Click here to Find a Contractor in your area.
In fairness to all, we don't discuss pricing on the Wall. Thanks for your cooperation.
Need to contact us? Visit

Infloor Radiant Heat issue

RCORCO Member Posts: 51
Hello.  We just recently purchased a property that has this system in the concrete slab.  The cottage is under 1000 sq ft and has 2 loops in the floor with an Electromate electric boiler.  The problem we are having is that the system can't maintain the set temp of 68 or 69 once it gets dark at night.  The temp will drop 6 - 8 degrees and won't catch back up until late AM the next day.  Of course we realize that it takes the system sometime to heat up from the 55 degree setting we keep it at when we are not there.  We have found a solution to this situation as a neighbor is going to turn the heat up 10 - 12 hours before our arrival.  But the 3 times we spent there thus far, the system will be right on at the set temp during the day but drops at night. 

We have a vaulted ceiling which is 23 ft in height.  One half of the cottage has a loft above.  We also have 3 windows side by side on both the northwest  and northeast corner as well as 6 windows (3 on each side) on the north side.  These are quality Andersen double pane units.  This property was completed in 2009 by the former owner.  We understand from the builder that their is R19 insulation in the ceiling. 

We had a local plumbing/heating contractor recommended by our realtor in to inspect the system.  We had to do this via phone and help from our realtor as we are 275 miles away.  The contractor indicated that the system seemed to be working as it should and seemed to be sized adequately for the square footage.  He spoke with a contact at the local electric provider to find out what setup for usage we were at...restricted or unrestricted.  We have no restrictions and, of course, are paying the higher rate for electricity as we don't have a dual fuel source.  His recommendation was to install a gas wall heater to assist the radiant heat in keeping up.  His opinion was that even though the system was adequate for the square footage.  It didn't account for the vaulted ceiling, loft area, windows, and lower insulation value of this type of ceiling.  His recommendation with the gas heat was to enable us to have a lower electric rate for our heat to bring the electric costs down. 

I believe that is one option.  However, it doesn't address the inefficiency or inabilility of the current radiant system keeping up with the demand.  I'm not sure I want to spend the $2000 - 2500 to install this gas heat, tank, and meter/electric hookup to see how this will work.  There is also the unknown as to how much gas we will be using to supplement the system.  The other issue is the space for the gas heater.

I realize that I don't have a lot of info regarding the current system but plan to find out the boiler size and take pictures if necessary.  I've talked to various contractors, company reps, and other owners of radiant heat systems.  I guess there are just too many variables to give different views on the problem.  We plan on talking with the builder and hopefully the cement contractor to see if the slab was insulated properly.  I've been told that you would be able to see heat loss around the foundation if it wasn't insulated on the sides and also the reverse.   That the heat would go down into the ground??  I also do not see any snow melting off the roof of the property so it must be fairly well insulated.

Anyway, in closing, I would appreciate any help, suggestions, things to check for, or other advise you might have.

Thank you!


  • Mark EathertonMark Eatherton Member Posts: 5,584
    Need lots more information...

    Need boiler model/size.

    Need pump size.

    Need actual square footage served.

    A heat loss calculation should have been performed by someone. Check with the GC and see if you can get a copy of it.

    It might also be a good idea to have a blower door test performed on the dwelling to see if there are a lot of air leakage issues.

    Some boiler room photographs would be helpful as well, showing the near boiler


    As far as slow reaction is concerned, there are numerous devices on the market that will allow you to call your house and turn the system up before you get there. It will also call you if the homes interior drops below a certain adjustable temperature.

    Get back to us.

    It's not so much a case of "You got what you paid for", as it is a matter of "You DIDN'T get what you DIDN'T pay for, and you're NOT going to get what you thought you were in the way of comfort". Borrowed from Heatboy.
  • GordyGordy Member Posts: 7,122
    dwelling location

     I'm not a professional as Mark is, but just some thoughts.

    With key words like cottage, 1000 sf, loft, and expansive north facing glass which is not ideal to have. Would this be a lake/river view property, or some type of mountain view location?


       If so could it have been built as a summer occupancy only property with a heating system designed to get through shoulder heating months only to be closed up for dead of winter retreat?


     Does the heating system contain a glycol mixture instead of straight water?



     Is the 1000 sf including the loft? If so how many radiant sf on the main floor.


     What size (diameter) is the tubing supplying the slab?


     Btu output of electric boiler?


     Floor coverings what kind?



     The two loops need be figured out for spacing to the sf of main floor. With only two could be wide center spacing, really long loops with close spacing, or smaller sf covered then I'm thinking. Right now guessing 250sf loft 750sf main floor.


     If dimensions are as I think that is two loops at 375' each with 1' spacing, or 15" spacing at 300' each loop. 


     Trying to get in the system designers head is part of the task.


  • RCORCO Member Posts: 51
    Heat Issue

    Thank you for the quick response to my issue.  I'm heading up there this weekend so will try to obtain the info requested.  The floor covering is ceramic tile.  At this point, it is a weekend/vacation home.  The original owner built to use in all seasons.  Unfortunately, the heating contractor is no longer in the area so can't go to him for any info.  I also forgot to mention that I believe the thermostat is a standard air temp unit.  I've read where a person should use slab thermostats for this type of heat??

