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Takagi demand water heater set to 160 degrees

caryatid
caryatid Member Posts: 11
I have heard that by using a remote controller one can make a Takagi water heater output 160 degree water. The Takagi info contradicts itself though, so I'm not sure if it will work. Anybody have experience with this?

I have a Takagi indoor TK-310C using natural gas going through 900 feet of 1/2 inch pex under a wood floor in an old house with uninsulated brick walls. Its 140 degree output is not hot enough for the house to stay comfortable on very cold days. I believe 160 would do the trick; it certainly would help.

Thank you.

Comments

  • Leon82
    Leon82 Member Posts: 684
    I was told Bosch had a 160 degree board that could be swapped for dishwasher use in commercial kitchens. Maybe it is the case with yours also.
  • kcopp
    kcopp Member Posts: 3,990
    Noritz use to do that. Sounds like you really need a boiler to do the work there... not a water heater.
    Ironman
  • pecmsg
    pecmsg Member Posts: 2,887
    caryatid said:

    I have heard that by using a remote controller one can make a Takagi water heater output 160 degree water. The Takagi info contradicts itself though, so I'm not sure if it will work. Anybody have experience with this?

    I have a Takagi indoor TK-310C using natural gas going through 900 feet of 1/2 inch pex under a wood floor in an old house with uninsulated brick walls. Its 140 degree output is not hot enough for the house to stay comfortable on very cold days. I believe 160 would do the trick; it certainly would help.

    Thank you.

    at 160 you wont be walking on the floors.

    You have a emitter problem if 140° isn't high enough. What's the return temp?
    Ironman
  • tim w
    tim w Member Posts: 6
    Radiant supply temperature should never be this high, if the heat loss for the area is greater than your rad floor output is capable of.... consider adding other emitters such as the heating edge HE2 lower temp baseboard to the area. At 160F boiler temp you also "lose" some boiler efficientcy
    Ironman
  • GroundUp
    GroundUp Member Posts: 1,402
    In what manner is the tubing installed? Just tubing hanging loose or are there transfer plates of some sort?
    Ironman
  • caryatid
    caryatid Member Posts: 11
    Thank you for all the responses.

    In answer to the questions that have come up:

    1 The tubing is fastened to the underside of the old plank flooring using transfer plates. I have since learned that I did not use the good (extruded) plates but the folded sheet aluminum ones.
    2 The floor with the heater set to 140 degrees is warm, but certainly far from hot. The transfer through the floor is clearly not efficient.
    3 The return temperature is close to the supply temperature, maybe ten degrees lower. I will check when I get down there next.
    4 I am thinking of adding a large radiator to the system also because not enough heat is coming through the floor. I have easy access to the floor from below to install it and an available loop on the manifold. It will transfer heat much better. Will it affect the underfloor part in some way I haven't considered?

    To add a little to my OP, Takagi has a remote controller it says can be used to make the temperature higher than the usual 140, up to 160. What is not clear to me is whether that is for all their models or only some of them.

    Thank you for your help.

  • Ironman
    Ironman Member Posts: 6,868
    160* SWT is way too hot for a wood floor; it will destroy it.

    You need more emitters, not hotter water.

    Was any form of design and heat loss calculation done?
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
    kcopp
  • Snowmelt
    Snowmelt Member Posts: 1,334
    Call the technician department up, I had a tk 3. Doing a commercial dishwasher were I needed 180 degrees water for sanitation purposes, it been a while but I think if you have the remote and turn the temp up before the machine starts it will go above the 140 degree mark
  • DZoro
    DZoro Member Posts: 1,048
    What do you have for insulation below the tubes?
    Do you have 2 pipes inside each joist pocket?
    D
  • caryatid
    caryatid Member Posts: 11
    Yes, heat loss was done, that is where I got the linear feet of pipe needed.

    I have R19 below the tubes, with two tubes in each joist space.

    The supply temp at the manifold is 120, the return is 110. That seems like a lot of drop from the Takagi to the manifold over a distance of 12 feet. Maybe the Takagi isn't actually putting out 140 degree heat, though its display says it is.
  • Ironman
    Ironman Member Posts: 6,868
    What was the heat loss for the house?

    The best output to be expected with good heat transfer plates would be about 20 btus per ft2 @ 120* SWT.

    A 300' loop of 1/2" will give about 4-5k btus max @ 120 SWT. So, the output of your floor is somewhere around 12-15k btus. I seriously doubt if your heat loss is that low.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • DZoro
    DZoro Member Posts: 1,048
    Can you post a pic of the boiler and piping, try to get as much in one pic as possible. We can always zoom in if we need to.
    D
  • caryatid
    caryatid Member Posts: 11
    I will take a picture.

    I didn't do the heat-loss myself, but I think you are right IronMan, I expect it should be more like 40 BTUs PSF for this old house. The design had 35 BTU's per square foot, but I am not getting that output through the wood floor it seems. One correction: There are 1500 feet of tubing, not 900, for 1000 square feet of space. The design calls for 130 degree water, with a max of 150, which I am also not getting.

    So I think I need to add some radiators. Hotter water in those would give me more heat.

    I have figured out that, because I am using a heat exchanger, the water is down to 120 degrees by the time the heat gets into the floor with the Takagi putting out 140. It comes back at 110.

    If I were able to get the Takagi to put out 160, presumably the water would be about 140 going into the floor, returning at 130. Is that too hot to put into the floor (3/4" old tongue and groove yellow pine, with no subfloor)? I have a temperature sensor in the floor from an Azel thermostat, so I understand that the floor doesn't get above the thermostat set point, 70 degrees, before the system shuts off, though presumably the bottom of the floor is hotter where the pipes actually touch it.

    Thank you again for sharing your knowledge and advice.




  • Alan (California Radiant) Forbes
    Alan (California Radiant) Forbes Member Posts: 3,246
    edited December 2019
    See page 42:

    http://www.takagi.com/media/54102/2000534692.pdf

    It looks as though 140*F is your max.

    You can possibly add a radiator with some research. You can also replace the plates with Ultra-Fin. Proper heatloss calc's. are required before you do anything.

    http://www.ultra-fin.com/
    Often wrong, never in doubt.
  • Ironman
    Ironman Member Posts: 6,868
    Yellow pine with no subfloor? I definitely wouldn't go above 120* SWT.
    What are the dimensions of the plate HX?
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • hot_rod
    hot_rod Member Posts: 16,293
    Basically a radiant floor heat output is close to 2 btu for every degree difference between floor surface and ambient room.

    Most consider low 80's as the high end of what a floor surface temperature should be, 80- 82°, skin temperature, ideally.

    So the math looks like this for a 70° room temperature:

    82-70= 12 X 2 btu/ft= 24 btus/ sq foot of radiant panel. So you often see mid 20's btu/ sq. ft as a reasonable, acceptable radiant floor output.

    If in fact the room load is 35 btu/ sq ft, either the floor surface needs to increase, or lower the room ambient.

    85 surface- 68 ambient X 2 = 34btu/ sq ft. But a consistent 85° surface would not be barefoot comfortable :) and 68 may not be a comfortable room temperature.

    This, 34 btu/ sq ft may be doable and acceptable in a commercial shop for example where low air temperature and workers with shoes and sox are on the floor.

    Put heat in concrete, outside on a 30° day with a 100° supply 100-30= 70 X 2= 140 btu/ sq ft output

    Heat transfer is all about the delta T.

    The next part of the equation is what SWT it would take to drive thru the floor assembly to allow that acceptable surface temperature, and is it an acceptable temperature for the wood fibers.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream