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Originally Posted by opiesche
Interesting that you mention this. You're correct about the pipe spacing (it's almost exactly 6" for the room interior). One thought I've been playing with is, later on, installing solar water heating panels - water could go from the tubing returns into the panels (at an estimated 3F or so less than the feed temperature) to be preheated before being dumped back into the water heater. I'm a bit unclear as to how to control the temperature and prevent it from getting too high for the floors, short of using a mixing valve with cold water though.
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There are several approaches to the temperature control issue. In Europe where hydronic floors are usually high mass, the most used approach is to have the pumps circulating continuously, and the temperature of the water is continuously changed to maintain the desired set point. In this case, your heat stays on all the time, day and night and a night-time set back is not applicable due to the very large mass.
In the US, even with high mass floors, pumping is intermittent as is heating.
But low mass floors are not at all uncommon in the US, as you can attest. So, night time set back would be possible, due to lower thermal mass. With a low mass floor, your 'buffer tank' would be your thermal mass, and in your case, if you are using a water heater, it is your buffer tank, too.
Vlad had a very interesting, and complex controller that sensed outside temp and inside temp, and because he was using the same water heater for domestic hot water water and floor heating (the floor water was kept separate from the domestic hot water by using a heat exchanger), his controller would admit shots of hot water into the circulating floor water, as needed to maintain comfort.
Quote:
Originally Posted by opiesche
What sort of temperatures can one expect from solar panels? If my estimates turn out to be good and 85 degree water is enough for our heating needs, is there a possibility to go only with solar heated water and turn the gas heater off altogether?
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You should go on over to
Build It Solar and check around. Gary lives in Colorado, as I recall, and is using solar for heating with gas back up.. and he has radiant floors just like you built. He's pretty good about keeping records.
Quote:
Originally Posted by opiesche
That's great information to have, thanks! I was wondering what size would be best and had a hunch that bigger would be better - sounds like basically, the smaller the heater, the more it'll be running, so I'll try to go with a larger option.
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This is the kind of thing that you'd be best to find out locally. You might ask a local hydronics outfit, they probably won't be too insulted if you ask them for advice.
Quote:
Originally Posted by opiesche
While it's still reasonably warm outside, I can take a no-heating run of measurements (maybe this weekend) during the day and at night. Days are currently between 78 and 82, nights between 52 and 65, so I could get a series of temperatures in, say, 2-hour intervals or so of interior and exterior temperature without heating. Then, when the heating system is active, I could do the same, while correlating it with water feed and return temperatures. Is there any other data that would be useful?
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Well, one thing you could record is what temperature outside, with no heat and no cooling, makes your house a comfortable temperature (say about 68 to 72) inside? So
lower comfortable would be the temperature you plan to heat it at in the winter, and
higher comfortable would be the temp a little bit before you wish that the AC was running. So you're looking for the outside temps that produce the inside temps you like. This could be useful to you later.
Otherwise, just wait until the heating season gets rolling and record the temperature of the water that goes into your floors to provide heat and the temperature of the water coming back from the floors. at first the difference between these temps will be big, but then the difference will stabilize... this will give you an indication of the efficiency of your floors. Vlad ran some kind of design program for his floors and the program indicated that his water temp should be about 115 F, as I recall. He said that if he had kept the floors at 115 F he would have cooked his family. So he dialed it back to between 90 and 95, as I recall. He really did a very good job of insulating... curiously he said that his system keeps his house comfortably warm, but the floors don't feel warm. I take that to mean that he has really cut his heat loss way down.
Vlad, where are you, we need your input!
Best,
-AC