    Thank you!
  • RCORCO Member Posts: 51
    heat issue

    Sorry....forgot to mention that this property is not on a lake......a 1/4 mile from the lake.  It is in the woods so wind isn't as big an issue as say where my permanent home is in South Dakota!  The location is in N Minnesota so temps can get rather cold.
  • Jean-David BeyerJean-David Beyer Member Posts: 2,532
    In floor radiant...

    I have that too; copper tubes in a concrete slab. One thing to be aware of is that if you change your set point, it takes 3 to 6 hours (YMMV) to notice the effect, and 12 to 24 hours for the system to re-stabilize, due to the high thermal mass of the slab. So I hope your system has outdoor reset and that it can be adjusted properly.

    One reason for using outdoor reset is so that as the outdoor temperature drops, the water temperature in the slab can be increased even before your house gets too cold. Of course if your boiler is already going at its maximum, outdoor reset will not get any more out of it. And you will probably not want to put more than 120F water into the slab anyway. For this to be most helpful, it helps if you adjust the reset curve so the circulator runs a lot of the time; e.g., 12 to 18 hours a day. Some people advocate 24 hours a day, but I do not do that. But I am not a professional, so I have experience only with my own boiler. For my system, doing setbacks in the zone heated by the slab does not make sense except for vacations when I will not be here because the recovery time is so long. Before I thought about it, I had to start the night setback around lunch time, and the recovery for the next day around 10 PM. Even that was not satisfactory because the outdoor temperature does not change the same every day, and if the inside temperature does not drop enough, the boiler and circulators do not run. I do a little setback in my upstairs (baseboard) zone, but even there, I do only 2F of setback and it takes quite a while to recover since I use low water temperatures in the baseboard.

    About having a neighbor turning on the heat before you get there. It is probably a good idea to have that done the day before you get there. I have an alternative, a thermostat that can do a setback for up to 255 days and at the end of the setback it will turn on the heat in the morning, daytime, evening, or night. It is a Honeywell CT3600; However it is discontinued. It looks as though a VisionPRO 8000 7-Day Programmable Thermostat will do this.
  • GordyGordy Member Posts: 7,122
    edited February 2011
    Thats a start

     Ceramic tile is radiant friendly so no high r value floor coverings is a plus. Being sheltered in the woods good also.  So I can assume the north facing glass is do to lot orientation.  Are you sure the R 19 insulation is not the walls instead of the roof?

    Even though its cathedral you should be able to get at least an r 30-38 in the roof. R 19 in the roof is not much for northern MN. If he designed for year around occupancy.

     Double check to see if the slab at least has perimeter insulation installed you should be able to visually see that. It may be covered with a skirting material.

  • GordyGordy Member Posts: 7,122
    edited February 2011
    Good points

     JDB, But they are reaching setpoint during the day, and losing it over night.  And they are bringing the slab up from a 55* set point. Not a real cold start up but if the system is border line to the load its a chug. We do not know conditions as far as outdoor temps, how long occupied while the problem is occuring.

     IF no insulation under slab then there is a heat sink issue to overcome. No perimeter insulation heat sink just got bigger.

  • Jean-David BeyerJean-David Beyer Member Posts: 2,532
    Two different issues.

    I think we all lack sufficient information about the system in question. Heat loss? Amount of radiation, insulation, presense or absense of reset an how it is adjusted if present, etc.

    There seem to be two issues.

    1.) Time to recover from long setback to 55F. With a concrete slab, at least like mine, that would take over 24 hours to recover. Once my old boiler quit sometime late Friday or Saturday and they did not come to fix it until Monday morning. My house is quite well insulated, so the temperature did not become objectionable unitl Sunday night, and I resorted to sweaters and an extra blanket at night. Once the problem was fixed, heat started, but it was not until sometime during the day Tuesday that things were back to normal. That boiler burned 70,000 BTU/hr and my heat loss is less than 35,000 BTU/hr, so I definitely had enough heating capacity, but I did not wish to turn up the water temperature and burn my feet. About the only solution I can think of is to turn on the heat a day or so before he comes home, either by having a friend do it, or by getting a fancy thermostat to do it.

    2.) If he has barely enough boiler, or barely enough radiation, so he can maintain the setpoint during the day but not at night, we cannot escape the need for the heat loss study results. It may be hopeless with the current system (without changes). If it is only slightly marginal, it might be that he could set up the system to pump most of the time, with the boiler modulated way down, and as it gets colder outside, have the outdoor reset turn up the water temperature to get a head start at warming up the slab for night time.
  • RCORCO Member Posts: 51
    More Information

    Hello.  Just spent the weekend at our place.  I have a correction as far as the make of the boiler.  It is a Thermolec boiler, model B10U-M, which has the capacity to produce 34,120 BTU's.  I'm not sure how we came up with ElectroMate???- possibly the contractor had inadvertently said that brand.  Anyway, we spoke with the contractor on Friday afternoon.  He indicated that there are 3 loops in the slab.  He said the most heat you will ever get out of that system is 27,000 BTU.  It may be sufficient for the square footage based on 8 foot ceilings.  But with the vaulted ceiling, loft, and window area, it is just not enough.  I asked what he would have done had he been the contractor during construction.  He mentioned he probably would have gone with in floor heat in the loft as well which would have required a larger boiler. 

