recognize that spirited debate should be allowed to happen to offer the best help for the users . In an effort to remain a viable source of information to those needing help I will not engage unless it is absolutely unavoidable .
    You have chosen a DHW mixing valve so my comment about circ location may not be accurate , when we use hydronic mixing valves the circ should be located on the mixed temp pipe , pulling through the valve . I still urge you to think about locating the circ INSIDE the MIXED LOOP .

    @ hotrod , do the Caleffi valves have a maximum diff like the Tacos ? Tacos diff temp is 27* max . If using 180* water and returning 130* water will it even work ?
    I also would have used a 1/2 valve for your install as it has the same Cv and a smaller valve has to sift through less water content to reach and maintain your setpoint .
    Your calculations would assume that you require 35.71 BTUh per sq ft . This is a bit high and we do not know if this is accurate and how or even if your install will perform . That is where the heat loss calcs come into play . Did you perform heat loss calcs ? If not , post the sq foot of each room , exposed wall length and height , , orientation of each wall , window size and type , any doors and their size and type . I will perform the loads for you before you end up with a possible disaster .

    It seems your head losses will be miniscule due to the length of the loops being discussed also considering the S & R lengths .

    Rich, when I posted this question all I really wanted to know was if 3/4 copper should be used instead of 1 inch. You guys are really thorough and that is a good thing. I should have posted the entire design. But that is long winded, guys give help and suggestions designing is a lot of time and work and that is not done for free. But here goes.

    The guy that did the heat loss calculation I feel just took the square feet and multiplied by 35 and came up with 8820 btu's needed to heat the room. This room has a lot of glass in the west and south wall. The north wall is 14' and no glass the east wall is 18' and shares 11' feet with the house, the other 7' has a 3' door with glass in it. the south wall has 2, 5'x6' windows in it. the west wall has windows totaling 5'x12' in it. walls are 2"x6" thick. The windows are thermopane Anderson's. The walls are 8' high with a 2x12 vaulted ceiling.

    The north wall will have a cabinet on the entire wall so I will lose 2 feet of floor space for heat. i thought the floor would put out 25 btu's per sq. ft. with 120 degree water running through it. I see from Hot Rods post it is 20 to 24 btu's per sq. ft. Using the lower number the floor will put out half the btu's needed to heat the room 4480, using 224 sq. ft. I was planning on using a Beacon Morris K42 kick space heater under the cabinet on the north wall. that will put out 4375 btu's using 180* water at 2 gallons per minute. That would heat the room if the heat loss calculated by multiplying 35X252 sq. ft. is right. Your placement of the pump was strongly suggested by the people that I bought the pex manifolds and pex from.
    The lower room has no windows in it just a 6'door on the west wall. The north wall of this room is shared with the boiler room wall and the east wall shares 11' of wall with the house. I have a small unit heater with 3/4 inch piping that I was planning on using to help heat this room. It may have a BTU output of 10,300, not sure, this heater had no manufacture information on it and looks like it is a little over kill.

    The mixing valve I thought about using I thought could be used for DHW or heating. The caleffi product brochure says, The Caleffi MixCal three-way thermostatic mixing valve is used in systems producing domestic hot water or in hydronic and radiant heating systems. If you have a better idea I am open to suggestions.

    Nothing going to these rooms is built yet or purchased. My goal this summer is to build the header in the boiler room and hard pipe it to the boilers. I have been working on correctly piping together those 2 boilers for several years. I feel I have that figured out and hopefully I will have that part done this summer.
    When I installed this system 30 plus years ago it worked but not correctly and the original install would not support the 2 additional rooms. I am wanting to install a system that works correctly and with the correct parts.

    I do not expect you guys to spend a tremendous amount of time on this. Just simple suggestions. I do appreciate the help that I have been given. But this is a really long winded post.
  • hot rodhot rod Member Posts: 6,848
    Maybe back up a few steps and have a more proper and accurate heat load calculation performed. Or do one yourself with the free Slantfin or US boiler apps.

    Taking a square footage and multiplying by an arbitrary BTU/ square foot number is bad science. As a result all you calculations and valve and pipe sizing will be suspect.

    Granted you are talking small square footages, but the math needs to be correct. IF in fact the loads are that high, radiant floor alone may, will not be the best solution.

    Adding a kick space heater will help catch up to a big load, but may require a higher fluid temperature and more piping and mixing, get a better handle on that load, anything in the 30's is questionable and better money may be spent lowering that load first.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
  • cuttercutter Member Posts: 145
    hot rod said:

    Maybe back up a few steps and have a more proper and accurate heat load calculation performed. Or do one yourself with the free Slantfin or US boiler apps.

    Taking a square footage and multiplying by an arbitrary BTU/ square foot number is bad science. As a result all you calculations and valve and pipe sizing will be suspect.

