Quote:
Originally Posted by Drake
MS, I am interested in your use of hydro tubing flow to redistribute heat throughout floor do you do this with just continuous flow or additional tubing and pumping. A mixing valve only adds heated water to a loop if the temp in the floor loop requires it correct? I don't know if it is possible but if solar could ever heat the floor mass and thus floor loop water beyond a comfort temp is there a way to remove/shunt/temper w/cooler water the loop? Maybe just controlling(shades/blinds) the windows would be the simplest overheating solution.
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Hello Drake: Sorry, but I don't understand the first sentence above. I'll just give a short description of our system. It is extremely simple, no zones or zone valves. Ours is a 2000 SF house with 1100 SF having floor heat. No heat in the bedrooms. The heated floor has ten 220 LF x 1/2" OD tubes run in large coils at 6" spacing except somewhat closer in the baths. Two manifolds serve the ten loops. One circulating pump delivers hot water from a heat exchanger to the floor, and a second circulates hot water from our Bock water heater to the heat exchanger. When the thermostat calls for heat, both pumps, which are 1/25 hp, run. The heated water could come directly from the Bock heater eliminating one circulator, but I believe the literature that says you shouldn't keep introducing new, oxygenated water into the floor system which could degrade the tubes, so a heat exchanger isolates the floor water.
A tempering valve adds *cool* water to a system. In DHW systems, it acts as a safety device to prevent scalding. They can be preset to provide a specific, lower output water temperature regardless of the input temperature. In a floor system, the valve injects a measured amount of the cooler water coming back from the floor into the hotter water going out to the floor in order to lower its temp to the acceptable level. In our case, it reduces the heated water from 120-125 to 110 deg.
My experience with radiant floors tells me that one must abandon all concepts of quick or instant heating or cooling. We have a very small thermal mass, i.e. 3/4" tile over 1-1/2" concrete. The heat tubes are in the concrete. This is all on plywood with insulation under. Still, if we turn the system off, and the house cools down, it takes a full day to bring the house back up to 70 degrees. Larger masses would be far slower to change, but the advantage for me is the stability of the heat once it is at the optimum level. I'm trying to speak to your questions, so sorry if I'm getting off the subject, but what I mean is that if you have overheating in a room because of solar gain, taking heat out of the mass of the floor will be a long, slow process. My guess is that, yes, you should simply shut the blinds.
I suspect that water heated in solar collectors can be used for floor heat, but the problem is always one of heat storage. A 120 gallon water tank heated by solar to 140 degrees and distributed to your floor until the temperature of the water is down to 100 will provide you with only 38 kBtu, and there are additional shortcomings. The 120 gallon tank, if heated by some alternative source, will be full of hot water in the morning when the solar collectors start to perform unless you take measures to prevent it, so there won't be any place to store the solar gain. Timing and storage are two of the big issues with solar and radiant heating. The sun is out when you don't need additional heat; it's cold and dark when you do.
I've got to stop. I think all my blah, blah is likely to be trying your patience. I've thought about this stuff a lot and installed quite a bit of it over the years, and I can yak about it forever. Sorry. mm