    So we are trying to determine our next step to solve our heating issue.  I did take several measurements and I'm going to give the info to our electric coop so they can do a heat loss analysis.   The square footage of the main level is 720 sq ft (24' x 30").  The peak is 23 ft and walls in the open area are 10'8".  This area is around 14' x 24".  So 16' x 24' consists of the kitchen area, utility closet, bedroom and closets, bathroom, and hallway.  This is all under the loft which has a 9 foot ceiling.  The loft area is around 235 square feet.  It has a 10' x 15" area as well as a 6' x14' area which includes the stairway.  The height of the ceiling in the loft is 11' 6". 

    I have a difficult time with directions when back in the woods area.  It appears that the home is mostly facing east to southeast.  There are 2 windows on the front side - 1 bedroom and 1 bathroom that are 30" x 58" and front door that is 36" x 80" with 2' x 3' glass area.  The loft has 2 small windows side by side on the front that are 22" x 22".  The backside which would face west to northwest has 2 windows on each side of the fireplace for a total of 4.  They are 34" x 70" each.  On each side in the back corners are 4 windows facing south to southwest and north to northeast for a total of 8.  These are 22" x 70" each.  There is a side door on the north side into a screen porch.  This is a 36" x 80" door with a 2' x 4' glass area.  Above the back windows on each side of the fireplace are 2 windows (total of 4) - a triangle shaped unit that is 30" x 30" x 42" and a trapezoid that is 40" x 32" x 66" x 36".  The fireplace is a 76" wide x 23" tall by 30" deep construction with cultured stone applied.  This is a wood burning unit.  Also the insulation is R38 in the ceiling and R19 in the walls as confirmed by the builder.  He also confirmed that the slab was insulated below the heat tubing as well as around the perimeter of the slab.  I believe that I have everything I could think of in measurements. 

    The heating contractor suggested that we do install a slab thermostat so we could use some other source of heat such as the fireplace or infrared heater without have an impact on the thermostat as we would on the current stat.  He agreed with us that we really don't have a lot of room to place a gas wall heater so suggested we look into electric panels for the loft.  We are currently paying $.09 per kwh (raising to $.0943 in April) for electric as we do not have a dual fuel source.  So we would need to look at a gas (propane) supplemental heat to qualify for this rate which is $.0526 (increasing to $.0552 in April).  I did get some pictures of the current system but haven't downloaded them as of yet. 

    So, that pretty much lays it out as to what we're dealing with on our heating issue. 

  • Mark EathertonMark Eatherton Member Posts: 5,584
    Something's not right...

    I come up with around 34 btu/sq ft/hr which should be MORE than enough to keep your home warm. At that rate, you should have floor temperatures of 85 degrees F.

    I also disagree with the contractor about the output of the boiler. It appears that he is derating an electric boiler by 20%, which is pure bunk. You don't derate the output o an electric boiler. It is 99.99% efficient.

    I'm thinking that you have some elements that are fried, or a contactor that is not pulling in, or a control that is not properly set. Depending upon the R value of floor finishes, the operating temperature of the boiler should be between 110 and 140 degrees F.

    You didn't happen to look at the temperature and pressure gage to see what temp it is running did you?

    It's not so much a case of "You got what you paid for", as it is a matter of "You DIDN'T get what you DIDN'T pay for, and you're NOT going to get what you thought you were in the way of comfort". Borrowed from Heatboy.
  • GordyGordy Member Posts: 7,122
    edited February 2011


      Could it be he is basing his 27000 btu's by sf output?  720 sf of radiant floor at 35 btus sf is 25200 btus capacity If the floor temps are 85*. So he may be basing on a little higher floor temps.

      But you will lose some of that available output floor minusing kitchen base cabinets closets etc. Even if the tubing were layed out underneath them.

     Another BUT is it is all done right good insulation for structure. Slab is insulated etc. Sounds like good window orientation to capture winter sun, better than north facing.  So the heat loss should not be that much for 1000 sf structure of that type of build. And I do agree that the floor is not meeting its full output potential.

     So I do agree something is not right.  The boiler has the capacity to meet that load.  I also agree some supplemental in the loft area may be helpful. Panel rads maybe. 

     MRT is probably laging with a 12 hour fire up window to get things warmed up could have some effect, but not for long.

  • Mark EathertonMark Eatherton Member Posts: 5,584
    Theoretical versus Reality...

    I hear what you are saying Gordy, and in a sense you are probably correct. However, the reality of the matter is that it is a well built/insulated home, with a load more likely less than 20 btu/sq ft/hr (except possibly for mega infiltration beyond the end users control) and it is a well know, documented fact that when coming out of a deep set back, that the slab will suck up every BTU thrown at it until things get stabilized.

    The reality of the matter is, that the space is dropping considerably at night, and it shouldn't. The daily energy load shouldn't change that much between day and night, except for solar gains. I suspect dead electrical elements in the boiler... There are enough to handle the day time loads, but not enough to carry it through the night.

    And you are correct, that the loft could probably use some emitters to increase human comfort in close proximity. The GC was probably going under the impression that radiant heat "Rises". Fiddle faddled by the misguided finger of fate...

    When the wood stove is running, convection will kick in, and it's heat WILL rise, probably to the point of discomfort. Shoulda installed a destratification fan...

    It's not so much a case of "You got what you paid for", as it is a matter of "You DIDN'T get what you DIDN'T pay for, and you're NOT going to get what you thought you were in the way of comfort". Borrowed from Heatboy.
  • GordyGordy Member Posts: 7,122
    Agreed Mark

      Would like to see the pics.  One other simplistic question would be where is the thermostat located?  Could it be in a location that could give false ambient readings by day, or night for that matter?  Is it possible that the tstat could be slipping in to a set back setting at night that the user did not realize was happening?

     Gotta cover all the bases

  • RCORCO Member Posts: 51
    More Info

    Thanks guys for the feedback!  I'm attaching pictures of the heating system I took this weekend.  If they are clear enough the water temp should be visible on the gauge.  I may have inaccurately explained what the contractor was saying.  He indicated that do to the amount of lines in the floor, the most the slab would ever produce is 27,000 BTU's, I believe. 

    The thermostat is located on the corner of the entrance hallway.  However, it is outside the closet that houses the heating system.  Another question I have is whether or not area rugs would make a difference on suppressing the heat from the floor?  We have an 8 x 10 wool rug down in the main living area.  I think I mentioned in an earlier post that we have ceramic tile throughout the main floor.  There is also a 3 x 8 rug in the hallway. 

    I've probably posted more than enough attachments for this post.  I can post pictures of the interior and exterior of the home if needed. Again, this system is just around 1.5 years old as the home was finished in the fall of 2009.  But I would imagine that failure in the boiler could happen at anytime.  Possibly it could still be under warranty??

    Thanks again!
  • GordyGordy Member Posts: 7,122
    edited March 2011

     Do reduce output its like throwing a piece of insulation over the floor. Remember the floor is your heat emitter. And wool to boot. About 104 sf of reduced output area. Not a huge deal, maybe 3640 btus. 

     Temp gauge on boiler is saying 120* at that moment could stand to be higher130- 135ish.  It would be nice to know the reading on the temp gauges at the manifold supply, and return also.  flow meters appear to be in the half way range.

      More visual stimulation never hurt anything. share more pics if you wish.

  • RCORCO Member Posts: 51
    Some more info

    Here are a few pictures of the property - inside and out as well as a spreadsheet showing electric usage from 12/19/10 - 2/1/11 for whatever its worth.  If I understand, it would be a good idea to possibly roll up the rugs and store for the winter to keep from blocking the heat?  Would it be worthwhile to go with a slab stat in place of an air temp stat?  I suppose there is some risk in hitting a line trying to drill for the sensor at this stage of the game??  I hope the pictures of system and property will assist in helping solve the problem.

  • RobbieDoRobbieDo Member Posts: 131
    Just my opinion

    I don't like putting the pump that close to the air scoop. Is this pumping away from the scoop, I can't tell? After the pump looks like it goes right to a 90? Well, anyway this isn't a real huge issue I just don't do it that way. You said there was 3 loops in the slab, is that 1/2"? How long are the loops?
  • GordyGordy Member Posts: 7,122
    edited March 2011
    Very nice

        I would do a floor sensing thermostat. 

       Your loop lengths should be fine 3 loops at 1' centers is 240' each loop, or could even be 9" centers at 312' each if 1/2' dia. tubing should be just fine either way may even be 5/8" better yet. This all has to do with the pumping head generated by the friction of the water flowing through the tubing. The longer the tubing loops the more head loss, and the smaller the dia the more head loss. glycol in the system also contributes to head loss

        If you want to find the center spacing. Buy a cheap infrared thermometer 50 bucks. Run it across the floor to find the hottest spot then move until the next peak hot spot. You may have to spend some time in an area to get the jest of which way the tubing is laid. The thermometer will also assist in putting in a sensor, and checking floor temps all around the floor.

        Heavier grade window treatments do wonders in reducing heat loads. Closing window treatments during night time hours can reduce heat loss dramatically. A long with controlling summer time heat gains.

        One other question I would like to ask is what thickness was the concrete floor poured?  The thicker the more mass to warm up even though it is insulated.

        I do not think you have real serious issues. Just think things need dialed in, and make sure the boiler is functioning properly.

     So step one is make sure Boiler is functioning properly as Mark stated earlier.

     Step two make sure the loops are purged of any air.

        Check floor temps with an infra red thermometer to see what they actually are. Check all around the main floor for even temps. a cold section could indicate a loop that is not getting enough flow, or air bound. Once you get a feel for the loop layout you can even find where the loop starts being the warmest, and where it ends being cooler.

        See what supply return temps are at the thermometers mounted on the manifold there should be about a 10-20 degree difference or delta T in the supply, and return temps say 130* supply and 110* return. This needs to be done once the system is steady state. When its coming up to temp out of set back that number (delta T) will be quite a bit larger, and diminish as the system gets closer to steady state when the thermostat is actually satisfied.

      What I would do is observe the system once at steady state say 68* tstat setting. Wait for the next heat call. When it goes check temps at the boiler, then the supply manifold, and then the return manifold. watch them through the whole heat call until the tstat is satisfied. If at the end of the heat call the delta t is 10* to 20* at the supply, and return manifolds. then you have good flow, and you need to bump up the temp of the boiler a little more.  If you have a large delta t more than 20 then you may need to increase flow at the flow meters. It takes time so be patient.

