Radiant Floor Heat Electrical Energy Requirements

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pHredd9mm
pHredd9mm Registered Users Posts: 15 ✭
in General Solar Power Topics #1
Not the electrical floor heat, but the hot water radiant floor heat.

I was in a house a while back that had just their bathrooms with hot water radiant floor heat. It was a system which used the radiant floor system to also cycle their hot water to their hot water faucets with a very small electrical pump to keep instant hot water at their taps. I think it would be considered a combo or hybrid open/direct system.

The home owner said his biggest regret was not using the floor radiant heat throughout their entire home (all floor tile throughout house).

The actual water in the system can be heated by a variety of means: propane, electrical, solar or even wood. I have that part figured out.

My question is: Does anyone have PRACTICAL experience using (hot water) radiant floor heat. I am looking for the electrical energy requirements used by the pumping systems. It looks like normal installs on these systems have small constant running electric pumps to constantly circulate the hot water. I am looking for the electrical energy used for the pumps to figure out if they are a practical system for an off-grid home.

Thanks,

-Ed-
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  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    #2
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    Re: Radiant Floor Heat Electrical Energy Requirements

    In one sense, it is pretty easy to calculate. Figure out the current draw of the circ. pumps and the run time. Sizing circ pumps. Is pretty important to produce the ideal flow rates.

    Once you know the current draw and run times, you can figure out how many WH a system might draw daily. As for the efficacy of such a system depends on the size of the off grid PV system. For example, a 1kwh/day draw on my system would be a kill,,, but on a larger system might be perfectly doable.

    Tony
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  • techntrek
    techntrek Solar Expert Posts: 1,372 ✭✭✭
    #3
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    Re: Radiant Floor Heat Electrical Energy Requirements

    This guy does it: http://www.solarhouse.com/

    Its been a while since I browsed the site, but I believe he has full descriptions of his solar PV and solar heat systems. I think he has 1000 gallons of hot water storage, for domestic hot water and air heating.
    4.5 kw APC UPS powered by a Prius, 12 kw Generac, Honda EU3000is
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  • sawmill
    sawmill Solar Expert Posts: 93 ✭✭✭
    #4
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    Re: Radiant Floor Heat Electrical Energy Requirements

    I use radiant floor heat from a outdoor wood furnace. The Taco circulating pump draw 70 watts. I use a (time & temp) wall thermostat for for control of the circulating pump. Once the outside temps fall below 20f ( with wind) the hot water exchanger located in the duct work is used with the HVAC fan. This fan draws about 290 watts. Usually once the house is brought up to temperature this fan stays off and the radiant heat will maintain comfort.
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  • n3qik
    n3qik Solar Expert Posts: 741 ✭✭
    #5
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    Re: Radiant Floor Heat Electrical Energy Requirements

    Have baseboard radiant heat. My Taco circulating pump using about 100 watts.
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  • pHredd9mm
    pHredd9mm Registered Users Posts: 15 ✭
    #6
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    Re: Radiant Floor Heat Electrical Energy Requirements

    For sawmill & n3qik: So I assume the pump(s) cycle on and off depending on the thermostat setting and air temperature.
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  • n3qik
    n3qik Solar Expert Posts: 741 ✭✭
    #7
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    Re: Radiant Floor Heat Electrical Energy Requirements

    That is correct.

    Here is a chart of the Bedroom heat. Have not have to turn on the Living room as of yet.

    Attachment not found.
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  • wrdaigle
    wrdaigle Solar Expert Posts: 65 ✭✭✭✭
    #8
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    Re: Radiant Floor Heat Electrical Energy Requirements

    Radiant heat off the grid is very attainable...if it's done right. If it's not done right, it can be a major energy sink. I've been struggling with this at my house. I'm the second owner of an off-grid house. The previous owners installed in-floor radiant heat with a pretty traditional setup: one circulator pump for the boiler and one pump for each of 2 zones. When I heat with wood, , my total energy usage is about 3000 - 3500 watts. When I use the boiler, I double it. Generally, I heat with wood, so it's not too much of a problem, but when I'm away I don't have that option. I started the following post on a diy plumbing forum to help figure out how to remedy the problem:

    http://www.terrylove.com/forums/showthread.php?44951-Radiant-heat-replace-mutiple-circulating-pumps-with-single-variable-speed-pump

    Basically, I plan to eliminate the two zone pumps and replace the main pump with a high efficiency variable flow pump. My current pumps use about 85w (255w total) each. The high efficiency pumps use between 5 and 45w. I have done all of the calculations and this should be plenty of pump for my house. Here are links to a couple of different high efficiency pumps:

    http://www.pexuniverse.com/grundfos-alpha-15-55f-lc-circulator-pump-w-ifc-1-6hp-115v
    http://www.younits.com/wilo-stratos-eco-16f-high-efficiency-circulating-pump-115v-p-1314.html?utm_source=Google+Base&utm_medium=cpc&utm_campaign=comparison_shopping

    Here is a case study of the Alpha used in an off-grid house:
    http://grundfos.oreilly-depalma.com/2010/alpha-circulator.shtml

    Ivan labs also sell low wattage dc pumps that can run directly off batteries. They are lower flow than the AC units listed above, but if leave meet your specs they may be just what your looking for.

