Solar-ready radiant floor heating

ReinierReinier Registered Users Posts: 13
I am thinking about installing radiant floor heating that initially uses conventional heating only, but that can be connected to solar panels in the future. This could be a situation where the solar panels will do pre-heating of the water. Does anybody have any advice on or experience with this approach?

Thanks,
Reinier

Comments

  • BB.BB. Super Moderators, Administrators Posts: 31,765 admin
    Re: Solar-ready radiant floor heating

    This may help:
    BB. wrote: »
    Solar Thermal can be a nice source for space heating and hot water... And usually is "cheaper" per kWhr/BTU vs Solar PV Electric. Also, Solar Thermal lends itself very well to do it yourself projects. Note, these are plumbing projects and have their own issues (leaks, pump failures, installation issues trapping air, anti-freeze, storage, heat exchangers, etc.):

    Solar Shed and other Solar Thermal Links

    A good place to start reading is Home Power Magazine... They have a free past issue online--and have a lot of articles you can read for free. I don't always agree with them and their reviews--but they are a fun and enlightening read:

    Home Power Mag

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • GreenPowerManiacGreenPowerManiac Solar Expert Posts: 453 ✭✭✭
    Re: Solar-ready radiant floor heating

    It's complicated, yet had an idea for making your own solar thermal system. Buy some 1/2" PEX hot water tubing with plenty of connectors, T fittings and ring crimps. Only downfall is you'll have to rent or buy a PEX crimper. Design a grid on paper and piece it together, inlet on bottom right, outlet on top left. Paint it with some high temp flat black paint. Get a small DC circulation pump that'll run on a small solar panel, so when the sun is shining fierce, the pump is going fastest. Get a DC programmable timer relay to cycle the pump (one minute) every 10 minutes. Make an enclosure like a solar oven made of wood lined with tin foil to capture the heat and maybe a thicker glass piece cover to enclose from some old window panes (Don't use plastic, it might melt). Next, run the in/out lines to an old water heater (with a heat exchanger if you can find one) for a tank with hookups. I'd make several solar thermal collectors to hook up in series or you'll have limited supply of hot water. Initially, you'll have to make fittings to pump the coolant mix in the system to purge the lines with air pockets. My system has a pressure tank for expansion when hot, so you may need it depending on how hot it'll get. Hope this helps you get started on your journey.....
    Nature's Design & Green Energy on FaceBook : Stop by and "Like" us anytime.. Many up-to-date articles about Renewables every day.
    WWW.GreenAnything.Net    Ad free website.
    Lots of DIY Renewable Energy Projects on ETSY : Solar Panel builds, Wind Turbine builds, Rain Barrel build,etc.  
  • Organic FarmerOrganic Farmer Solar Expert Posts: 128 ✭✭
    Re: Solar-ready radiant floor heating

    I installed PEX tubing under our floor when I built our house.

    I have also attended a few workshops on the topic. When 'experts' do the math seeking optimum performance, they always come up with HUGE thermal banks [1,000 to 1,800 gallons].

    I tried six 50-gallon drums but the seams burst. Now I use four dead water-heaters as my thermal bank. I have a tiny fraction of the optimal size.

    I use our woodstove to heat the water. It heats our home twice. Once by it's direct radiant heating. Secondly by capturing exhaust heat into water, which heats the thermal bank and flows through our radiant floor.

    Once installed it can easily be modified. I have valves lined up that I can use our propane water-heater to heat our radiant floor, if I wanted. We tried it one year but the propane fuel bill was crazy.

    Our plan this summer was to go off-grid with photo-voltaic this year, and solar-thermal next year. A minor disaster struck and has set us behind a year. We still plan to do solar-thermal eventually.

    I think the ideal for us is to have two separate loops.

    The first loop to include:
    1- a row of solar-thermal panels;
    2- two 300-gallon horse water-troughs [using 50' of 3/4" copper-tubing in each] super-insulated;
    3- a surge-tank/pump feed tank [basically a drum with the circ pump mounted to it at the pump.

    The second loop to include:
    1- the second water-trough as a surge-tank with the circ pump mounted to it;
    2- the radiant floor loop.

    In the dead of winter, you have a bit over 4-hours of heat capturing. That heat needs to be stored in a thermal-bank. Then you have 20-hours until the next heat-recharge.

    If you design it correctly that first loop should 'natural convect', so you need to include that in your design.
  • icarusicarus Solar Expert Posts: 5,433 ✭✭✭✭
    Re: Solar-ready radiant floor heating

    You can also use a gas (lp or Nat.) fired demand water heater to ad in aux heat as needed. Rinnai, Paloma and Takagi make units that are designed for such flow rates and temps.

    Please also keep in mind that you ned to use the proper PEX tubing. You need to use O2 barrier type tubing if there's any iron in the plumbing,, including the pump systems.