     If you make adjustments let them work for a day or so. There is a lot of mass so changes are not instantaneous. But the slab being insulated does make it more responsive then a slab with no insulation.



  • Mark EathertonMark Eatherton Member Posts: 5,584
    It is supposed to be as close the the scoop/expansion tank as possible.

    What is your reasoning for NOT wanting to put it there?

    More to the point, the operating temperature of the boiler , if in fact it was operating when the photo was taken, is a little low. I'd crank it up to around 130 degrees F. If it can't achieve those temperatures, then there is definitely an issue with the elements.

    It's not so much a case of "You got what you paid for", as it is a matter of "You DIDN'T get what you DIDN'T pay for, and you're NOT going to get what you thought you were in the way of comfort". Borrowed from Heatboy.
  • RobbieDoRobbieDo Member Posts: 131

    Mark, I have had issues with air if it's that close, just from my experience. After I spoke with the Mfg. they recommended I move the pump father away during installation. Seemed to work have been doing it that way since.
  • Mark EathertonMark Eatherton Member Posts: 5,584
    Your milage may vary...

    I guess we all have different opinions and field experiences. I have been parking the pumps inlet as close as possible, and have not had any issues that you are having. What happens if there is any considerable distance between the inlet of the pump and the expansion tank is that a pressure DROOP occurs between the expansion tank and the pumps inlet. THis droop in pressure, can in some cases, cause oxygen to JUMP out of the water, thereby compounding any entrained air issues, and or cavitation issues on start up.

    With that said, I have seen systems that were TOTALLY screwed up that still produce circulation and heat. Noisy as all get out, but still had circulation and heat. Heat is not necessarily comfort, but is a required component of comfort.

    I used to believe that conventional air scoop (and still do) were adequate for good air elimination, but have come to realize that MBR's are significantly more efficient at initial air removal, so this old dog has started using more of the MBR's as opposed to scoops.

    I don't subscribe to some of the manufacturers claims that their devices are so good at air removal that they will suck air off the next closest planet with oxygen, nor will they address any trapped air at the top of the system. That comes down to good field practice in getting rid of the free air on initial purge. If you don't do a good job of that, you can expect ongoing problems with air.

    As long as we aren't talking feet of pipe between the expansion tank and the inlet you will probably be fine...

    It's not so much a case of "You got what you paid for", as it is a matter of "You DIDN'T get what you DIDN'T pay for, and you're NOT going to get what you thought you were in the way of comfort". Borrowed from Heatboy.
  • Jean-David BeyerJean-David Beyer Member Posts: 2,532
    I happen to believe...

    ... that microbubble rmovers are better than plain air scoops, especially for a dumb installation like mine with baseboard upstairs and no air bleed vents up there. But I am not a professionial, so I doubt my opinion has all that much weight.

    But one advantage of my Taco 4900 series, and I believe the Spirovent, is that there need be no straight run either before or after the device, and no need for a directional arrow on the device either.
  • RCORCO Member Posts: 51


    Concerning the question in regards to whether or not the system was operating at the time of photo.  Yes, it was approximately 10:45 AM about the same time I took a picture of the thermostat.  You can see the temp on that which had dropped down slightly lower than this temp the night prior. 

    Would it be good advice to get a 2nd opinion from another contractor to check out the boiler?  Again, it's not very old...but can't contact the original contractor either to see how it was set up. 

  • RobbieDoRobbieDo Member Posts: 131
    Pumping away

    I install so the pump is approx. 8"-12" away from Spirovent. That is just the issues I have had.
  • Mark EathertonMark Eatherton Member Posts: 5,584
    Follow up to your follow up :-)

    Here is a link to the O&M manual for your boiler.

    It appears that there are 2 5 KW elements, so it is entirely possible that you have a dead one. However, it also appears that your boiler comes with an outdoor reset, and it may be set to low.

    Have the service agent follow the instructions for troubleshooting as spelled out in the manual, and if everything proves functional, then have him increase the minimum or maximum settings to get warmer water out of the appliance.

    I would go with 95 degrees F at minimum and 130 degrees F maximum. That should keep you in a comfortable condition. Also, depending upon what the outside air temperature is doing when it is coming out of a deep set back during unoccupied conditions, as it gets warmer outside, it could take even longer to get the place up to temp, but theoretically, it shouldn't because the demand for heat is less.

    It's not so much a case of "You got what you paid for", as it is a matter of "You DIDN'T get what you DIDN'T pay for, and you're NOT going to get what you thought you were in the way of comfort". Borrowed from Heatboy.
  • Mark EathertonMark Eatherton Member Posts: 5,584
    Belief Busters..

    JD, I worked with a forensic engineering group out in California during my work as an expert witness on the Entran 2 trials. They tested the MBR against the conventional air scoop and determined that they both took the water to the same o2 content. The MBR did in fact get there quicker, but it didn't remove any more oxygen than the scoop did.

    As for straight pipe, I have seen one manufacturer that recommended the straight pipe requirement before and after their device. THeir assumption is that in a district loop heating system, the water will be flowing at maximum velocity ALL of the time. In residential space heating systems with zone valves, that occurs for 2 % of the time.