    Bill
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  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    #9
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    Re: Radiant Floor Heat Electrical Energy Requirements

    Try backwoodssolar.com for high efficiency DC hot water circulator pumps. --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
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  • sawmill
    sawmill Solar Expert Posts: 93 ✭✭✭
    #10
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    Re: Radiant Floor Heat Electrical Energy Requirements

    You are correct about thermostat control of the circulating pump. My system turns off at 10pm and back on at 4am, with the temperature set at 71.
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  • n3qik
    n3qik Solar Expert Posts: 741 ✭✭
    #11
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    Re: Radiant Floor Heat Electrical Energy Requirements
    sawmill wrote: »
    My system turns off at 10pm and back on at 4am, with the temperature set at 71.
    Sounds like some thing is not right. Unless you are letting the wood furnace burn out at night.
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  • Volvo Farmer
    Volvo Farmer Solar Expert Posts: 209 ✭✭✭✭✭
    #12
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    Re: Radiant Floor Heat Electrical Energy Requirements

    I'm using a Grundfos UPS 58 15 FC. It's a 3 speed pump and I just measured it. It uses 49W on low, 61W on medium and 73W on high.
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  • Dave Angelini
    Dave Angelini Solar Expert Posts: 6,746 ✭✭✭✭✭✭
    #13
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    Re: Radiant Floor Heat Electrical Energy Requirements

    Exceptional low maintenance performance can be had with the Ivan labs 24vdc hot water pumps. You can even series them for 48VDC nominals.
    "we go where power lines don't" Sierra Nevada mountain area
       htps://offgridsolar1.com/
    E-mail offgridsolar@sti.net

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  • westbranch
    westbranch Solar Expert Posts: 5,183 ✭✭✭✭
    #14
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    Re: Radiant Floor Heat Electrical Energy Requirements

    Also the Laing Ecocirc Solar DC Pump Model D5 solar 090 B
     
    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
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  • sawmill
    sawmill Solar Expert Posts: 93 ✭✭✭
    #15
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    Re: Radiant Floor Heat Electrical Energy Requirements

    To n3qik, Turning off the circulating pump has nothing to do with the fire in the outdoor furnace. The water stove maintains the tank water temp by being air tight with no combustion air until needed. The water temp is maintained by the stove and the house temp is maintained by a programmable thermostat controlling the circulating pump. This stove requires loading twice a day during Winter temps and usually only once per day with the moderate days we have been experiencing. Since this stove also provides the domestic hot water during the heating system, once fired in the Fall this is maintained until warm weather.
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  • solarvic
    solarvic Solar Expert Posts: 1,071 ✭✭✭✭
    #16
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    Re: Radiant Floor Heat Electrical Energy Requirements

    Sawmill. Do you use a side arm on your waterheater? I was in the prosess of installing a classic boiler wood stove and a side arm kit on the waterheater. I never finished the install as I got a gaswell. Sold the furnace to one of the people that worked for the gas company. :Dsolarvic:D
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  • sawmill
    sawmill Solar Expert Posts: 93 ✭✭✭
    #17
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    Re: Radiant Floor Heat Electrical Energy Requirements

    Solarvic

    As the hot water from the outside furnace enters the crawl space I have a 17 gal pre-heat tank up stream of a on demand Rinnai. This tank is encircled with many turns of pipe on the outside tank surface. In case of a leak (just leaks to the ground) there is no danger of cross contimation with the domestic water. During the heating season this small tank stays appox 140 degrees. The times this is not enough hot water for the two of us the Rinnai picks up the slack. I don't have any knowledge about the sidearm type of exchanger.

    The one who helps stack our split wood is very envious of your personal gas supply, you are very fortunate.
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  • solarvic
    solarvic Solar Expert Posts: 1,071 ✭✭✭✭
    #18
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    Re: Radiant Floor Heat Electrical Energy Requirements

    http://www.centralboiler.com/media/CBBrochure.pdf Here is a broshure that shows the picture of a side arm for a water heater. Sounds like you have something that works. I had my side arm kit on a 40 gal electric water heater. A friend has one on an 80 gal waterheater and I knew another person that had one on a 40 gal waterheater. They just shut down the electric to a waterheater for the whole heating season. Before I got my central boiler I looked at one that was connected to 2 houses and it took care of both of them. Merry Christmas to everyone. :Dsolarvic:D Also there was an article in home power magazine that gives directions on how to make a side arm. Yes I am fortunate to have the gaswell and am hoping for it to last as long as I need it.
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  • pHredd9mm
    pHredd9mm Registered Users Posts: 15 ✭
    #19
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    Re: Radiant Floor Heat Electrical Energy Requirements

    sawmill: Can you tell us more about your pre-heat tank. What kind of tank? Dimensions (plus short and fat or tall and thin)? Type and how much tubing (copper or ?, diameter, length)? Did you fasten the tubing to the tank (solder, braze), or it just tightly wrapped? Did you insulate this whole contraption?

