Under floor heating questions

jmdraft
jmdraft Registered Users Posts: 5 ✭
in Solar Water Pumping #1
I’m not sure if this is the right forum, but………..

I have an off grid solar house at 9000 ft. I’m only there in summer but (at altitude); it gets cold at night, so I’ve been thinking about a little under floor solar heating. Basics: I know there has to be a heat source e.g. solar water heat panels on the roof, a pump or pumps for moving the water around, probably some kind of thermostat, tubes or mats for the hot water under the floor and, maybe some kind of holding tank between the heat source and the under floor tubes etc.

What I need to understand is the automatic parts of all this. How do the pumps know when to move the water (Some kind of trigger in the thermostat……..solenoid) from the heat source to the (if there is one) holding tank? How do they know when, how fast etc. to circulate the water in the floor tubes, when to replace it etc. Does it go back to the heat source for reheating………..or to the tanks, what, etc.

I’m looking for some kind of diagram/explanation of how all this works. Any suggestions e.g. websites, links etc.?
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Comments

  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #2
    Re: Under floor heating questions

    Here is some information on Solar Thermal Heating:
    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
    ...

    And there Heat Pumped bases solutions (hot water, air heating/conditioning, etc.)... Some people have been using (some models/brands) of heat pumps even with snow on the ground. Heat pump based water heaters work pretty down to around 55F or so.

    Have you done all of the insulation (lots of ceiling insulation, double pane vinyl windows, etc.) that you can already?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #3
    Re: Under floor heating questions

    Great reference site for this sort of thing: http://www.builditsolar.com/

    Depending on the system design, one thermostatic control can control circulation from the heat collector to holding tank (checking temp on both to be sure collector is higher than tank) and another activate circulating pump to floor radiators according to internal air temp.

    You might want to consider a less complex passive solar heat or air exchange system too.
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  • jmdraft
    jmdraft Registered Users Posts: 5 ✭
    #4
    Re: Under floor heating questions
    BB. wrote: »
    Here is some information on Solar Thermal Heating:



    And there Heat Pumped bases solutions (hot water, air heating/conditioning, etc.)... Some people have been using (some models/brands) of heat pumps even with snow on the ground. Heat pump based water heaters work pretty down to around 55F or so.

    Have you done all of the insulation (lots of ceiling insulation, double pane vinyl windows, etc.) that you can already?

    -Bill

    Thanks all

    Yes, at 9000 ft, freezing is a major problem. However, the house is “double envelop- https://www.google.com/search?q=doub...bih=643&dpr=1” and a good part of it underground. The envelop is bigger than normal (sides-4 ft & back 6 ft wide) and serves as storage as well as insulation. The idea (which I got the idea from the Anasazi and works well at Aztec Ruins- https://www.google.com/search?q=grea...&bih=643&dpr=1) is that often (Texas for sure), at about 5-6 feet below ground, the average temperature is about 55° year round. For this reason, various versions of Pit houses were once built by many cultures around the planet e.g. http://www.metmuseum.org/toah/hd/jomo/hd_jomo.htm,

    https://www.google.com/search?q=viki...&bih=643&dpr=1

    https://www.google.com/search?q=anas...&bih=643&dpr=1

    I am gradually insulating (R-30+) my envelop and the more I do it, the better it works. There is plumbing under the floor of the house interior which (so far) doesn’t freeze. I’m going to run the under floor heating under the envelop floor. I’m sure it will still need antifreeze and a lot of insulated chambers (tanks, pumps etc.) This is all on my website but I don’t know the policy of this forum for posting a link to it.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #5
    Re: Under floor heating questions

    It is fine to post a link to a personal website (or even your commercial site as long as it is relevant to the conversation).

    We are more concerned about somebody form Asia saying how great their solar installer in Seattle (or iphone dealer in Africa) has been for them.

    Our forum was founded and is paid for by Northern Arizona Wind & Sun--So we try not supply "free advertising" to drive by posters/spammers. But links to other sites in the course of normal discussions are fine.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • AceNZ
    AceNZ Solar Expert Posts: 104 ✭✭✭✭
    #6
    Re: Under floor heating questions
    jmdraft wrote: »
    How do the pumps know when to move the water (Some kind of trigger in the thermostat……..solenoid) from the heat source to the (if there is one) holding tank?

    There are a few options. Usually, thermostats in the floor trigger solenoid valves to route heated water through different manifolds or zones. The thermostats also trigger a relay, which turns on a pump to move the water.
    jmdraft wrote: »
    How do they know when, how fast etc. to circulate the water in the floor tubes, when to replace it etc. Does it go back to the heat source for reheating………..or to the tanks, what, etc.

    I built an underfloor system using natural gas some time ago. I have solar hot water now. Combining the two wouldn't be too hard.

    On one side, you would use thermostats and a controller that understands the temperature difference between your storage tank and the water coming back after passing through the floor. On the other side, a similar system pumps water to the solar collector and back. The systems connect in a storage tank, where you add water coming from the exchanger at the base, and send it to the floor from the top.

    One thing I would recommend with under-floor heating is to be sure to use tubing with a very solid oxygen barrier. Without that, oxygen can leak in through the tubing and corrode pipes, pumps and so on.

    I would also suggest avoiding copper piping under the floor. Although it conducts heat better than plastic, if your flooring settles or moves even slightly, it can easily break/crack/leak. Things that are easy to replace when they're out in the open are a pain when they're embedded in your floor.

    Be sure to pressure test the under-floor tubing before covering it up.

    Having a heat sink in your floor of some kind will help retain heat and get you through the night. Concrete is effective. It takes longer to heat, but also stays warm longer. Just make sure to adequately insulate the heat sink from the Earth underneath it, or it will never warm up.
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  • Organic Farmer
    Organic Farmer Solar Expert Posts: 128 ✭✭
    #7
    Re: Under floor heating questions
    jmdraft wrote: »
    Thanks all

    Yes, at 9000 ft, freezing is a major problem. However, the house is “double envelop ... and a good part of it underground. The envelop is bigger than normal (sides-4 ft & back 6 ft wide) and serves as storage as well as insulation. The idea (which I got the idea from the Anasazi and ...

    Freezing is a problem.

    The problem is not with the system in your house though.

    You said that it is only occupied in summer.

    If you leave water in the external panels, over winter, there is your focus.

    The underground storage capacity needs to be large enough, so that when you drain your panels before you leave for winter, your storage tank can hold that much anti-freeze mix.
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  • waynefromnscanada
    waynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    #8
    Re: Under floor heating questions

    Here's something new in in-floor heating that doesn't use warm/hot water.
    http://www.amcfoam.com/PDFs/LegalettAirHeat.pdf
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