    I have piped directly from a riser, through an elbow and directly into a scoop and not had problems, but have heard of one system that did have issues with that configuration.

    Your opinion is always welcome here. You bring a unique perspective to the class :-)

    It's not so much a case of "You got what you paid for", as it is a matter of "You DIDN'T get what you DIDN'T pay for, and you're NOT going to get what you thought you were in the way of comfort". Borrowed from Heatboy.
  • Jean-David BeyerJean-David Beyer Member Posts: 2,532
    I would not argue with an expert witness.

    And since I have a microbubble remover in there, there is no point removing it.

    Where it is is straight for a few inches on either side. The manufacturer says to keep the flow through it to less than 5 feet per second. My boiler manufacturer says to use at least one-inch pipe there, and my contractor used 1 1/4 inch, so that should reduce the speed. One zone runs 2.4 gpm (calculated, not measured) and the other runs something else -- I cannot tell what because it is mostly 1/2 inch copper tubing in a slab and I have no idea as to the length, driven by a Taco 007-IFC. The floor area is about 750 square feet and is five parallel circuits of unknown length. I suppose it is more than the other zone since the 5 tubes entering return through a 1-inch one, and the heat load there is about 4 times the other zone.

    It is not constant flow. Sometimes both circulators (no zone valves) run, and sometimes just one.

    "You bring a unique perspective to the class :-)"

    I like that. For me this web site really is a class.
  • jpjp Member Posts: 1,935
    edited March 2011
    insufficient insulation

    I suspect insufficient floor or perimeter insulation.  you have some pretty good low  outdoor temps. 2 inches of foam doesn't do well faced with single digit temps.   correcting perimeter insulation might make a big difference.

    try to find out how the place was insulated, get a "sketch" of what they did around the foundation, don't let them just tell you.  

    if the tstat isn' t satisfied the system should never shut off.   if you turn the pump off, the boiler will go up to the set point temp and turn off.  that will tell you what the boiler is trying to achieve or if it is achieving its set point.   you have those little temp gauges on supply & return with those little flow meters, so you can figure out(estimate)  btu's into the floor.

    check your water temps morning, mid day, and late evening.  maybe there is a night time set back working you are not aware of?

    a floor sensor is a waste at this point, wait til you get the room temps where they need to be.

    measuring floor temps at various places will give you more info on whats really happening too.

    to me, 120F supply water on a slab home seems high if you aren't below zero F.

    I like this idea for insulation.  from mich residential code book.
  • GordyGordy Member Posts: 7,122
    edited March 2011
    Slab insulation detail


      That detail shows nothing under the slab for insulation??

      Not to say its right to do, but I have seen a lot of radiant slabs with NO insulation perform well, and able to heat the structure.  Efficient no, Able to perform yes.

      I think Mark is on the right path.

  • RCORCO Member Posts: 51
    Appreciate all the input

    Thanks to all for your comments and suggestions.  Mark, I appreciate the manual on the boiler.  The only info I had from the previous owner was the installation instructions that were left with other info on appliances, etc.  jp, I also appreciate the comments on the slab insulation.  However, I'm not sure how I will ever know exactly what insulation was used.  I'll have to take the builder for his word on what he witnessed that it was insulated.  I guess I can contact the contractor who did the concrete work but the heating contractor is no longer in the area. 

    I had a call from the heating contractor we have been working with this afternoon.  He had an estimate for me for installing a TecMark slab stat.  Not sure of the model but his estimate was around $450.  I had just told my wife that I think we should hold off on the stat until we solve the problem of the major heat loss at night.  It was good to see that advice.  I don't believe I want to spend that money and still have the same issues. 

    Mark - I do know that this system has an outdoor sensor.  The reason I know is because the contractor unhooked it as it was buried in the snow.  As a homeowner with very little knowledge of radiant heat, I'm at the mercy of the person whose supposed to be the expert on this type of system.  He indicated that it wasn't functioning as it should buried in the snow and with it unhooked it would put out 120 degree water temp as he set it that way??  Again, I've gained much knowledge in my research but still don't understand the system in all aspects.  I'm assuming that the sensor keeps the water temp regulated by how warm or cold it is outdoors.  But I've a feeling from your comments that it may do more than that?? 

    Our realtor had recommended him to look at the system and I've heard many positive comments about their work.  Just having doubts that he knows this type of system that well.  It's very difficult to work with this issue when we're 4 -5 hours away.  I guess that goes with the territory of owning a cabin/vacation home.  

    From most of the comments made in regards to my issue, I gather that the concenses is this size boiler and loops within the slab should do the job of keeping the heat at the desired temp day and night.  I know there are some things we can do to address some issues, such as add shades to the windows for insulation ( we've discussed that this past week) as well as possibly pull up the rugs during the winter as to not suppress the heat in those areas.  We can also use an infrared heater (Sunheat) for the loft area if need be for comfort. 

    Again, I appreciate the comments and please feel free to add more.

  • Mark EathertonMark Eatherton Member Posts: 5,584
    edited March 2011
    Tell me more about your fire place...

    It's wood burning, but is it an air tight stove or an open hearth fire place?