    Tony
  • Organic FarmerOrganic Farmer Solar Expert Posts: 128 ✭✭
    Re: Solar-ready radiant floor heating
    icarus wrote: »
    You can also use a gas (lp or Nat.) fired demand water heater to ad in aux heat as needed. Rinnai, Paloma and Takagi make units that are designed for such flow rates and temps.

    I spoke with a Rinnai salesman. He told me that if your on a well, it would violate the warranty. Not an independently controlled quality of water source?


    ... Please also keep in mind that you ned to use the proper PEX tubing. You need to use O2 barrier type tubing if there's any iron in the plumbing,, including the pump systems.

    Tony

    I agree.

    I also included a filter in my system next to the circ pump. Years later it is still clean, but I felt it was a good idea at the time.
  • SkippySkippy Solar Expert Posts: 308 ✭✭
    Re: Solar-ready radiant floor heating

    When I purchased my Apricus High efficient solar water heater, I asked the salesman, "will this make enough hot water for 1 shower a day, year round". . the answer . . . yes , yes, and yes !
    So far over that last 3 years, I do not need any other water heater from april until november . . nothing but the sun. . . from around november too april . . it never gets above 70 - 75 F . . and I am NOT taking a shower in that ! That is why I installed the on demand water heater at the same time.

    As for using it to heat the radiant floor slab - is 75 F hot enough ? I don't know.

    Just my experiences here in Ontario Canada.
    2 - 255W + 4 - 285W PV - Tristar 45 MPPT CC / 3 - 110W PV -wired for 36V- 24V Sunsaver MPPT CC / midnite bat. monitor.
    1 KW PSW inverter 24V / 2.5 KW MSW inverter-24V ~ 105 AHR battery.
    3 ton GSHP.- 100 gallon warm water storage / house heat - radiant floor / rad
    9 -220W PV - net meter - Enphase inverters and internet reporting system.
    420 Gallon rain water system for laundry.***  6" Rocket Mass Heater with 10' bed for workshop heat.
    Current project is drawing up plans for a below grade Hobbit / underground home.
  • westbranchwestbranch Solar Expert Posts: 5,183 ✭✭✭✭
    Re: Solar-ready radiant floor heating

    Skippy, how many tubes is your collector?
     
    KID #51B  4s 140W to 24V 900Ah C&D AGM
    CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM 
    Cotek ST1500W 24V Inverter,OmniCharge 3024,
    2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge,
    Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
    West Chilcotin, BC, Canada
  • peakbaggerpeakbagger Solar Expert Posts: 341 ✭✭✭
    Re: Solar-ready radiant floor heating

    This issue of Home Power has a great article on radiant for low temperature sources like solar. It is written by John Siegenthaler who is regarded as one of the "god" of heating.

    PS: Link to Home Power Magazine (-BB)
  • SkippySkippy Solar Expert Posts: 308 ✭✭
    Re: Solar-ready radiant floor heating
    westbranch wrote: »
    Skippy, how many tubes is your collector?

    I am not sure - either 30 or 32 tubes. . . in the summer time, it reliably reaches 170 - 180 F in the 60 gallon storage tank. Good time to do all my hot water laundry washing !

    I am currently looking at getting rid of the grundfos pumps. . 100 watts. . and going to the Elsid pumps . . 10 watts or so. . .

    It's at about a 45 - 50 degree slant, so it should catch the winter sun, the btu's are just not there. . . but then I bought it for the summer time usage anyways, I knew I would need back up in the winter, so I did not sweat it too much. . . from april till november using straight solar hot water is pretty good in my book.
    2 - 255W + 4 - 285W PV - Tristar 45 MPPT CC / 3 - 110W PV -wired for 36V- 24V Sunsaver MPPT CC / midnite bat. monitor.
    1 KW PSW inverter 24V / 2.5 KW MSW inverter-24V ~ 105 AHR battery.
    3 ton GSHP.- 100 gallon warm water storage / house heat - radiant floor / rad
    9 -220W PV - net meter - Enphase inverters and internet reporting system.
    420 Gallon rain water system for laundry.***  6" Rocket Mass Heater with 10' bed for workshop heat.
    Current project is drawing up plans for a below grade Hobbit / underground home.
  • westbranchwestbranch Solar Expert Posts: 5,183 ✭✭✭✭
    Re: Solar-ready radiant floor heating

    Have you looked at the Alpha pumps? they look to be a good fit...
     
