Saskatchewan Floor Heat

Discussion in 'Maintenance and Troubleshooting' started by BatocheBob, Dec 3, 2015.

  1. BatocheBob

    BatocheBob Member

    Since implementing a new zone I've been trying to fine tune and get around some issues. One item has peaked my curiosity- floor temp. My system is controlled by a thermostat that senses air temperature. I don't know that I'm in a position to change anything but I'm interested in what is the ideal system for controlling floor heat. Why I ask is when my thermostat reaches set point the system shuts off. Maybe because my house is super insulated, by the time the thermostat calls for heat again the floors have gone quite cool. How do folks maintain a fairly constant floor temperature without overheating the room? Thanks
     
  2. urthbuoy

    urthbuoy Well-Known Member Industry Professional Forum Leader

    This is a tough one sometimes. You can definitely heat a well built radiant house with floor temperatures that a human would still consider cold. The hot/warm floors is not necessarily something one will feel when our 98.6F skin touches an 85F floor to create a 72F room.

    So if your air temperature is holding, then that is a good operating system.

    If there is a lag in your slab system, such that the air temperature drops while the floor takes too long to heat up again, then one can look at slab sensors for their thermostats.

    edit - I'm basing this on that your slab temperature is the issue, not that the zone isn't heating to setpoint.
     
    Last edited: Dec 3, 2015
  3. docjenser

    docjenser Well-Known Member Industry Professional Forum Leader

    Some people have a floor sensor in there. The best way in my opinion is to have an outdoor reset controller, fine tune it, and have the supply temp going up and own with the changing heat loads.
    That means that the circulation pump runs much longer and the floors are more constantly heated at a lower temp. To do this efficiently one needs a variable speed circulation pump, which revs up if more zones are calling.

    Here is an example

    http://welserver.com/WEL0384/
     
  4. BatocheBob

    BatocheBob Member

    I appreciate your comments Chris & Doc. I should be so lucky as to have a floor that reaches 85F. This is the bathroom that is underfed with 5/16. I have insulated the floor joist space and all the feed tubes; the best I get is 81F on the floor which is OK considering. When the thermostat goes off the floor cools to around 68F. This isn't a really big deal was just wondering what other people do. I had though a floor sensor was one answer and I will see if I can find a two wire thermostat that accomodates both air temp and a remote sensor. Anyways thanks for addressing my curiosity.
     
  5. geoxne

    geoxne Active Member Forum Leader

  6. ACES-Energy

    ACES-Energy Member Industry Professional Forum Leader

    my opinion is the HBX-0100 is better than the tekmar and easier to use
     
  7. ACES-Energy

    ACES-Energy Member Industry Professional Forum Leader

    my opinion is the HBX-0100 is better than the tekmar and easier to use
     
  8. BatocheBob

    BatocheBob Member

    I appreciate the suggestions for a floor sensing Thermostat. Gotta admit the THM 0100 looked interesting but unfortunately availability is a big issue. here in Canada. Products that are readilly available in the US are often hard to find here. Such is the case with HBX; I would need to go to the next province, pay shipping and I don't have a wholesale account there. Bit the bullet and purchased the Tekmar 519. It's amazing how you can take a $30 tStat, add a remote sensor and a computer chip and you end up with a $180 thermostat. Fortunately my wholesale account eased the burden and hopefully the wife will have warm feet and be happy;-) Again, thanks for the input.
     
  9. BatocheBob

    BatocheBob Member

    With regard to Chris's comments, that would appear to be the problem; because the house is super insulated it retains the heat very well and I presume that because heat rises the floor temp cools off much sooner than the ambient sensing point does. Hopefully the introduction of a floor sensor will keep the floor warm without overheating the room. This will mean that the system will be working more and have a higher cost of operation. Seems kinda' ironic to me, you build a high-efficiency house in terms of insulation and then have to start putting in extras to maintain a certain comfort level. Oh well!
     
  10. docjenser

    docjenser Well-Known Member Industry Professional Forum Leader

    The whole point is that they will overheat the house, unless you have a mean to throttle back the supply water temperature on warmer days. That is what outdoor resets are for. An the internet combined with FedEx or UPS, in case you have supply issue.
    Yes, more efficient houses have lesser loads, and you simply cannot build a heating system they way it was built 50 years ago. Then you will have the issues you are having.
     
  11. BatocheBob

    BatocheBob Member

    Color me thick but obviously there is something I am not understanding about floor heat.

    First I appreciate how outdoor resets work but have not been able to tell me how I can incorporate an outdoor reset with my current Ranco 11
     
  12. BatocheBob

    BatocheBob Member

    Sorry for the false post above. I was having trouble trying to articulate.

    What I was trying to say is I think I understand the merits of an outdoor re-set control and if it is so important I have to wonder why it wasn't incorporated into my original design, especially given they knew we had Winter swings that can go from around 32F down to -22F or lower but that's in the past.

    Anyways if I did incorporate an outdoor reset I'm pretty sure heat output would be reduced as the water temperature is decreased . Regardless of the outdoor temperature the idea is to maintain the room at 72F and have the floors remain warm to the touch, after all I thought that was one of the primary benefits of radiant floor heat. Unfortunately the design of my system is less than adequate in my humble opinion and I have trouble trying to maintain the desired temperature some of the time. That is why I was forced to raise my water temperature from 90F to 100F. I wonder if I reduced the temperature in the milder weather (32F) if I would still get sufficient output to maintain the rooms at 72F and the floors around 80F.

    Also, if I have a floor sensor installed that tries to maintain the floor at say 80F and I reduce the water temperature to the point where it cannot raise the floor to 80F will the system run continuously in an attempt to raise the floor to a temperature that is unattainable? That doesn't sound very efficient.

    And finally, as I was trying to say in the previous post I can't seem to find anyone around here who can tell me how I can incorporate an outdoor reset with my existing Ranco ETC, if it's even possible. I enquired about the Tekmar 256 but the rep wasn't clear how that would work with a geothermal heat pum. She said I would still need an additional boiler reset control. Maybe the best thing I can do is live with what I got and be happy. All in all the house isn't that bad although I must admit it's a bit inconsistent, OK by me but the wife is cold many times. Thanks.
     
  13. urthbuoy

    urthbuoy Well-Known Member Industry Professional Forum Leader

    I'll take a stab at this.

    Smart controls is what you're missing (on top of the PEX layout you've mentioned). With a dumb control like an aquastat, it is just off/on based on your tank water temperature. They work with that limitation.

    A smart control system like Tekmar (or HBX) for radiant will control the tank temperature based on outdoor temp, has outdoor shutoffs, looks for calls from the zone and the tank temps, etc.

    If you just replaced the Ranco with a Tekmar you would need to short out the Boiler Demand signal to be always on. You don't have communicating thermostats that would normally be this call. So then the tank setpoint, dictated by the outdoor reset, would provide the call to turn your heat pump on/off. This is the simplest (in my mind) way to attach outdoor reset to your system.

    If using a floor sensor, you can have the floor sensor being that room setpoint. Basically it will ignore the air temperature and use the floor setting as the setpoint. Or it will maintain a minimum floor temperature - not allowing it to cool off too much. You would want 26C to 30C floor slabs to feel like it's warm.

    For best energy savings, having your water in 30C range would save you the most money. For comfort though, in your case, you may want warmer water.

    So even if you want minimum 38C water to 50C water on the coldest days, outdoor reset would still be a valuable benefit. It also shuts off the system in summer.

    edit - I should add the HBX system will work with non-communicating thermostats as it just wants a dry switch signal.
     