    Granted you are talking small square footages, but the math needs to be correct. IF in fact the loads are that high, radiant floor alone may, will not be the best solution.

    Adding a kick space heater will help catch up to a big load, but may require a higher fluid temperature and more piping and mixing, get a better handle on that load, anything in the 30's is questionable and better money may be spent lowering that load first.

    Hot Rod, You always have good ideas and suggestions. I tried to do a slant fin heat load calculation and did not have much luck. That was over my head. My daughter will be here Easter weekend and I will ask her to show me how to do it.

    I have heard that #35 being used as an approximate number quite a bit. If it was pulsed up a little you might be safe. I would rather be safe though. So I will have my daughter help me. Is #35 too large for a safe guess?

    I feel radiant alone will not be enough The room is 14'x18' now take away the perimeter wall and you get 13'x17', now take off the 2 feet for the cabinet and you get 13'x15', =195 sq. ft. 195X20 btu's =3,900 Btu's. That doesn't sound like enough Btu's.

    For the kick space heater I would pipe water to that first then run the pipe to a mixing valve, then to the pex supply manifold, then the return pex manifold back to the boiler return. That was the original idea.

    The Cafeffi mixing valve I suggested using, is that a good choice or should the Caleffi valve without the check valve be used?
  • cuttercutter Member Posts: 145
    I have done the heat calcs. and it looks like I need a lot more heat in that room than I thought using the heat loss calcs. from Aqua Therm in Brooten MN.
    Slant Fin said I need 18,944 Btu's.
    HVAC fundamentals, volume 1, all new 4th edition says I need 17,412 Btu's. The HVAC fundamentals formula uses average values or factors. like their net wall surface area multiplier of .32, is that for a wall with R11 or R19 or R21 insulation in it? sounds like an average of all three. their glass factor is 1. I called Anderson and got the U value from them and used that in my calculation. The HVAC fundamentals did not even ask how much insulation is in the ceiling.
    So it looks like I will need two of the Becon Morris kick space heaters. Maybe model #84 and just use the heated floors for the warmth,not the heat. The flow went up to about 3.5 gallon per minute or almost 4 if Slant fins calc. is used.

    Is there a more accurate calculation available somewhere. A calculation that asks for U values for walls and ceilings. Is there somewhere that U values can be got for different insulation installs?
    It looks like 3/4 copper can still be used for the supply and return to and from the room. I will use the Taco mixing valve instead of the Caleffi.
  • IronmanIronman Member Posts: 3,328
    cutter said:

    hot rod said:

    Maybe back up a few steps and have a more proper and accurate heat load calculation performed. Or do one yourself with the free Slantfin or US boiler apps.

    Taking a square footage and multiplying by an arbitrary BTU/ square foot number is bad science. As a result all you calculations and valve and pipe sizing will be suspect.

    Granted you are talking small square footages, but the math needs to be correct. IF in fact the loads are that high, radiant floor alone may, will not be the best solution.

    Adding a kick space heater will help catch up to a big load, but may require a higher fluid temperature and more piping and mixing, get a better handle on that load, anything in the 30's is questionable and better money may be spent lowering that load first.

    Hot Rod, You always have good ideas and suggestions. I tried to do a slant fin heat load calculation and did not have much luck. That was over my head. My daughter will be here Easter weekend and I will ask her to show me how to do it.

    I have heard that #35 being used as an approximate number quite a bit. If it was pulsed up a little you might be safe. I would rather be safe though. So I will have my daughter help me. Is #35 too large for a safe guess?

    I feel radiant alone will not be enough The room is 14'x18' now take away the perimeter wall and you get 13'x17', now take off the 2 feet for the cabinet and you get 13'x15', =195 sq. ft. 195X20 btu's =3,900 Btu's. That doesn't sound like enough Btu's.

    For the kick space heater I would pipe water to that first then run the pipe to a mixing valve, then to the pex supply manifold, then the return pex manifold back to the boiler return. That was the original idea.

    The Cafeffi mixing valve I suggested using, is that a good choice or should the Caleffi valve without the check valve be used?
    That will probably not work well, if at all. The toe kick and the floor need to be piped parallel, not in series. You may be able to connect both to the same manifold, if the radiant's SWT is hot enough for the toe kick to produce the required btus. That would also require a low temp aquastat on the toe kick or setting it up so it doesn't use an aquastat.

    It may be better to pipe the toe as a higher water temp zone directly off of the boiler before mixing down the SWT.

    There's really not a lot of difference between 17.4k btus and 18.9k as far as your project goes. If those numbers are correct, you either need to supplement the floor or you don't. At 18.9k btus, your heat loss comes to 75 btus per square foot. That's sounds extremely high, unless you have a lot of glass and/or exposed walls. Most rooms are usually 30 btus per sq. ft. or less, depending on construction.