    KID #51B  4s 140W to 24V 900Ah C&D AGM
    CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM 
    Cotek ST1500W 24V Inverter,OmniCharge 3024,
    2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge,
    Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
    West Chilcotin, BC, Canada
  • wrdaiglewrdaigle Solar Expert Posts: 65 ✭✭✭✭
    Re: Solar-ready radiant floor heating

    I will second the suggestion for the Alphas. They use more electricity than the El-Sids, but they move a lot more water. I did a blog post we updated our 3 taco pumps to a single Alpha: http://bluecloudpowerco.blogspot.com/2012/01/toasty-warm-feet-with-energy-to-spare.html. So far so good!
  • Volvo FarmerVolvo Farmer Solar Expert Posts: 209 ✭✭✭✭✭
    Re: Solar-ready radiant floor heating

    Oooh! Interesting. We are using a UPS15-58F and it draws 48W on low speed. Thanks for the heads up on that Alpha. Looks like a nifty pump!
  • DantonDanton Registered Users Posts: 3
    Re: Solar-ready radiant floor heating
    Skippy wrote: »
    I am not sure - either 30 or 32 tubes. . . in the summer time, it reliably reaches 170 - 180 F in the 60 gallon storage tank. Good time to do all my hot water laundry washing !

    I am currently looking at getting rid of the grundfos pumps. . 100 watts. . and going to the Elsid pumps . . 10 watts or so. . .

    It's at about a 45 - 50 degree slant, so it should catch the winter sun, the btu's are just not there. . . but then I bought it for the summer time usage anyways, I knew I would need back up in the winter, so I did not sweat it too much. . . from april till november using straight solar hot water is pretty good in my book.

    I have been reading your thread about radiant floor heating. I am new to solar, but have always wanted to have it. I just commissioned my grid-tie 3 KW PV system. I have been having some fun with my old 10' dish TV collector that I made by covering it with tin foil and replacing the TV receiver with a water pot. I ran water from my pool and set up tracking, and it raised my 5000 gal pool 7* in 7 hr. That = 42.000
    btr/hr. It is around 75 sf of surface area and that = 560 btu/sf/hr. It would make steam if I stopped the water flow. If I ever build a down size retirement home I plan to heat it with radiant floor heat, store it in a small above ground pool in the walk out basement, Wood stove and propane backup heating. My question is the output of the dish collector as good as factory flat commercial units. I plan to replace the mesh and tinfoil with thin polished aircraft alum. and that will up the output. Well what do you guys think?

    Thanks for you coments
    Danton
  • GreenPowerManiacGreenPowerManiac Solar Expert Posts: 453 ✭✭✭
    Re: Solar-ready radiant floor heating

    Any hot water source needs to be very insulated to maintain the heat. Good luck with the 5000 gallon pool. Hot wood stove with circulated radiant water heat should be enough to heat the floors whenever it's cooking by itself.

    I've run my stove lines in an out of my 3 storage tanks, 40 gallon backup, twin 120 gallon heat exchanger tanks. This should heat up the tanks while the radiant floor heating isn't operating, and supplying radiant heat when in use. The biggest problem is when hot water is being used, if you're married you know what I mean. Cold water replaces the hot in the tanks to draw down the temps. It's almost a lost cause. All my electrical lines to any of the solar/wind/and pumps are running off of a 2-3kw solar array during those sunny cold days.

    Sounds like you'd be better off with an isolated radiant floor/hot stove setup. Not hooked up to backup hot water heater at all.
    The BTU's are going to come from somewhere, and in winter time the suns rays are only about 26% efficient and that's when the sun is shining.

    That's funny someone said, "My LP gas bill was crazy", I've done that my first year with radiant floor heating too and the water heater is almost constantly running. What I've done to that system is this: My floor heating is on a controller to 3 zones of flooring to heat on a 24v system (controller). All I did was took an old dial furnace thermostat and clipped it's resistor and set it to "Cooling". Installed it to one of my hot water pipes above the tank inside a small foam insulated box. Set the temperature of that controlled environment to a point where it switches the zones on after the tanks temp gets 125 degrees or better and shuts off the loop when lower (so the backup water heater doesn't come on). The controller has a light switch to ultimately control the controller to the zones. I call it the "Summer(off) Winter(on) switch". This is the one thing that works on its own during the winter when we have excess heated water, for what little time it turns on to run. Lack of this feature in the controller pissed me off to the point of creating the controlled environment just spoke of.
    Nature's Design & Green Energy on FaceBook : Stop by and "Like" us anytime.. Many up-to-date articles about Renewables every day.
    WWW.GreenAnything.Net    Ad free website.
    Lots of DIY Renewable Energy Projects on ETSY : Solar Panel builds, Wind Turbine builds, Rain Barrel build,etc.  
  • DantonDanton Registered Users Posts: 3
    Re: Solar-ready radiant floor heating

    It was just something that I was thinking about. I have not tested the dish in winter and I think it would take at least 3 units to work. You could insulate the out side of the pool, under the concrete slab, and use a solar cover on top. I would keep the hot water heating separate from the house heat. Sounds like you have your system working well. Thanks for your thoughts and input.
  • BB.BB. Super Moderators, Administrators Posts: 31,765 admin
    Re: Solar-ready radiant floor heating

    Generally a fixed solar thermal collector (flat array on roof) is fine for heating a pool... You do not need very hot water and don't want the chance that you can generate live steam in the system (scalding hazard and even an explosion hazard).