    Last edited: Dec 9, 2015
  14. BatocheBob

    BatocheBob Member

    Chris, Thanks. I think you hit the nail right on the head in more ways than one. Every time I look I am convinced that I have a really dumb system-literally. You would think $17K (components only) might have bought a bit more but I can make it work. I am in the process of converting the remainder of the floor heat system to 1/2" PEX. Bit of extra work but after I see how that works I think I have found an option to add another port to the manifold and create a decorative wall heat panel. It won't be big, 24" x 32", but with 1/2" tubing hopefully it will add sufficient BTU to make the bathroom a bit warmer and with the floor sensor the floors will stay a bit warmer. I'm pretty confident that the latest area, with 1/2" Pex will provide plenty of heat out in the mudroom and laundry

    As for an outdoor re-set, I'll keep that on the backburner for a little bit. I'm going to experiment with cutting my water temperature back and see how that affects my floor temperatures throughout the house. I'll also be watching to see how it affects my runtime and the overall ambient temperature. If I see some acceptable results I might make the move to an HBX 0550. I was reading the manual and it doesn't have the setback range I had expected. I may be reading things wrong but it appears the the lowest outdoor temperature you can set is -18C. This suggests to me that at -18C you will be producing your warmest water and it will modulate towards cooler as the outdoor temperature warms. Around here the average temperature during the winter months is -17. That means that as the outdoor temperature plummets to the -40s you will have already reached the limit of your hot water. Anyways, thanks for the insight
     
  15. docjenser

    docjenser Well-Known Member Industry Professional Forum Leader

    A couple things are important:

    1) The lower you can keep your water temperature coming out of your heatpump, the higher your geo efficiency is. That also means that your delivery system (your radiant) shall be designed to have the highest possible output at the lower water temperature.

    2) The amount of heat your house needs fluctuates between colder and warmer days. In the old days, you just turn the circulator for that zone on and off, and it was pumping warm water through for lesser hours on warmer days. That is why your floors get cold on waker days, cause the house or the room needs lesser BTUs.

    3)Nowadays, it is more comfortable and efficient to lower your water temperature on warmer days, then the geo heatpump runs more efficient, and you pump colder water for longer, so your floors stay evenly warm, just not as hot when they are on.

    4) To pay not more for running your pumps more in that case, many on/off constant speed pumps (one for each zone), are not very elegant anymore. You would use a much more efficient variable speed circulation pump (1 pump!), which revs up and down, depending how many zone valves are opening up.

    You have multiple constant speed pumps in your profile picture......

    Sorry to bring those news to you. But I hope it helps explaining the issue you are experiencing.
     
  16. urthbuoy

    urthbuoy Well-Known Member Industry Professional Forum Leader

    Doc et al,

    Hijacking this thread a bit, but it's what is on the computer in front of me. I've a 80,000 btu/10 zone radiant system I'm laying out. I'm gearing towards trying out a delta T pumping strategy which made a few general questions come up in my mind.

    I can size one pump for everything, but the efficiency guy in me thinks breaking it down into two (or more) variable speed pumping strategies may work. I'm very adverse to putting in a pump that takes 3 weeks to backorder for the client as well. So smaller, more readily available pumps, is in my strategy generally.

    Is there a decision tool you guys use to decide between one pump for everything or multi? Say, sizing pumps to max 10gmp flow, or 50,000 btus, or whatever? Or just go with one variable speed for everything design?
     
  17. BatocheBob

    BatocheBob Member

    Doc,

    I appreciate you taking the time to reply. As you can probably tell, I am quite frustrated with my system given that I paid a fair amount of money and got something that would seem to be less than optimal.

    I understand that lower water temperatures are desirable and that is what is so frustrating. I have had to raise my water temperature from the design temp of 90F up to 104F, quite contrary to what you are saying. Given what I have learned about flow and differential I am currently trying to drop my temperature to see how it affects my heat output. This water temperature thing has made me realize that my delivery system may not have been designed to provide the highest possible output at the lowest possible temperature. To this end I have been trying to 'reverse engineer' my design just so I can see what went wrong but unfortunately I don't think I have enough smarts to do this. i.e. I know I need 8540 BTU for a given area. I'm trying to calculate how many feet of tubing I should have in four loops for that zone at what flow and temperature.