    Bob Boan







    You can choose to do what you want, but you cannot choose the consequences.
  • cuttercutter Member Posts: 145
    Ironman, I must have typed that last post way too fast. I was planning on piping to the kick space heaters first then mix for the floor.
    I thought the Btu's were high also, the room has 105 sq ft. of glass.with a U factor of .28. The room below that room has no glass and the HVAC calcs. said that room needs 12,000 Btu's. The walls are R21 insulation, the ceiling is R42. and the upper room has 53 ft. exposed. The lower room has 39 feet exposed. That is why I was wanting to know where to get U values for the R21 and maybe a calc that includes taking into consideration the ceiling.
  • MikeGMikeG Member Posts: 137
    Don't most of the heat loss programs have factors to pick where the actual mat is figures in. U value 1 divided by the R value. To be more exact for a wall using the stubby pencil method you need to look at how it's built. R21 insulation does not cove the entire wall. A percentage is wood studs with a different R value. You basically try to get an average R value for the wall. The insulation is Rxx, the drywall is Rxx, the outside sheating etc, siding, air film and so on. I would think the heat loss programs factor most of that in with a fudge factor.
  • cuttercutter Member Posts: 145
    Mike I would think a wall with 5 1/2" of insulation would have less heat loss than if the wall was 3 1/2". Same for the ceiling, 12" of insulation would be better than 6", and factor in the studs and plates accordingly. I feel I am a little strong on heat loss, but that is better than being a little weak. But with a -20 design it doesn't stay -20 all the time. Years back one day it was -14 at 6 AM and -25 at 1 PM the same day. That is rare.
  • ZmanZman Member Posts: 3,414
    Your heat loss numbers cannot be correct.
    The entire discussion is irrelevant until you get accurate numbers.
    I can't do it til next week, but if you post your plans, I am sure someone will calc a couple rooms for you so you can move on to designing this.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • hot rodhot rod Member Posts: 6,848
    Zman said:

    Your heat loss numbers cannot be correct.
    The entire discussion is irrelevant until you get accurate numbers.
    I can't do it til next week, but if you post your plans, I am sure someone will calc a couple rooms for you so you can move on to designing this.

    I agree with Carl, you need to get the load number as accurate as possible. It becomes the road map to a sucessfull and efficient system design and installation.

    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
  • cuttercutter Member Posts: 145
    Zman said:

    Your heat loss numbers cannot be correct.
    The entire discussion is irrelevant until you get accurate numbers.
    I can't do it til next week, but if you post your plans, I am sure someone will calc a couple rooms for you so you can move on to designing this.

    Here are the plans
    hot rod said:

    Zman said:

    Your heat loss numbers cannot be correct.
    The entire discussion is irrelevant until you get accurate numbers.
    I can't do it til next week, but if you post your plans, I am sure someone will calc a couple rooms for you so you can move on to designing this.

    I agree with Carl, you need to get the load number as accurate as possible. It becomes the road map to a sucessfull and efficient system design and installation.

    I would post the plans on here but I do not know how. Would I have to use the Simple HTML link to post a picture? I did a heat loss for my 888 sq ft. garage with 9.5' ceilings and 3 sky lites with a 70* design temp and came up with 38,000 btu's. That was done with the HVAC book I have. My daughter did the slant fin calc. because that is a smart phone app and I don't know how to run a smart phone yet. When I learn how to post a picture I will post the plans. I am thinking the picture posting process has changed.
  • Paul48Paul48 Member Posts: 4,192
    Over the dialogue box you type in, there is a series of options you can choose from.
  • cuttercutter Member Posts: 145
    Paul, thank you for telling me what those icons were for.
    Here is the drawing finally. I feel I am pretty close to the BTU's needed. For the glass calc. I used the Andersen glass factor of .28. The top of the drawing was cut off that part gave the 11 FT that is connected to the house. The bottom that was cut off said there is 39 feet of wall exposed to unheated area for lower room. and at the glass area the total glass area for the room is 105.41 sq feet.
  • ZmanZman Member Posts: 3,414
    I did a quick heat loss and attached the screen shots. Do double check the inputs to be sure I did not misinterpret your drawing. The air change number is always the SWAG on these. A blower door test is the only way to be precise on that one.

    After seeing your floor plan, I am concerned about the window heat loss and the comfort of that area. Sure you can crank the floor up to 31 Btu/ft ,the problem is, when you are hanging out enjoying the view, you will have hot feet and cold bodies because of the large windows.

    If you ran all the floors at a max of 23 btu/ft (approx 120 SWT) then sized some low temp panel radiators to go under the windows, I think comfort in that area would be greatly improved.

    It looks like the Runtal UF-2 at 120 degree SWT puts out 228 BTU/lf.
    A couple 8 footers would do the job.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
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