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Old 11-22-09, 10:46 PM   #29
AC_Hacker
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Default Post from Maxis (in US units)

This post, originally by Maxis, is full of useful details of a radiant floor install he is doing in Latvia (if I remember correctly). He is retrofitting a house and interestingly is using three different approaches (different approach for each floor) in his retrofit. I have relocated this post here, since it is more relevant to radiant floors than to Homemade Heat Pumps.

To make his information more accessable, I have added units that should be more familiar to American readers. I may have been a bit heavy-handed in my conversions, so they should be viewed as 'ballpark' attempts, and not as engineering data.

-AC_Hacker

* * *

Quote:
Originally Posted by Maxis View Post
The first I should say that this will be the first winter with HP and radiant floors in my house. I could say something about results only after some time -when it will get colder.

Answers to your questions:
Quote:Originally Posted by AC_Hacker
A) Did the minimum bending radius of the PEX determine the pipe spacing? Did you use bending forms, or did you just allow the pipe to bend as it would and put concrete on top?

I have read that one meter of 20mm (3/4 in) pipe could give about 18W (61 BTU/hr) heat with standard temperatures. That means, if you put 5m/m2 (3/4 in. PEX, spaced 7 3/4 on center) than you will get about 90W (300 BTU/hr). In our area the heat loss range is from 60W to 150W per m2. I have used 16mm pipe and I put about 5 to 6m/m2 (5/8 PEX, spaced 6 1/2 in. to 7 3/4 in.) - I have not less than 15cm (6 in.) between pipes and then bending is not an issue - I didn't use any bending forms. Actually pipes should be put as spiral (not snake) and then you have only 90 degree bends. With spiral you also will get equal temperature in all room.

Quote:Originally Posted by AC_Hacker
C-1) How thick was your polystyrol (polystyrene? EPS?)? What kind of mesh did you put on top?

It was 75mm (3 in.) thick. The recommended thickness is 100mm (4 in.), but I had limitations and couldn't put more. The polyethylene film should be put on top to not allow concrate to flow between plates. Then I put 5mm (7/32 in.) (to be able to walk on it ) steel reinforcement mesh with 150 x 150 mm (6 x 6 in.) cells (than you don't have to measure the distance between pipes - just follow the mesh).


It is metal sheet used as roof or wall material. Look in pictures for details

The reinforcement mesh pieces was fixed to each other with special steel wire


As I said I could comment results after some time. But I have read thet there in Latvia it works fine.


Average temperatures C in my area in each month:
Jan -4.7 C (23.54 F)
Feb -4.3 C (24.26 F)
Mar -0.6 C (30.92 F)
Apr 5.1 C (41.18 F)
May 11.4 C (52.52 F)
Jun 15.4 C (59.72 F)
Jul 16.9 C (62.42 F)
Aug 16.2 C (61.16 F)
Sep 11.9 C (53.42 F)
Oct 7.2 C (44.96 F)
Nov 2.1 C (35.78 F)
Dec -2.3 C (27.86 F)

Possible minimum C in each month:
Jan -33.7 C (-28.66 F)
Feb -34.9 C (-30.82 F)
Mar -30.3 C (-22.54 F)
Apr -13.1 C (8.42 F)
May -5.5 C (22.1 F)
Jun -2.3 C (27.86 F)
Jul 4 C (39.2 F)
Aug 0 C (32 F)
Sep -4.1 C (24.62 F)
Oct -8.7 C (16.34 F)
Nov -18.9 C (-2.02 F)
Dec -31.9 C (-25.42 F)


Heating season = 203 days, average temperature 0,0 C (32 F)

Insulations:
Basement: 120mm polystyrol (4.75 in. EPS)
1st floor: walls are 210mm (8.25 in) logs - cutted from both sides + 50mm (2 in.)wood/concrete plates from outside
2nd floor - 200mm (7 7/8 in) rockwool


I didn't use this method, but there is different reflection materials, some are insulation + reflection sheet in one, some are just reflection material. There is the link to one page where you can find how to make it by yourself:
Solar Shed -- House Heating

Best regards
Maxis
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