    Points 2 & 3 reference an outdoor re-set which does make sense but researching that just leads to more frustration. I looked at the HBX control which can be set as low as -17C for the outdoor temperature. Assuming I have a max water temperature of 39C this tells me that the control would modulate the temperature from 39C when the outdoor temp is -17 and gradually cool the water down as the outdoor temperature rises. When the outdoor temperature plunges to -40C do I assume that the 39C water is still going to provide the same heat output? I would expect not.

    Point 4 would seem to suggest using variable speed pumps. I'm not sure what you are looking at in my profile pic. The main circulation pump (left center) is a fixed speed pump but the zone pumps are delta P variable circulation pumps. I believe that may be part of my problem. I understand delta P variable circ pumps are not the best choice for zones that are controlled by an on/off thermostat
     
  18. docjenser

    docjenser Well-Known Member Industry Professional Forum Leader

    I am looking at your profile picture and I am seeing an awful lot of pumps. Why would you have a main circulator, followed by zone pumps? Why don't you have just one circulator?
    Since some zones come on and some go off, the amount of pressure needed to push the same amount of water through a certain individual zone is always the same.
    In other words you need always the same pressure, but the flow requirements fluctuate. Thus you need only one constant pressure variable flow pump, dial in the pressure you need, and let it run. The pump will sense the drop in pressure and rev up if an another zone comes online.
    Thats it!

    You describe your pumps as variable pressure, kind of the opposite of what you need.

    PS: Don't know the HBX, but the Tekmar 260 for example goes down to -51C outdoor design.
     
  19. docjenser

    docjenser Well-Known Member Industry Professional Forum Leader

    Chris,
    One variable speed pump for everything, hands down, in my world.

    We used to do everything with one pump (a second one if you are running your domestic hot water off your system), see WEL 664 below.

    http://welserver.com/WEL0664/

    Nowadays we use direct to load (buffer tank bypass) concept which requires a constant pressure variable flow pump for the zones, and another pump, which can be constant speed, for the load side of the heatpump.

    The buffer tank bypass saves about 16% energy, if you design with a delta T of 10F on the radiant side, which would be the case with 10 gpm and 50KBTU.

    http://welserver.com/WEL0384/

    In WEL 384 we use it for heating and A/C.

    We use exclusively Wilo stratos pumps, they are of high quality and simple to set up. But Grundfos and others come out with pretty neat products as well.

    I buy them exclusively from John Manning.
    http://phoenixflowcenters.com/phoenixStore/index.php

    He can get them to me overnight. But I am sure they have distributors in Canada.

    I have used the Wilos from 3 gpm to 150 gpm, John Manning has used them in parallel in over 1000 gpm applications.

    The key is to use high CV motorized zone valves, we use 3/4" Tacos or Belimos with a minimum CV of 10.

    80 KBTU/H would be a 10 ton heatpump in my book.

    Do you want to make the domestic hot water with the same heatpump?
    Or use 2 x 5 ton heat pumps?

    Let me know.

    Attached is the conceptual idea of the direct to load. The simplicity and efficiency is so far unmatched, as far as I know.
     

    Attached Files:

  20. urthbuoy

    urthbuoy Well-Known Member Industry Professional Forum Leader

    Doc,

    We've done a fair number of variable speed radiant systems and bounce around on pumping layouts. Your layout shown is what we work from.

    The suppliers are my limitation. Wilos, is through a wholesaler I'd prefer not to deal with. They don't even know these pumps exist until I say they are the wholesaler. So nothing stock and nothing timely.

    Taco, Grundfos, and B&G are more readily available in general, just not when I need 230V variable speed ones. So, I was sort of weighing the option of working with smaller pumps and keeping them as stock items. Basing our work around certain units of distribution. Units I hadn't nailed down.

    On the same note, 2 weeks for Belimos as well.

    -21C (-5.8F) is generally our design temp in my immediate area, but we have some altitude adjustment calculations as we have clients 2000' higher than this commonly. I'd love to see 10ton residential sized units.

    I have bought off Manning - customs and shipping kills it.

    Maybe I have to start meeting one of you guys at the border with my cube van:)

    Or become a distributor...
     

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