    Do you commonly fire it up at night?

    Does it pull outside air for combustion? Does it have glass doors? Do you run it with the doors open or closed?

    Does there seem to be any co relation between the drop in temperature and the use of the fireplace?

    Also, are there a lot of can lights in the ceiling?

    It would appear, based on photographs and newly acquired information (disconnected OSA sensor) that the boiler is working OK, but you could confirm it a couple of ways. One would be to look at the gage when the house is the coldest. Also, on your supply and return manifolds are thermometers. Tell us what they are doing when it is cold in the home.

    Might be worth while to drop a few bucks at home Depot on a non surface contact thermometer so you can see what the floor temperature is, and also look for leaks in the thermal envelope.

    Based on what I read in your manual, the OSA reset only does reset and not set back.

    Hang in there. We will find your comfort. It might just be an induced infiltration issue.

    It's not so much a case of "You got what you paid for", as it is a matter of "You DIDN'T get what you DIDN'T pay for, and you're NOT going to get what you thought you were in the way of comfort". Borrowed from Heatboy.
  • GordyGordy Member Posts: 7,122
    Available radiation

     I'm starting to wonder a little about how many sf of furniture, closets, cabinets, and stairways there are verses the 720 sf of radiated floor area.

     We keep thinking max floor output with every sf available.  Deduct 30sf for an enclosed stairway, 28 sf for a couple of couches,  30 sf for some kitchen base cabinets, 18 sf of fireplace built to theinside, and some closets coupled with the 108 sf of area rugs..... thats 214 sf You get down to 20- 21000 btus of max radiation.  A weekend is just a short period of time really to get a stabilized mrt.  That expansive stone fireplace will really soak up some btus

     Just a thought

  • Jean-David BeyerJean-David Beyer Member Posts: 2,532
    Might be worth while to drop a few bucks at home Depot on a non surface contact thermometer

    How good do these seem to be? Not questioning their temperature accuracy that seems OK, but size of measuring spot, accuracy of the measuring spot vs. where I think it is pointed, etc.

    I have a Black & Decker TLD100 and it seems to work OK, but I really do not think I have been able to find where my copper tubes in my concrete slabs are. Some parts of the floor are warmer, some are cooler, etc, but I do not know that I could tell if I had one foot separation or something else, or if they go lengthwise or widthwise in the room.

    There may be some technique in using the thing that I am unaware of.
  • Jean-David BeyerJean-David Beyer Member Posts: 2,532
    Come to think of it, ...

    Is the pressure not kind-of high, too? Looks like maybe 30 psi. Hard to be sure, blurry and all. This would have nothing to do with the problems, but should be looked into.
  • Mark EathertonMark Eatherton Member Posts: 5,584
    Using an IR gun.

    JD, I only use to have the IR non surface contact thermometer. They work great except when reading shiny hot metals, especially copper. If in doubt, cover the pipe with a small piece of masking tape and the emissivity will be corrected.

    Before I had my hand held IR imaging camera, I use to place a grid of masking tape on the floor on 2" centers, and would go through and hold the gun directly at the intersection of tape (actually holding it right on it) and mark the temperatures. A digital image if you will. I would then focus in on the highest numbers on a 1" on center basis to fine tune it. It worked, not as well as my imager, but it gave me a mental picture from which to build upon in my minds eye.

    As for finding tubes in a floor, you have to have "IDEAL" conditions under which to work. First, you must allow the floor to cool WAY Down, like 5 degrees F lower than the normal MRT. This could take days, depending upon the prevailing conditions. Once cooled down, you then turn the stat up, and allow the floor to start coming out of the deep recovery. I find that it needs about 1 hour per inch of slab thickness. At that point, using my IR imager, the lines are very well defined. Start too early, and they are blurred. Start too late, and the heat has dissipated so much that it just looks like a large mass of glowing heat. It's as much art as it is science. If you have an ODR, it is best to bypass that function and hit the slab with as hot a water as you can get.

    In your case, I would check wit the county energy conservation department and see if you can "borrow" their IR imager for a day so you can "see" what is going on.

    FWIW, I got an email from FLIR yesterday. THey now have an imager that starts at $1,200.00. I paid $5K for mine less than 2 years ago! I suspect that the Chinese are getting into the IR imager business, and the American companies are trying to corner the market, but that's just my international conspiring minds theory :-)

    For purposes of just getting a surface temperature, the Cheapo Depot guns work fine for under a hundred bucks.


    It's not so much a case of "You got what you paid for", as it is a matter of "You DIDN'T get what you DIDN'T pay for, and you're NOT going to get what you thought you were in the way of comfort". Borrowed from Heatboy.
  • Mark EathertonMark Eatherton Member Posts: 5,584
    Maybe, but...


    EVERY house with RFH has these issues and items in place and rarely suffer daily drops in temperature. It could have some impact on this home due to its occasional occupancy usage, and need for acceleration but in the case of furniture, couches in particular, they slow the flow, but don't stop it.

    I have a high backed couch directly in front of my radiant wall in the mountains, and when I first start it up, the couch is cold, but eventually warms up to around 75 degrees F. It's more a matter of time and MRT coming up and averaging out.