    I believe for radiant heating, you need a better thermal collector to generate higher temperatures (a pool can use a simple black plastic collectors; domestic hot water would need metal plate+metal tubing, glass cover over an insulated box).

    Solar thermal lends itself to DIY type projects pretty nicely. DIY build of solar PV (electric panels) not so much.

    Build it Solar has lots of such projects.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • SkippySkippy Solar Expert Posts: 308 ✭✭
    Re: Solar-ready radiant floor heating
    Danton wrote: »
    It was just something that I was thinking about. I have not tested the dish in winter and I think it would take at least 3 units to work. You could insulate the out side of the pool, under the concrete slab, and use a solar cover on top. I would keep the hot water heating separate from the house heat. Sounds like you have your system working well. Thanks for your thoughts and input.

    I would have to agree with the advice that in the winter time, the sun is not nearly as strong as in the summer. Just take my solar collector as an example. In the summer, its 170 F easily, but in the winter, it barely reaches 75 F . . For my area, in the winter time, the heat is just not there. :cry:

    Thanks for the link on those pumps, I will have to have a look at em .:D
    2 - 255W + 4 - 285W PV - Tristar 45 MPPT CC / 3 - 110W PV -wired for 36V- 24V Sunsaver MPPT CC / midnite bat. monitor.
    1 KW PSW inverter 24V / 2.5 KW MSW inverter-24V ~ 105 AHR battery.
    3 ton GSHP.- 100 gallon warm water storage / house heat - radiant floor / rad
    9 -220W PV - net meter - Enphase inverters and internet reporting system.
    420 Gallon rain water system for laundry.***  6" Rocket Mass Heater with 10' bed for workshop heat.
    Current project is drawing up plans for a below grade Hobbit / underground home.
  • alia176alia176 Solar Expert Posts: 33
    Re: Solar-ready radiant floor heating

    I too am thinking of using SHW (solar hot water) to meet the needs of water heating in our house. We have baseboard water heating using a propane fired boiler, a DWH (domestic water heating) 80 gallon tank using propane and a hot tub that uses 220vac heating. In an ideal world, I'd like to size a SHW collector system on the roof to heat up a sizeable solar water tank, probably somewhere around 500-700gallons. This tank will be under ground so hopefully the native soil will be a good insulator for this purpose in addition to the 2" polyisocyanurate insulation. As stated, Build it Solar site is a fantastic resource for this type of DIY project. Living in the SW, our solar fraction is pretty desirable for this type of project.

    I'm currently enrolled in a local community college SWH installer program and learning a ton of info. I'm hoping that next year, I'll be prepared to move on this project.
  • SkippySkippy Solar Expert Posts: 308 ✭✭
    Re: Solar-ready radiant floor heating
    westbranch wrote: »
    Have you looked at the Alpha pumps? they look to be a good fit...

    Would you be able to hook up a kill-o-watt meter to one of these Alpha pumps ? I will be hooking my elsid up to the meter to see how much power its using, with the 120 V transformer. I will let you know. . .. and yes, it probably does move alot more water than the elsid . . but I am interested in how much power it draws...
    2 - 255W + 4 - 285W PV - Tristar 45 MPPT CC / 3 - 110W PV -wired for 36V- 24V Sunsaver MPPT CC / midnite bat. monitor.
    1 KW PSW inverter 24V / 2.5 KW MSW inverter-24V ~ 105 AHR battery.
    3 ton GSHP.- 100 gallon warm water storage / house heat - radiant floor / rad
    9 -220W PV - net meter - Enphase inverters and internet reporting system.
    420 Gallon rain water system for laundry.***  6" Rocket Mass Heater with 10' bed for workshop heat.
    Current project is drawing up plans for a below grade Hobbit / underground home.
  • wrdaiglewrdaigle Solar Expert Posts: 65 ✭✭✭✭
    Re: Solar-ready radiant floor heating
    Skippy wrote: »
    Would you be able to hook up a kill-o-watt meter to one of these Alpha pumps ? I will be hooking my elsid up to the meter to see how much power its using, with the 120 V transformer. I will let you know. . .. and yes, it probably does move alot more water than the elsid . . but I am interested in how much power it draws...
    The alpha comes in 2 different versions; one is hardwired and one plugs in to a standard 120v outlet. The plug in version could certainly be connected to a kill-o-watt meter. This alpha actually displays the instantaneous wattage on its digital display while its running, so the kill-o-watt may be overkill.
Sign In or Register to comment.