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Old 08-13-12, 05:25 PM   #9
opiesche
Helper EcoRenovator
 
Join Date: Jul 2012
Location: Rohnert Park, CA
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Quote:
Originally Posted by AC_Hacker View Post
For instance, I assume that your parents in Germany are using pipe spacings at around 6", or whatever the metric equivalent is... [
However, if you had used the same spacings as your parents, it would open up the possibility of using low intensity heating to it's best advantage. Low intensity heating could be something like solar heating, where feed water only occasionally gets up to the temperature level that you can rely on with natural gas.
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.

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?


Quote:
Originally Posted by AC_Hacker View Post
But when you mentioned the foam underlayment, is it over or under your hydronic floor?
It's on top of the hydronic system, between it and the hardwood floor. It was primarily to keep the floor quiet and comfortable to walk on - it's only about 1mm thick, so its insulation value is relatively small. Good crawlspace insulation is still a must, of course

Quote:
Originally Posted by AC_Hacker View Post
If you go with a larger size water heater (maybe even bigger than 40 gal), it will reduce the frequency of the 'heat-up' cycles. There is an efficiency curve that describes each firing of your water heater... the efficiency increases in the beginning of the firing, and levels off until the end of the cycle. By having fewer and longer firings, you will reduce the overall lower efficiency part of the cycle.
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.


Quote:
Originally Posted by AC_Hacker View Post
I'm very interested to see how it all works out. One thing we very badly need is a database of performance from DIY installs.
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?


Quote:
Originally Posted by AC_Hacker View Post
There are dual-sensor thermostats that are specially designed for hydronic heating, for applications exactly like yours. They cost maybe $200 or so. They even have an adjustable setting to find-tune for the thermal mass of your house, so that there is minimum over-shoot or under-shoot.
Again, great info! These would be measuring both exterior and interior and decide turn on and off based on both measurements, I assume?


Thanks for the advice, it's much appreciated. It's good to be able to have a conversation about this sort of thing as I install and tune the system to avoid some of the inevitable pitfalls


Olaf
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