    But as we say, your milage may vary ;-)

    It's not so much a case of "You got what you paid for", as it is a matter of "You DIDN'T get what you DIDN'T pay for, and you're NOT going to get what you thought you were in the way of comfort". Borrowed from Heatboy.
  • Jean-David BeyerJean-David Beyer Member Posts: 2,532
    IR cameras, etc.

    I looked at the current offerings of FLIR cameras. I am AMAZED at how low the prices have gotten. I have to control my equipment junkie tendencies. I have resisted getting a digital combustion analyzer.  I do have a pH meter and an IR thermometer. But as a retired person on fixed income, I should not be spending these monies.

    With my W-M Ultra 3, it is trivial to set the outdoor reset to whatever temperature I want. And since my heat loss when it is 0F outside is well under half the boiler output, I imagine I could put 180F into the slab, though I imagine that would be a really bad idea.

    It occurred to me that I might try this in the late spring or summer. By then, I expect the slab would be no hotter than the ambient temperature, say 80F. I could turn off the warm weather shutdown and diddle the reset curve to get 90F or 100F into the slab.  I would want the windows open, though. Living room would be diffciult (carpet with underlay), but the rest is either ceramic tile, marble tile, or asphalt tile right on top of the concrete slab, Since I am not looking for leaks, but just trying to guess spacing and lengths, this should be good enough, I imagine. I assume all th3 spacing is the same, though I could be wrong, of course.
  • jpjp Member Posts: 1,935
    frost free protection

    Hey gordy,

    I think that diagram was for frost free protection of a slab?  but I like that idea for perimeter insulation, going down deep then outward.

    even those cheapo IR guns give you details of the area it looks at based on distance from target in the directions book.   I'm pretty sure it just picks out the hottest region.   I like my $30 gun.  and the laser pointer is most likely pretty darn close.  so it should work better for finding hot spots opposed to cold spots.

    for starters you can poke around the foundation below the siding.  the chimney side shows part of the foundation below the siding.  if you hit concrete right away, well thats not a good sign.   adding some preimeter insulation wouldn't be that hard.  even if you dug down only a foot and used 3 inch foam.  up here northern mich there was an inspector that FORBID the owners from insulating their perimeter foundation, now they grow flowers year round :)   all thanks to the building inspector.   
  • RCORCO Member Posts: 51
    Wood Burning Fireplace

    I'll try to answer your questions Mark. 

    This is not an airtight unit.  It's a Heatalator brand and has an open hearth with glass doors (not very air tight).  I believe it has an air intake vent on the outside.  We've primarily kept glass doors open until the fire is burning quite well.  But I don't believe I've noticed any difference in drop from either operating it or not.  In fact, the end of January, we started the fireplace later in the evening after our kids got back from town.  The temp had dropped by that point.  So I don't think it has a lot of influence on the guess anyway.

    I believe we have some canned lights in the kitchen area....I would need to look to make sure.  The vaulted ceiling in the main area has some recessed lighting. 

    When you're talking about the temp readings on the boiler and lines, check those when it drops at night?  I could have my neighbor look at them as it is now.....but the stat is set at 55 degrees.  Although, no one has been there to prove, I believe it is dropping back from 55 degrees when we're not there.  The reason I say this is because my wife found the olive oil coagulated in the kitchen cupboard.  This may be compounded by the fact that I need to address the microwave/hood which is vented to the outside in the screen porch.  The vent is approximately 12" or so long with a hood over top....but no flap to cover when fan not running.  You can feel the cold air under the hood as well as in the microwave.

    I'm adding a few more pics of the layout inside the property.

  • GordyGordy Member Posts: 7,122
    edited March 2011
    Monitoring temps.

      The easiest way since you are not there all the time is this.

    Buy  4 indoor outdoor thermometers they have a 10' probe. 10 to 15 bucks a piece.

    Take two of them in the boiler room, and tape one probe to the supply pipe by the manifold, and the other to the return pipe on the return manifold with a piece of pipe insulation covering the probe.


      These will tell you the minimum and maximum temps each pipe sees over what ever period you check them just don't forget to reset them for the next go around of monitoring. 

      So in other words in place while you are gone for the week, and return for the weekend you can look at the minimum, and the maximum temps that occured while you were gone during the week while the system was in setback on the supply, and return lines. So the max of each probe would be while the system was running, and the minimum on each probe would be probably when the sytem started a heat call.


     The differences between the two mx temps would be the delta T, the same goes for the minimum.

     Take the other two thermometers, and set up a couple of feet in from each outside wall in the center of the house put the probe on the floor with a piece of insulation on it. Now these will tell you the minimum, and the maximum temperature the floor achieve while you are gone during set back.

     Now you have a monitoring system that you can check when you go there on the weekend.

     You can also do the same with these while you are there to see how all the temps react during setpoint.

     You could get anal, and get a fifth thermometer for the center of the room also. That way each loop is monitored.

     Those temps would really help trouble shooting how your system is reacting. Because you don't really know if you are losing setpoint at setback temps during the night while you are not there do you.

      Having these thermometers will also save staring at the temp gauges in the boiler room for hours. You can reset them when you go to bed, and check them in the morning to see the highs, and lows the supply, and return temps, and floor areas achieved over night no watching required.


Sign In or Register to comment.


It looks like you're new here. If you want to get involved, click one of these buttons!