    I envision a pre-heat tank I am thinking about building that would probably be larger than 17 gallons and would have two sets of tubing wraps -- a daytime solar heated set and a set for a wood-fired water heater night and cloudy). The tubing would be wrapped in parallel with each set going to/from its respective heated water source.

    Thanks to all... always a learning source here. By the time I get around to building new homestead in a couple years I should have everything already designed and ready to build, buy, install :-)
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  • Blackcherry04
    Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    #20
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    Re: Radiant Floor Heat Electrical Energy Requirements

    If I may throw a little .02 in here. I built a system similar to this once. It finally blew up from a steam or air lock. Maybe I didn't have enough popoff's or air eliminators, the air or steam collected in it and eventually caused the pump to stop circulating. The automatic Damper could have failed. The stove / boiler blew up and a lot of the tubing and almost set my house on fire.

    It seem to work fine until the water temperature got around 160 deg. Perhaps the boiler could have made steam, I didn't think it could have, but that's my story. In the end, it just wasn't worth the effort and I did away with it.
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  • pHredd9mm
    pHredd9mm Registered Users Posts: 15 ✭
    #21
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    Re: Radiant Floor Heat Electrical Energy Requirements

    Blackcherry04: The reason I asked the questions was to use the experiences of those who have tried similar ideas. Seems to be a balancing act of producing enough hot water and not letting it just sit somewhere and get hotter and hotter. Thanks for the info. I appreciate all answers and experiences.
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  • solarvic
    solarvic Solar Expert Posts: 1,071 ✭✭✭✭
    #22
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    Re: Radiant Floor Heat Electrical Energy Requirements

    In post 18 I put a link there that explains lots of answers to the questions you want answers for. If you search the new home link and look at parts or catalog you see what you need. http://www.centralboiler.com/?src=googlecb&gclid=CP_uu9uco60CFZNY7Aod9isO4Q . Basically what you need is a bypass valve you could divert the water when it gets too hot. I think I would want at least a 30 0r 40 gal waterheater so the rinella,s wouldn,t be needed during heating season. I am not trying to push the classic boiler but am pointing out that it is one of the most effecient ones. It doesn,t make any difference what wood furnace you use. Thier website is a good reference of ideas of how to accomplish what some are wanting. :Dsolarvic:D
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  • sawmill
    sawmill Solar Expert Posts: 93 ✭✭✭
    #23
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    Re: Radiant Floor Heat Electrical Energy Requirements

    pHredd9mm-- I used an electric hotwater heater from a camper hence the 17 gallon size. My crawl space opening is limited in size so I couldn't use a standard 40 or 50 gal tank. All the sheet metal was removed and the tank was wrapped with as many turns as it would hold of 1/2 inch pex. I then used webbing to wrap the pex holding it tight against the tank. Then 8 inches of conventional insulation was wrapped around tank and held with duct tape. Works great. I know copper would be better but here our minerals in the water make a short life for copper.

    Like Solarvic states there are several good water stove manufacturers and some not so good, do your research and if able look at some that have been installed and talk with the owners. My particular stove is not pressurized and is open to atmospheric pressure. In case of boiling, the water spills out the top with no danger of pressure build-up in the waterstove.

    In the event that no domestic hot water is used for a period of time then the pressure build up in the small preheat tank just backs against the (no check valve)incoming cold water supply. If your incoming pressure is too great for this, the pressure relief on the Rinnai or other hotwater heater will provide an outlet. When our outdoor furnace is no longer needed (warm weather) I switch to solar collectors for the domestic hot water needs.

    Hope this helps.
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  • pHredd9mm
    pHredd9mm Registered Users Posts: 15 ✭
    #24
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    Re: Radiant Floor Heat Electrical Energy Requirements

    I want to thank everyone for their answers and responses. As I try to design my dream "homestead" and retirement home I appreciate all the work that has happened before me. I am learning more and more about electrical energy conservation coming before energy production. Again, thanks to all.
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  • pHredd9mm
    pHredd9mm Registered Users Posts: 15 ✭
    #25
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    Re: Radiant Floor Heat Electrical Energy Requirements
    n3qik wrote: »
    That is correct.

    Here is a chart of the Bedroom heat. Have not have to turn on the Living room as of yet.

    Attachment not found.

    n3qik: going back and looking at this thread again. What are we looking at here? Is this the power used by the pump as it cycles on and off? What is the time frame covered? thx.
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  • n3qik
    n3qik Solar Expert Posts: 741 ✭✭
    #26
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    Re: Radiant Floor Heat Electrical Energy Requirements

    That is the on time for the pump. End to end is 24 hrs.
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  • wrdaigle
    wrdaigle Solar Expert Posts: 65 ✭✭✭✭
    #27
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    Re: Radiant Floor Heat Electrical Energy Requirements

    I just finished upgrading my circulating pumps from 3 taco 007s to a single grundfos alpha. Total power consumption went from 265w to 20w! I have more details on my blog if anyone's curious: http://bluecloudpowerco.blogspot.com/2012/01/toasty-warm-feet-with-energy-to-spare.html
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